FEARS of bird strikes involving US Air Force jets at RAF Fairford prompted the Ministry of Defence to write to Swindon Borough Council.

Planners at the council are working through an application by Biomethane Castle Eaton Ltd to expand an existing anaerobic digestion waste plant in Castle Eaton.

The company wants to put a fourth, much larger, digester on site as well as an effluent lagoon for run-off from the new silage storage bays it is looking to build, together with a rainwater pond, an office building and a weighbridge.

The plans have drawn significant opposition from many who live in the village south of Fairford. They are concerned about the increase in lorry traffic they say will be needed to keep the plant fed with digestible material.

And because the site is close to RAF Fairford, the MoD has also written about its concerns.

Its letter to the council says: “The principal concern of the MoD is the creation of new habitats may attract and support populations of large and/or flocking birds close to the aerodrome.

"The principal concern in relation to this development in the vicinity of RAF Fairford relates to the potential increase in bird strike risk to aircraft operations as a result of the following: The addition of new silage clamps has the potential to result in an additional food source for hazardous birds such as rooks. The rainwater and effluent lagoons likewise have the potential to attract birds such as gulls.”

RAF Fairford is a forward operating base used by USAF aircraft, including the B2 stealth bomber. Air activity is expected to increase between now and 2024 as more aircraft are deployed.

The MoD has asked planners at the council to ensure if the scheme is approved the silage is covered when not in use, and the rainwater and effluent lagoons should be as small as possible, with steep sides and surrounded by a bird proof fence.

The MoD is also worried about the use of cranes when building the new plant and how that might endanger aircraft and has asked that the applicant must submit a plan for how tall structures will be used during construction and get it signed off before starting work.

The ministry’s letter concludes: “If Swindon Borough Council decides to grant planning permission contrary to our advice then we must be notified 28 days prior to a decision being made.”

The application is expected to come to the council’s planning committee later this year.

What is anaerobic digestion?

Anaerobic digestion is a way of using waste organic material, getting energy from its breakdown and keeping it out of landfill, where its decomposition gives off methane – a harmful greenhouse gas. 

It is an increasingly popular way for farms to diversify their use and earn extra money. 
Material such as farm waste and slurry or even domestic food waste is kept in large airtight containers. 

The absence of oxygen – hence anaerobic – allows microorganisms in the waste itself to start work breaking down the material.

The process takes longer than if the piles of material were allowed to compost naturally – but what comes out of the digester is more useful.

Digestion produces biogas, which is mainly a mixture of methane and carbon dioxide. That can be burnt in generators which produce both heat and electricity. It can be fed into the gas grid or transported by truck to where it is needed.

The solid material left is nutrient-rich and can be used as a fertiliser – when the Castle Eaton plant was given permission for two digesters in 2012 it was the intention the fertiliser would be used by local farms.