Estimation of material flow and greenhouse gas emissions from different piggery sewage treatment methods at the swine manure treatment system

<p>A livestock manure treatment is one of the sources of greenhouse gas emissions (GHG), CO₂, CH₄, and N₂O emissions through manure handling. The amount of these emissions differs from the manure handling type and the quantity and quality of wastewater and solids. The solid-liquid separator would increase and decrease GHG emissions due to changes in the material flow in manure handling systems. For example, the equipment reduces the BOD (biochemical oxygen demands) volumetric loading during the aeration process of purification, changing the quantity and quality of wastewater. Therefore, we evaluated four pig manure treatment systems (scenarios of a feces-and-urine separation system, a feces-and-urine mixture system, a sewage-dewatering system, and a sludge-dewatering system) to clarify GHG emissions from livestock manure treatment systems, including the effects of the solid-liquid separator, using the LCA method.</p><p>We assumed four manure treatment system scenarios based on 2,000 fattening pig farm scales. The system boundary was the processes of manure discharged from the livestock barn to composting and purification, and the evaluation stage was considered equipment construction and operation. The evaluated GHG emission was carbon dioxide, methane, and nitrogen dioxide. A comparison of the feces-and-urine mixture system, the sewage-dewatering system, and the sludge-dewatering system revealed the following. The sewage-dewatering system, separating sewage and sludge into solids and liquids, reduced GHG emissions by approximately 26% compared to the feces-and-urine mixture system. On the other hand, the sludge-dewatering system, which separates only sludge from solid to liquid, generated about 17% more GHG than the feces-and-urine mixture system.</p>