Solid State Digestion of Poultry Litter
This part of research is more fundamental with the goal of obtaining scientific information for developing advanced treatment technologies for poultry litter. Different from much of the past work in anaerobic digestion of poultry litter where dilution of substrates prevails to reduce the negative effect of nitrogen, high solids digestion is gaining interest among researchers because it can obviate the dilution treatment. The basic idea of high solids digestion is to extract the ammonia, which is detrimental to the digestion process, before digestion. After reducing the ammonia content in the poultry litter, the solids fraction can undergo anaerobic digestion while the extracted ammonia can be used as crop and vegetable fertilizer. There are a number of methods to extract ammonia from poultry litter including using water, chemicals, and even ammonia strippers. However, soaking poultry litter in water to solubilize ammonia initially present is a simple but potentially more applicable method that has not been extensively examined. After soaking, the mixture can be treated with chemical settling agents such as polyacrylamide to remove solids that can undergo high solids anaerobic digestion, while the remaining liquid rich in ammonia can be used as fertilizer or a substrate for other uses. More research is needed to determine the maximal solids level that the digestion process can handle despite reported values found in literature ranging from 10 to ̴ 22% (at which level the digestion process was completely inhibited). The outcomes from this project may lead to an applicable technology for on-farm treatment of poultry litter cost effectively.