Thursday, June 16, 2011

Is anaerobic digestion an ideal sustainable technology?

Anaerobic digestion plant on a farm
Between three and five terawatt-hours of energy could be supplied by anaerobic digestion by 2020, according to the Government's new Anaerobic Digestion Strategy and Action Plan.

The Plan contains guidance on the cost and benefits of AD for developers and local authorities, and tactics for training and developing markets for the biogas and fertilisers produced by the technology.

″Getting rubbish and waste rot in landfill is madness when we can use it to power our homes and cars,″ said energy secretary Greg Barker. ″We are already making it financially attractive to turn waste into electricity under the Feed-in Tariffs scheme and soon there'll be similar incentives to generate heat too.

"The Anaerobic Digestion strategy and action plan will help us unlock the potential to get more energy from waste to reduce emissions in the fight against climate change.”

Rightly, the Strategy describes AD as a beautifully flexible technology - "plants can be built on many different scales, from large facilities treating sewage sludge or municipal waste, to smaller ones handling materials from a particular farm or a small community. The construction of AD facilities can be comparatively swift, and compared to some other waste management technologies can be relatively inexpensive.

"The inputs and outputs of the technology are also flexible, meaning that the plants can be designed to meet local requirements for feedstock or outputs, while remaining connected to the national electricity and/or gas grid."

It has further advantages, too, over other renewable energy technologies. "The energy is generated constantly, unlike wind, tidal and solar power, and can be stored in the grid (in the form of gas)" - methane.

Methane is one of the few renewable fuels suitable for Heavy Goods Vehicles (HGVs), and has the potential to reduce reliance on imported gas.

So it can process waste and produce heat and electricity.

And, "by providing low carbon fertilisers for agriculture, AD helps deliver a sustainable farming sector, where resources are reused on-farm to reduce GHGs and provide secure and sustainable inputs, particularly phosphate", the Strategy says.

The Anaerobic Digestion and Biogas Association (ADBA) said the plan "should help make it easier to grow the industry. Developments such as a best practice scheme for AD will ultimately help break down barriers to plant development, reduce the risk of investing in AD and deliver the industry's potential to UK plc."


However, they qualified this by adding that the accompanying Waste Review "should have been bolder and called for as much organic waste to be treated through AD as possible.

"We are disappointed by the lack of recognition of the importance of source-segregating food waste, in reducing waste arising, allowing easier recycling of products from other materials such as plastics, and creating a quality fertiliser from AD which will help decarbonise food production. With 1.1% of overall UK emissions coming from artificial fertilisers, and oil prices increasing their costs and the cost of food all the time, this is a huge environmental and social issue."

And, the Action Plan does not offer the prospect of additional funding.

Instead "it promises that the Government is working to ensure that the financial incentives available for AD under the Renewables Obligation (RO), the Feed-in Tariffs (FITs) Scheme, the Renewable Heat Incentive (RHI) and the Renewable Transport Fuel Obligation (RTFO) provide the revenue support that investors need."

If AD is so good, it should be supported more than photovoltaics – and certainly should be made more attractive to developers.

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