Guardian Labs/Emily Reynolds: Poo power: is it time to embrace our waste as a source of renewable energy?

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Poo power: is it time to embrace our waste as a source of renewable energy?
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Whether it’s being used to fuel the local bus, or help tackle social challenges around the world, the value of human sewage could be greater than you think

Emily Reynolds @rey_z

Thu 26 Apr 2018 18.10 BST

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Methane-rich biogas – created from sewage – has the same quality as natural gas. Photograph: Audrey Shtecinjo/Audrey Shtecinjo / Stocksy United

Poo: not the most glamorous topic, is it? Aside from the occasional bit of scatological humour (scatology being the study of faeces … delightful), most of us happily steer away from regularly talking about it, for fairly obvious reasons.

But, if you push past the initial icky revulsion of talking about human waste, you’d find out that it actually contains a vast amount of potential value in terms of energy, providing a sustainable form of fuel that we could all help supply.

In 2015, research by the United Nations University found that human waste was a potential fuel source and if all of it was collected worldwide, annually it would be “great enough in theory to generate electricity for up to 138m households” – which is all of Indonesia, Brazil, and Ethiopia combined. An equivalent amount of natural gas would cost $9.5bn (£6.7bn).
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Poo-powered innovations are already happening, too. Earlier this year, a Worcestershire man made headlines when, fed-up with seeing bags littered across the scenic Malvern Hills, he designed a street lamp that runs on dog poo – two hours of light for every 10 bags of poo.

There are companies across the UK that are also starting to explore the potential of poo power on a larger scale. Bristol-based renewable energy company GENeco is using sewage waste from the city to create green gas, which is then supplied to homes across the UK by Bristol Energy.

“When sewage waste arrives at GENeco’s treatment plant in Bristol, it is treated and turned into what’s called ‘sludge’,” explains Bristol Energy renewables and origination manager Simon Proctor. “This forms the raw fuel for the anaerobic digestion plant.”

During anaerobic digestion, organic matter – in this case, the sewage sludge – is broken down by microorganisms in an airtight container; Proctor compares it to “the way a cow’s stomach breaks down grass”.

This process produces methane-rich biogas, which is treated to remove impurities and ensure emissions are odour-free. The enriched biomethane is then injected into the gas distribution network. “It has the same quality as natural gas, and can be used in our homes as an alternative to fossil fuels,” Proctor says.

The results are impressive. According to Bristol Energy, an average household’s weekly flushes could produce enough biomethane to cook a fry-up; two weeks’ flushes could cook a roast dinner; and annual flushes from every household in Bristol could fry 83m eggs.

Biomethane was also used as fuel by GENeco to run a “Bio-Bus” shuttle to and from Bath and Bristol airport and also on a regular bus service within Bristol, aptly named the “number two route”. The bus travelled more than 180 miles on a tank of gas produced by the annual food and sewage waste of just five passengers.

Sustainability is at the heart of the entire process. “Producing biomethane from sewage waste means that we don’t have to use fossil fuels,” Proctor says. “Burning fossil fuels is one of the biggest sources of CO2 emissions in the UK. Switching the average UK home to renewable energy can save more than 1.5 tonnes of greenhouse gas emissions a year, that’s equivalent to taking a car off the road for six months.”

He also points out that while we can try to reduce other forms of waste, such as packaging, plastic or food, reducing the level of sewage waste “is obviously going to be more difficult” – making the process an important step towards a more sustainable world.

Bristol Energy will also invest its profits back into the city, creating what Proctor calls a “circular economy”. “Sewage waste from Bristol is recycled into green gas; our customers switch to a locally owned company and save money – and then our profits will go back into the local community,” he says.

That doesn’t mean there aren’t drawbacks, however, particularly in terms of the adoption of the process. Installation and maintenance costs for anaerobic digestion systems can be high, and many companies have been forced to rely on government initiatives to keep running. Proctor says that support under such schemes has been “very ambiguous at times”, which could be, in part, what is preventing more companies from adopting similar systems.

Prof Chris Metcalfe, director of the Institute for Watershed Science at Trent University in Canada, worked on the UN study into human waste. He believes that biogas should be considered a resource not only for energy production, but also as compost “for improving agricultural productivity” and for the recycling of water for irrigation.

“In most cases, we’re wasting this resource by either putting the solids into landfill or by discharging the liquid sewage into lakes and rivers,” he says.

The main issue, Metcalfe believes, is not the technology – in fact, he says there are no real technological barriers to the use of human waste as fuel. Instead, it’s “people’s attitudes about using human waste” that causes problems. “In many countries, the idea of collecting and using human waste is not culturally acceptable, even though animal manure is often used for biogas production,” Metcalfe explains.

But Proctor says human waste is already being used more widely than we may think. This is evident across the world, where the process is increasingly being used to improve sanitation in developing countries. In India, where $20bn (around £14bn) of government funding has recently been put towards building sanitary toilets, social project SHRI (Sanitation and Health Rights India) uses an anaerobic biodisgestion system to provide electricity to pump ground water that is later filtered and sold, with profits paying for the ongoing maintenance of the toilets.

SHRI views its project not only through the lens of sustainability. Open defecation is a social issue, too: 600 million people in India defecate in the open [pdf], something that SHRI describes as part of an “ongoing struggle for health equity and economic and social justice”. A 2016 study found that women who use open defecation are twice as likely to experience sexual violence as those with access to an indoor toilet. Here, the biogas system isn’t just providing fuel – it’s also helping provide an alternative to potentially dangerous practices.

Elsewhere in Uganda, a team led by Metcalfe have begun to produce biogas through human waste [pdf], he says. And in Senegal, sewage is also being converted into drinking water through a project funded by the Bill & Melinda Gates Foundation. According to Bill Gates, the water is “delicious”.

It may not be glamorous, sexy or particularly futuristic; it may still seem slightly icky. But it’s undeniable: whether it’s being used to fuel cars, buses or homes in the UK, or to improve sanitation conditions across the world, poo has the power to change lives.

To find out more about how you can support green energy and save money on your bills, visit bristol-energy.co.uk
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