From poo to power

Yorkshire Water in the UK is working with Esholt sewage works to build a biothelys sludge treatment plant that will create energy from human waste.

The multi-million pound project will take effluent from the Yorkshire Water 750 acre sewage works, which currently collects waste from about 700,000 people, as well as about 300 litres of wastewater which it treats before dumping it into the River Aire.

At the moment, about 26,000 tonnes of sludge is produced as a byproduct of the treatment process and this will now be used in Veolia's thermal hydrolysis system (biothelys), combined with anaerobic digestion, to produce biogas.

Instead of being disposed of in landfill, the sewage sludge will be broken down in a thermal hydrolysis process that uses pressure and heat, before going through an anaerobic digestion system which creates biogas that can be used for the production of energy.

The renewable electricity will be used to power the site so that it does not need to use mains electricity, which will reduce the costs of running the facility.

Following this new added treatment, the sludge can also be used as a fertiliser or soil conditioner for a range of crops.

Ben Roche, manager of energy and carbon at Yorkshire Water, says: ‘Each year we receive an overall electricity bill for approximately £45 million (€54 million) with 70% of our carbon footprint coming from electricity - a footprint that currently stands at 453,000 tonnes of CO2.’

‘At the moment we already generate a third of the energy we use on site at Esholt through renewable energy technologies, but our aim is for this huge facility to become fully energy self-sufficient by 2015,’ he continues.

‘This pioneering technology will enable us to save around £1.3 million a year at this site alone which will help us in turn to keep customers' bills as low as possible.’

The plant is expected to take about 18 months to build and will be commissioned at the beginning of next year.

Engineers Morgan Sindall and Grontmij have been chosen to work on the project.

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