Anaerobic Digestion

Anaerobic digestion (AD) is a growth area in renewable energy with increasing numbers of farm businesses involved with their own units or by growing feedstock.


  • The use of grass leys as a feedstock is attracting interest due to the range of advantages offered:

    • Grass as a crop is relatively cheap and easy to grow in our climate and soil types

    • It is cost effective compared to other biogas fuels (see Fig. 33)

    • Equipment and infrastructure to grow and handle this feedstock is already in place

    • Grass can be used fresh (offering the highest rate of gas production) and would be cut and carried on a rotational basis; it can also be stored and used as silage

    • Medium and long term grass leys offer a more environmentally sustainable option than crops requiring annual cultivations

    • Grass leys allow more opportunity to spread the waste products from the digesters, whether that is liquid or solid, without the need to plough back under

    • Blackgrass control:

    – Medium to long term grass leys cut three or more times a year will reduce
    the blackgrass seed production; by constantly cutting the ley there is little if any seed returning to the soil

    – The viability of old undisturbed blackgrass seed within soil reduces by 70% per annum, meaning after the 3 plus years of grassland the blackgrass seed populations are reduced dramatically

    – 65% to 75% of blackgrass volunteers germinate in the autumn, so establishing your grass ley in the spring (even under–sown to a cereal crop) will help to further reduce the blackgrass populations

    Download Brochure - 2018_Anaerobic_Digestion_NI.pdf

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