Sewage: The future of energy

  • Sewage: The future of energySewage: The future of energy
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Stop pinching your nose at sewage. It could be a clean solution for energy.

Today, 90 per cent1 of wastewater produced around the world goes untreated. Tomorrow, sewage could be used to power our cities.

The quest for clean energy has struck a new black gold, this time closer to home than we had imagined. The next time you flush a toilet, know that your body’s by-products may hold the key to an efficient, renewable, and carbon-neutral source of power.

Every year, the world produces 11.2 billion2 tons of solid waste, along with much more pollutants in the form of sludge comprising of fats, fertilisers, and compost. Most of this waste goes untreated; in low-income countries, as little as 8 per cent3 of waste undergoes any kind of treatment before being released into the environment.

Untreated sewage is not just a wasted economic opportunity; it’s also devastating to the environment. The pathogens in wastewater could infect already scarce freshwater sources and bring disease to rural and urban areas alike. Fertilisers dissolved in sewage cause unchecked algae growth in water bodies, decimating biodiversity. What’s more, decomposing waste produces large amounts of methane, a powerful greenhouse gas that contributes to climate change.

Waste not, fuel more

Fortunately, technological advancements are giving us a chance to reclaim our waste for clean energy. Using hydrothermal liquefaction – a process which uses high pressure and heat – waste can now be broken down into a substance that is strikingly similar to crude oil. When refined, the substance, which experts call biocrude, yields fuels that can be used in place of gasoline, diesel, or even jet fuel.

According to the US Department of Energy, which pioneered this technology in 2016, the amount of sewage processed in the US alone could generate the equivalent of some 30 million barrels of oil every year.

Similar projects of turning waste to fuel are taking flight globally. In 2018, the Spanish company Ingelia developed an industrial process to convert sewage into a solid, coal-like fuel. This new fuel, called biochar, is as efficient as coal but cleaner as well.

Lots of sludge everywhere

Sewage fuels have another key advantage – they are accessible to developing economies as well. Developing countries, which bear the brunt of sewage pollution, can easily adopt these techniques at the community level.

In Kenya, for example, the town of Nakuru has made headlines for creating a low-tech way to turn human waste into household fuel. In Nakuru, only 27 per cent4 of residents are served by the town’s sewage system. Hence, most of its waste ends up polluting lakes and low-income areas.

But thanks to a startup set up by the county government, this waste is now collected and carbonised into fuel blocks which can be used at home for cooking and heating. The conversion process relies on rudimentary materials that are easily accessible to impoverished countries.

The proliferation of sewage fuels would bring immense economic opportunities. Currently, sewage is mostly recycled for low-value uses such as fertilisers. If treated as an energy source, it can become a huge value added industry. Already, renewable energy industries in the US employ thrice as many workers as fossil fuel industries. Given its accessibility to less developed communities, the economic benefits offered by sewage fuels would unlock opportunities for the poorest regions worldwide.

Find out more about the United Global Innovation Fund, which invests in innovative companies across various industries.


  1. Source: Corcoran, E., C. Nellemann, E. Baker, R. Bos, D. Osborn, H. Savelli (eds). 2010. Sick Water? The central role of wastewater management in sustainable development. A Rapid Response Assessment. United Nations Environment Programme, UN-HABITAT, GRID-Arendal.
  2. Source: United Nations Environment Programme, “Solid Waste Management”, 2019.
  3. Source: United Nations University. “UN: Rising Reuse of Wastewater in Forecast but World Lacks Data on “Massive Potential Resource”, 2013.
  4. Source: Africanews, “Human poo transformed into clean fuel for Kenya's urban poor”, 2017.

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