Biogas is one of the ways in which Britain will improve utilisation of resources. The non-profit organisation WRAP is currently looking into the application of different biogas technologies and biomass types.

During spring 2011, the British non-profit organisation WRAP has commissioned two new biogas plants, the purpose of which is to demonstrate how the UK can become better at treating and utilising organic waste. Two more WRAP-supported plants are in the pipeline.

In return for financial and practical support from WRAP, the biogas plants are intended to help teach Britons how biogas technologies and waste streams can best be employed in developing the biogas market in the UK.

One of the first biogas plants has been supplied by Xergi Ltd. and is commissioned by Staples Vegetables, one of the UK's leading producers of vegetables. One of the project aims is to help demonstrate a modern thermophilic biogas technology less commonly used in the UK at present.

WRAP goals for the biogas area

WRAP stands for Waste Recycling Action Programme. For more than a decade, the organisation has been a key player in Britain's attempt to reduce waste quantities, increase waste recycling and, at the same time, create a basis for more cost-effective production.

According to WRAP, biogas implementation will be an important means by which to increase organic waste utilisation in the production of both green energy and fertilisers.

The organisation therefore aims to support cost-effective biogas production and to exploit the environmental benefits of anaerobic digestion (AD) of organic waste and of the products resulting from this process. Furthermore, WRAP wishes to exploit the full potential of biogas production in order to reduce the carbon footprint of the food supply chain.

Biogas at higher temperatures

"An ongoing evaluation programme will test and quantify that the biogas plants do in fact help WRAP achieve its biogas-related goals," states Claire Barker, WRAP's PR Manager.

And she explains that Staples Vegetables received WRAP support because the project will help to illustrate the cost-effectiveness of biogas production.

Staples Vegetables has opted for a plant which operates with ideal process temperatures in the biogas digester. This means that anaerobic decomposition in the digester takes place at a temperature in the range 47-50 degrees C, which is higher than in most other biogas plants in the UK, which operate at about 37 degrees C. 

Raising the temperature in the plant means that it yields more gas per unit of feedstock. Another important issue is, however, that a biogas plant does not always need to operate at high temperature.

"The ideal process temperature for any given biogas plant depends on the composition of the feedstock. The nitrogen content and pH value are decisive for the ideal process temperature," maintains country manager of Xergi Ltd. Colin Steel .

For this reason, Xergi designs flexible biogas plants that can operate at any temperature between 37 and 52 degrees C, so that the ideal process temperature can be set according to the specific nature of the feedstock in the digester.

Benefits for the climate and the environment

However, it was not only the potential for cost-effective biogas production that motivated WRAP to invest GBP 2 million in the Staples Vegetables biogas plant. The plant is also expected to help WRAP achieve another of its goals, i.e. maximising the environmental benefits of anaerobic digestion and its products, Claire Barker explains.

The electricity and heat generated by the CHP engines are used to reduce Staples Vegetables' reliance on fossil fuels. At the same time, the digestate is a valuable fertiliser replacement which reduces the company's consumption of inorganic fertiliser.

Claire Barker believes that Staples Vegetables has achieved a lower carbon footprint for the vegetables they grow, and that this achievement is due not only to green energy production as an alternative to burning fossil fuels, but also to the company's replacing inorganic fertilisers, the production of which demands intensive fossil fuel consumption.

Promoting biogas in the UK

"There is no doubt that WRAP is helping to expand the British biogas market, not only by contributing to broad-based knowledge sharing but also by formulating standards and regulations for the biogas industry," states Xergi's Colin Steel, applauding the WRAP initiatives.

At the same time, he is well aware of the importance of the Xergi biogas plant at Staples Vegetables as a shop window in the British market.

"It is an interesting project and it is crucial for us to have a reference plant which demonstrates that all the electricity, heat and digestate it produces can be put to good use. Staples has also installed a heat absorption unit that uses  the surplus heat and converts it to cooling which is used in the vegetable stores; nothing is wasted. This plant is an excellent example of the true potential of biogas production and usage," states Colin Steel.

According to a press release from the British Department of Energy and Climate Change in July 2010, annual organic waste production in the UK is about 100 million tons. All of this waste can potentially be converted into energy and fertiliser. In 2010 there were just under 40 operational biogas plants in the UK and approx. 60 on the drawing board.

To learn more about WRAP, click www.wrap.org.uk