Towards sustainable energy‐crop cultivation: feasibility of biomethane production using a double‐cropping system with various sorghum phenotypes

To achieve sustainable energy crop production, energy crops should not compete for land against feed and food crops. One option for sustainable energy‐crop cultivation is the use of double cropping systems with minimum tillage use and digestate as natural fertilizer, where, in the same growing season, a second crop for biomethane production is planted after a first crop used for feed/food. Different sorghum phenotypes were evaluated in the present study as first and second crops in a double cropping system. A principal component analysis of the various sorghum phenotypes showed that starch content positively affected methane production. However, sorghum chemical composition did not influence the profitability of bioenergy production as much as the total solid biomass yields of the different sorghum phenotypes. The highest total solid biomass productive sorghum phenotype led to the highest methane hectare yield. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd