Table of Contents

Page No

Executive Summary                                                                                          i-vi

1.         Introduction                                                                                                                 1-6

            1.1        Background of the project                                                                                      1

            1.2        Historical development of biogas technology                                                            3

            1.3        Potential of biogas technology in Bangladesh                                                           4

            1.4        Objectives                                                                                                             5

            1.5        Methodology                                                                                                         5

2.         Biogas Technology                                                                                                    7-14

            2.1        Types of biogas plants                                                                                            7

            2.2        Experiences in developing countries                                                                        9

                        2.2.1     Lessons learned from biogas projects of China, India and Nepal                  11

            2.3        Experience with biogas in developed industrialized countries                                   12

            2.4        New developments                                                                                              13

3.         Application of Biogas Technology in Bangladesh                                                   15-24

            3.1        History of biogas development in Bangladesh                                                         15

            3.2        Experiences with different models                                                                         17

            3.3        Operating conditions                                                                                             19

            3.4        Cost of biogas plant construction                                                                           19

            3.5        Socio-cultural acceptability                                                                                   20

            3.6        On-going and planned projects                                                                              21

            3.7        Success stories and failures of biogas projects                                                       21

4.         Experiences with Biogas Utilization in Commercial Enterprises                           25-31

            4.1        Experience with the production of biogas                                                               25

            4.2        Experience with the use of biogas                                                                         26

            4.3        Experience with the use of slurry                                                                          29

5.         Test Results                                                                                                                  32

6.         Scrubber Technology                                                                                               33-36

7.         Policies                                                                                                                         37

8.         Technical Potential of Poultry Litter-Based Biogas Plants in Bangladesh                 38

9.         Observations                                                                                                            39-41

10.       Financial Analysis                                                                                                     42-50

10.1            Assumptions and results of analysis                                                                       42

            10.2      Sensitivity analysis                                                                                               46

                        10.2.1   Effect of varied expenditures and incomes                                                 46

                        10.2.2   Effect of varied capacity utilization                                                            48

                        10.2.3   Effect of electricity price variation                                                            49

                        10.2.4   Effect of different equities                                                                        50

11.       Major Findings and Recommendations                                                                   51-52

            11.1      Major Findings                                                                                                     51

            11.2      Recommendations                                                                                                52

Acknowledgement                                                                                                                    53

References                                                                                                                           53-54     

List of Tables

Table 1.1:         Raw materials for biogas plants                                                                              4

Table 1.2:         Potential of biogas and organic fertilizer in Bangladesh                                             5

Table 3.1:         Biogas plants surveyed by LGED in 1992                                                              23

Table 4.1:         Comparison of crop yields by using slurry and chemical fertilizer (BCSIR, 1998)      30

Table 5.1:         Test results of dry biogas produced from poultry litter in a biogas plant at Maona  32

Table 5.2:         Test results of poultry feed prepared and tested by Agro-Organic Food

                       Complex Ltd., Faridpur.                                                                                       32

Table 8.1:         Estimated sizes of poultry farms                                                                            38

Table 10.1:        Costs for biogas plant and pit for slurry storage                                                      43

Table 10.2:        Assumptions for biogas plant operation                                                                  44

Table 10.3:        Calculated results of NPV, IRR and BCR                                                             44

List of Figures

Figure 1.1:        Pattern of biomass consumption in rural areas of Bangladesh                                    1

Figure 1.2:        Flow chart of a biogas plant                                                                                    3

Figure 2.1:        Floating-dome biogas plant                                                                                      8

Figure 2.2:        Fixed-dome biogas plant                                                                                         8

Figure 2.3:        Balloon-type biogas plant                                                                                        9

Figure 2.4:        KVIC Model                                                                                                       10

Figure 2.5:        Deenbandhu biogas plant                                                                                      11

Figure 3.1:        Organization-wise biogas plants installed in Bangladesh                                          17

Figure 3.2:        Fixed dome biogas plant, BCSIR model                                                                 18

Figure 3.3:        Fixed dome biogas plant, LGED model                                                                  19

Figure 3.4:        Cost of biogas plant installation in Bangladesh (BCSIR, 1998)                                 20

Figure 6.1:        Scrubbing of hydrogen sulfide                                                                               34

Figure 6.2:        Scrubbing of carbon dioxide                                                                                  35

Figure 6.3:        Basic flow diagramme of amine treated process for CO₂ and H₂S removal              36

Figure 10.1:       IRR at different plant sizes                                                                                   45

Figure 10.2:       BCR at different plant sizes                                                                                  46

Figure 10.3:       IRR at different incomes                                                                                      46

Figure 10.4:       IRR at different incomes                                                                                      47

Figure 10.5:       IRR at different incomes                                                                                      47

Figure 10.6:       IRR at different incomes                                                                                      47

Figure 10.7:       IRR at different incomes                                                                                      48

Figure 10.8:       IRR at different capacity utilization                                                                        48

Figure 10.9:       IRR at different capacity utilization                                                                        49

Figure 10.10:     IRR at different costs of electricity                                                                        50

Figure 10.11:     Return on equity per year at different equity ratios                                                 50

List of Photos

Photo 1.1:         Biogas plant                                                                                                           2

Photo 1.2:         Cooking in traditional way in rural areas of Bangladesh                                            2

Photo 1.3:         Cooking with biogas                                                                                               3

Photo 2.1:         Biogas Plant at Wolperthausen, Germany                                                              13

Photo 2.2:         Biogas Plant at Mauternach – Luxembourg                                                           13

Photo 3.1:         Poultry Farm                                                                                                        15

Photo 3.2:         Biogas Plant Inlet                                                                                                 16

Photo 3.3:         Inlet with fertilizer pit                                                                                            22

Photo 3.4:         Study team visiting biogas plant                                                                             22

Photo 4.1:         Biogas plant with gas carrying pipe                                                                        25

Photo 4.2:         Biogas plant with gas distribution lines                                                                   26

Photo 4.3:         Boiler for preparation of poultry feed run by biogas                                                26

Photo 4.4:         Pipe carrying biogas to household                                                                          27

Photo 4.5:         Cooking with biogas                                                                                             27

Photo 4.6:         Commercial biogas stove used for preparing sweetmeats                                        28

Photo 4.7:         Hajjak light based on biogas                                                                                  28

Photo 4.8:         Power generator (locally retrofitted) based on biogas                                              29

Photo 4.9:         Power generator based on biogas                                                                          29

Photo 4.10:       Use of slurry as fertilizer                                                                                      30

Photo 4.11:       Use of slurry as fertilizer for vegetable cultivation                                                  30

Photo 6.1:         Biogas power generator with water trap (hanging on the wall)                                34

Photo 9.1:         Slurry from poultry farm dumped beside a road                                                      39

Photo 9.2:         Slurry from a biogas plant                                                                                     40

Photo Anx-1:    Expert Meeting                                                                                                    67

Annex-1: Terms of Reference                                                                                                55-56

Annex-2: Findings of the field visits                                                                                          57-65

Annex-3: Focus Group Discussion at Maona                                                                                63

Annex-4: Invitation letter for Expert Meeting                                                                           64-65

Annex-5: Minutes of the Expert Meeting

Annex-6: Participants’ List of the Expert Meeting                                                                         70

Abbreviations and Acronyms

Executive Summary

Bangladesh is a densely populated country with a population of about 140 million, about 72% of which live in the rural areas. The overall energy consumption in Bangladesh is still very low. In 2000, per capita consumption of commercial energy and generation of electricity were 200 kgoe/year and 120 kWh/year respectively. The energy consumption in the rural area is even much lower. The supply of natural gas is limited to urban areas, mostly in the eastern part of the country. Only about 5% of the population have access to natural gas, whereas about 32% to grid electricity. About 60% of total energy consumption of the country is being met from biomass. Agricultural residues, animal dung, trees, leaves, twigs, etc. are the main sources of biomass fuels. There are indications that consumption of biomass energy has already exceeded the regenerative limit and there prevails energy crisis in the rural areas of Bangladesh. Because of energy shortage, more and more agricultural residues and animal dung are being used as fuel depriving the soil of organic matter and essential micro-nutrients. As a result, soil fertility is declining and the farmers are becoming more and more dependent on chemical fertilizer. Moreover, use of biomass as fuel in traditional stoves is responsible for in-door air pollution causing health hazards to the users. It is apprehended that, with population growth, the energy crisis, environmental degradation, deforestation, declining of soil fertility, etc. will sharpen further if the things move as usual and no alternative measures are undertaken. Biogas offers a sustainable solution, at least in part, to all these problems Bangladesh is currently facing.

In the backdrop discussed above, GTZ-PURE has initiated a project “Promotion of Biogas Production and Use in Commercial Establishment” to support promotion of biogas use in suitable commercial establishments. It is intended to develop and test a marketing approach for promotion of biogas use with the focus on suitably sized poultry farms. Bangladesh Centre for Advanced Studies (BCAS) with Energy Consulting Services (ECS) as Sub-Consultant conducted the feasibility study during May – July 2005. This report presents the results of the study.

