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Thermochemical Processing of Solid Biomass
Tomasz Mirowski and Eugeniusz Mokrzycki
Contents
1.1Introduction
1.2Energy Resources from Biomass
1.3Biomass Conversion Technologies
1.3.1Combustion
1.3.2Gasification
1.3.3Pyrolysis
1.4The Hydrothermal Carbonation Process
1.5Conclusions
References
1.1 Introduction
There is no clear definition of biomass. In the scientific and technical literature there are various definitions of biomass, depending on the needs of the issue being discussed. Under EU legislation, ābiomassā means the biodegradable fraction of products, waste, and residues from agriculture (including vegetal and animal substances), forestry, and related industries, as well as the biodegradable fraction of industrial and municipal waste (Directive, 2009). The law in individual EU member states clarifies the definition of biomass, taking into account the specificity of the resources possessed and the possibilities for their management.
In Poland, biomass is understood as a biodegradable fraction of products, waste, or residues of biological origin from agriculture (including vegetal and animal substances), forestry, and related industries, including fisheries and aquaculture, processed biomass, in particular in the form of briquettes and pellets, of biocarbon, and the biodegradable fraction of industrial or municipal waste of plant or animal origin, including waste from waste treatment installations and waste from water and wastewater treatment, in particular sewage sludge, in accordance with the provisions on waste concerning classification of the energy recovered from thermal treatment of waste (Act, 2015). The introduction of new concepts to the definition of biomass in Poland, such as biocarbon, has enabled wider use of humid biomass with a low calorific value (6ā13 MJ/kg).
The energy value of plant biomass comes from solar energy used in the process of photosynthesis. It should be emphasized that biomass has a significant share in the energy consumed in developing countries. In addition, developed countries have shown considerable interest in biomass in relation to waste management and air protection.
The aim of this chapter is to discuss biomass conversion technology. Owing to space constraints of the publication, attention is focused on thermochemical processes of biomass processing only.
1.2 Energy Resources from Biomass
There is an increased interest in biomass as a potential source of energy for the following reasons (Dreszer et al., 2003):
ā¢Economicāacquiring biomass (not energy from biomass) is relatively cheap.
ā¢Striving for energy self-sufficiency owing to the allocation of other energy sources (especially fossil fuels).
ā¢Environmental protection, in particular the reduction of the greenhouse effect.
ā¢Reclamation of fallow and waste lands.
Biomass resources for energy purposes are diverse and can be divided into the following:
ā¢Primary energy sources, mainly used to produce biomass: wood, straw, and energy crops.
ā¢Secondary energy sources: liquid manure, organic waste, or sewage sludge.
ā¢Processed energy sources: biogas, bioethanol, biomethanol, biodiesel, and bio-oil.
The form of solid biomass (wood, straw) that is fed to the boiler is of decisive importance for the technical solutions used for its combustion, and thus significantly affects the economic performance of the investment.
The energy efficiency of cereal straw depends primarily on its moisture content, the composition associated with the type of straw (cereals, rapeseed, maize), and vegetation conditions of the plants. The average net calorific value of straw with a moisture co...