Biomass and renewable resources
Biomass - definiton
A variety of terms and definitions are used when referring to biomass. Defining the term broadly, biomass denotes the totality of all living entities, of the present or the past, including the dead matter that remains from organisms that once lived. In the context of renewable energies, all organic matter of plant or animal origin that can be used as an energy source is characterised as biomass.
In its Renewable Energy Directive, the European Union defines biomass as follows: biomass is the biologically decomposable part of products, waste and residual material based on agriculture and of biological origin (including animal-based and plantbased substances), from forestry, and from associated sectors of business, including fishing and aquaculture. According to this definition, the biologically degradable part of waste matter from industry and households also counts as biomass.
Thus, biomass is (among other things)
- plants, constituent parts of plants, and the energy sources produced from plants and their constituent parts;
- waste and by-products (of plant and animal origin) from agriculture, forestry and fisheries and the respective downstream processing operations;
- waste wood from the forest-based industry;
- material from landscape conservation and various organic matter obtained by maintenance of water bodies, including their banks;
- waste wood and
- municipal organic waste.
The term biomass does not encompass biogenic fossil fuels such as petroleum, coal, natural gas and peat, as these do not replenish anytime soon, so they do not fulfil the criteria of renewability.
Wood, with its various points of origin, is currently the most significant energy source from biomass. Wood does not solely come from the forest. Apart from forest waste wood, the following should be mentioned as significant providers of wood (among others): waste/used wood from industry, wood from landscape conservation activities and from agriculture (like agroforestry or shortrotation coppice).
Read more about biomass considered within BIO-PROM.
Biomass - biochemical basics
In essence, biomass emerges through photosynthesis by plants. By means of solar energy, the carbon dioxide of the air, water and various nutrients combine to form biomasses which can be subdivided into the following groups of substance:
- wood and stalk-materials (lignin, hemicellulose and cellulose)
- sugar, starch and cellulose (carbohydrates)
- oils and fats
Photosynthesis takes place with oxygen being released in the process. The biomass produced as a result mainly consists of carbon, hydrogen and oxygen. Solar energy thus stored as chemical energy, e. g. in the form of wood, sugar, oils and fats. Photosynthesis is often displayed with a simplified formula, using sugar as an example.
6CO2 + 6H2O + light = C6H12O6 + 6O2
If biomass is used as energy, depending on the type of use, the carbon dioxide cycle remains closed to a large degree. Thus the CO2 balance is decidedly positive compared to fossil-based fuels, because the CO2 re-released at the time of use was removed from the atmosphere at the time when the plant grew and formed chemical bonds. However, the CO2 calculation should include the additional energy expended in harvesting, transporting, processing and converting the organic matter (into heat, electricity or fuel), in so far as this use of energy is not covered by renewable sources. For wood fuels such as firewood (typically logs), wood chips or wooden pellets, this additional expenditure of energy is particularly low, accounting for less than 5 percent of the fuels' energy content.
If fossil-based fuels such as coal or petroleum are substituted by biogenic energy sources, this makes an important contribution to avoiding additional CO2 emissions.
Viewing the possibilities and potentials, energy crops will have the largest contribution to make in the planned expansion of energy generation from biomass. Energy crops are cultivated specifically as an energy source and, according to choice, provide
- substrates for biogas production (cultivation of maize, grass, grain, sorghum, sugar beets and other crops);
- woody biomass or biomass containing lignocellulose for use as a solid fuel (e. g. rapidly growing trees, miscanthus and other tall grasses) and/or
- sugar, starch, or plant oils for biofuels (e. g. cultivation of rapeseed, grain, maize or sugar beets).
Energy crops generate regular and sustainable yields of biomass, as one-year and multi-year crops. Energy crops are part of renewable resources.