The utility will start work today on a £30 million project at the company's Esholt sewage works on the outskirts of Bradford, to install the UK's first BioThelys Sludge Treatment Plant which will be used to create energy from human waste and effluent.

The 750-acre sewage works is one of Yorkshire Water's largest facilities, serving a population of 700,000 people and receiving up to 300 litres of waste water a second which it treats to a high standard before discharging it into the River Aire.

As a bi-product of the treatment process, around 26,000 tonnes of sludge is produced at the site each year and the company is legally obliged to dispose of the majority of it either through incineration or landfill, in line with common industry practice.

The Esholt works has operated a sewage sludge incinerator for many years, but Yorkshire Water is pioneering a more sustainable route for sludge disposal using Veolia's thermal hydrolysis system (Biothelys) combined with anaerobic digestion.

Thermal hydrolysis uses heat and pressure to break down sewage sludge prior to treatment by anaerobic digestion which creates energy rich biogas that can then be burned to produce electricity which in turn will be used to power much of the plant.

Not only does the process create green energy to fuel the plant, but the digested sludge generated following thermal hydrolysis is classified as 'enhanced treated' which means it can be legally applied as a fertiliser or soil conditioner for all crops including cereals, vegetables and salads as well as for horticultural purposes.

Work will result in completely energy-neutral site

Ben Roche, Manager of Energy and Carbon at Yorkshire Water, commented:

"Each year we receive an overall electricity bill for approximately £45 million with 70% of our carbon footprint coming from electricity - a footprint that currently stands at 453,000 tonnes of CO2e.

"For some years now, as the environmental impact of energy usage has been more widely understood coupled with the increasing cost of energy prices, we've been exploring how we can reduce our energy consumption and our reliance on grid electricity, as well as our environmental impact, through renewable energy generation and other activities.

"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.

"We're hoping to realise this through the creation of the UK's first BioThelys thermal hydrolysis plant, which will not only enable us to put our sludge to good use in an environmentally friendly way, but will also mean that our site is completely energy-neutral making it one of the greenest plants in the UK.

"In addition, 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 new plant will take around 18 months to complete and is expected to be commissioned in early 2013.

Engineering specialists Morgan Sindall and Grontmij will be undertaking the work, in what is one of the biggest contracts ever awarded by Yorkshire Water.

The thermal hydrolysis plant is the latest project to be progressed by the company as it looks at innovative ways to reduce its environmental and carbon impact, and its overall annual electricity bill which currently stands at £45 million, with the company's Esholt site leading the way.

In 2010/11, use of its own renewable energy sources produced around 10% of the company's overall electricity needs, with Yorkshire Water aiming to increase this figure to around 16% by the end of 2015 and to more than 25% by 2020.

Amongst the existing renewable energy technologies at Esholt are the UK's first sewage screw hydro-generator, which uses two, 10 metre long Archimedes screws which harness the energy created by the waste water as it flows downhill from the inlet to the first stage of treatment, creating around 5% of the site's daily energy requirements.

Groundbreaking energy generation in prospect

In what is a world-first, the company is also currently trialling a process at its Esholt plant to enable it to recover energy from some of the waste products which enter its sewage works, such as sanitary wear, cotton wool buds and toilet paper - all of which have traditionally gone to landfill in line with standard industry practice.

Early indications show the potential for significant, ground breaking energy generation, further enabling the company to deliver cost-effective electricity whilst securing an environmentally and financially sustainable route for these problematic waste products. The trial is sect to complete in March 2012 with plans already underway for commercial deployment within Yorkshire Water.

On a wider level, the company is also working with Encos on a trial to create carbon-neutral building bricks out of sludge and vegetable-oil-based binders, which is again helping to reduce the amount of sludge sent to landfill. If the trial proves successful and the bricks are approved for building use, it has the potential to revolutionise both the construction and water industries.