Renewable energy

 

Providing a source of renewable energy is probably the biggest contribution that UK forests can make to reducing emissions of carbon dioxide. The Forestry Commission is working with other parts of government, industry and with society at large to realise this potential. Generating energy from renewable sources such as wood offers a number of benefits that include reducing fossil fuel usage – a major contributor to climate change – and other environmental and social benefits such as opening up markets to provide local employment and offering business opportunities for farmers and landowners.

Energy that is derived from trees, plants and other biological sources is known as ‘bioenergy’ and the materials used to provide this energy are known as ‘biomass’ or ‘biofuels’. The raw materials that can be used to produce biofuels are widely available across the UK and come from a large number of different sources, and in a wide variety of forms. Biofuels may be produced from virgin wood, purpose-grown forest crops or from the by-products of the forestry and sawmilling industries. These forms of biofuels are known as ‘woodfuel’ or ‘wood energy’. Other forms of biofuels include, for example, agricultural residues and the by-products of the food and other industries.

Biofuels can be used directly for heat energy or converted into gas, electricity or liquid fuels. These energy sources are referred to as ‘renewable’ because the trees and plants used to make them can be replaced. In contrast, fossil fuels such as coal, oil and gas are non-renewable. This is the vital difference between energy that is produced from biomass and that which is produced from fossil fuels. Burning fossil fuels releases carbon dioxide that has been locked up for millions of years. By contrast, burning biomass simply returns to the atmosphere the carbon dioxide that was absorbed as the plants grew and there is no net release of carbon dioxide if the cycle of growth and harvest is sustained.

Fossil energy is usually consumed in producing bioenergy, but research shows that usually the energy used is a small fraction of the energy produced. Typical energy balances for relevant forestry and agriculture systems indicate that roughly 25–50 units of bioenergy are produced for every 1 unit of fossil energy consumed in production. Producing liquid bioenergy requires more input energy, with roughly 4–5 units of energy produced for 1 unit of fossil energy consumed, but still reduces fossil fuel consumption overall. (Calculation of the energy balance for liquid bioenergy production is very complicated and the estimate shown here represents an average and is for example only.) Net carbon emissions from generation of a unit of electricity from bioenergy are 10–20 times lower than emissions from fossil fuel-based electricity generation.