Environmental Engineering Reference
In-Depth Information
a gas connection with new buildings. The cost advantage of wood pellets compared
to oil and gas is in the lower running costs of pellet heating. Depending on usage
and the price development of fuels, wood pellet heating can be amortized in just a
few years. The fuel prices for log heating are lower than with pellet heating. The
operating costs are therefore even lower.
The demand for biofuels is clearly increasing worldwide due to high oil prices and
the simultaneous increase in energy demand. This is also putting additional pressure
on food prices. Grain and corn prices have reached new records in recent years.
This development has also raised some ethical issues. Is it right that the quantity of
food products being processed into biofuels is increasing when more and more
people are unable to afford basic food as it is? An alternative is offered by second-
generation biofuels such as BtL fuels and biogas, which can be produced from the
non-edible parts of plants.
The Renewable Energy Law in Germany regulates the feed-in-tariff rates for
biomass power plants. These tariffs show the current rates needed to operate com-
mercial biomass power plants. The tariffs can differ considerably depending on the
biomass fuel used and power plant output. The maximum plant output eligible for
compensation is 20 megawatts. In 2009 the feed-in-tariffs ranged from 4.16 cents
per kilowatt hour for a 5-megawatt power plant using methane up to 11.67 cents
per kilowatt hour for a 149-kilowatt biomass power plant. In addition, bonuses of
up to 16 cents per kilowatt hour are given for power-heat coupling, the use of renew-
able waste and innovative plant technology. The amount of the tariff is based on
the year a plant starts operation and is then valid for 20 years.
12.7 Ecology
Biomass has also come under fi re for ecological reasons. For example, a farmer in
Indonesia who sets fi re to a hectare of rainforest in order to grow palm oil for
biodiesel to sell to Europe or North America is certainly not helping to protect the
climate. Priority should only be given to the sustainable production of biomass
raw materials if biomass really is to offer a long-term ecological alternative to
fossil fuels.
12.7.1 Solid Fuels
As explained earlier, biomass use is carbon-neutral. During its growth biomass
absorbs as much carbon dioxide as it releases again when it is burnt. However, the
prerequisite is that the use of biomass is sustainable. Therefore, the amount of
biomass that is used should be no higher than what grows back again.
In many countries, solid biomass fuels such as wood and straw usually come from
forestry or grain farming in nearby areas. Although the felling of trees, their trans-
port and fi nally the processing into fuel creates indirect carbon dioxide emissions,
these emissions are comparatively low. For cut wood from the direct vicinity they
