The effect of various thermochemical pretreatment methods on the biomethanisation of hemp (Cannabis sativa) hurd and kinetic analysis

In this study, the effects of different pretreatment methods on the biochemical methane potential (BMP) of hurds from two hemp species, namely Narlisaray (NS) and Futura 75 (F), were investigated. The effect of pretreatment on BMP was discussed on the basis of the change in the chemical constituents of the raw material. The highest BMP yields of 272 mL CH4/g VS (F) and 218 mL CH4/g VS (NS) were obtained when the combined alkaline and thermal pretreatment was applied which resulted in the highest amount of hemicellulose degradation. (143% for alkaline and 74% for thermal, respectively, higher than those from raw hurds). It was found that BMP yields and the efficiency of pretreatment for two hemp species depended on genotypes, not on the content of chemical constituents of raw material. Additionally, the first-order kinetic model and the modified Gompertz model were simultaneously used to estimate the CH4 yield results of hurd. The first-order kinetic model resulted in the best fit [R-2 >= 0.96; root mean square error (RMSE) <= 0.225] with predicted yield for untreated control; while for pretreated hurds, the modified Gompertz model was the best fitting one (R-2 >= 0.98; RMSE <= 0.503).