Biomass

Huge potential

Biomass use for power generation is comparatively minor. Only about 18.4 gigawatts were installed worldwide in OECD countries in 2000, which is about 1% of total power generation capacities. Nonetheless, the potential for power production from biomass is huge.

Worldwide, biomass could deliver 9% of global primary energy and 24% of electricity requirements by the year 2020. Biomass use in combined heat and power production systems is the most efficient.

According to a report by WWF and the European Biomass Association, biomass could meet 15% of OECD’s electricity needs by 2020.

Industrialized countries between them have over1,500 million hectares of crop, forest and woodland, of which some 460 million hectares are cropland. Achieving the 15% target could require an average of 1.25 million hectares of cropland per year to be converted to energy plantations. This represents just over 2%of the total land area in industrialized countries.

What is biomass?

Biomass is the name given to any recent organic matter that has been derived from plants as a result of the photosynthetic conversion process. Biomass energy is derived from plant and animal material, such as wood from forests, residues from agricultural and forestry processes, and industrial, human or animal wastes. Biomass is not fossilised material (like oil, coal and gas) but fresh material that can grow again after having been harvested. During growth plants use atmospheric carbon dioxide (CO₂) to build up their substance – if growth and use are balanced the use of biomass is carbon-neutral.

Bioenergy

The energy value of biomass from plant matter originally comes from solar energy through photosynthesis. The chemical energy that is stored in plants (and in animals because they eat plants or other animals), or in the wastes that they produce, is known as bioenergy. When burning, biomass produces energy in the form of heat, and the carbon is reoxidised to carbon dioxide and released back into the atmosphere.

A form of renewable energy

Of all the renewable sources of energy, biomass is unique in that it is effectively stored solar energy. Furthermore, it is the only renewable source of carbon, and is able to be processed into convenient solid, liquid and gaseous fuels.

Biomass resources

Biomass resources that can be used for energy production cover a wide range of materials. The use of biomass energy can be separated into two categories:

• Traditional biomass is generally confined to developing countries and small-scale uses. It includes fuel wood and charcoal for domestic use, rice husks, other plant residues and animal dung.
  
  
• Modern biomass usually involves large-scale uses and is a substitute for conventional fossil fuel energy sources. It includes forest wood and agricultural residues; urban wastes; and biogas and biofuels from energy crops (such as plant oils and plants containing starch and sugar).

Bioenergy applications

Bioenergy applications are extremely diverse, including heat supply, power generation and transport fuels. Biomass can be used directly (eg burning wood for heating and cooking) or indirectly by converting it into a liquid or gaseous fuel (e.g. ethanol from sugar crops or biogas from animal waste).

• Traditional biomass use in open hearths for cooking and heating continues to be very important in developing countries due to a lack of alternatives. Elsewhere, burning wood in small systems such as stoves or open chimneys for heating has a long tradition. Processed wood wastes in the form of pellets or chips are now used in innovative heating systems.
  
  
• Modern biomass is used to produce power and heat in large-scale facilities:
   -  Solid biomass such as wood discards, yard wastes and straw can be burnt in specially designed power plants, or together with coal in existing coal-fired plants. 
   -  Biogas can be extracted in special facilities from, for instance, agricultural residues such as slurry. It can either be fed into gas networks, or used to produce power and heat.
   -  Biofuel or biodiesel are generated from plant oils extracted from plants such as rape, sunflower or oil palm.  Plants containing starch and sugar (such as potatoes and sugar beet) yield bioethanol after fermentation. Solid biomass can also be processed to make hydrogen or methanol.

Environmental impacts

Biomass use for energy can make a major contribution to climate protection and resource conservation, regardless of whether wastes or specially cultivated crops are used. It can also be used in all applications - power, heat and fuels. Using biogas, digester gas and landfill gas for energy is beneficial for the climate, but also presents opportunities for farmers who can enhance the value of their slurry and reduce odour emissions.

However, bioenergy production can have negative environmental impacts such as acidification, eutrophication or summer smog. The production of energy crops can also have negative impacts depending on what agricultural or forestry methods are used.

In each application standards must therefore be set for the best possible methods of production – both for sustainable management of the landscapes and for maximum energy gain. WWF is working across its own programmes – climate and energy, forestry, agriculture, freshwater – to determine such standards.