Who could have imagined bioenergy rather than wind bioenergy supplying more than 50% of all energy produced from renewable resources? Statistics show that the proportion of wind, water, solar energy, biomass and soil heat is constantly growing. Estimates for 2005 show that 6.4 percent of all energy production comes from renewable sources; in 1998, the comparable proportion was as low as 3.1 percent.
Available renewable energy sources (Figure: BEE)
Mineral oils, natural gas, black and brown coal and nuclear energy are still the principal resources that satisfy our hunger for energy. Funding programmes, quota and political specifications have so far been unable to overturn this David and Goliath relationship between sources of energy. However, the enormous costs of fossil energy are gradually making renewable energies economically viable resources.
A sign of the growing significance of renewable energies is the fact that they are now also very much part of the industrial, political and employment agendas. The driving force behind the growing demand for renewable energies is the Renewable Energy Law (electrical energy market), the new EU guideline on biofuels and the Regenerative Heat Law (heat market), which the Federal Ministry of Environment Ministry intends to discuss soon.
The term ‘bioenergy’ has come to be used as a collective term referring to all kinds of energies produced from solid, fluid or gaseous biomass. According to the FNR’s (Agency of Renewable Resources - project management organisation of the Federal Ministry for Agriculture) definition, biomass is all organic substance produced or originating from plants or animals. Experts group energy that is produced from biomass into renewable resources, energy plants and organic waste.
Germany supports renewable resources: More than 1.4 hectares (=12%) of the entire agricultural area are used to grow industrial and energy plants (Figure: Agency of Renewable Resources, FNR)
Renewable materials include fast-growing tree species (such as poplars), certain annual energy plants, sugar- and starch-containing field fruit used to make ethanol as well as oil fruit such as rape, which is used for the production of fuel (biodiesel). The extended definition of bioenergy to eventually include organic waste from agriculture and forestry, industry and private households, is set to influence the statistical information in a big way. Organic waste will then include waste and residual wood, straw, grass, leaves, manure as well as sewage sludge and organic domestic waste.
Solar energy that is already stored
Bioenergy is no more than stored solar energy that is converted by photosynthetic plants into organic matter. In contrast to other renewable resources, plants can be seen as the natural storage medium of solar energy. Different technologies and methods are used to convert biomass, depending on the type of energy required and the purpose to which it is put. The classical process is the production of heat from wood that is cut into small pieces, pressed into pellets and burnt. This technology, which is also used in large-scale energy production, is primarily used for the small-scale production of heat although it can also be used for the production of electricity.
Purification to precede utilisation
Solid organic fuels are converted into solid, fluid or gaseous secondary energies in thermochemical, physicochemical and biochemical processes. Although a considerable amount of research is devoted to pyrolysis technology (liquefaction of biomass or BtL (biomass to liquid)), it is – according to expert opinion – still at the research and development stage. Numerous research institutions are currently developing different research and pilot technologies.
A biogenic, fluid energy source with a relative high-energy density can be transported easily and universally used. Suitable raw materials include wood-like fuels, straw or energy crops. Following gasification, fluid fuel is synthesised from the gas produced. The development of such designer fuels also involves partners from the mineral oil industry and car manufacturers. There is one particular German company that hopes to be able to produce 1 million tons of bioenergy per year by 2010.
Experts regard the gasification of biomass as a sustainable process for the production of electrical power. Nevertheless, the production of fuel gas is associated with numerous problems such as the problems of purification. Oil and fat extracted from rape or sunflower seeds can also be used for the production of bioenergy. Purified oil can be used as fuel in specific engines or for the production of heat and power (combined heat and power plant). Currently, these oils play a subordinate role (0.15 million tons in 2005). The use of fuels produced by the esterification of oils that can be used similarly to fossil diesel fuel is more common. The best-known example of this type of fuel is biodiesel (1.7 million tons in 2005).
Biogas is a true multi-talent
Biogas, a methane-containing gas mixture that is generated during the anaerobic degradation of organic substances, is becoming increasingly popular, thanks to the Renewable Energy Law. The gas, i.e. the methane contained therein, can be processed and used in gas burners or engines. Although the large-scale process engineering technology (in the case of gas from purification plants) has been established, problems are still encountered in the use of the heat produced. Potential applications are seen in its use as fuel. The major proportion of biogas activities in Germany is concentrated in Southern Germany.
High fuel prices have once again brought bioethanol (0.2 million t/2005) to our attention. According to information from FAO experts, agricultural ethanol made from sugar cane can compete with a crude oil price of 35 US $ per barrel. For cost efficiency reasons, biofuel is mainly produced in Latin America. In Europe, in particular in Sweden and France, but also in Germany, increasing efforts are being made to mix ethanol with regular fuels or to offer ethanol (E85) as an alternative for use with standard petrol engines, which is a major objective of Crop Energies (subsidiary of Südzucker). Experts also attest methanol’s growing importance, as it is the simplest of all alcohol fuels. It can be produced by gasification from dry biomass and used in petrol engines and fuel cells.
wp - 22.05.2006