Biogas Technology in Bangladesh

The first biogas plant in Bangladesh was installed in 1972. Since then several organizations have taken initiative to research, develop and disseminate biogas technology in the country. The most significant work has been done by IFRD of BCSIR and LGED. All major types of biogas plants - fixed dome, floating dome and bag type – have been installed in the country. Fixed dome type biogas plant has proved to be the most suitable and at the moment the only type of biogas plant that is being installed.

Several government financed biogas projects have been implemented with different degrees of success. Under these projects, more than 25,000 biogas plants have been installed throughout the country. Different types of raw materials like cow-dung, poultry litter, and human excreta are being used in these plants. Biogas from cow-dung or poultry litter is well accepted by the people. After initial hesitation, biogas from human excreta is also proved to be accepted.

Different approaches for dissemination have also been tried. Through trial and learning, Bangladesh has gained substantial experience on biogas technology. Different organizations have also worked towards capacity building. As a result, there is skill and know-how on the biogas technology. There is also awareness among the people about the advantages of biogas plants. There exists a conducive atmosphere for large-scale biogas programme.

However, very few biogas plants are currently being installed. There is no on-going public sector  biogas project. Some private sector entrepreneurs are trying to construct plants on their own efforts as a part of their business. In some locations, they are providing after-sale services.

At the moment, some movements are being observed in the biogas sector. Grameen Shakti has undertaken initiative to disseminate biogas plants. BRAC also is conducting a research project on power generation from biogas in Manikgonj and Tangail districts. The Netherlands Development Organization (SNV) has planned to start large-scale programmes for domestic biogas in a number of Asian countries including Bangladesh. Another initiative has been undertaken by the GTZ under its PURE project. The present study is a part of this initiative.

Biogas Utilization in commercial enterprises

Dairy farms and poultry farms are run on a commercial basis. Biogas plants installed in the country are mostly based on cow-dung and poultry droppings. The focus of the study was poultry-based biogas plants. During this study, it was found that the poultry based biogas plants were situated in areas not covered by gas line.

Biogas is used as cooking fuel for the household mostly by owners, when the owners reside near the farm, and also by neighbours. The neighbours usually pay 300 Taka per month for a biogas connection. Besides household cooking, biogas is used for lighting, although to a less extent. There are also some cases where biogas is being used as fuel for productive purposes, e.g. preparation of food in big kitchens, preparation of sweetmeat, operating boiler and drying fish.

Biogas is also being used for power generation. Currently, no biogas generator is made in the country. In most cases imported petrol, LPG or natural gas generator is retrofitted for the use of biogas. However, there are problems regarding starting and continuous operation. The reasons are: the moisture and hydrogen sulfide contents. There is no experience in Bangladesh with removal of hydrogen sulfide. For removal of moisture, moisture traps are used by some.

Use of slurry

Slurry from biogas plant is used as fertilizer and as fish feed. The use of slurry as fertilizer increases the crop production significantly. It is more productive than the undigested dung. Litter from poultry has almost no market value. The fish farm owners or vegetable cultivators usually collect the dried litter for free, sometime at a cost of about Tk. 0.50 – 1.00 per kg. Often it is thrown in the nearest ditch and washed away with monsoon water.

The market for slurry as fertilizer is yet to be developed. However, the farmers in the neighbourhood of biogas plants are increasingly recognizing the quality of slurry from biogas plants. Currently, it is sold in moist form (moisture content around 50%) at a price of 0.80 Taka – 2.00 Taka per kg and in dry form (moisture content around 25%) at price over 5 Taka per kg. Packaging of slurry as well as addition of nutrients according to needs will add to the value substantially.

 Test results

Poultry-based biogas contains 55% - 65% methane, 35% - 45% carbon dioxide and traces of other gases such as hydrogen sulfide, moisture etc., composition varying with the nature and retention time of slurry. Methane is the only useful gas. Carbon dioxide does not do any harm except its effect as greenhouse gas and diluent of methane. Moisture content causes difficulties during burning. Hydrogen sulfide is a corrosive gas and corrodes metals that come in contact. To remove the unwanted gas, scrubbing of biogas is necessary.

The easiest way to get rid of hydrogen sulfide is to allow it to react with any gas/solution/iron oxide. Red oxide (in the form of steel wool, for instance) may be used. The used up red oxide may be recycled through exposing it to air for some weeks. For scrubbing moisture, simple water trap may be used.

A large number of scrubbing technologies are available. They are popularly called “gas sweetening” technologies and are applied in the processing of natural gas. They are applied at relatively high gas pressures and are able to handle large gas volumes. Both regenerative and non-regenerative processes are available.

Policies

Bangladesh has no specific biogas policy. However, National Energy Policy 1996, Draft Renewable Energy Policy and Draft National Energy Policy emphasize on harnessing biogas energy. National Energy Policy 1996 urged that conservation at end use level of biomass fuels is to be reached through technological intervention, primarily by dissemination of technologies like improved stoves and biogas digesters. The draft Renewable Energy Policy, which is yet to be approved and the new National Energy Policy (under preparation) have mentioned biogas technology more specifically.

The government has declared agro-based industries as a thrust sector and gives specific subsidy for poultry industry. Electricity consumption of poultry farms up to 1000 birds is charged at domestic tariff, whereas larger farms get a subsidy of 20% on electricity bill calculated on industrial tariff rate. Moreover, the interest rate for agro-based industries has been reduced to 8%.

Existing laws do not mention the production of biogas and its sale. Regarding power generation in private sector, GoB has approved several laws. Under the present law, electricity generation for own consumption (captive power) is allowed. It is also allowed to sell the generated electricity to the neighbors. Currently, Captive Power Policy Guidelines are being prepared by the Power Cell.  It is expected that this policy will regulate the costs of electricity produced by private sector to be supplied to the grid.

Draft Renewable Energy Policy mentions that the sponsor may use the existing transmission and distribution systems upon payment of a mutually agreed upon wheeling charge. Utilities (BPDB, DESA, DESCO, REB) will buy electricity generated from grid-connected renewable energy projects through mutually agreed “Power Purchase Agreement (PPA)”. GOB will not regulate the price of electricity generated from renewable energy source.

Technical potential of poultry litter-based biogas plants

It is rather difficult to get up-to-date and reliable data on poultry farms. A report from Poultry Sector Development Project gives a figure of 112,000 commercial poultry farms, which together produce about 5,900 tons of litter daily. Farms with less than 100 birds are not included in this estimation. Of these, 20% farms have a bird population of more than 1,000. The remaining farms are smaller in size and maintain 100 – 1,000 birds. It has been found that a poultry farm with more than 100 birds is technically suitable for a biogas plant. 

Financial Analysis

Financial analysis has been made for biogas plants based on 100, 250, 500, 1000, 5000, 10000 and 50,000 birds. It has been considered that gas and fertilizer will be sold. Power generation has also been considered for farms with more than 500 birds. The interest rate is 8%. It has been found that sale of gas and fertilizer makes all biogas plants viable. On the other hand, sale of only fertilizer or electricity does not make any plant viable. For farms with 500 and more birds, gas sale alone makes the plant viable. By bigger plants, sale of any two of the products - gas, electricity and fertilizer - makes it profitable; however, sale of fertilizer and gas (no power generation) is more profitable.

The prices of construction materials may vary over the period of time. Also the running costs (labor cost, cost of maintenance) may vary. As such sensitivity analysis has been done by variation in the price of investment, maintenance and labor cost, as well as in the sale of gas, electricity and fertilizer. It has been shown that with higher expenditure, IRR goes down and with higher selling price (in terms of income) IRR goes up. It has been found that the biogas plants are profitable in all cases of 20% expenditure hike and 20% income decrease, except the 100 birds plant. With expenditure decrease by 20% and income rise by 20%, IRR increases with plant size IRR is more sensitive to product sale than to expenditure increase.    

The output of the biogas plant depends on the availability of raw material i.e. litter, which is dependent on the number of birds of the farm. In poultry farms, the number of birds may vary over time, which affects the profitability of the plant. With decreasing capacity utilization, IRR decreases significantly. In case of 100 birds, biogas plant is viable only if over 80% capacity is utilized and for 250 birds, the capacity utilization needs to be over 60%. It is interesting to note that even at 40% capacity utilization, the biogas plants with 500 and more birds are viable if both gas and fertilizer are sold. It is significant, because it offers the farmer some operational flexibility and also allows profitably installing and operating a bigger size biogas plant with the option of increasing the number of birds later.    

