Conversion Technologies 79
Feedstock^1
Sugar and starch crops
Lignocellulosic biomass
(wood, straw, energy crop,
MSW, etc.)
Biodegradable MSW,
sewage sludge, manure, wet
wastes (farm and food wastes)
macroalgae
Photosynthetic
microorganisms,
e.g. microalgae and bacteria
Oil crops
(rape, sunflower, soya etc.)
waste oils, animal fats
(Biomass upgrading^3 ) +
Combustion
Transesterification
or hydrogenation
(Hydrolysis) + Fermentation*
or microbial processing
Gasification
(+ Secondary process)^4
Pyrolysis^5
(+ secondary process)
Anaerobic digestion
(+ Biogas upgrading)
Other biological /
chemical routes
Bio-photochemical routes
Conversion routes^2 Heat and/or power*
Liquid fuels
Biodiesel*
Ethanol*, butanols,
hydrocarbons
Syndiesel / renewable
diesel*
Methanol, ethanol,
alcohols
Other fuels and fuel
additives
Gaseous fuels
Biomethane*
DME, hydrogen
Figure 3.7Schematic view of the variety of commercial (solid lines) and developing bioenergy routes
(dotted lines) from biomass feedstocks through thermochemical, chemical, biochemical and
biological conversion routes to heat, power, CHP and liquid or gaseous fuels. Note: commercial
products are marked with an asterisk;^1 Parts of feedstock can be used in other routes;^2 Routes can
yield co-products;^3 Biomass upgrading can include densification;^4 Anaerobic digestion also produces
minor gasses;^5 Including related thermochemical routes like liquefaction. Reproduced with
permission from IPCC 2012: IPCC Special Report on Renewable Energy Sources and Climate Change
Mitigation. Prepared by Working Group III of the Intergovernmental Panel on Climate Change, Figure
TS.2.3. Cambridge University Press.
Pyrolysis– Pyrolysis as a process may be described as thermal decomposition
of a material under anoxic or limited oxygen conditions. The products of pyrolysis
depend on actual conditions of the transformation and are composed predominantly
of volatiles, gasses and to lesser extent high-molecular-weight hydrocarbons and char
(carbon enriched biomass) [18]. Pyrolysis is a platform for another two processes:
combustion and gasification.
Combustion– Combustion is process that releases energy from various products that
were obtained in the pyrolysis reaction. In excess of oxygen all these products (volatile
gasses and char) are oxidised to carbon dioxide (CO 2 )andwater(H 2 O) releasing sig-
nificant content of energy that can be captured. This highly exothermic process com-
pensates for the energy used in the processes of drying and pyrolysis and provides net
energy gain.
Gasification– Gasification is a process that transforms molecules through partial oxi-
dation, as opposed to combustion in which the transformation is performed in excess
of oxygen. Partial oxidation results in the production of less energy but higher quantity
of intermediate compounds that could be used as chemical feedstocks.
All these transformations take place in typical routes of thermochemical conversion of
biomass. These changes can be either endothermic or exothermic and produce various
intermediates that can become useful products when thermochemical conversion is
