Environment and harvest time affects the combustion qualities of Miscanthus genotypes

Miscanthus spp. are high-yielding perennial C-4 grasses, native to Asia, that are being investigated in Europe as potential biofuels. Production of economically viable solid biofuel must combine high biomass yields with good combustion qualities. Good biomass combustion quality depends on minimizing moisture, ash, K, chloride, N, and S. To this end, field trials at five sites in Europe from Sweden to Portugal were planted with 15 different genotypes including M. X giganteus, M. sacchariflorus, M. sinensis, and newly bred M. sinensis hybrids. Yield and combustion quality at an autumn and a late winter/early spring harvest were determined in the third year after planting when the stands had reached maturity. As expected, delaying the harvest by three to four months improved the combustion quality of all genotypes by reducing ash (from 40 to 25 g kg(-1) dry matter), K (from 9 to 4 g kg(-1) dry matter), chloride (from 4 to 1 g kg(-1) dry matter), N (from 5 to 4 g kg(-1) dry matter), and moisture (from 564 to 291 g kg(-1) fresh matter). However, the delayed harvest also decreased mean biomass yields from 17 to 14 t ha(-1). There is a strong interaction among yield, quality, and site growing conditions. Results show that in northern regions of Europe, M. sinensis hybrids can be recommended for high yields (yielding up to 25 t ha(-1)), but M. sinensis (nonhybrid) genotypes have higher combustion qualities. In mid- and south Europe, M. X giganteus (yielding up to 38 t ha(-1)) or specific high-yielding M. sinensis hybrids (yielding up to 41 t ha(-1)) are more suitable for biofuel production.