Barcelona Turns Human Waste Into Clean Fuel For Public Transport

For five years, passengers on Barcelona’s V3 bus line unknowingly rode on a vehicle powered by human waste.

The Nimbus project ran a bus using biomethane produced from sewage sludge as fuel, without foul odors, and generated significantly lower emissions than conventional fuels.

TechSpot reports that the project was developed by a partnership between Veolia, Barcelona’s public water distribution company, TMB, the city’s transport operator, and the Autonomous University of Barcelona.

Using the Baix Llobregat treatment plant, one of Europe’s largest, researchers refined wastewater into biomethane, a renewable fuel that emits 80% less carbon dioxide than natural gas, as reported by TechSpot.

The plant handles 400,000 cubic meters of wastewater daily, generating 250 metric tons of sludge. Biomethane from four cubic meters of sludge processed each hour was enough to keep the V3 line operating 100 kilometers daily.

Biomethane production requires refining biogas until it reaches 90% methane purity. Veolia’s process goes beyond standard practice by combining CO2 with hydrogen from water and renewable sources to convert nearly all biogas into biomethane.

The resulting fuel met Euro VI emission standards while producing small amounts of nitrogen oxides and fine particles.

Passengers who learned of the bus’s unusual fuel source reacted with surprise but approval. “I think it’s a fantastic idea. We already put animal waste to good use, so why not ours?” said Rosa Maria Gay, a 68-year-old retiree, as reported by Le Monde.

“If our excrement is useful for something, all the better!” added Leire Muños, a 32-year-old receptionist, reported Le Monde. “As long as it’s renewable energy and doesn’t smell bad, I think it’s great,” said Alessandra Spano, an 18-year-old computer science student, according to Le Monde.

After its success, Nimbus will now expand into a new project, SEMPRE-BIO, aimed at producing even more biomethane to fuel additional bus lines across Barcelona.