Bioenergy

What is bioenergy?

The energy stored in biomass (organic matter) is called bioenergy. This energy has generally been produced through photosynthesis or is an organic by-product from a waste stream.

Bioenergy can be used to provide heat, make fuels, and generate electricity.
Wood, which people have used to cook and keep warm for thousands of years, is the biomass resource people are most familiar with. Today there are also many other types of biomass we can use to produce energy. These biomass resources, also known as feedstocks, include agricultural, forest and livestock residues; energy crops; aquatic plants; landfill gas and wastes produced by cities and factories.

Through a variety of processes, these feedstocks can be directly used to produce electricity or heat, or can be used to create gaseous, liquid, or solid fuels. The range of bioenergy technologies is broad and the technical maturity varies significantly.

Some examples of commercially available technologies include small- and large-scale boilers, domestic pellet-based heating systems, and ethanol production from sugar and starch. Liquid biofuel production from algae is an example of a potential bioenergy technology at the research and development (R&D) phase.

Sources of Bioenergy

Biomass is all organic material, an example being plant matter. It is either:

  • the direct product of photosynthesis (for example plant matter – leaves, stems, etc.) or
  • the indirect product of photosynthesis (for example animal mass resulting from the consumption of plant matter).
Wood energy and supply chain: Wood fuels are available in a number of generic forms. These include wood wastes, forest residues and energy crops. Some wood fuels are processed to provide a higher quality and more user friendly product such as wood pellets and wood chips.
Liquid Biofuels i.e. fuels derived from biomass crops or by-products that are suitable for use in vehicle engines or heating systems.
Miscanthus is a perennial, rhizomatous grass, originating from Asia, which possesses the C4 photosynthetic pathway. The most common species is Miscanthus giganteus which is a sterile triploid hybrid of M. sacchariflorus and M. sinensis.

Bioenergy Technologies

There are a number of processes that can be used to recover energy from biomass fuels (liquid biofuels not included)

  • Combustion: Biomass (e.g. wood chips or wood pellets) can be burned to provide process and/or space heating. This process can take place in small domestic stoves or boilers. The combustion of biomass can also be used to raise steam to drive engines/turbines which are coupled to generators producing electricity. This process is then called Biomass-Combined Heat and Power (Biomass-CHP)
  • Anaerobic Digestion (AD): Biomass (e.g. animal manure) can be transformed to biogas by anaerobic digestion and the biogas, which consists mainly of methane and carbon dioxide, can be used to fuel a gas engine or gas turbine, or burned in a boiler to provide heat or to raise steam.

Other technologies for the exploitation of bioenergy include gasification and pyrolysis but these are not as commercially developed as combustion, Biomass-CHP and Anaerobic Digestion.

 


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