Due to the necessity for the reduction of the utilization of fossil fuels, the
share of renewable energy sources is expected to further increase in the near future.
Energy from biomass, alternatively defined as bioenergy, already provides the majority
of the renewable energy worldwide. In this chapter, the use of solid, liquid and gaseous
biomass as an energy source is presented, with particular emphasis being given to
biogas production by anaerobic digestion.
The chapter is divided into six parts: In the first, a brief description of the global energy
consumption and the expected trends are given. In the second part, the advantages and
disadvantages associated with the use of biomass as an energy source are discussed.
Furthermore, the sources of biomass (forestry, agriculture residues and energy crops,
waste), along with its properties are investigated. In the third part, potential fields for
the utilization of the three forms of biomass (solid, liquid and gaseous) for energy
production are described, along with ways for biomass upgrading.
In the fourth part, the process of Anaerobic Digestion is described in detail. Anaerobic
Digestion is a popular method of biological treatment that is suitable for many types of
wastes (sewage sludge produced by wastewater treatment, animal waste, the organic
matter of municipal solid waste) and leads to biogas production. Then, a common
model for the modeling of the process is presented. ADM1 (Anaerobic Digestion
Model No. 1) is applied on two wastewater treatment plants operating in Stockholm
and in Athens. In the fifth part, the factors that mostly affect Anaerobic Digestion are
discussed and the effect of selected parameters (temperature, digester volume, inflow
rate and number of digestion stages) is practically examined with the use of ADM1. In
the sixth part, the modification of ADM1 to enable its use on the treatment of olivemill
waste (wastewater and solid waste) is presented. The model is then applied to the
combined treatment of wastewater and solid waste of a small rural olive-mill. Finally,
in the Appendices, the suggested values of ADM1 parameters and the effect of selected
parameters of the model in biogas quantity and energy content are presented, along
with the suggested modification of the model parameters for its application on olivemill
waste.
Keywords: Bioenergy, Biogas, Energy Production, CHP, Power, Heating, Waste
Treatment, Anaerobic Digestion, Wastewater.