The Anaerobic Digestion brigade is continuing to produce hot air and gas in the run up to the General Election, in the hope of extracting some policy promises from any of the parties who might have a say in the future of this industry.

Yesterday saw a conference by the Anaerobic Digestion and Biogas Association at which it was claimed that AD produced a good quality fertiliser, in the form of the digestate left behind after the methane has been produced. In reality, what is produced is a good soil conditioner, not a good fertiliser. This study on digestate from farm slurry found found no increase in nutrient value but that there was an increased risk of Ammonia pollution; which causes environmental harm and human health problems. This review confirmed that most of the N available from digestate is in the form of active Ammonium, which  can be released into the atmosphere if handled incorrectly. The total Nitrogen in digestate from food is around 7 units per cubic metre and 4 from manure. For some strange reason the review does not consider Maize as an AD feedstock. This factsheet indicates that values for N can vary from 2.3 to 4.2 kg per tonne of digestate. This is less nutrient than would be supplied by farm slurry or farmyard manure.

As I have written on a number of occasions, Maize is becoming the Biogas crop de jure. Maize is a very nitrogen hungry crop – applications of 250kg per hectare are not uncommon. To deliver this level of N would require 65 tonnes of digestate per hectare – an enormous amount of material, which has to be transported (producing carbon) from AD plant to field. The whole notion of this being an economically, let alone environmentally efficient and effective process comes straight out of the Alice in Wonderland book of sustainability. Because in order to produce a digestate with 4kg per tonne of N, a crop of Maize requiring 60 times that much inorganic fertiliser has to be grown.

Chris Huhne (remember him?) popped up at the Conference waving the flag for AD biogas. Huhne is not speaking from an objective position: he was appointed head of US biogas company Zilkha Biomass Energy’s European Division shortly after his release from prison. Huhne said

“The rural economy is one of the success stories of the wider economy, partly down to the fact the rural community can diversify,”said Mr Huhne.

He said the nature of the technology meant it was cost effective, even though start up costs were often very high.

“Wind, solar and shale are all intermittent,” he said.

“AD has built in the fact we can dispatch the energy when we need it and that really needs to be taken into account. 

“Comparisons in cost do not give credit for that. We need to get that across to Government in the run up to the next General Election.”

I expect Huhne still has some fairly high level access to people like Climate Change Secretary of State (and his successor) Ed Davey. He will be able to walk in to meetings with senior civil servants at DECC and DEFRA. He will be able to lobby very effectively for Biogas (including from Maize).

Another speaker at the Conference was Surrey farmer Paula Matthews, who is trying to get planning permission for a 500kw AD plant on her farm. She said

“There is a huge misconception that we can only grow food or fuel but we are doing both, she said.”

“We are already selling hemp for the energy industry. The penny needs to drop.”

The farmer said beef production was at risk of becoming ‘unviable’ and AD offered a worthwhile and sustainable diversification. 

“If we don’t continue to farm we have several landlords who all need to be paid rent.”

This is Mrs Matthews’ farm, which lies within the Surrey Hills Area of Outstanding Natural Beauty.

The dark fields are maize. In this respect, if Mrs Matthews gets her AD plant, there won’t be any landscape change or further environmental harm, because it has already happened.

But if Mr Huhne and his chums get their way, this is the land-use coming to a landscape near you – especially if you are in the South West.