Beneficial Use of the Solid Fraction of the Digestates

Completing the digestion of poultry litter is only half the battle because the digestates from anaerobic digestion can be a disposal problem due to its high nutrients (liquid portion) and organic matter content (the solids fraction) that remains to be a threat to water bodies if long-term land application is the only option. Due to lack of lignocellulosic enzymes in anaerobic bacteria, the majority of the bedding materials will largely remain intact after the digestion treatment and end up in the solids fraction of the digestate. Unlike the liquid portion of the digestate that can be used as crop fertilizer, the solids fraction has limited use as fertilizer and transporting it away from the production site for disposal will certainly add to the production cost. Therefore, in this part of study, the beneficial use of the solids fraction of the anaerobic digestates will be the center of investigation, which also constitutes a component of fundamental research that may result in applicable technologies for poultry litter treatment in the future.

Although the lignocellulosic residues in the digestate are not degradable by anaerobic bacteria, they can be degraded by fungi, which have a wide range of enzymes that can break down lignocellulose. This has led to increased research in using fungi to produce edible mushrooms from agricultural residues. However, using animal bedding and residues such as poultry litter in this endeavor is still in its infancy and needs further research. According to past research, a number of fungal species are able to grow on lignocellulosic substrates through mushroom production such as Pleurotus ostreatus and Agrocybe aegerita. More knowledge is needed to clearly understand how poultry litter affects lignocellulose utilization in relation to enzyme production and mushroom yield by these two fungi. Therefore, experiments will be designed to accomplish this research objective. Since Arkansas is the #1 rice production state in the US, rice straw will be used to form the substrate for mushroom growth, which has not been reported in the current literature.