The energy prospect is generally assessed on the basis of available
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commercial sources of energy i.e., fossil fuel like gas, coal, oil etc. Worldwide, there is a major transition underway in the energy sector. Biogas can be a potential source of renewable energy, Residues from biogas also proven as a significant source of organic fertilizer. If there is proper policy and implementation, Bangladesh’s energy crisis and organic fertilizer demand can be control through biogas plant.
By 2020, the world is throwing into turmoil as demand for energy begins to greatly exceed the supply – crippling many economies and triggering widespread social unrest. Many countries in the West may experience a decline in living standards – with oil rationing and conservation measures introduced by governments and substantial reductions in travel, tourism and aviation. The crisis plays out for nearly two decades, gradually being resolved by a switch to renewable energy and alternative fuel technologies. In Bangladesh context, neither the decision-makers nor the experts pay due importance on proper extraction and use of renewable energy. Here grater population is using natural gas and imported oil, with the present rate of consumption, natural energy resources like gas will be exhausted shortly and this is high time to derive policy and practice for exploration and use of alternative renewable sources if we want to meet energy crisis in near future. Biogas has been found to be a proven renewable energy option.
Biogas, a cheap secondary renewable energy, is a gaseous fuel obtained from biomass by the process of anaerobic digestion or fermentation. Biogas fermentation is the process by which organic materials such as human or animal excreta, domestic wastage, agricultural wastage etc, are degraded, by huge quantities of various microbes of different functions, under anaerobic conditions, to yield methane (about 55-70% content), carbon dioxide (about 3045% content) and low amount of other gases in the end. Biogas can be used as a vehicle fuel or for generating electricity. It can also be burned directly for cooking, heating, lighting, process heat and absorption refrigeration. Cattle dung, agricultural residue, poultry dropping, water hyacinth, human excreta may be used as raw materials for biogas plants. A typical biogas plant consists of a digester in which the slurry (dung mixed with water) is fermented; an inlet tank used to mix the feed and let it into the digester; a gas holder/ dome in which the generated gas is collected; an outlet tank to remove the spent slurry; distribution pipelines to take the gas into the kitchen.
3. How Biogas produced
Biogas is produced by the anaerobic digestion or fermentation of biodegradable materials such as biomass, manure, sewage, municipal waste, green waste, plant material, and crops. Biogas comprises primarily methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulphide (H2S), moisture and siloxanes.
The gases methane, hydrogen, and carbon monoxide (CO) can be combusted or oxidized with oxygen. This energy release allows biogas to be used as a fuel. Biogas can be used as a fuel in any country for any heating purpose, such as cooking. It can also be used in anaerobic digesters where it is typically used in a gas engine to convert the energy in the gas into electricity and heat. Biogas can be compressed, much like natural gas, and used to power motor vehicles.
4. Advantages of Biogas Technology:
A potential source of renewable energy.
A source of improved organic fertilizer.
A mechanism for wastage management.
4.1 A potential source of renewable energy.
Energy is one of the basic ingredients required to alleviate poverty and socio-economic development. The energy prospect is generally assessed on the basis of available commercial sources of energy i.e., fossil fuel like gas, coal, oil etc. Worldwide, there is a major transition underway in the energy sector. It is happening due to the following three major reasons:
(I) A decline in fossil fuel availability, their predicted gradual extinction in the next Few decades and the resultant price volatility due to demand-supply gap. (ii) The need to drastically cut global emissions for mitigating climate change (80% Reduction by 2050).
(iii) The need for energy security. In Bangladesh efficient utilization of renewable energy resources is yet to assume commercial dimensions and hence rational policy dissemination on renewable energy usage is essential. The renewable energy includes solar, wind, biogas and biomass; hydro, geothermal, tidal wave etc.
Despite of above scenario biogas source can be use as a potential source of renewable energy.
4.2 A source of improved organic fertilizer.
Bio product of biogas plant is improved organic fertilizer. This fertilizer contains organic component like Nitrogen, Phosphorus, and Potassium &Micro Nutrients: Nitrogen:
Producing compost fertilizer Nitrogen losses calculated 50 % in every three months at the time of aerobic fermentation, on the other hand 10 % losses calculated while producing from biogas residues
Figure- 2 shows, Nutrition’s comparison between Chemical fertilizer and biogas residues from Biogas plant (Production in percentage):
Biogas can outline sustainable land use. Reduced use of fertilizers and insecticides compared with lands used for row crops, protection of riparian areas, and erosion protection for sensitive land areas.
4.3 A mechanism for Wastage management
Municipal waste is the abandoned materials which have been thrown away after use in daily life in the urban area. Municipal waste generally compose of food scrap, packaging materials, used plastic materials, tire etc. Due to the increasing growth of urban population in Bangladesh this municipal waste is getting high concerns from the management perspective. Also the management of this huge amount of waste is a worth of large expense. The
huge amount of waste in the urban areas of Bangladesh due the rapid growth of population can be a potential source of biogas production. The calculation shows that by adopting active biogas collection procedure in the major landfills of the main cities can produce 319989.36 KWh of electricity. Recommendations are given to develop this technology within minimized cost and ensuring environmental safety. The unhygienic dumping zones in every city could me turned into a potential source of renewable energy by adopting active gas collection technology instead of spending money to manage the waste in that areas and keeping a huge land area unused. To explore the untouched potential of biogas source of municipal waste following actions are recommended:
-To attract the investment in this sector government should demonstrate one pilot project with the help of foreign Development partners.
