The word “biomass” has two meanings. In basic biological terms, biomass is simply defined as all the living matter present on earth. The earth is constantly replenishing its biomass in the form of new plant growth and procreation among animals. Biomass also refers to the plant and animal matter used for fuel generation. Biomass is considered as a renewable energy source.
Generally, plant matter is used for fuel generation purposes. The plant matter may be obtained as a waste byproduct or grown especially for fuel purposes. Here are the types of biomass materials used:
Trees: This involves growing and maintaining forests for biomass purposes. The forests comprise of fast-growing tree species that are harvested every 5 to 8 years. Harvesting is carried out by a process called 'coppicing', wherein trees are cut off very close to the ground, allowing fresh shoots to grow again from the stump, to be harvested in the next cycle. Commonly used tree species are eucalyptus, sycamore, poplar, maple, willow, etc.
Grass: Prairie grass is another fast-growing biomass source. Grass varieties used are switchgrass, bluestem, sugarcane, and other local varieties. Grass requires fewer resources than growing trees, which makes it a popular choice.
Forest and agricultural residues: Farm residues and other waste products form a major component of biomass. Forest residues include unmarketable wood such as logging tops, culls and pre-commercial thinnings from logging operations. Paper, pulp, and lumber mills generate large amounts of biodegradable waste. Crop residues and animal manure from dairy, poultry and animal farms provide biomass from the agricultural side.
Although biomass can be produced from any natural substance, it is mostly obtained from waste matter of natural origin. This includes plant matter like twigs and dry leaves, organic waste generated by municipalities and industries, agricultural waste, etc. Biomass itself can be used directly as fuel but it provides comparatively less energy than when the biomass is converted to other energy sources, mainly to produce electricity.
Electricity can be obtained from biomass in three ways. Biomass may be incinerated to produce steam, which is used to power turbines that generate electricity. In the second method, biomass undergoes gasification to become a gas that runs through an alternator and an internal combustion engine to produce electricity. The third method involves anaerobic (without oxygen) digestion of biomass to yield methane, which is then used to generate electricity.