Bioenergy
We have to distinguish between the terms “bioenergy” and “biofuels”. “Bioenergy” is biomass which is used in energy systems to generate heat and/or electricity while the term “bio fuels” is used for liquid fuels for transportation. Biomass can be seen as a form of stored solar energy, because the energy of the sun is “captured” through the process of photosynthesis in growing plants. It is offered in form of firewood, bark and wood chips. During the burning of fossil fuels CO2 is released which has been locked up for million years in the ground. During the burning of biomass just CO2 is released that was absorbed as the plant grew. So we have a cycle that is called to be “carbon neutral”. In reality it is not so, because energy is also required for the production and transport of biomass. But by comparison with burning of fossil fuels the rate of released CO2 to the atmosphere is considerably lower: about 6 to 43 g CO2/kWh for solid biomass products compared with 247 g CO2/kWh (gas) to 452 CO2/kWh (lignite). It is the most significant difference in the energy production from fossil fuels and from biomass.
Bioenergy products can be separated into different categories:
- Solid Biomass
It is defined as organic, non-fossil material of biological origin which is directly used as fuel or converted into other forms before burning. Examples are wood, vegetable waste, animal materials, animal wastes…
- Fire wood, wood wastes, other solid wastes
- Renewable wastes
- Biogas
Biogas is generally composed of methane and carbon dioxide and is derived from the anaerobic fermentation of biomass and solid wastes. By combustion heat and/or power can be produced. Examples are landfill gas and sludge gas.
- Liquid biofuels
Typical liquid biomasses are fuels and bio-additives such as bio-ethanol, biodiesel, bio-methanol and bio-dimethylether. For the production of biodiesel initially rape seed and sun flower oil have been used as raw material, later frying fat was tested that offers also the benefit to be more cost effective. In recent years also developments have been made on the market for neat biodiesel. A big advantage of biodiesel production plants is their flexibility in view of the quality of the raw material used (cooking oil or animal fat). Generated by-products such as glycerine and solid fertilizers can be sold and contribute to the economic efficiency of biodiesel production.
- help topics
