Since June 2022, Seafield has been a net exporter of renewable electricity producing more than 108% of the electricity it requires to run the site, with generation on some days being in excess of 125% of the site's needs.
Seafield WwTW is said to treat waste for a population equivalent of approximately 850,000 people from Edinburgh and the surrounding area which equates to 300 million litres of waste water every day. As the UK water industry uses around 3% of UK generated electricity for pumping, water treatment and waste management, achieving energy self-sufficiency is a key milestone. By implementing a range of innovations covering anaerobic digestion, thermal hydrolysis and 3.9MWe of combined heat and power technologies, the site produces its own renewable biogas supply from the wastewater treatment, and uses this to generate renewable electricity and heat to support the site’s operations. The success of the energy plant has enabled the site to exceed its target of energy self-sufficiency, taken pressure off the grid, and cut carbon emissions and energy costs.
A further benefit of the processes is the by-product it produces which can be used by farmers as a fertiliser. Around 36,000 tonnes are produced each year and act as a low cost alternative to traditional chemical based fertilisers that are normally used to provide soil nutrients for agriculture. This effectively lowers the need for carbon intensive synthetic soil improvers which can help reduce the carbon footprint of food production.
Gavin Graveson, Veolia senior executive vice president Northern Europe Zone, said: “Recent estimates indicate that the water industry could be self-sustaining for electricity by harnessing the 11 billion litre annual flow of waste water. Our application of technology to this process at Seafield demonstrates how we can help deliver greater sustainability, make a significant contribution towards delivering renewable energy targets, and take pressure off the National Grid.
"This achievement really demonstrates what is possible now, and the future shows an even greater potential for this technology. If all available 130 million tonnes of untreated feedstocks, such as wastewater, agricultural slurry, food and green waste were treated through anaerobic digestion (AD) this could supply renewable electricity equivalent to powering 10.2 million homes."