Chesterfield BioGas Ltd (CBG) has announced an order from Centrica plc, the owners of British Gas, to supply one of the UK’s first biogas upgrading plants.

The new plant will produce clean biomethane, for direct injection into the national gas grid for use by all consumers.

Biomethane is similar in its properties to the natural gas currently supplied through the grid, except that it is generated from organic waste products such as cattle manures, horticultural, food and household waste. In this particular case, the source is biogas naturally produced during wastewater treatment at the Didcot sewage works of Thames Water in Oxfordshire.

The order, worth in excess of £600,000, has resulted from a partnership between Centrica, Thames Water and Scotia Gas Networks – the installers of the raw biogas collection equipment. CBG has been working with the partnership to integrate the upgrading unit into the overall system. Currently, a proportion of the gas from sewage processing at the site is flared to the atmosphere.

Instead, once the newly revealed project is operational, it will clean the biogas – upgrading it to 98% pure biomethane. Unlike many other ‘green’ energy solutions, the ‘closed loop’ production process for biomethane is environmentally sustainable and consequently, is expected to make a significant contribution to the achievement of the UK’s carbon reduction targets.

Pioneering technology
The upgrading plant to be located at Didcot uses pressurised water scrubbing technology that was pioneered in New Zealand. It is being successfully employed in plants already operating in many parts of the world, including Germany, Japan, France and Spain and particularly in Sweden, where CBG already has experience of co-operating on similar projects.

The upgrading unit is of modular design and will be manufactured in future in Sheffield, UK by Chesterfield BioGas, as exclusive UK manufacturers and under licence from Greenlane Biogas Ltd.

The unit or plant has the capacity to process up to 130 Nm3/hr of raw biogas.

Provided there are normal levels of carbon dioxide and other trace impurities present in the input raw biogas, the process achieves the upgrade in a single pass, utilising specially developed media within the scrubbing tower. Almost all siloxanes are removed and hydrogen sulphide carryover is only 0.1ppm. The water used in the process is cleaned and recycled within the unit.

Centrica’s order follows the publication of the tariffs under the UK Government’s Renewable Heat Incentive (RHI), which will begin operating in April 2011. Under the RHI, feed-in tariffs will reward generators of renewable energy from a variety of sources. The gas generated from this kind of project will attract a tariff of 4.0p/kWh.

CBG are currently in discussion with a number of other potential operators of the upgrading system in the utilities, local government, food and transport sectors.