New pilot study effectively created renewable energy gas from sewage sludge –helping communities to sustainably clean up waste and save money
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Researchers have developed a new method to treat sewage sludge to create renewable natural gas, potentially cutting both emissions and costs for wastewater treatment plants.
The work, published in the Chemical Engineering Journal, could help communities sustainably clean up waste while simultaneously getting renewable natural gas for their energy needs.
For the study, the research team – from Washington State University – treated sludge at high temperatures alongside adding a bacterial strain that converted biogas into renewable natural gas. In doing so, they produced 200 per cent more renewable natural gas compared to current practices. As well as this, the process cut costs – reducing the final disposal cost of sludge by nearly 50 per cent.
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The team has since patented the bacterial strain and is working with an industrial partner to develop a larger-scale project.
Wastewater treatment facilities use large amounts of electricity to treat wastewater, accounting for between three and four per cent of total electricity demand in the US. Their treatment processes also contribute significantly to global warming. In a single year, they add around 21 million metric tons of greenhouse gases to the atmosphere – equivalent to adding around four to five million cars to the world’s roads.
So, with wastewater plants among the largest energy users in many communities, the new approach discovered by scientists could help shift away from being significant energy consumers.
The renewable natural gas produced in this process can be used in the same way as fossil-fuel-based natural gas for a wide variety of uses, such as electric generation, home heating or transportation – all without the same climate effect as fossil fuels.
While pilot results are strong, scaling such a project up onto large municipal systems may be a different story. However, if these challenges are adequately addressed, wastewater facilities could be primed to contribute to renewable energy production rather than be a source of emissions.
‘This technology basically converts up to 80 per cent of the sewage sludge into something valuable,’ said corresponding author on the paper Birgitte Ahring. ‘If we can replicate this work on other organic materials, we’ll have a waste treatment technology that is world-class when it comes to efficiency.’
