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James Hart, Director of J J Power Ltd, small scale, Gloucestershire


The 700ha farm includes 630ha arable, 100 suckler beef cows, 4 broiler chicken sheds and did have a 400 sow pig unit. On a daily basis the 350kW plant now uses 3 tonnes of chicken litter and makes up the rest with forage maize and hybrid rye as well as a small amount of pasteurised food waste from a neighbouring AD plant.  This is significantly different from the envisaged feedstock ration and is more expensive than was originally intended.

Why AD:

With large levels of dilute liquid slurry and concentrated chicken litter, it seemed to make sense to put it through an AD plant.  The energy generated from those manures isn’t massive but potential odours are reduced through digestion. The loss of the pig slurry is not huge in terms of energy replacement though that replacement comes at a cost rather than “free”. The digestate is effective and reduces our fertiliser bill, albeit not by quite as much as we had hoped. The annual cost to spread is the same as we used to spend on the raw manures though it is difficult to spread at less than the cost of buying fertiliser so it remains a significant cost.


Being tenant farmers, one of the greatest barriers was raising £1.4 million and we were lucky enough to get a sizeable European grant.  Planning was not an issue for us as we weren’t importing extra material in the initial plan. The addition of the food waste permit was very expensive and not viable were it not for the agreement with a local company to deliver sufficient material each year

Another challenge has been budgets from 2010 which suggested that electricity prices would rise each year.  The reality is that they haven’t, and we are currently selling at 80% of the price budgeted in 2010.

Making AD work:

An AD plant needs “full time” monitoring, even when operating smoothly, to get the most out of it and cannot be the last job done in the morning. If there are problems it can take all day to resolve and so you can’t expect a plant to flourish without you investing sufficient time.  As we pass our 4th birthday we are beginning to wear things out and our running costs are sure to increase from now on as we spend more and more repairing and replacing worn out equipment.

Advice to others considering AD:

Initial suggestions of feedstock requirement was over optimistic and so we need more feedstock that was initially budgeted for. Doing your homework before investing in a plant is therefore very important.

While there were issues with AD in 2010 in terms of available UK knowledge, the domestic market has now developed substantially offering the necessary technical and advisory support. Consultants can still be unreliable, however, as headline figures are often not suitable as every situation is different and so talking to other AD operators is the best way to really get an idea of what you should expect and what the pitfalls are. It is also important to have the Environment Agency on side from the beginning as they have a big say in design due to ever tightening restrictions on what we can and can’t do regarding plant inputs, and most importantly the storage and use of digestate.

Digestate is useful if you can store and spread locally to the plant. Using umbilical onto arable and grass land is the only way to get close to revenue neutral.  As soon as it is transported anywhere the costs far outweigh the fertiliser benefit and become another pressure factor on the bottom line.

We would say that AD is a good fit for some but not all.  To realise the potential of an AD plant you MUST have an on-site use for the heat and electric.  Only then will it make for a profitable business that adds to the existing business.

What would we have done differently:

If we were to do it again we would look to co-locate the CHP near a local school or business with a substantial heat and electric requirement.

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