Digesting the problem

Britain has fallen well behind much of Europe when it comes to utilising manure from farms and waste from abattoirs and food processors to create gas and electricity. But that could soon change. Terry Slavin reports
Terry Slavin
The Guardian,
Wednesday July 30 2008

Looking at the cows on his dairy farm in Devon, Winston Reed does not see what many environmentalists do: animals burping up vast quantities of methane, a greenhouse gas 21 times more potent than CO2. He is more concerned with what comes out of the animals' other end - and it offers hope for the planet. As Reed says: "The poo from four cows can produce enough energy to heat and light a house for a year."
Unlike the methane that cows and other ruminants exhale as their stomachs convert grass into milk, and which is believed to be responsible for up to a quarter of "manmade" methane emissions worldwide, the gas in their manure can be harnessed as a force for good. And the same goes for all other forms of organic waste that would otherwise rot in landfill sites.
Reed, 35, is seeking planning permission to build an energy centre on his farm, in a rural community on the outskirts of Tiverton, near Exeter, taking in manure from local farms and waste from local abattoirs and food processors. It would not be the first of its kind in the UK, but it would be by far the most ambitious - creating electricity to light 6,000 local houses and £700,000 worth of heat for local industries, including a sawmill plant making wood pellets for biomass boilers. Since Tiverton's population is only 20,000, it will go a long way to making the town self-sufficient in energy, he says.
More than that, it will help address the issues of food and fuel security by making them more sustainable, at a time when both are in short supply.
The plans hinge on a technology called anaerobic digestion (AD). Organic material is fed into heated tanks, where natural fermentation breaks it down into methane and carbon dioxide - the same basic ingredients as natural gas. This biogas can then be burned to generate electricity in a combined heat and power plant, or, as many countries in Europe do, upgraded so it could be fed into the gas grid or used in vehicles modified to run on compressed natural gas. The only byproduct of the process is an organic fertiliser.
Such alchemy has been worked for decades in some parts of Europe - Germany has 3,000 on-farm AD plants - but has been relatively unknown in the UK, except in the sewage-treatment industry.
Play catch-up
That, however, is something that the Department for Environment, Food and Rural Affairs (Defra) wants to change. This month, three Defra ministers met with representatives from agriculture, the supermarkets, waste and water and energy companies, as well as local government, to discuss how Britain could play catch-up with Europe. The department sees the potential not only in terms of generating renewable energy but also in addressing the issue Gordon Brown highlighted at the G8 summit last month: the amount of food Britain wastes.
According to the Waste and Resources Action Programme (Wrap), UK households throw away almost a third of the food we buy: that's 6.7m tonnes of food waste. The CO2 generated in producing food that is wasted, and then the methane it gives off as it decomposes in landfill sites, results in the equivalent of 18m tonnes of avoidable CO2 emissions a year, Wrap says.
About a tenth of local authorities offer weekly food waste collection, but Defra wants to see this increased, and last year's waste strategy for England urged local authorities to consider AD for all their food waste. There are only a few large-scale AD plants in the UK, including one in Ludlow, south Shropshire, that processes 80 tonnes of kitchen and garden waste a week from 20,000 local homes and businesses. But earlier this year, Defra announced it would spend £10m to get more of these off the ground. Under proposed changes to the government's funding scheme for green electricity, AD plants will from next April earn double the Renewables Obligation credits, which can be swapped for cash.
However, Reed says the real key to success for AD may lie with major food retailers rather than the government. Many have been looking into AD as a solution for cutting food waste for some time.
Another pressing problem faced by supermarkets striving to cut their carbon footprints - the difficulty of sourcing "green electricity" - could also be solved by AD. Marks & Spencer is encouraging its suppliers to build AD plants on their farms, to process waste such as grass and manure, and is offering contracts to purchase the "green" electricity they produce. Richard Gillies, in charge of the company's £200m eco-plan, says AD not only makes sense from a carbon footprint perspective but is also a winning proposition for its suppliers. "It is an efficient way to deal with waste, which they would otherwise have to pay to dispose of," he says. "They get organic fertiliser, and they get an income stream from the electricity they generate. You are turning what would have been costs into benefits."
But there are even more efficient uses of AD than generating electricity, says John Baldwin, managing director of CNG Services, a member of the Greener for Life consortium that will build the Tiverton energy centre. He points out that one of the problems with generating electricity with AD is what to do with the spare heat, which, unlike electricity, must be used near where it is generated. Only 20% of it is used to heat up the digester. The rest, unless piped into a nearby leisure centre or hospital, goes to waste - and there isn't much call for a leisure centre near a sewage treatment plant or landfill site.
Unless there is a local use for the heat, it is far more efficient to do what countries such as Sweden do: clean up the biogas produced and put it straight into the gas grid. "The Swedes would not dream of burning valuable renewable methane for electricity production alone," Baldwin says. " If we had AD plants everywhere in the UK, we could get 20% of our gas from this very renewable resource."
At the moment, there is no incentive to do this in the UK. Only electricity from AD plants, not biogas, is lined up to get double credits from next year. Baldwin says the UK is also far from exploiting AD's other great potential: converting biogas into a compressed natural gas and using it to fuel cars and buses. This is what is happening in the French city of Lille, where most of the city's buses and refuse lorries are running on biomethane generated by domestic household waste and sewage.
Baldwin points out that biomethane has the lowest "well to wheel" CO2 emissions of any transport fuel, being almost twice as efficient as diesel at turning biomass into transport fuel - with no particulates and almost no other emissions. The problem, of course, is having the cars and lorries that can run on compressed natural gas, and infrastructure to support them. Unlike in Europe and even in a countries such as India - the city of Delhi runs most of its buses and taxis on it - CNG vehicles are not commercially available in Britain.
Fleets of lorries
Reed says Britain's retailers, with their fleets of delivery lorries, could again provide the answer. Tiverton's energy centre will initially use biogas to create electricity, but longer-term plans are to upgrade it to biomethane. This will then be combined with 7% hydrogen to create hythane, an even greener fuel, with half of biomethane's emissions.
The ideal customers for the fuel would be supermarkets, with their big fleets of lorries that can fuel up at centralised distribution depots, and Reed says he is currently in discussions with a retailer trying to tie up an agreement.
"It all boils down to food and fuel security," he says. "You can't have one without the other." And the cows on his farm are as good a place as any to start.
Biogas
· The UK generates about 30m dry tonnes of agricultural manure and food waste each year - capable of producing methane with an energy content equivalent to 6.3m tonnes of oil. That could meet 16% of transport fuel demand.
· Just 6m tonnes of food waste could produce enough biogas to generate 1GWh of renewable electricity - about the same as a power station.
· Biogas-fuelled vehicles can reduce carbon emissions by between 75% and 200% compared to fossil fuels, but there is virtually no refuelling infrastructure in Britain. Germany has installed 800 natural gas filling stations in the last three years.
· Biogas gives lower exhaust emissions than fossil fuels, improving air quality.
· Experts say biogas could be produced in the UK for 50p-60p per kg, about the same as the current price of compressed natural gas.
· Running a vehicle on biogas is 40% cheaper than on diesel, and 55% cheaper than petrol. But high capital and maintenance costs make HGVs the only economic biogas vehicles so far.