The methane productivity of silage of four crop species - Zea mays L, Sorghum saccharatum, Miscanthus x giganteus and Miscanthus sacchariflorus - was investigated. The experiments revealed that at a hydraulic retention time 01 60 days the volumetric methane yields from the Z. mays L or S. saccharatum silages were higher than those from the Miscanthus x giganteus or M. sacchariflorus silages because of the higher crude fibre content in Miscanthus spp. However, at comparable lignin concentrations in the feedstock, methane productivity for M. sacchariflorus (0.19 +/- 0.08 L/g volatile solids) was twice that of Miscanthus x giganteus (0.10 +/- 0.03 L/g volatile solids). The efficiency of cellulose conversion varied from 83.6% (S. saccharatum) to 52.1% (Miscanthus x giganteus), and hemicellulose from 88.9% (Z. mays L) to 59.7% (Miscanthus x giganteus). Conversion of cellulose and hemicellulose depended on the ratio of these polysaccharides to the lignin concentration of the feedstock. (C) 2010 Elsevier Ltd. All rights reserved.