3. Biomass availability in Bangladesh The common biomass resources available in Bangladesh are agricultural crop residues, wood residues, animal waste and municipal solid waste, etc. The resources can be utilized on a larger scale for electricity generation.
3.1. Agricultural crop residues Rice, maize, wheat, coconut, groundnut, bean, vegetables, jute and sugarcane etc. are the main agricultural crops in Bangladesh. Agricultural crops produce residues that can be used to generate energy. Crop residues are collected either at the same time or after harvesting of the primary crops. Depending on the period of residues collection, there are two types of crop residues. One is field residue and other is processing residue. Field residues are generally used as fertiliser and collected from the field after harvesting. Process residues are collected from the mills, where the crops are further processed. Rice straw, rice husk, bagasse from sugarcane and jute stick cover about 46% of the total biomass energy. Crop residues are used not only for renewable energy source, but also for cooking and raw manufacturing material. In Bangladesh, there is no commercial supply of gas in the rural areas. Therefore, village people use agricultural crop residues (straw, husk, etc.) as the major source of cooking fuel followed by dry cow dung, leaves and twigs, woods and kitchen by product, etc. The generation ratios for crop residues have been employed for accounting total generation of the corresponding residues. In the current study, the percentage of residues generation and recovery ratios for agricultural crops are followed from the studies of some neighboring South Asian developing countries. The residues recovery rate has been assumed as 35% for field crop residues and 100% recovery in case of process crop residues.
Rice is the main agricultural crop in Bangladesh that covers 76% of the total agricultural area and supplies 70% of the total calorie requirement for the nation [24]. Table 6 presents the status of agricultural crops production from FY 2009–10 to FY 2010–11. According to BBS, the volume of rice production in FY 2010–11 was 33,541.101 kilo tons (kton) of which Aus accounted for 2132.821 kton, Aman 12,791.500 kton and Boro 18,616.780 kton. Total rice production in FY 2009–10 was 31,975.251 kton, of which Aus, Aman and Boro accounted for 1709.127, 12,207.162 and 18,058.962 kton respectively. By this period, the land area for rice cultivation has increased from 28,05,715 acres to 2,84,88,926 acres. Rice straw, rice husk and rice bran are the main residues produced from rice. Rice straw is the dry stalks of cereal plants which are collected as field residues. On the other hand, rice husk is the outer surface of the rice grain and rice straw and is categorized as process residues. In Bangladesh, generally, rice straw and rice bran are used as food for cattle, poultry and fish etc. Nowadays, rice husk is being used for electricity production in a small scale.
3.2. Animal manure: Animal manure is a mixture of organic material, moisture and ash. The mature can be decomposed both in aerobic and anaerobic conditions. Under aerobic condition, carbon dioxide and stabilized organic materials are formed. On the other hand, at anaerobic condition, methane, carbon dioxide gas and stabilized organic materials are created [26,27]. Cattle, goats, buffaloes and sheep are the general sources of animal manure in the country. Animal manure is often used as fertilizer. Biomass energy production and power generation using animal manure may become an effective energy and power demand solution in remote and rural areas of Bangladesh. Thus bad odors of manure and annoyance gas emissions from the application of raw manure are also reduced. Biogas produced from manure can meet the cooking fuel demand. Additionally, gas production from slaughter house waste has a possibility to generate electricity in a small scale. The quantity of manure production from the animals depends on age, breed and feeding habits. Also, the amount of dung yield varies with the seasons. For example, the dung yields are generated more in the rainy season than that of summer, since grasses grow more during raining.
3.3. Municipal solid waste: Municipal solid waste (MSW) is the heterogeneous composition of wastes that is organic and inorganic, rapidly and slowly biodegradable, fresh, hazardous and non-hazardous, generated from various sources in urban areas due to human activities. Overall, per capita waste generation depends on the economic status, food habit, age, gender of household members and seasons. The increase of solid waste in every Asian city is mainly attributed to population increase, industrialization and the improvement of living standards. The governments have realized that Green Productivity (GP) measures such as reduction, recycling, reuse, and recovery are essential elements in solid-waste management as a form of checking the rapid growth rate of waste in the cities. National awareness campaigns on GP measures are held regularly to promote recycling activities. Bangladesh, like most of the developing countries, is facing a serious environmental problem due to huge amount of MSW generation and its mismanagement. The main sources of municipal solid waste (MSW) in Bangladesh are households, commercial areas, industries and hospitals.