It has been a long time since a discussion about the scarcity of energy cum fuel is going on in Bangladesh. As there is no uninterrupted energy supply, the public life as well as the economic progress is under obstruction. The necessity of renewable energy is a burning question since many years, as the conventional sources (natural gas, oil etc) are insufficient in our country.
Though renewable energy has much possibility, in our country, the usage of it is not enough. The solar powered electricity has been used mostly in Bangladesh as a renewable energy. But other renewable energy sources are not much common. One of those renewable energy sources is the Biogas plant. In spite of much possibility, the lack of taking proper steps is ruining its prospect. In villages, some family formatted Biogas plants are seen at a small range, but not any large ones. With proper plans and steps, Biogas plant can become the best source of energy.
What is Biogas?
Biogas is formed through the degradation of organic materials. The process of degradation has to develop in the Anaerobic environment- which means the absence of Oxygen. Garbage, stools or crops (which have high organic elements) are generally used to generate Biogas. These materials are called Substrate.
Organic materials are mainly a mixture of various proportions of Carbon and Hydrogen (and other elements too). In the absence of Oxygen, some bacteria grow which can break these organic substances. The breakage of these organic substances creates Methane (CH4), Carbon di oxide (CO2), Nitrogen(N2), Hydrogen sulfide (H2S). The fuel value of any gas depends on the proportion of Methane in it. Biogas can have 50-75% Methane depending on the nature of the Substrate. With the amount of Methane in Biogas, it can be used as an alternative of natural gas in cooking or in any other oven. But it cannot be used to produce electricity directly. By removing or filtering Hydrogen sulfide, the refined Biogas can be used to produce electricity.
How does Biogas plant work?
The main parts of Biogas plant are Digester, Inlet chamber (the chamber in which the substrates are delivered) and Gas collector. Along with these, few other parts are also there mainly for safety, measurement and operation.
Digester is the main part where the process of digestion takes place. Substrates are delivered to the digester through the inlet chamber. The digester remains completely air tight which assures the absence of Oxygen in it. After 5 to 7 days, gas starts to produce. In this time necessary microorganism or bacteria starts to develop. The amount of Biogas depends on the composition of substrate.
Usefulness of Biogas plant
Biogas has some extra benefits than any other sources of energy. Other renewable fuels work only as a source of energy; in addition to that, Biogas plant does the following works:
-collects nutrients from garbage which are reusable.
–produces organic fertilizers which can be used in farming.
–takes a role in reducing garbage from the environment.
So, we have to consider the overall benefits of biogas, not only as a source of energy. For example, to remove the municipal garbage, the city corporations spend a lot of money, but this work is limited in collecting and removing the garbage outside of the city. Because of the wrong process of collecting garbage it has no usefulness at present. But, by taking few steps, these trashes can be used to produce Biogas and organic fertilizer. So that, the diseases and reek, which are spreading from the scattered garbage now, can be restrained. The Methane from the trashes (which is the most injurious green house gas) can also be used properly. That means, the garbage, which has no use at present, can be used appropriately through this technology of Biogas plant. Biogas plant can be used not only to remove urban waste, but also to refine waste water. In many counties, this kind of model is already successfully going on.
The garbage, which has organic materials in high amount, can be used as substrate in Biogas plant. Such as, domestic waste, waste water, agricultural waste, excrement etc. besides some crops can also be used in biogas plant.
Possibilities of Biogas plant: focusing Bangladesh
Though Biogas plant has much possibility in Bangladesh, its usage is still very limited. There are very few Biogas plants developed under single or combined effort in villages at a small range, which are still the maximum ones. Very few poultry farm and agricultural farms have Biogas plants.
During summer, the temperature of Bangladesh remains under 30-40digree siliceous, which is very adequate to produce Biogas. That is why Biogas plant in Bangladesh is a demand of time.
