A pilot-scale anaerobic digestion plant currently under construction at Teagasc Grange is due to be commissioned this year. The plant will produce biogas using grass silage and cattle slurry.
Anaerobic digestion is a multi-step process whereby organic waste and residues are converted into biogas by a group of microorganisms in an anaerobic environment. Biogas could be used as any of the three energy vectors – electricity, transport and heat. In Ireland it would be most useful if used for renewable heat or transport. Biogas refers to the gas prior to upgrading, which contains approximately 55% methane (CH4), while bio-methane refers to the upgraded gas, containing approximately 97% CH4.
Anaerobic digestion plants can be fed a wide range of organic feedstocks. There are many suitable feedstocks for biogas production from the agricultural sector, including crops such as maize specifically cultivated for biogas production, animal slurry and manures as well as waste and by-products from agro-industries.
When fully-operational, expected nominal gas production will be 70 m3/hour. The bio-methane produced will be pressurised for transport by road tanker to the national gas grid at the injection point in Nurney, Co. Kildare. Alternatively, the bio-methane can be used for natural gas-powered trucks with refuelling on site. In addition, the option of using a natural gas tractor on the research farm at Grange will be explored.