Waste Agricultural Biomass for Energy

An estimated 5 billion metric tons of agricultural biomass waste is produced annually – equivalent to approximately 1.2 billion tons of oil. The term biomass refers to those organic materials, which do not directly go into foods or other products. Mostly, this biomass is in the form of residual stalks from crops, leaves, roots, seeds and seed shells etc. Common examples are wheat and paddy straw, bagasse (residue from sugarcane milling in sugar production), seed hulls (rice husk, ground nut husk) waste wood from timber processing, waste from animal husbandry etc. In some case animal metabolic wastes are also considered as biomass. Currently, especially in developing countries, most of the waste agricultural biomass is left in the field to decompose naturally or is open-burnt. Apart from bagasse, and in some cases rice husk, there is hardly any productive use being made of biomass.

A major advantage of using waste agricultural biomass (WAB) as a source of energy or materials is its renewability. This is a clean source of energy as the carbon cycle loop is closed (the carbon dioxide released by combustion is again sequestered in the next crop) and usually there are no harmful emissions (such sulfur oxides, heavy metals). The material is available abundantly and is virtually free. Commercial use of biomass can also provide additional income to farmers and poorer sections of society thus helping in poverty alleviation.

The Climate Change (CC) benefits i.e. GHG emission reduction could come from two sources:

(a) By replacing fossil fuels with fuels derived from waste agricultural biomass. This is easy to estimate as it will be equal to the CO2 which would have been otherwise released by the amount of fossil fuels that has been displaced (after accounting for the energy consumption in producing it).

(b) By avoiding generation of methane when left in the field to rot. Volumes are difficult to determine because estimates of methane generation by natural rotting of different types of waste agricultural biomass are still not available or are imprecise and vary significantly depending upon many factors.