A water management company and a car manufacturer normally might not have much to say to each other, but in Spain, Aqualia and SEAT are teaming up to develop a sustainable fuel from wastewater. The project, known as Life Metha-morphosis, is aimed at creating a biofuel from treated organic waste, which can then be used to power compressed natural gas (CNG) cars, whose CO2 emissions would be cut by up to 80 percent.

The program is built around producing biomethane, an emerging biofuel that's already been demonstrated in powering homes, buses, trucks and ships. Life Metha-morphosis, like some other projects, collects biomethane by employing bacteria to break down the solid waste, in a process called anaerobic digestion (AD).

Two different facilities are being built to demonstrate new ways to handle the task. The UMBRELLA prototype set to be installed at a sewage treatment plant that serves metropolitan Barcelona uses a new anaerobic membrane bioreactor (AnMBR) process to separate the gas from the solid waste. Another system called Annamox ELAN then removes nitrogen from the biogas, before it's further cleaned, refined and compressed into CNG for use in vehicles. The company also says that the treated water the technique produces is cleaner than what usually comes out of treatment plants, and the nitrogen that's removed from the gas can also be reclaimed.

A prototype called METHAGRO, meanwhile, will be built at a plant that deals with animal manure from agriculture and farming, creating biomethane to power cars or to be fed back into the public natural gas infrastructure.

The companies involved say a mid-sized plant can treat about 10,000 cubic meters (353,000 cu ft) of wastewater per day, which in turn creates 1,000 cubic meters (35,000 cu ft) of biomethane. That's enough fuel for 150 vehicles to travel 100 km (62 miles) each day. Auto maker SEAT will provide some CNG cars to test the new fuels in over a total distance of 120,000 km (74,500 mi).

Overall, taking into account both the use and production of the biogas, CNG cars running on biomethane made this way should belch out 80 percent less CO2 than gasoline-powered cars. By developing these facilities, the Life Metha-morphosis project is intended to at least partially comply with the European Union's Energy Efficiency Directive targets for 2020, as well as Spain's own Energy Saving and Efficiency and Renewable Energy plans.