Renewable Energy Sources for the mCCHP-SE-RES Systems - Design for Micro-Combined Cooling, Heating and Power Systems - page 103

biomass covers a wide range of products, by-products, and wastes from forestry,
agriculture, livestock, and municipal and industrial wastes. According to the
Renewable Energy Directive

biomass is the biodegradable fraction of products,
waste and residues from biological origin from agriculture (including vegetal and
animal substances), forestry and related industries including

“

fisheries and aqua-
culture, as well as the biodegradable fraction of industrial and municipal waste ” .

Biomass energy or “ bioenergy ” includes any solid, liquid, or gaseous fuel, or

electricity derived from biomass.
Under different forms, solid, liquid, and gaseous, the biomass can be converted
through various technologies in heat, electricity, and biofuels for transportation.
Biomass as raw material is presented in various forms, which are abundant in all
parts of the world including Europe. In recent years have been developed advanced
technologies for the conversion of biomass into fuels and for ef cient combustion.

Of course, not all resources can be used to produce energy. Biomass is also a source
of food, timber, paper, and some valuable chemicals. For this reason, the use for
energy production should be integrated with other priority applications.
All life on the Earth is based on green plant that converts atmospheric carbon
dioxide and water into organic matter and oxygen using the energy provided by the
Sun. This process is called photosynthesis. When the biomass is burned, the carbon
contained in plant is released into atmosphere in form of carbon dioxide. Therefore,
biomass is considered a neutral energy source in terms of the greenhouse gas
emissions. The chemical composition of biomass varies greatly depending on the
species, but it can be said that plants contain, on dry basis, (15 30) % lignin and

carbohydrates. The representative categories of carbohydrates are (40

-

- 45) % cel-

lulose and (20 - 35) % hemicellulose.

3.1 Biomass Sources and Technologies

The actual EU biomass potential is estimated to be 314 Mtoe and it will increase to
429 Mtoe in 2020, and will fall to 411 Mtoe by 2030 [ 13 ]. The agricultural residues
class (manure, straw, and cuttings/pruning from permanent crops) seems to have the
largest potential and the most substantial

increase is envisaged for dedicated

perennial crops.
At present, the biomass can be used to produce three different types of energy:
electricity, heating, and transport fuel (Fig. 9 ).
Electricity can be generated from following biomass sources:

solid biomass which was mechanically pretreated (wood chips, pellets, bri-
quettes, straw, dry manure, fuel derived from municipal solid wastes) can be

￿

fired power plants. This is a low-cost option
due to comparatively low investment. The conversion ef

red or co fired in conventional coal

ciency is practically
the same as for the fossil fuel. Small-scale boilers using biomass are often
integrated in cogeneration systems (having higher conversion ef ciency) to

compensate for lower electric ef ciency and higher costs;