In recent years, Barcelona has made headlines with a number of successful urban planning initiatives. One of the most famous ones is the superblock — a car-free zone that prioritizes pedestrians and cyclists by diverting traffic to major roads outside the city center.

Greener transportation

The radical superblock program was implemented with the goal of reclaiming the streets from the noise and air pollution of traffic. Now, in a bid to complement these efforts, the city has devised plans to fuel its immense bus fleet with sewage sludge.

Barcelona has a fleet of 1,100 buses, about 900 of which drive through the city’s streets during rush hour. The vast majority of these vehicles run on fossil fuels, thus diminishing the city’s air quality and contributing to climate change.

Aiming to find a more sustainable fuel alternative for its enormous bus fleet, the city has recently put together plans to start a pilot project to produce biomethane — a renewable natural gas — from sewage sludge. The initiative is part of the Nimbus Project, which aims to encourage a circular economy in the city, starting with green public transportation.

From sewage sludge to biofuel

The process will involve gathering sewage sludge at water treatment plants, where the material is created as a by-product of the water purifying process. The sludge, in turn, creates biogas — made of methane and CO2 — which is typically stored in silos and burnt at a later stage to power part of the plant, reports euronews.

The new initiative, however, will remove CO2 from the biogas to create biomethane, which will be compressed at high pressures and used as fuel for a bus. “At first, it will power a single bus. The idea is to use it to power many more in the near future,” said Mauri Poch, a strategic developer engineer working at the Baix Llobregat wastewater plant, where the project will kick off in March.