Environmental Engineering Reference
In-Depth Information
Figure 12.12 The Königs Wusterhausen biomass power plant in Germany (left) and a wheel loader
for biomass fuel transport (right). Source: MVV-press photo.
Apart from its use in pure power plants, biomass is also appropriate for heat power
plants. In addition to electricity, these plants produce heat which district heating
grids distribute to consumers. Heat power plants generate both power and heat,
which is known as power-heat coupling. Heat power plants normally use biomass
fuel more effectively than pure power plants that only generate electricity. The
important thing is that a buyer can always be found for the heat that is generated.
Heat is not often needed during the summer months. During this time of the year a
heat power plant may operate less effi ciently than a power plant that is purely opti-
mized to generate electricity.
Heat power plants are also built in lower output classes so that they can be suitable
for industrial buildings, houses and apartment blocks. As these plants are usually
offered in a modular confi guration for a building-block style, they are referred to
as cogeneration units. However, the effi ciency of smaller systems is frequently
lower than that of large centralized systems. In addition to solid fuels like wood
shavings and pellets, cogeneration units use biofuels and biogas.
12.4 Biofuels
Fluid and gaseous biofuels are more versatile than wood. In addition to generating
heat and electricity, biofuels can be used directly as fuel in the transport sector,
replacing petrol and diesel. Production methods are available that can convert dif-
ferent biomass raw products into biofuels. Unlike with food production, the prefi x
'bio' in this case does not stand for controlled organic cultivation with minimum
effect on the environment. On the contrary, the raw materials for biofuels are usually
produced using conventional farming methods.
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