Grass for Biogas Production—Anaerobic Methane Production from Five Common Grassland Species at Sequential Stages of Maturity
Grassland biomass represents the most significant feedstock resource in Ireland, accounting for approximately 91 % of the 4.3 million hectares of agricultural land. Grass can be an excellent energy crop and may be classified as a high yielding (up to 15 t dry matter ha− 1 a-1), low input perennial crop. Consequently, grass will be a dominant feedstock for anaerobic digestion (AD) on Irish farms. This study investigated the effects of stage of maturity of five grass species on methane production using dried, milled samples in a small-scale (160 ml), high-throughput batch digestion test. Five common grass species (perennial ryegrass, Italian ryegrass, cocksfoot, timothy and tall fescue) were grown in field plots (with three replicate blocks) under a high nitrogen fertiliser input (125 kg N ha− 1) and harvested at five sequential dates (fortnightly from 12 May to 7 July; n = 75 plots) in the primary growth. Of the five grass species investigated, average total CH4 production was highest (P <0.01) for the perennial ryegrass. On average, the rate of digestion decreased (P < 0.001) with increasing plant maturity. Although total CH4 production decreased numerically with advancing plant maturity, this difference was not significant (P >0.05).
KeywordsAnaerobic Digestion Methane Production Grass Species Tall Fescue Volatile Solid
Funding for this research was provided under the National Development Plan through the Research Stimulus Fund (#RSF 07 557), administered by the Department of Agriculture, Fisheries & Food, Ireland.
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