The Higher Heating Value (HHV) Estimation Method for Biomass Crops and Differences in HHV among Species

Abstract

A higher heating value (HHV) for an energy crop as a directly combustible material is an indices for choosing a herb species. HHV is measured by calorimetry; however, measuring a large number of samples for studies such as a plant breeding study is difficult. Therefore, we developed a method to estimate HHV from chemical composition. We investigated HHVs of some herb species as energy crops. Eight varieties of seven herb species were cultivated for 3-4 years with two fertilization levels and were harvested once or twice per year. Using calorimetry, HHV was measured from chemical composition for 31 of 165 samples. The actual values, the values estimated using the nutritive value of the feed (estimating method 1), and those estimated using carbon content (estimating method 2) were compared. Significant correlations were observed between the actual values and both estimated values. The actual values and those estimated by method 1 were not different, whereas a significant difference was detected between the actual values and those estimated by method 2. This result suggests that estimating method 1 was suitable to estimate HHV of herb species’ energy crops. The mean of the estimated HHV for all samples was 18.1 MJ/kg (dry weight), and the standard deviation was 0.29 MJ/kg (dry weight). Significant differences were observed among the herb species using analysis of variance.