AD chance mustn’t be wasted

Biogas experts recently gathered for a conference on co-digestion. Claire Smith joined them in Glasgow to find out about opportunities for the water industry

The first commercial use for methane produced by the anaerobic digestion (AD) of sewage came in England in 1895 – when the gas was used to power street lamps in Exeter. Fast forward to 2010 and the water industry is still the leading producer of biogas in the UK – with 220 out of the 283 plants operating in the UK.

Biogas is now beginning to be seen as an important renewable resource – while the AD process is seen as a potential solution to dealing with other wastes – such as farmyard slurry and domestic waste. However, the UK interpretation of waste and animal byproducts regulation – as well as the regulatory restraints on the way water companies can use their assets for commercial purposes – are creating obstacles for an industry that should be on the brink of a massive expansion.

International engineering company Veolia, along with Aqua Enviro Technology Transfer, hosted a conference in Glasgow in May to allow water industry delegates to explore the options and to discuss the benefits and the pitfalls of co-digestion.

As Dorian Harrison, technical director of Monsal and director of Anaerobic Digestion & Biogas Association (ADBA), told delegates: “The water industry should be taking the lead.”

Both household waste and farmyard slurry can be mixed with sewage to feed co-digestion plants – and some experts believe up to a third of the capacity of the anaerobic digesters currently operating in the water industry is currently unused.

Adopting the process would help the UK meet targets to reduce the use of landfill as well as contributing to the production of renewable energy. Yet while continental Europe is surging ahead with biogas production – with 4,500 plants in Germany alone – the UK is making slow progress

Ken Shapland, environmental regulation manager of Severn Trent Water, said that both the complexity of waste disposal licensing, and the financial regulation of the water industry was making progress difficult.

“We need clarification of how Ofwat is going to treat water sector AD assets. I would encourage Ofwat to move things forward at a very quick pace. We need clarification of how we treat the assets we have got.”

Among the most serious anomalies of environmental legislation was the fact that biogas was classified as a waste rather than a product: “It should never be regarded as a waste. It should be treated as a valuable resource – as a product or byproduct.

“What we have is a regulatory system which is hampering good practice.”

Alison Fergusson, senior analyst at Ofwat, told delegates: “There will be some companies that want to go for co-digestion and some that don’t – and we have got to make sure there is no difference to consumers depending on how that decision is made.”

She said there was an issue about water companies using their assets for co-digestion – which is outside their core business. “We need to define that regulated/non regulated boundary and defining where that should be.

“What we want to do is to make sure there is a clear and fair framework for water and sewage companies to asses for themselves whether they want to proceed with co-digestion.”

Bertrand Masure, of Veolia Water Outsourcing Scotland, described several successful, large-scale co-digestion plants in Hungary, the Czech Republic and Germany. He said: “The objective of the water industry is not to develop the capacity to treat food waste, but to develop their existing capacity.”

He gave the example of a treatment plant in Germany that was producing 72% of its electricity after introducing co-digestion – compared with 30% before.

George Paschke, of Edinburgh engineering consultancy Wren & Bell, said: “We owe it to ourselves to be trying to make as much use of these plants and equipment as possible. The experience of continental Europe shows it can be done. The economics do add up.

“There is an opportunity for organisations to look at this, a solution to deal with what is regarded as a problem, but which could be part of the solution.”

However, Ian May, senior process engineer at AECOM, explained that for South West Water the economics did not add up. Approached by a local council to see if it could process household waste, the authority created economic models of how co-digestion could be adopted at three existing AD sites in Devon and Cornwall.

After doing the sums the company realised that the gate price for disposing of household waste would have been too high once all the costs had been met – largely because of the great distances involved.

“At South West Water we don’t make an investment in something outside our core business unless there is a sound economic basis. The small scale of the plants was a problem – you have to have the economy of scale to make the investment pay.”

And, he added: “The regulations are a real barrier – we could improve regulation.”

Bill Barber, a technical expert from United Utilities, gave delegates an overview of the economic implications for the water industry.

The water industry, he said, was currently producing 90% of the biogas in the UK – and that the total production could be increased by a third if it was using all its spare capacity. With extra technical innovation productivity could be more than doubled.

The UK was currently producing 20-100M tonnes of farmyard manure a year and 12-20M tonnes of food waste. But, he said, taking advantage of these potential raw materials was troubled by major hurdles and lack of incentives.

Barber also pointed out that the spare capacity currently unused by the water industry was a fraction of what was needed to process all the food waste and farmyard slurry in the UK.

Christopher Maltin, director of Organic Power and the inventor of a double-barrelled anaerobic tank, said that AD itself provided the model everyone should be following.

“You can forget the science. Nature knows what to do. The bacteria are very very clever and all you have to do is let the bacteria do what they do best. All we have to do is create the

right conditions.”

Maltin said he had successfully operated his double-barrelled digester in many countries around the world, but had ‘largely given up’ on the UK: “Government departments are not like the environment, where everything affects everything else. There is no such thing as waste. Waste is just poor processing.”

Clare Lukehurst, of the International Energy Agency Bioenergy Task 37, gave an example of co-digestion in practice describing how a famer on a 900acre farm had saved £22,000 a year on fertilisers after beginning to produce digestate using a farm-based co-digestion plant.

She said that both biogas and digestate production made co-digestion worthwhile and she had no doubt that the industry was on the verge of a breakthrough in the UK.

“We have more anaerobic digestion plants in the water industry than any other country in Europe. Practically all the plants currently being built are now are co-digestion plants.

“We are very much at the beginning of the anaerobic digestion industry.”

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