DEAR SIR:
I am long retired from an area of work where anaerobic digestion was part of my remit. Hence, I would like to provide some useful comments to Kevin Pollard’s letter on the production of renewable energy from animal waste in the Irish Farmers Journal of 19 March 2016. At the outset, let me state that animal manure should never be construed as a waste; it is indeed a valuable source of plant nutrients and organic matter as well as being a potential source of renewable energy.
Due to the importance of bovines within the Irish livestock industry, most of the manure available for processing will inevitably come from “wintered” cows and cattle. Such a byproduct has, at best, a potential to produce only some 25 cubic metres of biogas per tonne of manure.
To optimise gas production, the manure needs to be fresh at the time of treatment. Current systems of manure collection/storage are seldom if ever conducive to attaining this objective.
Storage tanks, separate from those providing the digester feedstock, will be required to store the treated liquid until circumstances permit its utilisation on land.
It is almost certain that “winter contracts” would have to be made with neighbouring farmers to provide an adequate and constant supply of manure. It is also likely that these providers would have to accept and store the treated liquid.
Where electricity generation is the ultimate goal, it would be desirable to increase gas output by the inclusion of some high energy source(s) such as poultry manure and/or offal. To ensure a continuous supply of these byproducts, some research would be required on the part of the owner/operator of the plant.
SHARING OPTIONS