Abstract
The semi-solid dairy manure from the loose housing system contents relatively large amount of sawdust as bedding material. In this study, the introduction of solid-liquid separation process by screw press in wet anaerobic digestion treatment system, which can treat the semi-solid manure, was investigated for composting the solid fraction without adding any secondary material and increasing the concentration of organic matter in the liquid fraction to improve fermentation effi ciency. The manure was mixed in digested liquid to pump easily to the separator in advance. The water content of the solid fraction decreased with either decreasing total solids in the mixture or increasing back pressure, and was easily achieved under 73.0 %, suitable for composting. EC was decreased by 30 %. The separation effi ciency of dry matter from the semi-solid or the slurry manure was at 79.3 % or 58.5 %. This was caused by sawdust almost completely removed. The ratio of easily decomposable organic matter to volatile solids in the liquid fraction was at 79 %, compared with 40 % in the initial manure. Moreover, the concentration of easily decomposable organic matters estimated to be more than twice by repeating mix of the manure in liquid fraction and separation three times.
