Bio-energy is renewable energy made from material of recent biological origin derived from plant or animal matter, known as biomass.
Biomass is a versatile fuel that can be used in different ways and at different scales, from householder installations, through community scale projects, to large electricity generating stations:
Dry biomass can be burned through a range of conventional boilers, combined heat and power units, and more innovative advanced thermal conversion technologies to produce heat and/or to make steam to drive a turbine to produce electricity.
Wet biomass can be anaerobically digested to produce a flammable biogas (mainly a mixture of methane and carbon dioxide). This biogas can then be used for heat or electricity generation. Alternatively, the biogas can be further processed and refined to around 100% methane, ‘biomethane’, and injected into the national gas grid.
The UK has a binding target under the European Commission’s Renewable Energy Directive [External link]to source 15% of our overall energy from renewable sources by 2020. To achieve this we need to use all our available renewable resources in the most cost-effective way. Bio-energy will play a key role as it has the potential to provide about 30% of our 2020 target.
SOURCES OF BIOMASS
There are a wide variety of biomass sources in the UK. Imports will also play a part. Biomass used for heat and power is generally derived from the following:
Virgin wood from the conventional management. of trees. This includes thinning, felling and coppicing of sustainably managed forests, parks and urban trees;
Wood residues from sawmills and other wood processing industries;
Agricultural energy crops such as short rotation coppice (SRC), or miscanthus (a tall, woody grass) which may be grown on land unsuitable for food crops;
Agricultural residues such as straw, husks and kernels;
Wet waste including sewage sludge, animal manure and food waste that would otherwise be disposed of in landfill.
Organic biodegradable proportion of municipal solid waste, commercial and industrial waste, and construction and demolition waste.
WHAT ARE THE BENEFITS?
Bio-energy has a wide range of benefits, including:
Helping to mitigate climate change by reducing greenhouse gas emissions;
Providing very cost-effective energy, relative to other renewables technologies;
Providing a controllable energy supply, so balancing intermittent technologies such as wind and solar;
Reducing our reliance on imports of fossil fuels, giving us a more secure energy supply. This also helps reduce the impact of changes in global oil & gas supplies and their spot prices;
Creating green jobs across the fuel supply chain, particularly in rural areas.
HOW DOES BIO-ENERGY REDUCE CARBON EMISSIONS?
Carbon is absorbed from the atmosphere during the growth of the plant. When used as a fuel, the carbon is released back into the atmosphere. By comparison, the use of fossil fuels such as oil and coal releases carbon captured millions of years ago and so adds to the overall carbon emissions to the atmosphere.
The carbon savings from biomass can vary widely because the savings are offset by the fossil energy that is used for cultivation (such as fertilisers), harvesting, processing and transportation. Major land use change, particularly deforestation and draining of peat bogs, can completely negate the carbon saving, as well as cause damage to biodiversity and other ecosystem resources. It is therefore critical that biomass resources are grown sustainably.