The energy efficiency analysis of sorghum waste biomass grown in a temperate climate

Sorghum is the fifth most important cereal worldwide. Mostly it is grown in tropical and dry types of climate. This study aimed to investigate the amount of the energy and heat produced during anaerobic digestion from sorghum waste biomass from cultivation for grain in the climatic conditions of Central Poland. The analyzed varieties have not been previously tested for their biogas and methane efficiency. Moreover, none of the studies were based on waste biomass from sorghum grain cultivation from regions as far north (above 50°N latitude). Four prospective varieties of sorghum were selected for field research. Straw with deseeded panicles constituted the research material. The tested parameters were i.a., biogas and methane efficiency. The biogas efficiency was determined from 437.76 m3‧Mg−1 FM to 494.67 m3‧Mg−1 FM. For all analyzed varieties, the amount of electricity that could be produced from 1 Mg of total solids of raw material ranged from 1.00 to 1.12 MWh, while in the case of heat generation it ranged from 3.75 to 4.16 GJ. The results indicate that it is possible to effectively cultivate sorghum above 50° North latitude in Europe. High drought resistance and great yield potential indicate sorghum as a preferred crop in the changing climatic conditions of central and northern Europe. The obtained results may be important also for the Northern states of the USA and parts of Canada.