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Renewables special: AD revival could be on the cards

The anaerobic digestion (AD) sector has experienced a tumultuous few years due to uncertainty over subsidies and regulatory changes, but there is still much it can deliver for the rural economy. David Burrows reports.


In June 2011, the Coalition Government published an AD strategy and action plan.


It was, Ministers said, ’the first and key step to enabling a thriving AD industry to grow in England over the next few years, delivering new green jobs as well as new green energy’.


With its potential to manage waste, cut greenhouse emissions and produce renewable energy for farms and rural communities, it was little wonder the technology was flavour of the month.


Farmers, with 90 million tonnes of waste manure and slurries every year, were a target market for the ’huge increase’ the Government desired.


This was an opportunity to turn trash into treasure, via attractive incentive schemes including the Feed-in Tariffs (FiTs) and, later on, the Renewable Heat Incentive (RHI).


The NFU even set a target of 1,000 on-farm AD plants by 2020.


“Despite a slow start in Britain, it looks like the AD industry is robust, innovative and set for further rapid growth, putting it well on track for the widely shared ambition of 1,000 plants by 2020,” it noted in December 2013.


Back then, there were 125 farm-fed plants in operation.




By April 2017 – around the halfway mark towards 2020 – and it was up to 277, according to NNFCC, a bioeconomy consultancy which tracks uptake of AD in the UK.


The latest figure, due to be published this month, is 329 – but new projects have almost ground to a halt.


NNFCC senior consultant Michael Goldsworthy says: “It has gone from hundreds of applications to tens.”


So what has happened and what does the future look like for on-farm AD?


For one, FiTs have been tapered off and there have been changes to the RHI.


The good news is many are expecting a post-Easter boost to RHI once reformed legislation is laid before Parliament.


The Anaerobic Digestion and Bioresources Association (ADBA) says the restoration of tariffs for heat generation – as the Government strives to meet its targets for renewable heat – will be a welcome boost.


This will restore tariffs for heat generation to ’levels which would stimulate deployment and provide tariff guarantees to give long-term certainty to investors and those generating renewable heat’, says the association’s chief executive Charlotte Morton.


Some projects have been on hold for months as RHI reforms were sidelined due to the Brexit vote and the snap election last year.


The new tariffs are certainly expected to open the floodgates for those which have been waiting patiently to press ‘go’ on their plans.


However, this could be a ’last flurry’ before things fall off the cliff-edge again, according to Mr Goldsworthy.


“There will be a spike in activity, then the budgets will fall and the incentives will follow,” he says.


To keep the scheme within budget the Department for Business, Energy and Industrial Strategy (BEIS) lowers the tariff rates for new applicants if uptake of the scheme is higher than expected it looks like it will overspend – a mechanism called degression.


What happens then is far from clear.


The idea is that the technology will have had enough support to stand on its own two feet. But there is another factor which could see uptake continue to stutter – the need to use fewer crops and more waste.


As well as the shift in levels of incentives there have also been changes to the criteria farmers have to meet in order to get them.


Most notable is that, under the RHI, only 50 per cent of the gas output can come from crops. There are grey areas, for example, crop residues such as straw and turnip tops are classified as waste, but could the restrictions make farmers think twice about AD?


Ms Morton says she has not seen any data to suggest that is the case. Others are not so sure.

Typically, between 80 per cent and 90 per cent of gas from an on-farm digester comes from crops and only 10 per cent to 20 per cent comes from the waste.


"Per tonne of manure you get 10 times less gas than you do from a crop,” Mr Goldsworthy adds, which means a farmer would need about 10,000t of manure for ever 1,000t of crop.


“It will have a meaningful impact and certainly affect deployment in the future,” he says.


Maize recieves ongoing criticism


Maize growers are not happy about the restrictions.


Maize has been ’the most successful’ energy crop for AD, explains John Morgan, of the Maize Growers Association (MGA).


“It has the highest gas yield per unit of land and is incredibly good environmentally in terms of nutrient recycling. I look at a maize field for biogas and it is like a living solar panel,” he says.


That is not to say that maize does not come with baggage.


The dramatic increase in the crop being grown for AD has attracted the attention of environmentalists.


George Monbiot has led the charge: a biogas plant with a capacity of one megawatt of electricity, for example, requires 450-500 hectares (1,111-1,235 acres) of land, he wrote in 2014, citing Farmers Guardian figures.


An offshore wind turbine will give you 4MW.


“One concrete pillar in the seabed or 450ha of land – can there be any doubt about which is the better option?” he wrote.


“And this is not any old land, but prime arable fields.”


A report by the Soil Association in 2015 also suggested that the biogas produced from maize, while described as ‘renewable energy’ was not providing any net benefit to the environment because of damage to soils and fresh water.


The NFU’s plan to hit 1,000 sites was a major worry, says the association’s policy director Peter Melchett.


The changes to the RHI seem to have stopped that, he adds.


“New AD plants should be geared towards long-term farm waste like slurry and secure supplies of domestic waste – that is the sensible use of [this technology].”


Mr Morgan and the MGA are obviously frustrated by the ongoing criticisms – especially the food versus fuel one.


“Maize is not replacing land which could be used for food,” he says.


“It is replacing land used for alcohol production – the crops would be for beer, lager and Scotch. The food versus fuel debate should not be pinned on energy crops, it should be pinned on alcohol crops too,” he adds.


A fair point – but with beer and whisky two of the UK’s top exports, it is not a debate the Government is likely to listen to anytime soon.


Analysis by ADBA suggests 1,000 on-farm plants would use about 220,000-235,000ha (543,630-580,700 acres) of land – or about 1.3 per cent of all agricultural land (currently it is 0.6 per cent).

“The growing of crops for AD is not having a significant impact on animal feed or human food outputs,” says Ms Morton.


Still, the nervousness around energy crops persists.


The construction of plants designed to take 80,000 tonnes of maize does not look like a great result from policies which were designed to turn waste into energy.


But to see the debate as ’waste is good and crops are bad’ is a ’very naïve view of sustainability’, adds Mr Goldsworthy.

AD feedstock

One thing most seem to agree on is that unavoidable food waste should be first in line when it comes to AD feedstock.


Could farmers start constructing plants which take food waste from the surrounding area?


It is a fine idea but far from simple.


“Food waste does not seem to align very well with farming operations from what I have seen,” Mr Goldsworthy says.


Indeed, there are transport and regulatory headaches to consider, as well as potential opposition from the local community.


There also is not enough food waste going around – in England, where separate collections of food waste from homes and businesses are not mandatory, anything which is there tends to be hoovered up by the big waste contractors to feed their own sites.


John Morgan, of the Maize Growers Association, says he cannot see much movement in the figures for on-farm AD unless there is a shift in the incentives or energy prices.

“Is that a bad thing? I do not know,” he adds.


“I am a great believer in things standing on their own two feet.”


It looks like AD has little choice but to do just that.

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