Production of biogas from the industrial hemp variety, Tiborszállási

Abstract

The suitability of industrial hemp as an alternative substrate for biogas production was evaluated. The influence of the growing stage and fertilization regimen on biogas and methane production was determined. The effectiveness of a common NPK fertilization strategy was compared with the application of biogas plant (BGP) byproducts (liquid and solid phase of the digestate). Hemp biomass was harvested four times during the growth cycle (five leaf pairs, flower formation, beginning of flowering, seed maturity). The samples of hemp biomass from the tested combinations (vegetation period × fertilization strategy) were subjected to anaerobic digestion in laboratory batch reactors for 60 days, and the amount and composition of the released biogas were determined. The yield of biomass and dry matter content increased with the age of plants reaching up to 12.0 t/ha and 32%, respectively. The highest methane production was observed for hemp in the first sampling (309-316 L CH4/kg of organic dry matter, ODM); the lowest production came from hemp at full maturity (289-302 L CH4/kg ODM). Due to a significant growth of hemp biomass during the vegetation period, methane hectare yield (MHY) grew from 142-175 m3/ha for the first growing stage to 2780-3230 m3/ha for the final stage. The average methane content reached approximately 60%. There was no observed significant difference in biogas production between the different modes of fertilization; thus, BGP byproducts were an effective alternative source of nutrients for hemp planting.