Environmental Engineering Reference
In-Depth Information
option for heating that is being adopted by many industries and households that
are looking to use more sustainable energy sources.
In the European Union (EU) a set of binding laws called the Climate and Energy
Package were introduced to ensure that the EU would meet its ambitious climate
and energy targets by 2020. These targets, known as the “20-20-20” targets, are
expressed in three key objectives:
1. to reduce EU-wide greenhouse gas emissions by 20% relative to their 1990
levels;
2. to increase the share of EU energy consumption generated from renewable
resources to 20%; and
3. to increase EU-wide energy efficiency by 20%.
Meeting these targets will require action on several fronts, including the develop-
ment of various different bioenergy products that are tailored to match the
resources and facilities available in different regions. In addition, it will be impor-
tant to identify pre-existing infrastructure that could be used to facilitate the tran-
sition to a more bioenergy-focused system. Finally, economic, environmental,
national security, and technological factors must be considered for each of the
affected countries.
In general, biomass-derived fuels may be solids (e.g. chips, pellets), liquids
(e.g. ethanol, biodiesel), or gases (e.g. biogas, hydrogen). They can be classified
based on the processes used in their production, which include physical upgrading
(Section 7.2), microbiological processes (Section 7.3), thermochemical processes
(Section 7.4), and chemical processes (Section 7.5), as described in Figure 7.1.
7.2
Physical Upgrading Processes
7.2.1
Refinement of Biomass into Solid Fuels
The production of solid fuels from renewable resources (e.g. biomass) has become
more important due to the growing global demand for energy and environmental
concerns. Upgraded or refined solid biofuels include powdered fuels and densified
fuels such as briquettes and pellets. Some of the most common raw materials for
pellet production are shavings and sawdust from sawmills. However, there is also
an increasing interest in alternative biological raw materials such as grasses and
agricultural residues including corn stover, olive seeds, wheat straw, and peat [1].
7.2.2
Wood Powder
Wood powder is an upgraded fuel that is burned in large-scale combustion plants
for heat production. However, it is also suitable for power generation. It is made
from sawdust, shavings, and bark. The raw material is crushed, dried, and milled
into fine particles in order to obtain a fuel with optimal properties. Many different
grades of wood powder can be produced that differ in terms of physical properties
