Scotland’s largest wastewater treatment works achieving net zero

Global resource management company Veolia announced that it is helping Scottish Water to achieve net zero by increasing the amount of renewable energy generated at Scotland's largest wastewater treatment works (WwTW): the Seafield WwTW in Leith, Edinburgh.

“Scottish Water has one of the most ambitious Net Zero emission targets in the industry,” says Gordon Reid, net zero emission general manager at Scottish Water. “We are a very large energy user and achieving energy self-sufficiency at a site like Seafield is a key milestone for us.”

Since June 2022 Seafield has been a net exporter of renewable electricity, producing over 108% of the electricity it requires to run the site, with generation on some days being in excess of 125% percent of the site's needs. This equates to Seafield exporting enough renewable electricity to power over 800 homes every single day during this period, and is the first time the site has been a net exporter for such a prolonged period.

Seafield WwTW treats waste for a population equivalent of approximately 850,000 people from Edinburgh and the surrounding area, which equates to 300 million liters of wastewater daily (79.3 million gallons per day).

The United Kingdom’s water industry is the fourth most energy intensive sector and uses around 3% of UK generated electricity for pumping, water treatment and waste management. 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 nutrient rich byproduct it produces, which can be used by farmers as fertilizer. It acts as a low cost, highly effective alternative to traditional chemical based fertilizers that are normally used to provide vital soil nutrients for agriculture. The facility produces around 36,000 tons of this fertilizer each year. This effectively lowers the need for carbon intensive synthetic soil improvers, which can help reduce the carbon footprint of food production.