The aim of this paper is to calculate how much energy or chemicals can be potentially produced using anaerobic digestion (AD). Five feedstocks were considered: the organic fraction of municipal solid waste (OFMSW), cattle, pig and poultry manure, energy crops, agricultural residues and sewage sludge. Carbohydrates, proteins and lipids were assumed to be the biodegradable components of the feedstocks. COD (Chemical Oxygen Demand) was assumed as a basis for the calculations of methane and chemicals production. Methane production was calculated assuming that AD converts the biodegradable COD to methane with a yield of 80 % COD/COD. The potential production of chemicals, i.e. acetic, propionic, butyric and lactic acids, ethanol and hydrogen, was calculated assuming conversion yields of carbohydrates, proteins and lipids from the literature. Globally, with the assumptions done in this study, AD of the considered feedstocks can potentially satisfy 17–20 % of the total energy consumption and 33-39 % of the electrical energy requirements. Potentially, AD can generate organic acids at rates which are hundreds or thousands of times their current production rates. Ethanol and hydrogen can be produced by AD at rates which are up to 2-3 times their current production rate. The paper also discusses the main challenges to overcome in order to achieve the large potential of AD.
Bibliographical noteThe authors wish to acknowledge CAPES (Coordination for the Improvement of Higher Education Personnel), Brazil, for funding the PhD studentship of Igor Silva. The University of Aberdeen is also gratefully acknowledged for the Elphinstone Scholarship awarded to Ifeoluwa Bolaji.
- anaerobic digestion
- organic waste
- volatile fatty acids (VFAs)