Prediction of livestock manure and mixture higher heating value based on fundamental analysis

The ongoing availability of livestock waste presents an opportunity for its utilization as renewable energy resource through biological or thermochemical conversion. However, the conversion efficiency and the potential energy content of livestock waste needs to be estimated in order to design such a renewable energy production system. To address this, eight types of livestock waste were collected from each of 12 commercial farms from April to May 2009. The higher heating value (HHV), which represents the actual energy content, along with characteristics of livestock waste was determined. Moreover, equations for estimating HHV from proximate, ultimate, and chemical analysis were established by regression analysis. The developed equations were then validated using additional livestock waste data. The HHV of livestock waste was found to be in the range from 11.92 to 19.44 MJ/kg dry matter. The equation, HHV = 0.1970VM + 0.3955 represents the best-fit equations derived from proximate analysis with an Average absolute error (AAE) value of 9.17%. The equation, HHV = 0.1865CH + 0.2671PR + 0.2141F − 0.2151 is best-fit equation derived from chemical analysis with an AAE value of 5.31%. The equation derived in this study, HHV = 0.3198C + 0.0803O + 0.4704N − 1.4502S + 0.9364, was compared with ten recently published correlations based on ultimate analysis and showed better accuracy by having the lowest AAE values of 8.57%. All developed equations can be used to estimate HHV of various livestock waste with the exception of swine manure. The main reason for this limitation arises from the unique characteristics of pig manure in comparison to other livestock waste found in this study.