Designing adapted sorghum silage types with an enhanced energy density for biogas generation in temperate Europe

Sorghum is regarded a promising bioenergy crop and may be an alternative to maize for biogas use in temperate Europe in the near future. Presently, the principal shortcoming compared to maize besides chilling sensitivity during juvenile development is that current sorghum varieties fail to combine a high dry matter yield with adequate dry matter content for silage and satisfying methane yield. Our major goal was to evaluate whether early-maturing silage type Sorghum bicolor hybrids with a higher contribution of panicles and grains to total dry matter may allow an improvement of methane yield, representing a novel, alternative variety type for biogas use in temperate Europe. Our results indicate that under adequate conditions, they reach higher dry matter contents. Due to enhanced methane yields per dry matter unit which offset slightly lower dry matter yields, their methane yield per area unit is similar or superior to existing biomass type varieties. Since panicles account for up to 50% of total dry matter yield, seed set and maturity in cool environments represent critical factors for yield stability. Breeding efforts focus on chilling tolerance during flowering to avoid male sterility and on the development of appropriate parental lines combining earliness and adequate height. While selection for maturity can be reliably conducted on per se performance of parental lines, hybrid yield is predominantly determined by general combining ability. (C) 2015 Elsevier Ltd. All rights reserved.