Major Findings

i)       So far, about 25,000 biogas plants, mostly family-size, have been set up in Bangladesh. Most of them are based on cow-dung and poultry droppings. All the plants now in operation are fixed dome plants and their durability is reported to be more then 20 years. Oldest fixed dome plant in proper operation now in the campus of BCSIR was established in 1990.

ii)      BCSIR and LGED have so far trained more than 1,800 engineers, supervisors and masons on the construction, operation and maintenance of fixed dome biogas plants. This is an important aspect for undertaking a dissemination project as there is sufficient number of expertise available all over the country.

iii)     So far, over 2,000 poultry-based biogas plants have been constructed. Plants with birds ranging 100 – 5,000 are in operation.

iv)     Interviews with the owners and neighbors of poultry farms reveal that construction of biogas plants in each poultry farm is a necessity because of the bad odor that poultry droppings spread in the area. Since poultry industry is booming in Bangladesh, poultry-based biogas plants also should be booming in future.

v)      Financial analyses of plants for farms ranging from 100 birds up to 50,000 birds have been done. The results are shown in Figures 10.1 – 10.10. It can be concluded that

a)      With 100 birds using both gas and fertilizer, if sold at a price 300 Taka/connection and 0.80 Taka per kg of fertilizer, the plant is financially viable. However, with either of them alone, the plant is not financially acceptable assuming an interest rate of 8%.

b)      With 500 birds and above, all plants are financially acceptable with gas sale alone but none of the plants is viable if only electricity or only fertilizer is sold. But electricity and at least any one of other two (gas and fertilizer) makes the project viable, 50% of the gas assumed to be used for electricity generation.

c)      Sensitivity analyses with 20% cost increase in plant construction, operation & maintenance and 20% decrease in revenue received have shown that all plants above 250 birds are viable.

vi)     Biogas plants are financially viable, even for a farm as small as 100 birds.

vii)    Larger farms may go for electricity production, but selling of gas is more profitable.

viii)    Most of the poultry farm owners are capable of financing biogas plants on their own. The small farmers will, however, prefer micro-financing. Most of them will avoid bank loan because of hassles associated with bank loan being approved and received. Micro-financing would be a very good option for them.

ix)     Economic benefit derived from biogas plant in terms of fuel and fertilizer saving can have notable impact on national economy. Biogas technology may pave the way for booming poultry industry in the country.

x)      Large biogas plants owners are selling biogas at a rate of TK 300-400 per connection. This is an encouraging aspect for the commercialization of the technology.  

xi)     Following drawbacks, which need be reduced / eliminated, have been detected during the field visits:

a)            Moisture and hydrogen sulfide contents of biogas should be removed for the better functioning of the cooking burners and electricity generators.

b)            In many plants charging rate and slurry / water ratio are not properly maintained.

Recommendations of the Study

1.            Since biogas technology is now well established with the availability of expertise in the country, the technology is set to take off provided financial support coupled with appropriate marketing measures is made available.

2.            A promotional drive in a selected area, e.g. the upazila with the highest number of poultry farms should be undertaken immediately. The promotional work should have an objective of installing a biogas plant in every poultry farm of the upazila. However, for successful implementation, a marketing plan with appropriate strategies should be developed before embarking on this. It should also be followed by monitoring with corrective measures, if necessary.

3.            (a)    For cooking purpose, biogas has proven quite appropriate, even in the presence of small amount of moisture and hydrogen sulfide. It can therefore be safely recommended that a large-scale programme be undertaken for dissemination of poultry-based biogas.

         (b)    Field visits have shown that, in almost all cases, initial construction cost is not readily available. For dissemination therefore, some kind of funding will be necessary.

4.            In order to solve the above problems associated with hydrogen sulfide and moisture, some experiments should be carried out in a suitably sized plant.

5.            Setting up of a biogas plant should be made mandatory for poultry farms and should be included in the national policy documents.

6.            Measures to popularize fertilizer from biogas plants should be undertaken.

7.            Know-how to add value to bio-fertilizer from biogas plant should be acquired and disseminated.

8.            For updating the knowledge base of the technicians, training need be provided on a continuous basis.

9.      A dedicated organization for biogas is necessary. This may be a Biogas Foundation. The objective of this organization will be to promote biogas plants all over the country in a concerted manner. It will coordinate all activities related to biogas e.g. policy, research, training, and dissemination. The Foundation will be run by a Board of Directors consisting of representatives from the Govt. and biogas related organizations.

10.     A revolving fund to be administered by the Biogas Foundation will be created for multiplication of biogas plants and administration of biogas related activities. However, till the formation of the Biogas Foundation, a suitable organization may volunteer to create and administer the revolving fund.

Recommendations of the Expert Group Meeting

• ·         Intensive activities for biogas technology dissemination would be started in Maona of Sreepur and Savar. These two areas would work as piloting area and demonstrate, hopefully, the success of biogas technology before the whole country so that other areas might follow this.

•  

• ·         Grameen Shakti would work in Maona and LGED in Savar.

•  

• ·         GTZ would provide money in the form of a revolving fund for the activities in Maona.

•  

• ·         At the current stage, no foundation would be formed, but a forum would be created, which would act as a pressure group. BCAS would work as the secretariat.

•  

• ·         BCAS would work on awareness building and monitor the progress.

•  

• ·         IPSU would provide support for 5 demonstration biogas plants in Savar and 5 in Maona, Sreepur.

1.    Introduction

1.1        Background of the Project

Bangladesh is a densely populated country with a population of about 140 million, about 72% (BBS, 2001) of which live in the rural areas. Bangladesh is endowed with a proven natural gas reserve of about 450 billion m³ and 1.7 billion tons of coal. The overall energy consumption is still very low. In 2000, per-capita consumption of commercial energy and electricity were 200 kgoe/year and 120 kWh/year respectively (Draft NEP 2002). The energy consumption in the rural area is even much lower. The supply of natural gas is limited to urban areas, mostly in the eastern part of the country. Only about 5% of the population have access to natural gas, and about 32% to grid electricity. More than 60% of total energy consumption of the country is being met from biomass (Islam, 2004). Agricultural residues, animal dung, leaves and twigs, and trees, etc. are the main sources of biomass fuels. There are indications that consumption of biomass energy has already exceeded the regenerative limit and there prevails energy crisis in rural areas in Bangladesh (Asaduzzaman and Latif, 2005). This is one of the causes of deforestation that is going on in an alarming rate.

Figure 1.1: Pattern of energy consumption in rural areas of Bangladesh (Asaduzzaman and Latif, 2005)

Over 90% of energy consumption in rural areas of Bangladesh consists of biomass with a per capita concumption of 2.93 tonnes per year in 2004 (Asaduzzaman and Latif, 2005). Figure 1.1 shows the pattern of biomass consumption in rural areas. Firewood consists of mainly twigs, residues of timber production and used timber (trees and bamboos); The trunk of trees is usually used as fuel for the urban areas and brick industries. It is evident from the figure that agricultural residues and animal dung play a significant role in the rural energy scene. These have however an important alternative use as organic fertilizer. Because of energy shortage, more and more agricultural residues and animal dung are being used as fuel depriving the soil of organic matter and essential nutrients (Eusuf, 1993). As a result, soil fertility is declining and the farmers are becoming more and more dependent on chemical fertilizer. Organic matter content in 50% of agricultural land of Bangladesh has decreased to alarming less than 1.5%, which should be more than 3% (Sinha and Rahman, 2005). The results of this development are not only financial and economical losses to the people and country, but also to the environment and ecosystem. Moreover, use of biomass as fuel in traditional stoves is responsible for in-door air pollution causing health hazards to the users, mainly women and children who cook and stay much time in the kitchen.

It is apprehended that with population growth, the energy crisis, environmental degradation, deforestation, declining of soil fertility, use of chemical fertilizer and declining of agricultural yield will aggravate further if the things move as usual and no alternative measures are undertaken. Biogas offers a sustainable solution, at least in part, to all these problems Bangladesh is currently facing.

Photo 1.1 : Biogas Plant

Photo 1.2 : Cooking with biomass fuels in rural areas of Bangladesh

In the backdrop discussed above, GTZ-PURE has initiated a project “Promotion of Biogas Production and Use in Commercial Establishment” to support promotion of biogas use in suitable commercial establishments. It is intended to develop and test a marketing approach for promotion of biogas use with the focus on suitably sized poultry farms. With this aim, PURE called for proposals. In response to the call, Bangladesh Centre for Advanced Studies (BCAS) with Energy Consulting Services (ECS) as a Sub-Consultant submitted a proposal and was awarded the contract for conducting the feasibility study. The Terms of Reference (TOR) has been attached in Annex-1.

The study has been conducted by BCAS and ECS during May – July 2005. This report presents the results of the study.

1.2    Historical Development of biogas technology

The anaerobic digestion process producing biogas has been known since 18^th century. However, it is being regarded as a useful method since the beginning of 20^th century (FAO, 1999), when it found its first applications in the treatment of sewage and offensive material. With time, the utilization of anaerobic digestion has grown steadily. It provides exciting possibilities and solutions to such global

 

Photo 1.3: Cooking with biogas

concerns as alternative energy production, handling human, animal, municipal and industrial wastes safely, controlling environmental pollution, and expanding food supplies. Biogas technology not only supports national economies and the environmental protection, but also provides for a wide range of improvements in overall living conditions. Sanitary and health conditions are improved and the quality of nutrition is enhanced by improved energy availability.

