Membership Matters

on sand it has been found on other sites that this is a bad idea when you have an AD system. The sand fills the digester and eventually the amount of organic matter reduces and the reaction stops. Removal of the digester cover, removal of the sand in an enclosed space (requiring specially trained operators wearing PPE) and re-starting the reaction can take up to ten weeks and cost tens of thousands. For this reason, Jim still beds his 400 head of milking cattle on rubber mats covered with straw where there is no problem of it being introduced to the digesters.

Of Jim’s total acreage on average 2000 acres (60-70%) is planted with feed maize, 1000 acres (25-30%) is planted with rye or oats and the rest as grass. He mainly rotates the maize and rye/oats. The end digestate is then spread back on the land as it is high in phosphates and potash.

Long term Jim’s plan is to build a third digester. This additional 50% capacity would allow the digestate to remain in the higher volume system for longer which in turn gives 20% more for a 15% reduction in feedstock added.

Thanks go to Jim Butler and Andy Mercer for their time and hospitality. Also to branch committee members Richard Robinson and Nigel Anstee for organising the visit.