Appropriate management of household, post-consumer and food production waste, together with animal manures and crop residues, enables both a reduction in pollution and production of renewable energy. The means to achieving these outcomes is treating organic wastes using anaerobic digestion to produce a methane-rich gas, biogas. In the UK/EU, regulatory controls and fiscal incentives have been applied to promote the use of anaerobic digestion to treat such wastes, reducing greenhouse gas emissions from landfilling food waste, while simultaneously producing renewable electricity, heat and biomethane. A brief review of the anaerobic digestion process and main process types is provided, in addition to considering different feedstock types. Reference is made to two anaerobic digestion technology scenarios that sought to identify the optimum technology combination to deliver gases/fuels to the commercial marketplace, based on the efficiency of energy production, energy capacity, avoided CO2 emissions and capital/operating costs. Project capital and operating costs vary with feedstocks, technology combinations and the outputs/end-uses, and developers/investors need to compare the estimated capital/operating costs of proposed projects to assess their economic viability. Using different metrics, it can be seen that organic wastes of different types can be treated successfully using wet/dry digestion technologies to produce biogas for on-site/off-site use as a fuel for gas engines/fuel cells, upgraded to biomethane for grid injection and/or liquefied for off-site use, or converted to hydrogen. The choice of plant size and technology combination/option are influenced by the choice of feedstock(s), which in turn influences both the capital and operating costs of a proposed plant and hence its viability. Anaerobic digestion is a technically and financially proven option, able to assist developed and developing countries to support many of the 17 UN Sustainable Development Goals, including helping end poverty; zero hunger by promoting sustainable agriculture; ensuring availability and sustainable management of water and sanitation; and ensure access to affordable, reliable, sustainable and modern energy; responsible consumption and production; climate action to combat the adverse impacts of climate change. The main focus of this chapter is how the anaerobic digestion of organic wastes provides positive outputs across a number of sustainability goals while minimizing the adverse environmental impacts of landfilling such wastes.
