Bio-Energy, Biomass, Biofuel and Biogas
Bioenergy is renewable energy made available from materials derived from biological sources.
In its most narrow sense it is a synonym to biofuel, which is fuel derived from biological sources.
In its broader sense it includes biomass, the biological material used as a biofuel, as well as the social, economic, scientific and technical fields associated with using biological sources for energy.
This is a common misconception, as bioenergy is the energy extracted from the biomass, as the biomass is the fuel and the bioenergy is the energy contained in the fuel.
Biomass is any organic material which has stored sunlight in the form of chemical energy. As a fuel it may include wood, wood waste, straw, manure, sugar cane, and many other by-products from a variety of agricultural processes.
Depending on the type of biomass, it can be combusted either to generate heat or to produce electricity. It can also be digested to generate biogas, processed to produce bioliquids for heat or power generation, or used as a transport fuel, a "biodiesel".
Why use Biomass?
Biomass is a renewable, low carbon fuel that is already widely, and often economically available. Its production and use also brings additional environmental and social benefits. Correctly managed, biomass is a sustainable fuel that can deliver a significant reduction in net carbon emissions when compared with fossil fuels.
Categories of biomass materials
Biomass in various forms can be used for a range of energy options, through a variety of technologies, to achieve various end purposes.
Within this definition, biomass for energy can include a wide range of materials. There are five basic categories of material:
- Agricultural residues: residues from agriculture harvesting or processing
- Food waste, from food and drink manufacture, preparation and processing, and post-consumer waste
- Industrial waste and co-products from manufacturing and industrial processes
- Virgin wood, from forestry, arboricultural activities or from wood processing
- Energy crops: high yield crops grown specifically for energy applications
Using biomass to achieve a carbon balance
The combustion (direct or indirect) of biomass as a fuel also returns CO2 to the atmosphere.
Source: Environment Agency (2009): 'Minimising greenhouse gas emissions from biomass energy generation'
However this carbon is part of the current carbon cycle: it was absorbed during the growth of the plant over the previous few months or years and, provided the land continues to support growing plant material, a sustainable balance is maintained between carbon emitted and absorbed.
Biogas is a flammable gas that accrues from the fermentation of biomass in biogas plants.
Biogas is produced by anaerobic digestion or fermentation of biodegradable materials such as biomass, manure, sewage, municipal waste, green waste, plant material and energy crops. This type of biogas comprises primarily methane and carbon dioxide.
Biogas can be used as a low-cost fuel in any country for any heating purpose, such as cooking. It can also be used in modern waste management facilities where it can be used to run any type of heat engine, to generate either mechanical or electrical power. Biogas can be compressed, much like natural gas, and used to power motor vehicles.
Biodiesel is a biosynthetic fuel with similar properties as mineral diesel.
It is a biodegradable transportation fuel for use in diesel engines that is is typically made by chemically reacting lipids (e.g., vegetable oil, animal fat) with an alcohol.
It may be used either as a replacement for or as a component of diesel fuel (distinct from the vegetable and waste oils used to fuel converted diesel engines).
5 Good reasons to use biomass as a sustainable fuel:
- Correctly managed, biomass is a sustainable fuel that can both offer a significant reduction in net carbon emissions compared with fossil fuels.
- Biomass can be sourced locally, contributing to security of supply.
- Biomass can offer local business opportunities and support the rural economy.
- The establishment of local networks of production and usage, allows financial and environmental costs of transport to be minimized.
- Woodlands, forestry and agriculture are generally perceived to be an environmentally and socially attractive amenity by the population, providing opportunities for recreation and leisure activities.