Figure 1.2:  Flow chart of a biogas plant (Rehling, 2001)

For many years the rationale behind using biogas technology was the search for renewable sources of energy. In the meantime, other environmental protection aspects have gained additional importance. A technology which previously just filled a “niche” is now becoming a key environmental technology for integrated solid and liquid waste treatment concepts and climate protection both in industrialized and developing countries. Another major environmental target is the mitigation of deforestation and soil erosion through the substitution of firewood as an energy source with biogas.

1.3    Potential of biogas technology in Bangladesh

Organic matters such as animal and human excreta, agricultural and industrial waste, water-hyacinth, etc. may be used as raw material for biogas plants. Bangladesh has plenty of these biomass resources. Table 1 gives a list of potential raw materials for biogas plants (Parveen, 1995).

Table 1.1: Raw materials for biogas plants

Bangladesh is predominantly an agrarian country. Most of the households keep livestock, although small in number and poor in quality. The way of land preparation and transport in rural areas, for which cattle are used, is being changed; mechanical devices such as tractors are being increasingly used. As such the use of cattle is decreasing. On the other hand, rearing of dairy cattle and poultry is being viewed as a means of alleviating poverty and in fact, dairy cattle and poultry are increasingly contributing to improving the livelihoods of landless and marginal farmers. Larger farms with hundreds of cattle are being set up. As a result, the number of cattle has remained almost constant at around 22 million over the last two decades.

The usage pattern of cattle dung in the country shows: fuel 34%, manure 46%, building materials 5%, and waste 15% (Eusuf, 1993). The portions used as fuel and fertilizer (in total 80%) may be made available for biogas production. 

Poultry litter is another important raw material for biogas plants. Over the last two decades, poultry sector has grown rapidly in Bangladesh. However, poultry litter is being managed very poorly and being dumped in open pits near the farms. Poultry litter is being regarded as a problem for the poultry owners and neighbours, not only because it spreads bad smell, but also because the pits are breeding places for flies and insects and give poor aesthetic look. Organized human excreta may also be used as a raw material in biogas plants.

Water-hyacinth grows very rapidly and is capable of rapid multiplication in every place where water exists. It is menace in agriculture, fisheries and navigation and is available in plenty in the bils, haors, ponds, and rivers. Yield per acre is estimated at 20 tons per year (Eusuf, 1995).

Table 1.2: Potential of biogas and organic fertilizer in Bangladesh (BCSIR, 2001)

1.4    Objectives

The general objective of the study is to assess the feasibility of the application of biogas technology in the suitably sized poultry farms in Bangladesh. The specific objectives have been formulated as:

(a)          To assess availability of raw materials in the suitably sized poultry farms.

(b)          To examine technical and financial viability of biogas generation in poultry farms.

(c)          To identify legal issues relating to the implementation of the project, its constraints and suggest mitigation if needed;

(d)          To examine environmental aspects of the project and suggest mitigation if necessary;

(e)          To assess socio-economic condition of the probable customers, their affordability and acceptability;

(f)           To examine social, cultural and religious barriers if any and suggest probable mitigation if any.

(g)           To review sustainability of the programme.

1.5    Methodology

The study was conducted following the methodology described below: 

·        Collection of documents on biogas projects (IFRD and LGED) and literature, including internet search

·        Review of documents and literature

·        Field visits to poultry farms in Sreepur, Savar, Manikgonj, Faridpur, Pabna, Bogura, Panchagar

·        Interview with

-                organizations involved with biogas plants (LGED, IFRD, BRAC, GS, DoE)

-                experts on bio-gas technology (IFRD, LGED, BCAS, BUET, DoE)

-                owners of poultry farms with biogas plants

-                owners of poultry farms without biogas plants

-                neighbours of poultry farms/probable customers

-                biogas users, who purchase gas for cooking

-                members of Poultry Farm Owners’ Association

-                policy and decision makers (Ministry, DoE, DoL)

·        A participatory meeting with poultry farm owners, biogas plant owners, neighbors, representatives of local governments (30 participants) was held in Maona, Sreepur of Gazipur District

·        Chemical analysis of poultry food, slurry and biogas

·        Technical and financial analysis of collected data

·        Meeting with banks (Dhaka Bank, Sonali Bank, Krishi Bank, and Islami Bank)

·        Preparation of draft final report with some recommendations

·               Experts Group Meeting

·               Preparation of Final Report

2.    Biogas Technology

2.1    Types of biogas plants

Different types of anaerobic bacteria are responsible for anaerobic digestion of biomass and production of biogas. Temperature plays an important role in biogas production. The bacteria are able to work over certain temperature ranges. Mesophilic bacteria work best around 38°C, while the thermophilic types work around 60°C. Depending on the active bacterial type and temperature range, digesters may be classified into mesophilic digester and thermophilic digester. If temperature sinks, the gas production decreases. Thermophilic digesters require extra heating which adds to extra running costs, while a mesophilic one would only need a little extra heating during the winter period. Thermophilic digesters have a place in industry, however, when the feedstock temperature has already been elevated by the industrial process, such as the hot water used for washing abattoirs and fruit canneries.

Biomass can be fed into the digester in batches or continuously. Depending on feeding, a digester may be batch digester or continuous feed digester. A batch digester operates on a single charge until it is exhausted, i.e. when gas production comes to an end. At the end of the digestion cycle, the batch digester is emptied, cleaned, recharged and restarted for a new cycle. This cycle time, called retention time, depends on the biomass type. Operating the batch digestion system requires two or more digesters for a more or less continuous gas supply.

On the other hand, continuous-feed digesters have increments of fresh charge added and digested slurry subtracted on a daily (semi-continuous) basis to provide an ongoing replenishment of charge materials and water. The amounts withdrawn and replaced should be the same, otherwise the digester may become either over-loaded or under-loaded. These digester systems are less expensive. Most biogas plants operating nowadays are semi- continuous feed digesters.

Depending on the design, biogas plants may be classified into three basic types:

-                floating dome,

-                fixed dome, and

-                balloon (or bag type).

Floating dome biogas plant

A floating dome plant consists of a digester and a moving gasholder. The gasholder floats either direct on the fermentation slurry or in a water-jacket of its own. The gas collects in the gas holder drum, which thereby rises. If gas is drawn, it falls again. The gas drum is prevented from tilting by a guide frame.

Advantages: Simple, easily understood operation, constant gas pressure, volume of stored gas visible directly, few mistakes in construction.

Disadvantages: High construction cost of floating dome, steel parts liable to corrosion resulting in short life (up to 15 years; in tropical coastal regions about five years for the drum), regular maintenance costs for painting.

Figure 2.1: Floating dome biogas plant (Sasse, 1988)

Fixed-dome biogas plant

A fixed-dome biogas plant consists of an enclosed digester with a fixed, non-movable gas space. The gas is stored in the upper part of the digester. When gas production commences, the slurry is displaced into the compensating tank. Gas pressure increases with the volume of gas stored.

Figure 2.2: Fixed-dome biogas plant (Sasse. 1988)

Advantages: low construction cost, no moving parts, no rusting steel parts, hence long life (20 years or more), underground construction, etc.

Disadvantages: plants often not gas-tight (porosity and cracks), gas pressure fluctuates substantially.

Balloon Type biogas Plant

Figure 2.3: Balloon type biogas plant (Sasse  1988)

A balloon type biogas plant consists of a plastic or rubber digester bag, in the upper part of which the gas is stored. The inlet and outlet are attached direct to the skin of the balloon. When the gas space is full, the plant works like a fixed-dome plant. The fermentation slurry is agitated slightly by the movement of the balloon skin. This is favorable to the digestion process. Even difficult feed materials, such as water hyacinths, can be used in a balloon plant.

2.2    Experiences in the developing countries

Many developing countries in Asia, Africa and Latin America are working on biogas technology and harnessing the benefits of this technology. Among them, China and India have played the pioneering role in adopting this technology for the masses. Nepal has also achieved commendable success. Most of the biogas plants installed in China, India and Nepal are household type. The experiences of China, India and Nepal are discussed below in brief.

China

Work on biogas technology was started in China in 1930, however with little success. The first success came in 1958, when some plants were installed in Shichuan Province. The real breakthrough came in 1968, when the Government extended support to this technology. A massive effort was undertaken to develop low cost and effective biogas plants. Besides developing efficient and low-cost biogas plant, thrust was given on the dissemination of the technology. The government agency, BRTC, coordinated all biogas plant related activities. R & D on different processes and designs were carried out. As a result of intensive R & D, a design of low cost fixed dome biogas plant was finalized that was disseminated all throughout China. By now about 10 million biogas plants have been set up throughout China. Most developing countries are now following the Chinese fixed dome model in their biogas programmes.