-Private sectors should be given incentives to invest in biogas from municipal waste.
-The technologies used in the countries successfully adopted waste to electricity system should be imported with necessary subsidies.
-To facilitate the consciousness media should be used properly.
4.4 Save Environment.
The greenhouse effect is caused by gases in the atmosphere (mainly carbon dioxide, CO2) which allow the sun’s short wave radiation to reach the earth surface while they absorb, to a
large degree, the long wave heat radiation from the earth’s surface and from the atmosphere. Due to the “natural greenhouse effect” of the earth’s atmosphere the average temperature on earth is 15°C and not minus 18°C.
The increase of the so called greenhouse gases which
also include methane, ozone, nitrous oxide, etc. cause a rise of the earth’s
temperature. The World Bank Group expects a rise in sea levels until the year 2050 of up to 50 cm. Flooding, erosion of the coasts, Stalinization of ground water and loss of land are but a few of the consequences mentioned. Until now, instruments to reduce the greenhouse effect considered primarily the reduction of CO2-emissions, due to their high proportion in the atmosphere. Though other greenhouse gases appear to be only a small portion of the atmosphere, they cause much more harm to the climate. Methane is not only the second most important greenhouse gas (it contributes with 20% to the effect while carbon dioxide causes 62%), it has also a 25 times higher global warming potential compared with carbon dioxide in a time horizon of 100 years. The Bio gas plant effectively reduces the amount of methane directly released into the atmosphere, by trapping it and facilitating its use as a green fuel. After burning, methane only releases harmless gases in air.
Other uses of biogas:
With the help of biogas we can drive gas generator to produce electricity in rural area. We can use gas incubator to produce poultry chicken from egg. We can use gas lantern by using bio gas in night time in village area. Hotel and restaurant can use biogas for cooking purposes by using the residue of vegetable and food waste. We can drive gas hitter for hitting water during winter season. Different poultry and dairy farm can mitigate their need of gas by using their own animal excreta.
5. Biogas significance in Bangladesh
As a country of large population and for the convenient environment Biogas might be the potential source of energy. Though recently government has initiated some pilot project with the help of some foreign NGOs, but the utilization of the full potential is yet to reach. The main problem is lying in lack of public awareness and social prejudices. Government should supply the needed equipments to the private organization with less expense to encourage the involvement in this sector.
5.1 Types of Biogas Digester invented by Bangladesh government
There are three types of basic designs of biogas plants tried in Bangladesh: (I) Floating cover digester: It works on the principle of constant pressure, changing volume. The digester, cylindrical well, commonly made from brick and cement, is covered with a floating steel cylinder with an open bottom (Fig. A). As the cylinder has a constant weight, it moves up when gas production is higher than consumption and comes down under the reverse conditions.
(ii) Fixed cover digester: It works according to the principle, constant volume, changing pressure. When the rate of gas production is higher than that of gas consumption pressure inside the digester rises and expels some digester contents into the outlet compartment. When the consumption is higher than production, pressure inside the digester falls and the expelled materials in the outlet compartment run back to the digester (iii) Plastic Cover digester: A long cylindrical polythene/PVC bag, half-buried longitudinally in the ground, is fed with fresh cow-dung slurry at one end and discharged at the other. With the formation of gas, the bag swells like a balloon and the gasis led out to the point of use through a pipe by putting pressure on the balloon form outside In early 80’s, the floating type design was used for biogas plant. But dueto corrosion of the steel dome, the gas leakage problem happened and it could not be removed. Later on BCSIR tried with fixed done type design and it has been successful in all biogas plants. The plastic bag type designs not used in Bangladesh it is used in China. In this project, the fixed dome type design has been proposed.
5.2 Availability of biomass in Bangladesh for energy generation. The total annual generation and recoverable amounts of biomass in Bangladesh are about 165 and 9 MT/year respectively. Agricultural residues represent 48% of the total recoverable biomass followed by 23.9% from animal wastes and poultry droppings. In 2006, the biomass consumption for energy in Bangladesh was about 350 pico-Joules (PJ). At an average annual growth rate of 1.3%, the consumption in 2010 will be about 370 PJ. The total recoverable biomass energy of the country in 2006 was about 1250 PJ from which about 820 PJ of biomass energy was available for electricity generation. On the other hand,
the total biomass
energy consumption in 2006 was about 473 PJ. Assuming the same average annual growth rate of 1.3%, the biomass consumption in 2010 will be about 286 PJ. Therefore, the amount of biomass energy available in 2006 was 777 PJ, which is equivalent to 216 terawatt-hours (TWh). According to these two estimates and considering that the consumption of biomass for non-energy purposes is negligible, the annual available biomass energy potential for electricity generation in Bangladesh is in the range of 216- 250 TWh.
