Biomass is fuel derived from organic materials, a renewable and sustainable source of energy used to create electricity. Some examples of biomass fuels include; forest debris, scrap lumber, crops such as sugar cane, manure, waste residue. With a constant supply of waste from construction and demolition activities to wood not used in paper making to municipal solid waste, green energy production can continue indefinitely. Biomass is a renewable source of fuel because waste residues will always exist( in form of scrap wood, mill residues and forest resources) and properly managed forests will always have trees and crops and the residual biological matter from those crops.
Biomass power is carbon neutral electricity derived from the burning of renewable organic waste that would otherwise be dumped on landfill sites, openly burned or left in the forests. In biomass power plants the organic waste such as wood waste are burned and produces heat. The heat generated produces steam when water is heated. The steam is then used to drive a turbine which is connected to a generator that produces electricity.
There are several methods used for converting biomass for practical use as fuels. These are;
- Thermal conversion
- Chemical conversion
- Biochemical conversion
- Electrochemical conversion
This process uses heat as the dominant mechanism to upgrade biomass into a better and more practical fuel. The methods include torrefaction, pyrolysis and gasification. There are other less common and more experimental processes like hydrothermal upgrading. Some have been developed for use on high moisture content biomass including aqueous slurries and allow them to be converted into more convenient forms.
A range of chemical processes can be used to convert biomass into forms that are convenient to store, transport and use, or to exploit some property of the process itself. Many of these processes are based on similar coal based processes like the Fischer- Topsche synthesis. Biomass can be converted into multiple commodity chemicals.
As biomass is an organic material, many highly efficient biochemical processes have developed in nature to breakdown the molecules of which biomass is composed. Many of these conversion processes can be harnessed. In these processes microorganisms are used in the conversion processes which include; anaerobic digestion, fermentation and composting. Glycoside hydrolases are also used in the degradation of biomass such as polysaccharides present in starch and lignocellulose. Thermostable enzymes are also increasingly used especially for biomass that require thermal treatment for efficient degradation.
Biomass can be converted to electricity directly via electrochemical oxidation of the material. This can be performed in a direct carbon fuel cell, direct liquid fuel cell such as direct ethanol fuel or direct methanol fuel cell, direct formic acid fuel cell and microbial fuel cell. The fuel can also be consumed indirectly using a fuel cell system containing a reformer which converts the biomass into a mixture of CO and H2 before it is consumed in the fuel cell.