Uses of biomass

USES OF BIOMASS

Biomass can produce three useful forms of energy, depending on the type of biomass and the techniques used:

•  Thermal,
•  Electrical,
•  Mechanical.

Biomass can also be converted into gaseous fuel (biogas, biomethane) or liquid fuel (biodiesel, ethanol)
Three processes of biomass valuation can be distinguished:

•  The dry process,
•  The wet process,
•  The biofuel production.

The dry process: It uses the thermochemical process which includes three technologies: combustion, gasification and pyrolysis:

(click on image to enlarge)

Dry process

• Combustion produces heat through the complete oxidation of the fuel, generally by presence of excess air. Hot water or steam thus obtained is used in industrial processes or urban heating networks. Steam may also be sent to a turbine or a steam engine to produce mechanical energy or, more importantly, electricity. The combined production of heat and power is called co-generation;

• Gasification of a solid biomass is performed in a specific reactor, the gasifier. It consists of a reaction between the carbon derived from biomass and reactant gases (water vapour and carbon dioxide). The result is the complete transformation, except the ash, of solid material, into a gas fuel composed of hydrogen and carbon monoxide (H2 and CO). This gas, after filtration and purification, is burnt in a combustion engine for generating mechanical energy or electricity. Co-generation is also possible with the gasification technology (Return to "Uses of hydrogen");

• Pyrolysis is the decomposition of the carbon-based material under the action of heat. It leads to the production of a solid - the charcoal, a liquid - the pyrolytic oil, and a gas fuel. A variant of pyrolysis, thermolysis, is being developed for the treatment of household organic waste or biomass contaminated.

The wet process:
The main process is methanisation. It is based on the degradation of organic matter by micro-organisms. It occurs in a heated digester without oxygen (anaerobic reaction). This process can produce:

• The biogas which is produced by anaerobic digestion of organic materials;

• The digestate is a by-product of methanisation. It consists of non-biodegradable organic matter.

For more information, see “Biogas”            ( click on image to enlarge )

Biomass plant diagram

Biofuels production:
Biofuels are liquid or gaseous fuels created from a reaction:

•  Between oil (rapeseed, sunflower) and alcohol in the case of biodiesel;

•  From a mixture of fermented sugar and gasoline in the case of bioethanol;

There are three generations of biofuels:

• 1st: biofuel created from seeds;

• 2nd: biofuel created from non-food crop residues (straw, stalks, wood);

• 3rd: biofuel created from the hydrogen produced by micro-organisms or from the oil produced by microalgae.

( click on image to enlarge )

Biofuel second generation

The second and third generations of biofuels have the advantage of not compete against food productions on agricultural land. Their industrial maturity, especially for the third generation, has yet to be established.
 
These biofuels can take different forms:

• •Vegetal Oil Methyl Ester (VOME or Biodiesel) produced, for example, from rapeseed;

• •Ethanol, produced from wheat and sugar beet, embeddable in unleaded petrol.                                                               

For more information, see “Biofuels”

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