Veolia and Southern Water turn to sewage to boost renewables generation

Southern Water has moved to reduce its carbon footprint by converting sewage into renewable energy, after waste specialists Veolia installed new combined heat and power (CHP) engines at treatment facilities in Hampshire and Kent.

Southern Water generates 17% of its electricity demand from 16 CHP sites. Upgrades to systems at Budds Farm, Fullerton and Gravesend has brought total renewable electricity generation to 48.3GWh across the sites.

The new projects have seen Veolia carry out project design, installation and operation of biogas cogeneration units, which converts wastewater from Southern Water’s 39,000km of sewage networks into biogas through anaerobic digestion (AD).

Veolia’s chief operating officer Gavin Graveson said: “Recent estimates show that biogas from the sludge resource could deliver an estimated 1,697GWh each year – enough electricity to power over half a million homes. This latest extension of the use of CHP by Southern Water clearly demonstrates its commitment to further the sustainability of the water industry.”

The new systems will reduce Southern Waters carbon footprint by 3,600 tonnes and in total, all CHP systems purchased by the firm will reduce CO2 emissions by 8,800 tonnes. This is comparable to removing around 5,800 cars from the road.

The biogas captured by this process will provide electricity to power Southern Water’s wastewater treatment operations. Any surplus electricity will be fed to the grid and heat recovered from the CHP units is used to speed up the AD process.

Southern Water’s energy manager Martin Ross added: “The capturing of biogas is a double win because not only do we collect free fuel but we also prevent the release of methane which has a global-warming potential 25 times more potent than carbon dioxide.”

Savoring sewage

Around 190 UK wastewater sites now use on-site biogas production methods. One of the more ambitious sites is Yorkshire Water’s Knostrop site in Leeds. The facility, which is set to be completed in 2019, will process 131 tonnes of dry sludge every day, generating 55% of the site’s energy requirements and helping to achieve 94% recycling of the region’s sludge by 2020.

Biogas from human waste is gaining prominence in the UK, but it could help curb emissions in developing countries. Research from the UN University’s Canadian-based Institute for Water, Environment and Health has suggested that safely obtained biogas from human waste could generate electricity to power all of the households in in Indonesia, Brazil, and Ethiopia combined.

Matt Mace

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