M S Islam and M R Islam

Each year some 590-880 million tons of methane are released worldwide into the atmosphere through microbial activity. About 90% of the emitted methane derives from biogenic sources, i.e. from the decompositionorganic substances like waste material, cow dung, poultry litter etc. Organic substances, when decompose under anaerobic condition, produce a colourless combustible gas called ‘Biogas’. Wastes generally spread bad odour but if they are decomposed in the biogas plant, bad odour cannot be spread and hence improve pollution free healthy clean environment. On the other hand, the cost of biogas plant now- a- days can be recovered within 3-4 years from the savings of cooking fuel alone. Environmental, CDM and other benefits like health and manure are bonus.

A unique feature of biogas technology is that it simultaneously reduces the need for firewood and improves soil fertilization, thus substantially reducing the threat of soil erosion. Firewood consumption in rural households is one of the major factors contributing to deforestation in developing countries. Rapid deforestation due to increasing wood consumption contributes heavily to the acceleration of soil erosion. This goes hand in hand with overgrazing which can cause irreparable damage to soils. In the future, investments aimed at soil fertilty preservation must be afforded a much higher priority than in the past. It will be particularly an important issue to enforce extensive reforestation.

As for an example of developing countries, Bangladesh is facing many challenges; the most important ones are the food production and security for her more than 160 million people in an area of 147,624 km² where cultivable land is decreasing and population is increasing at a rate of 1.54 per year (BER 2008). With an ever increasing population and limited cultivable land, Bangladesh is forced to maximize crop yields per unit area through intensive use of soil and land resources. As a result, continuous mining of nutrients from the soil is going on. Due to such intensification, the fertility of the soils has been declining day by day. Many soils are losing their productivity. The use of chemical fertilizer and pesticides without use of any organic fertilizer causes serious problems to the soils- such as hardness, low water-holding capacity, micro nutrient deficiencies, reduced soil microbial activities etc.

Moreover, Bangladesh is one of the low energy consuming countries of the world. More than 90% of the people are depending on the biomass, particularly woody type, for everyday cooking and other heating purposes. About 44 million tons of biomass fuels such as fuel-wood, branches, straw-leaves, agricultural residues, cow dung cake, briquettes etc. are being used annually (Islam and Islam 2011). The situation is extensive in areas where no natural gas supply system exists. Furthermore, the alternative fuels like kerosene and liquefied petroleum gas (LPG) are expensive for a majority of the people. Therefore, the largest parts of the country’s poor families have to rely on traditional fuels to produce energy. In this context, biomass energy plays a vital role in meeting local energy demand. There are huge number of wood shops supplying woody type biomass fuels in Bangladesh and causes serious deforestation and other environmental problems. Coupled with this, the efforts for planting trees to periodically replace felled-forests are sporadic and extremely rudimentary. This has resulted in accelerated depletion of forests in the country (NRBAR 2009).

To alleviate above mentioned problems, biogas can be an alternative source of energy. Grameen Shakti has, therefore, undertaken construction of biogas plants as an alternative to the energy produced from firewood, the cutting and burning of which is harmful for the environment. The technology uses cow dung, poultry droppings, water hyacinth and other biomass waste to produce biogas, thereby ensuring a smoke-free, odour-free, clean and healthy cooking environment for rural women. According to one estimate, 2 million tons of organic fertilizers are produced every year from households’ wastes, city wastes, crop wastes, and animal wastes.

The introduction of biogas has reduced the time that the rural women spend on cooking, in turn allowing them to engage in other productive pursuits. A three cubic meter biogas plant is capable of producing sufficient gas for cooking three meals a day for a family of 6-8 members. The owners of these biogas plants, after meeting their own requirements, sell extra gas to nearby families, restaurants, tea-stalls and bakeries. Some owners also use biogas to generate electricity for their own use.

Recently Grameen Shakti, the largest renewable energy facilitator of the country, has taken an initiative to install a 500 m³ biogas plant in Faridpur municipal area with the help of municipal authority and PEAR Carbon Initiatives Limited, Japan. Municipal Organic Solid Waste (MOSW) will be used as raw material in this plant.

The widespread production and utilization of biogas is expected to make a substantial contribution to soil fertility protection and amelioration. First, biogas could increasingly replace firewood as a source of energy. Second, biogas systems yield more and better organic fertilizer. As a result, more fodder becomes available for domestic animals. This, in turn, can lessen the danger of soil erosion attributable to overgrazing. The Government of Bangladesh has so far standardized 28 organic and organochemical fertilizers including Grameen Shakti Organic Fertilizer. Grameen Shakti has made an agreement with three companies to market bioslurry organic fertilizers from its constructed biogas plants under the brand name Grameen Shakti Organic Fertilizer.

Last but not least, biogas technology takes part in the global struggle against the greenhouse effect. It reduces the release of CO₂ from burning fossil fuels in two ways. First, biogas is a direct substitute for gas or coal for cooking, heating, electricity generation and lighting. Additionally, the reduction in the consumption of chemical fertilizer avoids carbon dioxide emissions that would otherwise come from the fertilizer producing industries. By helping to counter deforestation and degradation caused by overusing ecosystems as sources of firewood and by amelioration of soil conditions biogas technology reduces CO₂ releases from these processes and sustains the capability of forests and woodlands to act as a carbon sink.