Converting Residual Biomasses into Energy through Anaerobic Digestion

The continuously increasing production of wastes represents a terrific challenge to cope with in the today’s society. European Union, in the last years, has planned to carry out many actions for sustainable waste management as well as waste prevention and reduction. These actions, which represent a path toward the reduction of pollution and greenhouse gas emissions, fall under the “Circular Economy” umbrella and are of main concern in the EU. In the last years, many research activities have been carried out with the aim to maximize the bioenergy production from organic wastes, mainly food industry, urban waste sector and agricultural residues. Since organic wastes represent a largely available and cheap raw material, they are considered as the optimal substrates to be dealt with. In addition, their use for producing bioenergy or biomaterals could reduce or eliminate the need for their disposal in landfills, which adversely impacts on the environment. In this chapter, after an introduction in which a review of actions proposed by EU and statistical data on biomass use are reported for the whole EU and some European countries, a detailed description of the different charatcteristics of animal and agricultural residual biomasses is given, also discussing the potential negative impact of using crop residues for energy use. Dark anaerobic fermentation and the role of the microbial population on its different phases is also assessed focusing on the biogas production. A short description of the denaturing gradient gel electrophoresis (DGGE) is given to highlight the profile of bacterial communities in the different substrates and theirdynamic changes during dark fermentationas affected by different operational parameters (e.g., pH, temperature). Some specimen results are presented to show that water buffalo manure can be used to produce H2 and CH4 by the anaerobic digestion process without any addition of nutrients or external microbial communities. Also, optimal process conditions for hydrogen and methane production are reported. The use of biogas, both biomethane and biohydorgen, as fuel for energy equipment is at last discussed, focusing on the different systems, their costs and pros and cons, highlighting the large possibilities of using biogas with different energy devices.