Energy Group Gives Conditional Support to Crediton Biogas Plant

28 June 2016

Planning Application for Construction of an anaerobic digestion plant at Lords Meadow Industrial Estate

Application reference 16/00825/MFUL

Sustainable Crediton Energy Group supports anaerobic digestion to treat and recycle farm wastes and in the process to provide a source of renewable energy either as electricity or biogas. However we do have some concerns, conditions and questions about this particular planning application asset out below. If the Applicant can respond satisfactorily , we can certainly support in principle the planning application at Lords Meadow Industrial Estate.

Stated Benefit from Annual Biogas Gas Production Incorrect

The Applicant stated at the February presentation to the Crediton Town Council that the amount of biogas injected into the gas grid would be enough to continuously supply about 5000 homes. Using data provided by the applicant, we estimate the plant is actually capable of producing gas for fewer than 3500 homes. By taking account of the fossil fuels used in the transportation and production of the purpose grown crops to feed the Anaerobic Digestion Plant, the net benefit is the production of renewable gas for 2100 homes. This is still a worthwhile benefit. This benefit could be significantly improved by changing the balance of feedstocks and by choice of agricultural practices for the purpose grown crops.

We also note that there is no other alternative form of renewable gas currently on the market.. Gas is the only source of renewable power that is easily stored, transported and produced all year round under all weather conditions. This is base load power that would compete directly with traditional fossil fuels , nuclear and fracked gas.   

Crops as Feedstock

At a presentation given to the Crediton Town Council in February the applicant made statements to the effect that the feedstock for the anaerobic digester would be a mixture of farm wastes and "break" crops. We were told that the "break" crops would be crops that were planted to give fields an annual rotational break and that would improve the fertility of the soil. We have been advised by the applicant that the annual feedstock will be 15,000 tonnes of farm wastes comprising 3000 tonnes of farm yard manure, 6000 tonnes of chicken litter and 6000 tonnes of straw. This will be supplemented by 26,600 tonnes per annum of locally grown crops comprising 3500 tonnes of hybrid rye, 5000 tonnes of fresh grass, 15000 tonnes of fresh maize and 3100 tonnes of oats. We do not consider these crops to be "break" crops. These crops could be used for animal or human consumption. We also have a concern that the growing of maize for anaerobic digestors is having a detrimental effect on soil fertility and soil run-off.

We would prefer that the feedstock was 100% farm wastes and that the maize/grass/oats/rye silage proposed for the digester feedstock was used as animal feed, that is good agricultural land is used for food production rather than energy production. However we do recognise that adding a modest amount of crop material can increase the energy yield from anaerobic digestion dramatically compared with using farm waste only. We also recognise that although the proposed proportions of farm waste and crops is not ideal from a sustainability perspective and that the Government is consulting on the introduction of feedstock restrictions to minimise the use of crops in anaerobic digestion plants, we believe that having the facility in place then allows the business/farming community and other community stakeholders to be creative in the future in finding / supplying alternative genuinely high calorific value waste feed stocks. If that waste was free or at low cost to the Anaerobic Digestor Operator then why wouldn't they use that instead of purpose grown crops?

We therefore propose two conditions for our support for this application:

Condition 1

That the Applicant works with the local business/ farming community and other community stakeholders such as Sustainable Crediton to find high calorific waste feedstocks to eventually replace the energy crops feedstock.

Condition 2

That the Applicant in the interim for the benefit of biodiversity grows the energy crops without the use of pesticides and herbicides and intersperse the rows of crops with nitrogenous plants such as clover to increase the fertility of the soils. Fossil fuel fertilisers should not be used in the production of such crops, but digestate from the Anaerobic Digestion Plant could be used.

Questions concerning the on-site processes

1. The off-gas from the digester will not be pure methane. It will be wet and will include a significant proportion of carbon dioxide, typically about 40% by vol. It may also contain some hydrogen sulphide.

A. How is it proposed to treat the off-gas ?

B. What is it intended to do with the separation products?

C. What method will be used to compress the methane to a pressure at which it can be introduced into the gas main?

2. How are the raw feed materials to be stored on site ? In particular can it be guaranteed that no odours will escape the site either from feed material or other operations on site?

3. How can the proposers justify the statement in their submission that no hazard is associated with methane on site?

We attach a link to a report undertaken to determine the frequency and causes of accidents in AD plants. A large number of incidents were identified, many resulting in serious injury and in some cases fatalities. The majority involved either biogas explosions or hydrogen sulpide poisonings. The number of incidents appears to result from an industry previously lacking a formal safety culture handling materials for which a more rigorous chemical engineering approach and procedures are required. Lessons learned and put into effect apply to all stages of an industrial scale AD project, from design, documentation and process review through project management to commissioning, operation and maintenance procedures.

4. As the digestate is to be spread on fields. Will it be pasteurised?

Traffic management

The number of vehicle movements in the Transport Statement appears to be consistent with the tonnages to be moved.

It is not made clear in the Application due to the general assumptions of 60% material originating from the south of Crediton and 40% from the north what the precise geographical locations of the feed material are likely to be. Without more information about the sources of feed materials it is impossible to predict the extent to which the vehicle movements may increase congestion at critical points, for example along Fordton, which already has serious congestion at harvest times. Where are the sources of the raw materials for digestion?

Other Considerations

We expect that the process will be designed so that  noise and odours from the site are limited and do not affect householders on the Bramble Lane estate.