
Biomass is carbon-based biological material, such as wood, crops (such as corn or sugar cane), leftovers from agricultural processes (such as corn husks, manure), certain by-products of food processing, and much industrial and post-consumer waste.
Biomass essentially stores energy from the sun (through the process of photosynthesis). This energy can be released in a number of ways, including burning, decay (rotting), or through processing to create biofuels (such as ethanol from corn) and biodiesel (from waste oil or vegetable oil). The following introduction from the Biomass Energy Centre is a good starting point for understanding biomass/solid waste and its role in energy production.
Biomass is biological material derived from living, or recently living organisms. In the context of biomass for energy, this is often used to mean plant based material, but biomass can equally apply to both animal and vegetable derived material.
Plant material
The carbon used to construct biomass is absorbed from the atmosphere as carbon dioxide (CO2) by plant life, using energy from the sun.
Plants may subsequently be eaten by animals and thus converted into animal biomass. However, the primary absorption is performed by plants.
If plant material is not eaten, it is generally either broken down by microorganisms or burned:
- If broken down, it releases the carbon back to the atmosphere, mainly as either carbon dioxide (CO2) or methane (CH4), depending upon the conditions and processes involved.
- If burned, the carbon is returned to the atmosphere as CO2,
These processes have happened for as long as there have been plants on Earth and is part of what is known as the carbon cycle.
Fossil fuels
Fossil fuels such as coal, oil, and gas are also derived from biological material; however, from material that absorbed CO2 from the atmosphere many millions of years ago.
As fuels, they offer high energy density, but making use of that energy involves burning the fuel, with the oxidation of the carbon to carbon dioxide and the hydrogen to water (vapour). Unless they are captured and stored, these combustion products are usually released to the atmosphere, returning carbon sequestered millions of years ago, and thus contributing to increased atmospheric concentrations.
The difference between biomass and fossil fuels
The vital difference between biomass and fossil fuels is one of time scale.
Biomass takes carbon out of the atmosphere while it is growing, and returns it as it is burned. If it is managed on a sustainable basis, biomass is harvested as part of a constantly replenished crop. This is either during woodland or arboricultural management or coppicing or as part of a continuous programme of replanting, with the new growth taking up CO2 from the atmosphere at the same time as it is released by combustion of the previous harvest.
This maintains a closed carbon cycle with no net increase in atmospheric CO2 levels.
Reading Assignment
Visit Department of Energy, Energy Explained.
- Under “Renewable Sources", read "Biomass" and all subpages.
Reading Assignment
Visit the EPA,
- Read Sustainable Materials Management: Non-Hazardous Materials and Waste Management Hierarchy
- Open Energy Recovery from the Combustion of Municipal Solid Waste (MSW) and read selected sections:
- The History of Energy Recovery from Combustion
- Frequent Questions on Energy Recovery from Combustion
Reading Assignment
- Read Biomass Under Fire (by Warren Cornwall, Science, Jan 2017)