India

The first biogas plant in India was installed nearly a century ago. During 1950s and 1960s, research on and dissemination of biogas technology began. However, wide-scale dissemination began in a concerted manner only in 1981 with the launching of the National Project on Biogas Development (NPBD) and its subsequent inclusion in the Prime Minister’s 20 point programme. It gained further momentum with the establishment of the Department (now Ministry) of Non-conventional Energy Sources. The Ministry adopted a decentralized, multi-agency and multi-model implementation strategy for this nation-wide initiative. At the state level, the programme is implemented through a nodal agency responsible for achieving installation targets, managing finances, monitoring, etc. Other agencies involved at the District level and below are several government bodies such as the District Rural Development Agency, the Block Development Office, local private sector entrepreneurs, local government (gram panchyats), dairy cooperatives and rural non-governmental organizations (NGOs). In addition, the national banks are also involved in the programme through the provision of soft loans to beneficiaries to partially meet construction costs. From the beginning, NGO participation has been an integral feature of the national biogas programme of India. Canada’s PARTNERS in Rural Development (formerly Canadian Hunger Foundation), India’s Action for Food Production (AFPRO) and their network of local NGOs, with assistance from the Canadian International Development Agency (CIDA) played an important role in development and implementation of India’s biogas programme.

Floating dome plants, popularly called the KVIC (Khadi & Village Industries Commission) plants, were standardized in 1961 and were the first to appear in the backyards of Indian rural houses. Even though a few modifications were made with regard to alternate materials, by and large this design has remained unchanged over the years. The KVIC model is costly and tends to more failures due to corrosion.

These considerations led to the emergence of fixed-dome plants. Different variants, e.g. Gobar Ganesh, Pragati, Janata were developed and introduced. In spite of its cost advantage, these models were still beyond the reach of most rural households. In the search to further reduce costs, a concerted effort was made, which resulted in the development of Deenbandhu model. The digester is connected with feeding pipe (inlet) and outlet tank. The upper part, above the normal slurry level, of the outlet tank is designed to accommodate slurry displaced out of the digester with the generation and accumulation of biogas (Figure 2.5). Deenbandhu model is the most popular model in India.

Figure 2.4: KVIC Model (Lichtman, 1983)
 

 Figure 2.5: Deenbandhu biogas plant (AFPRO, 2000)

Till 1997 about 2.9 million biogas plants of different models were installed. It is reported that about 200,000 new plants are installed every year in India.

Nepal

In Nepal, biogas was first introduced on an experimental basis in 1955. The initial experiences showed the feasibility of biogas technology for meeting a significant portion of rural household energy needs. Inspired by this, several organizations of Nepal with technical support from the Netherlands Development Organization (SNV) started Biogas Support Programme (BSP) in 1992. It was financially supported by Directorate General for International Cooperation (DGIS) of the Netherlands and Kreditanstalt fuer Wiederaufbau of Germany. During the three phases (1992 – 2003), a total of 111, 395 fixed dome biogas plants were installed. The model is a simple modification of Chinese fixed dome model. Since June 2003, BSP is being run by Biogas Sector Partnership Nepal (BSP – N) with SNV as advisor. The target has been set to 200,000 biogas plants by 2009 (SNV, 2004). 

2.2.1 Lessons learned from biogas projects of China, India and Nepal

Experiences from biogas programmes of China, India and Nepal are valuable for designing and for successful implementation of any biogas programme in Bangladesh. Therefore, lessons from those countries are briefly mentioned below:

·              China developed the present Chinese model fixed dome biogas digester long before and they are following the same model all over the country. Nepal is following the Chinese model with minor improvement based on their country situation. Most biogas plants of India are floating dome type, which has been developed by them long before. Recently, they are also constructing fixed dome biogas digester with some adaptation in the name of Deenbandhu model and Janata model.

·              Most of the plants in Nepal and China are connected to toilet, but India is still facing social barrier in promoting use of night soil as raw material.

·              Fixed dome type biogas digester is being used by China and Nepal, because it is durable and maintenance cost is negligible. Floating dome used by India is more efficient; construction is simple and the gas pressure remains almost constant.

·              In Nepal, 60 companies are involved and in India private contractors and NGOs are involved.

·              In India and Nepal, there is a provision of guarantee for after-sale services in the contract usually in the range of 5-10 years.

·              In most cases, biogas is used for cooking. Some are using biogas directly for lighting hazak. Some large farm owners and research organizations are using biogas for producing electricity. But these are still at initial and experimental stages.

·              In all the three countries, there is government will and commitment. As a result there is provision of government support in the form of subsidy. 

·              In all the three countries, there is strong policy support and institutional arrangement.

·              Although there is provision of capacity building and human resource development, yet these are not adequate.

The above lessons lead to the following conclusions:

-                Understanding the end-user / market needs are important to design a product that meets and addresses the concerns of users.

-                Cost-effective and simple design should be introduced.

-                Local people and NGOs should be integrated in the dissemination of the technology.

-                After-sale service is essential.

-                Financial incentives are needed to stimulate the market.

-                Concerted efforts are necessary.

-                Training to local masons is important.

-                Successful implementation strategies require good collaboration between the implementers and nodal agencies.

-                Projects should be formulated with the utmost care to integrate women from the beginning of the project.

-                Procedures involved in mobilizing bank loans should be simple.

-                Network structures and programme advisory committees help improve the overall performance of the project.

2.3    Experience with biogas in developed industrialized countries

The main purpose of biogas plants in the developed industrialized countries is not the production of biogas itself, but the environmental concern. Biogas plants, now-a-days built in developed countries, are of big sizes and include, among others, heat recovery, gas analysis system, scrubber technology, booster, biogas flare stack, and control elements. They are used in co-generation plants for producing electricity and process heat for different purposes, e.g. district heating. Heat is also used for maintaining optimum temperature in the digester, especially during the cold days.

Complete turnkey plants are available for installation. PRIVATE "TYPE=PICT;ALT="PRIVATE "TYPE=PICT;ALT="All process engineering components – biogas co-generation units (CHP), pumping stations, and membrane facilities – are fitted into standard containers. On delivery the containers are ready to be connected. No buildings are required. Digesters are mostly made of concrete or steel and equipped with stirring devices. PRIVATE "TYPE=PICT;ALT="To be fully operational, the container only needs a concrete foundation on site and connection to the gas, energy, and heat supply. Biogas plants with electric outputs of 500 to 1,250 kW are supplied on regular basis on plug and play.

With sharper environment pollution control and thrust on renewable energy, biogas technology is experiencing new impulse throughout Europe. As already indicated, biogas technology is “in” not only for its economic benefits, but more and more for its environmental benefits. Almost all European countries are supporting biogas technology in a great way both directly and indirectly. For example, German Renewable Energy Legislation (Erneuerbare Energien Gesetz EEG) grants guaranteed royalties for electricity produced from renewable sources of energy. For the next 20 years, this provides a safe and sound basis for the planning of biogas plants. PRIVATE "TYPE=PICT;ALT="With the new waste disposal legislation coming into force in 2005, more support packages are coming for biogas plants. Other European countries are also helping the development of biogas technology.

Photo2.1: Biogas Plant at Wolperthausen, Germany
(Gas production: 1800 m³/d, Electricity: 550,000 kWh/year)

Photo 2.2: Biogas plant at Mauternach – Luxembourg

 (Gas production: 1000 m³/d, Generator: 1x50 kW, 1x 75 kW)

2.4    New Development

Research on biogas technology is being done all over the world. Thrust is laid on developing processes that are more efficient in generating not only an alternative energy source, but also materials that are useful as fodder substitutes and substrates for mushroom and greenhouse industries in addition to traditional use as organic fertilizer (FAO, 1999).

As a result, several newer processes are being developed that promise to be more efficient. Thrust in biogas technology research is given on developing new bacteria that can accelerate the production of methane. Manufacture of standard concentrated and purified enzymes is relatively expensive. Apart from that, not all bacteria in a blend can turn all the organic substances in the biomass into methane. Researchers at the University of Bonn in Germany have developed a new process for increasing methane production in biogas plants and lowering manufacturing costs. Trials on fungi have been conducted as additional decomposition agents. The results showed that the fungi increase the biogas yield by thirty to fifty percent, if added in the right concentration. The production cost is only a fraction of the global market price for conventionally produced purified bacteria.

3.    Application of Biogas Technology in Bangladesh

3.1.   History of biogas development in Bangladesh

The first biogas plant in Bangladesh was constructed in 1972 at Bangladesh Agricultural University (BAU), Mymensingh campus for study purposes. This was followed by another plant in Phulpur that provided gas for cooking and lighting for a family of six members. Both these plants were floating dome type. IFRD of BCSIR started R&D on biogas technology in 1973 and constructed a family-size biogas plant (6.3 m³ digester volume and 2.3 m³ gas-holder volume) in 1976 following the design of India’s Khadi and Village Industries Commission (KVIC) in the BCSIR campus  (Eusuf, 1995). This was followed by a plant at the KBM College in Dinajpur in 1980. With the experience gained through the installation and operation of these plants, IFRD went for dissemination of the floating dome type technology. More than seventy plants were installed at the cost of the owners.

