Current state and future of biogas and digestate production

Over the past few years, the worldwide cost of energy has increased significantly, due to a growing global demand for energy and the decreasing availability of fossil fuel sources. Many countries are adopting environmental policies promoting the production and consumption of alternative, sustainable and renewable energy sources. Among these sources is green energy production through the anaerobic digestion of agricultural feedstock, like animal manure and food industry by-products, mainly aimed at producing biogas. Nevertheless, only a very small part of the biogas potential is currently used, while many European countries are facing huge problems caused by the overproduction of organic waste from industry, agriculture and households. Biogas production is an excellent way of using organic waste for energy generation, followed by the recycling of the digested substratum (digestate) as fertiliser. Many factors, like chemical composition and pH of raw materials, environmental temperature and microbial composition, influence the efficiency and reliability of the anaerobic digestion process. This paper reviews the current state and perspectives of biogas and digestate production, including the above factors influencing the biogas and digestate yields of anaerobic digestion.