Glossary

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• › A-Z Glossar Source: Agency of Renewable Resources
• › FAQ Source: Agency of Renewable Resources

1. What do we understand by the term "Bioenergy Carrier"?

Bio sources of energy are present in various form. Solid fuels include:

• Wood and wood off-cuts (residues) from industrial forestry and woodland management, from saw mills or from recycling wood,
• Energy wood, i.e. specifically cultivated, fast-growing tree species such as poplar and willow (Short Rotation Coppice - SRC)
• Agricultural residues (straw)
• Specifically cultivated energy plants on areas taken out of agricultural production (set-aside land).

Liquid bioenergy carriers which are of importance include:

• Sugar (cane, beet, etc.) which can be used for the production of ethanol,
• Oil plants such as rape seed and sunflowers for the production of vegetable oil.

As gaseous bioenergy sources:

• Biogas, which is produced by microbial digestion of agricultural residues such as liquid manure (also sewage and landfill)

2. What advantages do bioenergy carriers have?

• They are renewable, i.e. with prudent use & re-growth they can be replaced by natural processes.
• They are to a large extent CO2 - neutral, i.e. they do not contribute to the greenhouse effect.
• They store solar power, i.e. the sun's energy can be stored and used when required.
• They are available in solid, liquid or gaseous forms. This means that it is possible to use them in a wide range of areas.

3. Is there enough biomass available to create energy?

Estimations of the amount of biomass available for energy sources have been documented in many studies.

According to various studies it is possible to fulfill 5 to 10% of Germany's primary energy requirement by using biomass energy. In this case the equivalent amount of oil, natural gas, or coal would be replaced by biomass, so the replaced fossil fuels could be conserved. As renewable biomass would substitute fossil fuels, the released net amount of carbon into the atmosphere decreases, since renewable biomass energy is a zero carbon emitter.

Currently, however, biomass energy contributes only 0.8% to Germany's primary energy consumption. Just by using the presently available forestry and agricultural residues, Germany could increase primary energy provision from biomass by the factor 3.

Residues which could be used or partially used include:

• Straw from the cultivation of grain
• Grass cuttings from local areas
• Forestry residues

4. What are the technical aspects?

The oldest and still most common use of biomass energy is combusting. Therefore, over the recent years, most research and development has been done in biomass combustion. The plants available on the market today - either small firing, domestic or larger central heating stations - have all been developed to a high technical standard. They combine high efficiency with ease of use and comfort. They meet alt least the standards of semi-automatically and automatically fed plants or central heating systems running on natural gas or oil.

Wood chips are generally used for these systems. However, problems can arise from the storage of woodchips. In response to this, industrially manufactured, standardized fuel pellets have been produced. As a domestic fuel source the pellets provide a good solution since they combine high fuel quality with facilitation of transport and a long shelf-life.

5. What are the costs involved?

A high technical standard means that biomass technology is more expensive than the established gas and oil firing technologies. Another reason why biomass systems are more expensive is because they are not widely used, so there is only little competition. Furthermore, it is technically more complex to burn a solid fuel more efficiently and more emission-friendly than a gaseous or liquid source of energy. Thus, the initial costs for biomass systems, depending on size, are approximately 1.5 - 2 times more expensive than comparable fossil fuel systems. This additional financial expenditure can be at least partly reduced by the use of existing national advancement programs.

The operating cost of a such a plant is essentially determined by the fuel costs. Unfortunately, no fuel market exists for biomass systems so far in Germany. Biomass energy has not been able to establish itself in the market place, so there are very strong regional price differences, too.

6. What are the environmental implications of biomass energy?

The bio energy, like all renewable sources of energy, is particularly pollution free in terms of its production. In the first place there is the CO2 neutrality of these sources of energy.

However, biomass energy is usually burnt, so various compounds are released into the environment. Nitrogen oxides are released, since nitrogen is main part of air used with the burn. Aromatic hydrocarbons are also released. They cause the characteristic smell of a wood fire. Depending upon fuel, these pollutants are set free in quantities. The formation of water vapour is dominant, since biomass fuels are characterized by a high water content. This water vapour leads to the production of the water vapour flags, which can be seen from far away and are often mistaken for a high pollutant output. As long as uncontaminated fuels are used, emissions can be controlled with available technologies. However, if fuels are loaded with wood preservatives, high requirements for downstream emission control is necessary. Therefore, treated fuel materials require special combustion plants and should not be used in small firing plants.