Photo 3.1: Raj Poultry Farm, Faridpur

In 1981, Environmental Pollution Control Department (EPCD), predecessor of Department of Environment (DOE) started a programme under a government grant and installed 110 plants of fixed-dome model and over 150 plants of floating dome type through hired contractors. Other efforts were undertaken by BSCIC (a number of plants), DANIDA (few trench and bag type digesters) and DLS (about 70 plants). Grameen Bank installed 17 plastic bag digesters. In 1985, Local Government Engineering Department (LGED) started study, research, development and extension of biogas technology.

Under the “Fuel Saving Project” financed by the Government and implemented during 1989-1991, IFRD trained local youths who constructed a total of 126 floating dome biogas plants. In 1992, the IFRD in collaboration with Dhaka City Corporation built an experimental biogas plant of 85 cubic meter digester volume at Dholpur for treatment of city garbage. 

In June 1992, LGED constructed first Chinese-type fixed-dome model biogas plant in Karimpur village of Begumgonj, Noakhali. In the same year LGED constructed the first night soil based biogas plant at Faridpur Muslim Mission. In 1993, LGED constructed a biogas plant based on water hyacinth at Madaripur.

Photo 3.2 : Biogas plant inlet

In 1994, LGED constructed the first biogas plant from poultry droppings at Utter Khan, Dhaka and garbage-based biogas plants in ten towns. At the end of 1994, LGED constructed a total of about 200 biogas plants, out of which eight were floating dome type and the rest were fixed-dome type. Among these plants, 73 were based on night soil, one on water hyacinth, two on poultry droppings, 23 on garbage and the rest on cow dung.

The Government of Bangladesh undertook a Biogas Pilot Plant Project (BPPP). IFRD was selected as the implementing agency. 4664 and 17,194 fixed dome biogas plants were installed during the 1^st phase (1995-2000) and 2^nd phase (2000-2004) of this project respectively.

In the period from October 1998 to June 2003, the LGED implemented a parallel biogas project, under which 1,120 biogas plants were installed. Under “Secondary Town Infrastructure Development Project-II”, LGED installed 20 domestic biogas plants using human excreta only.

IFRD, BCSIR, LGED, DOE, DLS, BAU, BARD are government organizations, whereas Grameen Shakti and BRAC are non-government organizations. Figure 3.4 shows an approximate number of biogas plants installed till July 2005 by different organizations. It is to note that the figures published in the reports and journals differ to some extent. It is evident from the Figure that most of the biogas plants of Bangladesh have been installed by BCSIR.

Figure 3.1: Organization-wise biogas plants installed in Bangladesh

(http://www.ieiglobal.org/ESDVol7No2/cookstove.pdf )

3.2    Experiences with different models

All major types of biogas technology have been applied in Bangladesh. Different approaches for dissemination have also been tried. Through trial and learning, Bangladesh has gained substantial experience on biogas technology. Fixed dome type biogas plant has proved to be the most suitable for Bangladesh. At the moment it is the only design that is being applied in the country. The model promoted by IFRD, BCSIR in both phases of the BPPP is the local variant of the Chinese fixed dome model. In the original Chinese model, the outlet for cleaning and maintenance work in the digester is on the dome as a manhole, whereas in the IFRD model, the same is located on the side. LGED made small modification of the BCSIR model by revising the shape of the outlet (from rectangular to round) and by putting an RCC ring beam.

Different organizations have worked towards capacity building. As a result, there is skill and know-how on the biogas technology. There is also awareness among the people about the advantages of biogas plants. As such it may be concluded that there exists conducive atmosphere to go for large-scale biogas programme.

 Figure 3.2: Fixed dome biogas plant, BCSIR model (Aktaruzzaman, 1999)

 Figure 3.3: Fixed dome biogas plant, LGED model (LGED web site)

3.3        Operating conditions

The output of a biogas plant depends on the operating conditions. The optimum conditions for operating a poultry litter based biogas plant are given below (Adapted from LGED website): 

·               Total solid (TS) percent in the feed (6~10%)

·               Loading rate (8~10 kg/m³ digester volume/day)

·               Retention time (~40 days)

·               Pressure(60~120 cm water column)

·               Diameter to depth ratio(1:1)

·               Temperature (25~37⁰C)

·               Carbon to nitrogen ratio (25:1)

3.4    Cost of Biogas Plant Construction

IFRD estimated costs for different sizes of fixed dome biogas plants for its Biogas Pilot Plant Project (BPPP). These costs served as basic outlines for the field level implementers (constructors) and owners of the plants and are shown in Figure 3.4. Discussions with field workers have revealed that, the costs given in Figure 3.4 are valid and biogas plants may be constructed at these costs. However, the RCC ring beam for outlet as used by LGED, makes the plant costlier. 

Figure 3.4: Cost of biogas plant installation in Bangladesh (BCSIR, 1998)

3.5    Socio-cultural Acceptability

Social and cultural factors play important roles in the successful dissemination of any technology for masses. If any technology is not socio-culturally acceptable to the people, who would use it, it can not be disseminated. In case of biogas technology, raw material used in the biogas plant (cow-dung, poultry litter, night soil, etc.) is important. The success or failure of an even good design and cost effective biogas technology will depend largely on the attitude of the people to the product biogas and slurry. Experiences with different types of raw materials applied in the biogas plants of Bangladesh are summarized below:

·               Biogas from cow dung is well accepted by the people. Cow dung itself has no acceptance problem in Bangladesh. It has always been accepted by the people irrespective of religions and ethnic groups. The rural people do not hesitate to touch it by hands and are accustomed to prepare dung cake for using as fuel. It is widely used as construction material, as fertilizer and as fuel. The Hindus even regard cow dung as a material that makes unholy thing holy.  

·               Poultry litter does not enjoy similar acceptance as cow dung does. It smells bad. However, biogas from poultry litter is also well accepted by the people. Field visits and discussions showed that people of all religions would use this gas without any hesitation.

·               Biogas from human excreta has some acceptance problems. Hesitation prevails even among planners, who confuse whether the people would use the biogas for cooking meals. However, through motivational work undertaken by LGED and IFRD, acceptance problems have been overcome. After consulting the holy Quran, religious leaders have declared that the gas is cleaned as it is burnt. Representatives from Islamic countries such as Saudi Arabia visited the orphanage of Faridpur Muslim Mission and were satisfied to see the replacement of the expensive wood fuel by excreta-based gas (Aktaruzzaman, 1999). There are several hundred operational biogas plants in Bangladesh, where human excreta is being used as one of the raw materials and the users have overcome their initial hesitation. It seems the usefulness and convenience of biogas compared to solid biomass have helped convince them. 

3.6    On-going and Planned Projects

A few biogas projects were undertaken in Bangladesh, which have been mentioned in the previous sections. There is no on-going biogas project at the moment from any government agency. IFRD submitted a proposal to the Government for a new project with a target of 50,000 biogas plants, which is yet to be approved by the Government. However, it has not been included in the budget for the Financial Year 2005/06. As such there is no public fund for any biogas project in the current year.

A few agency holders, who were engaged in the BPPP, are trying to construct plants on their own efforts as a part of their business. In some locations, they are providing after-sale services, like maintaining the plants against fee. Discussions during field visits have revealed that many households with sufficient number of cattle or poultry are willing to install biogas plants. However, there is a rumor that the Government will start a new project, which will contain subsidy. As such the people are hesitating to go for biogas plants fully on their own costs. In effect, very few biogas plants are currently being installed.

Very recently, Grameen Shakti has undertaken an initiative to construct 200,000 biogas plants within 2010. As start, Grameen Shakti has targeted to construct 500 plants within 2005 (Barua, 2005). This project does not contain any direct or indirect subsidy. Grameen Shakti is offering two options: cash payment and installment payment (micro finance). For installment payment, an additional cost in the form of service charge @8% per year is being collected. Grameen Shakti has already achieved a remarkable success in installing solar home systems through micro-finance option. The same model is being replicated in the biogas plant programme. It is expected that the micro-finance option will enable the cash-constraint households to go for biogas plants. The initial experience confirms this. Within two months, till end of July 2005, 20 plants were installed. The initiative is still in the primary stage. Grameen Shakti is recruiting skilled personnel for this project and employing them in prospective unit-offices spread throughout the country.

BRAC, along with a US based enterprise “Emergence Energy”, has come forward to install biogas plants. The aim of this venture is to do business through supplying electricity in the remote un-electrified area and by selling bio-fertilizer. Two pilot biogas plants have been installed at two different remote locations, namely at Paschim Kustia Village of Manikganj and at Sakhipur of Tangail District. Currently, experiments are being carried out on different technical and business aspects. If successful, BRAC and Emergence Energy intend to disseminate biogas plants all over the country on a commercial basis.