5.3 Present biogas Generation Rate:
According to Infrastructure Development Company Limited (IDCOL) sources, Bangladesh has 215,000 poultry farms and 15,000 cattle farms where electricity could be generated by establishing biogas plants. So far, 35,000 biogas plants have been established for the production of gas for cooking purposes in the rural areas. IDCOL has set a target of establishing 60,000 biogas plants by 2012, each of which could produce, on average, 94.22 square feet of gas. At present, 3.3 million square feet biogas is being produced in the country.
Biogas is a proven technology; there is no risk of failure if proper design and supervision can be ensured. Most of the micro finance institutions are now convinced and took decision to provide loan for the construction of Biogas plants. Most of the urban poor can not afford gas connection as it costs Tk. 200 to Tk. 400 per month. Instead they can install Biogas plants with. Bank loan and repay the loan out of their fuel savings ‘domestic’ size Biogas plant of 100 cft capacity cost Tk. 15,000 to Tk.18, 000 and can meet the cooking energy need for a five- member family. Impact on health and environment: Large scale bio energy development in Bangladesh could bring significant environmental benefits. Sustainable bioenergy development could: Reduce higher level of deforestation. Reduce net greenhouse gas emissions. Improve air quality and reduce acid deposition. Improve soil quality and reduce erosion. Reduce land filling by adding value to residues.
5.5 Few case study:
Biogas plants in different institution: LGED has constructed 61 Biogas plants in different educational institutes, orphanages, hospitals, school/college hostels for solving the sanitation problems and getting biogas as an alternative energy source. One of these important plants is in Faridpur orphanage. There are 250students and staff in Faridpur orphanage. For their night soil disposal they needed to construct a septic tank for 250 users with Tk.60, 000. LGED in mid 1992 constructed a Biogas plant with Tk. 16,000which served the purpose of septic tank as well as a source of gas and fertilizer. This has reduced the investment by Tk. 34,000 and the mission has been saving Tk. 25,000 against fuel cost per year.
Case 1: Ganaktuli Sweeper colony, Dhaka:
There are five buildings for sweepers and 40 families reside in each building. The latrines of the buildings were not connected with any septic tank or sewerage system. Previously, night soil was passing through surface drain creating health hazard. To connect the latrines of building No-I to the nearby sewerage line Tk. 60,000 and to construct a septic tank for 221 users of the building Tk. 50,000 were necessary. Instead, LGED constructed a Biogas plant for Tk. 20,000 in 1993which is working till today without any problem giving sufficient gas to meet fuel need of all families of 1 building. There was some maintenance for leakage and Tk. 300 was spent. Observing the performance of the plant, residents of other 4 buildings created pressure on the city corporation to construct similar plant in those buildings. By now Biogas plants have been constructed in all the remaining 4 buildings.
Case 2: ‘Ecological Village’ Amgram/Uttar Hogla in Madaripur: LGED took up ‘Ecovillage’ project on experimental basis as pilot programme with the objectives to make the villagers aware about environment and technology, create clear, healthy and acceptable environment in the villages and inspire the people around the villages to accept such project. There are 662 people in the village in 123 families. Besides other socio economic activities, the following facilities were also provided: There was no latrine in the village and 95latrines were constructed. As an alternative source of energy 15 Biogas plants were installed, three persons were trained in the construction of Biogas plant. The Biogas plants are providing energy input to the villagers.
Different implementing agencies in Bangladesh, which are active in promoting bio gasification technology, are not paying sufficient attention to effective and focused groupcollaborative R&D aimed at renovating, optimising and improving the design for adaptation to local conditions. Limited R&D facilities and capabilities and lack of co-ordination among the researchers and implementing authorities may well pose a major stumbling-block towards the success of this endeavour. Moreover, the follow-up action program is also very limited. Sometimes, the plant-owners do not get proper technical guidance for the operation and maintenance of their plants.
Thus, the successful application and extension of this option depends on:
Institutional measures and close collaboration between sectors involved. This should include, among others, provision for soft loans and/or subsidy; availability of standard prototype for design and construction and site-specific maintenance guidelines;
meaningful public involvement which should aim at passing relevant information of this technology to the community to increase awareness and promote acceptability of this technology;
Accurate calculation of the benefits of this technology.
Biomass could play a role in reducing C02 emissions in both of these sectors. As the slurry remains in the digester for 30-40 days in anaerobic condition, the effluent becomes pathogen free and the output is smell-free combustible gas and organic fertilizer which is improving the environment and preventing diseases. At present Bangladesh meet 46.15% of its energy need by agricultural residue, 10.5% by cow dung, 12.9% by fuel wood and 33% by tree residue. This means that to meet our energy need we are depriving, ourselves from organic fertilizer and creating environmental imbalance by deforestation. One pragmatic estimate puts that the use of biogas will reduce energy deficit at least by 15%.
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