Sources of biogas from feedstocks such as “livestock farm-waste (e.g. various manures, slurries and waste waters) and agro-industrial waste (from abattoirs, wineries, vegetable-processing plants, etc.)” [12]. This is why biogas is also described as the fuel produced through anaerobic fermentation of manure and vegetable matter in digesters, or the fermentation of animal dung, human sewage or crop residues in an airtight container [5]. Hence, the general belief is that liquid-manure systems work best for anaerobic digestion in the production of biogas. However, this is not so, except that the generation of biogas was indeed first associated with liquid wastes and sludge. So Kiely [13] explained that anaerobic digestion is used world-wide for the treatment of industrial, agricultural and municipal waste-water and sludge: he also noted that, in recent years, it has also been applied for the treatment of municipal solid-wastes. Hence Vassiliou [12], after successfully generating biogas from wastes of raw manure plus wash-water from large livestock-farms, and the wastes from food and drink industries, explained that the second stage of any project should be to generate biogas from the organic components of source-separated municipal solid-wastes (MSWs).