The Netherlands Development Organisation, SNV, has planned to set-up and implement large-scale programmes for domestic biogas in a number of Asian countries including Bangladesh. The objective of the project in Bangladesh is to undertake a national programme with a longer-term vision to develop a commercial, sustainable biogas sector. The project envisages setting up of 36,450 biogas plants within 2009. Preparations for the project are currently underway. It is expected that the project will commence in January 2006. The initial target has been set to install 2,100 biogas plants within 2006.

Another initiative has been undertaken by the GTZ under its PURE project. The present study is a part of this initiative.

3.7    Success stories and failures of biogas projects

Since the installation of the first biogas plant in 1972, about 34 years have passed. Several R & D and dissemination projects were undertaken during these years. BAU undertook the first initiative to research on biogas technology, but did not continue. R& D works were then done mainly by IFRD of BCSIR. EPCD and LGED undertook also limited efforts. In educational institutions and universities, research activities on biogas technology are rather meager.

Photo 3.3: Inlet tank of a biogas plant in Savar

Photo 3.4: Poultry-based biogas plant at Faridpur Muslim Mission being visited by the Study Team

As discussed in Sec. 3.1, during 1972 – 1992, different organizations undertook initiatives in promoting this technology, however, without proper attention to appropriate technology and after-sale service. The results were very discouraging. An internal report of the Local Government Engineering Department in 1992 (Rahman et al.1996) says that about 75 per cent of the constructed biogas plants did not operate properly mainly because of design, construction and maintenance problems (Table 3.1). There is limited coordination among the researchers and implementing authorities. There is also a very limited follow-up action programme.

Table 3.1: Biogas plants surveyed by LGED in 1992 (Rahman et al. 1996)

As stated in Sec. 3.1, the Government of Bangladesh undertook a Biogas Pilot Plant Project (BPPP) 1^st phase with a target of 5000 fixed-dome biogas plants for the period 1995-2000. IFRD was the implementing agency. IFRD employed and trained 128 diploma civil engineers who were assigned responsibilities for motivation, installation and after-sale service throughout the country. In addition, 898 youths were trained to support the project. Memoranda of understanding were signed between IFRD and several other organizations like BRAC, LGED and DLS for training and dissemination of the biogas technology. The cooperation with BRAC was the most successful as it installed 1,200 biogas plants. This project provided a subsidy of Tk.5000 per plant and the rest of the cost was borne by the owner. At the end of the project, 4664 biogas plants were installed. An interim evaluation report made by IFRD in 1999 claimed 99% of the plants installed were in operation, while 91% of the owners could meet their household fuel demand through biogas. Slurry from the biogas plants was used in horticulture, pisci-culture and agriculture (BCSIR, 1999).

The 2^nd phase of BPPP with a target of 20,000 plants was implemented by IFRD during 2000-2004. The subsidy amount was increased to 12,500 Taka per plant (7500 Taka to the owner directly and indirectly in the form of a service charge of 5000 Taka to the installer) and a different approach was followed. In place of NGOs and other public agencies as was practiced during the 1^st phase, an agency system was introduced under which 50 agencies were engaged. They installed the plants and received the service charge. About 1,000 masons and youths were trained under the project. IFRD monitored the project. At the end of the project period, 17,194 plants were installed.

LGED implemented a parallel biogas project in the period from October 1998 to June 2003 aiming to install 1,900 domestic plants. The subsidy for this project amounted to 5,000 Taka, whereas IFRD provided at the same time 12,500 Taka. It proved to be rather difficult to motivate farmers for LGED biogas plant. As a result, the project was terminated prematurely after having constructed 1,120 biogas plants.

An evaluation report of BPPP (1^st & 2^nd phase) conducted by DPC group found that 88.5% plants constructed under 1^st phase and 97.27% plants constructed under 2^nd phase were in operation (BCSIR, 2004).

Monsof, as part of his Diploma-work at the University of Flensburg, undertook a survey of 80 biogas plants in Pabna District (Monsof, 2005), which were constructed under different projects (EPCD, BPPP 1^st and 2^nd Phases, LGED) at different times. Monsof found 50% of the plants were not working. Monsof identified following failures for non-functioning of the plants:

-                Technical failure: Leakage/cracking in the dome & gas holder, incorrect leveling of different parts, design problem, inadequate capacity of gas storage chamber, faulty location of plants, moisture in gas, etc.

-                Social Failure: Social barrier and land ownership.

-                Management Failure: i) Management failure from the consumer, ii) Management failure from the technology providers.

Monsof found that 55% of the non-functioning of the plants was due to technical failures. Most of these failures occurred after four years of installation.

Although projects undertaken by IFRD and LGED have not fulfilled the target completely, the projects may be termed as successful because:

1.      They have made the people throughout the country aware about the technology and its usefulness.

2.      The projects have contributed to in-country capacity building and created quite a large number of skilled workers who are able to design and install biogas plants on their own.

The initial failures may be understood as “children diseases”. By now, biogas technology is a proven and well-accepted technology in Bangladesh. Fixed dome type plants have proved to be most appropriate and cost effective for the conditions in Bangladesh.

4     Experiences with biogas utilization in commercial enterprises

Dairy farms and poultry farms are commercial establishments. Biogas plants installed in the country are based mainly on dairy farms and poultry farms. Experiences with biogas utilization may be classified into (i) experience with production of biogas, (ii) experience with slurry, and (iii) experience with use of biogas. These experiences are associated with important issues like social acceptability issue, hygienic issue, environmental issue, fuel issue, cost issue, etc. Experience varies with locations of the plants:

-                Area with electricity and gas grid,

-                Area with electricity grid, but no gas grid, and

-                Area without electricity and gas.

Photo 4.1:  Biogas plant with gas delivery pipe at Kazi Tea Estate, Tetulia

To get opinions and share experiences, individual interviews were made with biogas plant owners, organizations (government and non-government) and biogas experts. A group discussion was also held with owners and neighbors of poultry farms, as well as owners and users of biogas plants and community leaders. During this discussion, the participants articulated their views and experiences. This chapter gives a summary of the experiences of field visits and group discussions.

4.1    Experience with the production of biogas

Experiences with production of biogas include technology, design, cost, operation, maintenance,  availability of raw material, environmental aspects, hygienic aspects, etc. The focus of the project was poultry-based biogas plants. During this study, it was found that the poultry-based biogas plants were situated in areas with electricity grid but no gas grid.

Most of the poultry farms in Bangladesh are small in sizes and employ in most cases only one or two persons for the operation of poultry farms, including maintenance, feeding and vaccination of the birds. In bigger farms, more persons are employed. Production of biogas does not cause much additional work, because the farm owners have to clean the farm and dump the litter in suitable pits for keeping their farm operational. The only additional work is to mix the litter with water. Therefore, the same persons who work in the farm can do the work associated with the biogas plant operation.

Poultry-based biogas is socially and environmentally well-accepted by the people. The raw materials are locally available. Skilled technicians are also available. The cost of a biogas plant is within the financial capacity of the farmers. However, cash constraints hinder the massive dissemination. Availability of cash in the form of bank loan or micro-credit will ease the situation. 

Photo 4.2: Biogas plant with gas distribution lines at RDA, Bogra

The fixed dome biogas plants are a proven technology. Most of the users have good experience with the production of biogas. The biogas plants have a lifetime of at least 20 years. The oldest plant in Bangladesh was installed 15 years ago in the BCSIR campus and is still functional. In some cases, domes are exposed to atmosphere, which causes fall of gas production during winter period of November to January. The case of dome cracking is seldom.

The operation of biogas plant is easy. Usually, no maintenance is necessary. Some people have experienced that gas production decreases. In such cases raw material is either over fed or underfed.

4.2    Experience with use of biogas

Photo 4.3: Boiler for preparation of poultry feed run by biogas at Raj Poultry Farm, Faridpur

Photo 4.4: Overhead pipe carrying biogas to a neighboring household at Savar

In most poultry farms of Bangladesh, poultry feed is not prepared, rather bought from the market. Only a few large farms prepare feed, which needs energy as input. Preparation of poultry feed with biogas is cost effective. 

The biogas is supplied to the households of the farm owners, who usually reside in the vicinity, and to the neighbors. It is being used mostly as cooking fuel. Biogas is convenient and less polluting. The women using biogas like it very much. The cost of biogas, when sold, is usually set in relation to the natural gas supply by gas utility. Currently, biogas is supplied at a price of 300-400 Taka per connection, whereas gas supplied by utility is 375 – 400 Taka depending on one or two stoves. Compressed natural gas for vehicle is about 8.30 Taka / m³. Field visits reveal that biogas produced from litter of about 200 birds is adequate to cook two meals for an average rural household.

Photo 4.5: Cooking with biogas

Biogas from a few plants is being used for cooking food in institutions and for business enterprises. However, their number is very small. There is at least one case where biogas is used for preparing sweetmeats for sale.