1. To refine urban wastage: The rate of urbanization in Bangladesh is 33.5%  which means day to day the urban wastage is increasing. There is no proper policy or steps to remove and to refine this garbage. So the city authority’s duty is just limited in collecting the trash and throwing it to some junkyard. These reserved trashes are producing reek, disease as well as Methane gas (green house gas). However, by using Biogas plant technology, the garbage can be refined to improve the environment and also the produced Biogas and fertilizer can be used for trading. This means garbage can be a source of money and this model is proven in other countries.
Everyday 2 crores 25 lac ton  garbage is produced in Bangladesh. Almost 70%waste is organic waste  in it, which means almost 1 crore 60 lack ton organic waste are produced. In a research it is seen that, an area, where 1 lac people lives, produces 20 metric ton wastage which are perfect to make Biogas. By using this wastage, 1400 cubic meter gas can be produced which can be used in 1200 house for cooking everyday . So, the scarcity of domestic fuel can be reduced by using this large amount of waste appropriately.
2. To solve the problem of fuel scarcity in villages: In the cities of Bangladesh, the gas line is connected through pipe lines. Also the supply of gas cylinder is limited inside cities. In the rural areas, woods, stray and cow dung are commonly used as fuel (almost 94%) , so the forests are getting barren. Various organic materials are much available in villages than cities, so the Biogas plant can be a way to solve the problem of fuel scarcity in villages. Thus the environment will be improved.
3. To remove the trashes from dairy and poultry farm: There are a lot of poultry farm in Bangladesh which produce useful trashes for Biogas plant. Very few poultry farm have Biogas plant and these are successfully driven. Dairy farm can also use Biogas plant effectively.
Each ton of poultry litters can produce 30 to 100 cubic meter of Biogas . Each ton of cow dung can produce 15 to 25 cubic meter of Biogas . In a survey, it is seen that 30 kg cow dung or 200 poultry litters can make a oven burn for almost 3 hours . After the production of Biogas, the remaining garbage can be used as fertilizer. If all poultry and dairy farm start Biogas plants, it will be possible to produce Biogas and fertilizer at the same time which is very beneficial.
4. To produce electricity: It is easy to produce electricity by using the refined gas produces from the Biogas plant. As Bangladesh has a lot of organic materials, so there is a huge possibility to produce electricity through Biogas. Specially for the maximum use of organic materials, Combined Heat and Power-CHP. While the heat efficiency of coal and gas depended electricity is respectively 34% and 55%, it can earn up to 70% of heat efficiency by producing combined heat and power through Biogas . Though some private sectors have taken few steps, no such steps are taken by the government. One private institution maintains two Biogas driven generators of 200 and 100 kilowatt. Another institution produces 2400 cubic meter gas by using 30 ton of poultry litter daily and that produces 200 kilo watt electricity . Another one produces 1200 cubic meter gas with 15 ton poultry litters which produces 100 kilo watt electricity .
5. To refine waste water: In Dhaka city, planned waste water refining is limited to some certain areas. There is no plan to remove the waste water throughout a large area. This waste water overflows from the underground while raining. By using Waste Water Treatment Plant (WWTP) effectively, the waste water can be refined; also it can be used to produce energy.
6. To refine industrial waste: As the industrial waste has a little organic material in it, it is not beneficial to use it in Biogas plant. But to refine the injurious elements in industrial waste, Biogas plant can be useful. Some bacteria grow in the anaerobic environment which can take those injurious elements to a tolerable level. The research about this is still going on.
Though it has much possibility, the lack of taking proper steps is hindering the complete usage of Biogas in our country. In some private sectors, specially for cooking, Biogas plants are used. But for combined and large production of heat and power, no such steps have been taken by the government yet. By using the possibility of Biogas, to solve the problem of scarcity of fuel in Bangladesh, it is high time for the government to take proper steps, make appropriate policy, make roadmaps, do enough research and implement it.
(1) United Nations, Department of Economic and Social Affairs
(2)Waste Atlas. (2012). Country Data: Bangladesh
(4)Page 62, POPULATION AND HOUSING CENSUS 2011, SOCIO-ECONOMIC AND DEMOGRAPHIC REPORT.
(6) Prothom Alo, 28 November 2014, Page 1-2.