The value of plant biomass as additional input in the biogas process - i.e. as a co-ferment for anaerobic digestion - is mainly determined by the potential biogas yield of the considered substrate and its methane content. Laboratory scale batch experiments were conducted to investigate the effects of different plant species and growth stages on the biogas production. Cereals examined include barley (Hordeum vulgare), rye (Secale cereale) and triticale (X Triticosecale) at anthesis, milk and dough stage. First results show the milk stage as a probably optimum cutting stage for cereals. Further emphasis was placed on the use of natural silage as a conservation method for harvested herbaceous energy crops. In our study, all ensiled whole crop cereals resulted in higher biogas yields than did fresh matter of proposed co-ferments, whereby methane recovery was almost constant.
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