Photo 4.6: Commercial biogas stove used for preparing sweetmeats

Biogas is also used for lighting. Hajjak light is popular in some plants. Biogas is also used for power generation. Attempts have been made by several private and public sector organizations to produce power from biogas. No generator is currently made in the country. Most attempts made are to retrofit petrol generator or LPG / natural gas generator, with limited success. The users have reported that they have problems with starting and continuous generation. In most cases, the generators cease to work after some hours. However, Bogra Poultry Complex is operating a retrofitted generator for the last five years and meeting his power needs. Although REB grid electricity is available in the area, he has discontinued the REB connection and now uses his own power.  

Photo 4.7:  Hajjak light based on biogas

Photo 4.8: Power generator (locally retrofitted) based on biogas at Bogra Poultry Complex

Photo 4.9: Biogas-based generator developed by Bogra Poultry Complex

4.3    Experience with the use of slurry

As already mentioned, slurry from biogas plant is a good fertilizer. It is used as fertilizer and as fish feed in fish farms. The farmers have very good experience with the use of slurry and recognize the superiority of slurry over the chemical fertilizer. Through use of slurry, more yield of crop can be harvested. IFRD mentioned (quoting Chinese literature) that by using the digested slurry production of crops such as paddy, vegetables, potato, banana, onion, etc. can be increased significantly (Table 4.1).

Table 4.1: Comparison of crop yields by using slurry and chemical fertilizer (BCSIR, 1998)

Photo 4.10 : Biogas slurry being used as fertilizer at Kazi Tea Garden, Tetulia

The use of slurry of a biogas plant as fertilizer increases the crop production significantly. It is more productive than the undigested dung. Farmers also mention that fresh poultry litter may even destroy the crops. The substitution of commercial fertilizers with slurry produced by biogas technology reduces the impacts on balance of payments. The consequence of reliance on digested slurry is that valuable nutrients and organic matter are led back to the soil in an improved stage, raising agricultural productivity and soil stability.

 Photo 4.11 : Vegetable cultivation with biogas slurry as fertilizer, Raj Poultry, Faridpur

During field visits, the poultry farm owners were asked whether they used residue or not. The majority of the respondents mentioned that they used residue. During his survey, Monsof (Monsof, 2005) asked the farmers for which purpose they use slurry. He found the majority of the respondents (69%) used residue as fertilizer, 11% respondents used residue as fish feed and the rest 20% respondents used residue as both fertilizer and fish feed. Some of them did not use the slurry, but sold it. The market price of slurry is 0.80 Taka – 3.00 Taka per kg. In dry condition the cost is more than 4 Taka per kg. The farmers use slurry in dry condition, usually sun dried, whereby some nutrients are lost. Very few farmers know about the nutrients.

Technology for value addition is not currently available in the country. Packaging of slurry will add to value. Currently, one farm is marketing slurry in packets. Another company will launch bio-fertilizer sale soon. 

Opinions of the farmers were sought on whether the use of residue decreased the expenditure on chemical fertilizer. The majority of the respondents who used slurry mentioned that their expenditure on chemical fertilizer was decreased.

5.    Test results

Test results of biogas and poultry feed are given in Tables 5.1 and 5.2 respectively. The biogas was collected from a biogas plant in Maona and tested by IFRD, BCSIR. The poultry feed was prepared and tested by Agro- Organic Food Complex Ltd., Faridpur.

Table 5.1: Test results of dry biogas produced from poultry litter in a biogas plant at Maona

Table 5.2:  The test results of poultry feed prepared and tested by Agro-organic Food Complex Ltd., Faridpur.

  6.    Scrubber Technology

Biogas is a mixture of methane and carbon dioxide with small amount of moisture and hydrogen sulfide. Of these gases, methane is the only useful gas. Carbon dioxide does not do any harm except its effect as greenhouse gas and diluent of methane. Some people also opine that the space occupied by carbon dioxide is also disadvantageous. Moisture content causes difficulties during burning. The real problem is, however, hydrogen sulfide. It is a corrosive gas and combines with moisture to form sulphurous/sulphuric acids that can corrode all metal parts that come in its contact.  

Scrubbing is the operation that removes unwanted compounds from the biogas before it is used. Scrubbing of biogas is necessary mainly because of the hydrogen sulfide. Sometimes, carbon dioxide that simply 'takes up space' for no useful return is also removed.

The scrubber system needs to allow a fairly free flow of gas to minimize pressure losses in the gas system since the operating pressures are low. Typical system pressures are around 1.15 –1.25 bar. Since appliances usually operate at around 1.15 –1.25 bar, there's not much room to maneuver. Only little reduction can be tolerated, otherwise appliances may not work or the gas flow may even stop. In a system requiring carbon dioxide scrubbing, the low-pressure route will not work well. Instead, a series of pumps or a multi-stage pump/compressor is needed to pressurize the carbon dioxide scrubbing operation and for later methane compression for storage in high-pressure steel bottles. This more expensive storage method is usually only needed for use with vehicles to allow sufficient useful fuel to be stored or carried conveniently.

Scrubbing of hydrogen sulfide

The easiest way to get rid of hydrogen sulfide is to allow it to react with any gas/solution/metal-oxide. Red oxide (in the form of steel wool, for instance) may be used in a wide-necked bottle. It should be of clear glass with the gas inlet pipe running down to the bottom of the container and an outlet pipe coming away near the top. The whole thing must be gas-tight. The steel wool will corrode from the bottom upwards taking up the hydrogen sulfide by conversion to black iron sulfide that can later be reused after being oxidized to rust (ferric oxide) by exposure to air. When the black corrosion reaches about 75% of the height of the container, it's time to change the used steel wool for fresh stuff. It's probably better to run two or more similar bottles or containers connected one after the other to give some flexibility by providing some 'back-up' scrubbing capability.

The chemical reaction of red oxide with hydrogen sulfide is given in the following chemical equation.

Fe₂O₃ + 3H₂S                                                   2FeS + 3H₂0 + S

The regeneration of red oxide through oxidation in the air takes place according to the reaction below:

4FeS +70₂                                                         2Fe₂O₃ + 4SO₂

Figure 6.1: Scrubbing of hydrogen sulphide

Scrubbing of Moisture

For scrubbing moisture, a simple water trap shows good results. It needs only to drain the water gathered in the trap from time to time.

Photo 6.1: Biogas power generator with water trap (hanging on the wall)

Scrubbing of Carbon Dioxide

To remove carbon dioxide (CO₂), biogas is passed through a water (or lime-water) spray tower, (Figure. 6.2). CO₂ dissolves in the water which is then collected at the bottom of the tower and then sprayed down a second column to release the carbon dioxide gas from the water which is then vented to atmosphere. The water is then recycled back to pick up another load of carbon dioxide.

Figure 6.2: Scrubbing of carbon dioxide

CO₂ has no intrinsic fuel value and can complicate the jet and air settings of user appliances. The reason is that CO₂ percentage in biogas can vary from week to week of normal operation, particularly where differing feedstock constituents are used from time to time. In the situation where digester output quality is fairly consistent, CO₂ scrubbing may be dispensed with and the appropriate flow settings of user appliances adjusted to suit the overall lower fuel value of the combined CO₂/Methane mix.

Combined method of scrubbing

A large number of combined scrubbing technologies are available today. They are popularly called “gas sweetening” and are applied in the processing of natural gas. They are applied at relatively high gas pressures and are able to handle large gas volumes. Both regenerative and non-regenerative processes are available.

The non-regenerative methods are mostly used in the removal of small quantities of acid gases and are considered rather as product treating methods. They are not very economical to operate in the long run. They use caustic soda or lime carbonate as their sweetening agent, which goes to waste as soon as the acid gases removal has been completed. Regenerative methods are very common in the gas industries using sweetening solutions discovered and developed for this purpose by the gas processing industry. Regenerative processes may use liquid or solid sweetening agents.

Liquid sweetening methods are by far the most widely used by the natural gas industry. There are several types of liquid sweetening agents, the most popular of which are the alkanolamines. They use aqueous organic amines as their sweetening agents derived from ammonia (NH₃). Ethanol-amines are a series of weak bases having a great affinity for acid gases at low temperatures. The series include the monoethanolamine MEA, diethanolamine DEA and triethanolamine TEA.

The operating cycle and equipment required in a basic aqueous amine process is shown in Fig. 6.3. In this simplified sketch, the sour gas flows upward through a tower contactor countercurrent to an amine solution at approximately atmospheric temperature (25 - 40ºC). This lean amine enters the top of the tower and flows from bubble tray to bubble tray scrubbing the feed stream and picking up the acid gas. Intimate contact of lean amine and sour gas is necessary to absorb as much acid gas as possible and to obtain the sweetened gas overhead. The acid gas reacts with the amine and forms water-soluble salts, which stay in the solution.

Figure 6.3: Basic flow diagramme of amine treating process for CO₂ and H₂S removal