Biochemical methane potential of winter wheat (Triticum aestivum L.): Influence of growth stage and storage practice

The effect of growth stage at harvest and of storage practice on the biochemical methane potential (BMP) of winter wheat was investigated using batch-fed stirred mesophilic digesters. The wheat used was a single variety sown at the same time (autumn) and harvested at 3 different stages in its growth: medium milk (A), soft dough (B) and Caryopsis (C). Wheats (A and B) were ensiled whilst the later harvested material (C) with a higher dry matter content was treated by the alkalage process. The BMP values expressed on the basis of volatile solids (VS) were 0.360 ± 0.030, 0.346 ± 0.006 and 0.311 ± 0.016 l CH4 g−1 VSadded for A, B and C, respectively. A simple first order kinetic model gave only a poor fit to the experimental data but a close match was obtained using a modified first order pseudo-parallel model which explains the methane production curve on the basis of differences in biodegradability of the plant material.