In theory any type of organic material that can decompose can potentially be fed into a digester. Practically, however, there are a few basic types of organic material that are commonly used in digesters of which by far the most common type is manure. Cow manure spicifically is very suitable since cows have 4 stomachs which means that by the time the manure is produced, the microbial action is already well on its way. Most of the large digesters around the world use either cow or pig manure and the biogas produced is used to generate electricity. Other types of feed material includes blood from abbotoirs, wey from cheese factories, yeast waste in breweries and much more.
The digester design greatly determines the ideal type of material that it is most suited to digest: fixed and floating dome digesters can be fed only with manure/sewerage and mulched kitchen waste, the Puxin design with manure/sewerage and any type of organic mulched material, lagoon digesters primarily with pig manure, Plug Flow digesters mainly with cow manure, Complete Mix digesters with cow or pig manure and ultimately an Up-Flow Sludge Blanket digester with waste water containing less than 2% solids.