Producing fuel on Mars using astronaut wastewater

In future missions to Mars, astronauts will need to maximise the use of all resources available on site to produce essential supplies like oxygen, water and fuel. A team from Spanish technological centre Tekniker and the University of Cantabria is developing a system that uses sunlight to turn carbon dioxide and wastewater into methane, which can be used as fuel.

The researchers aim to create a reactor for the production of fuel on Mars using the planet's air, which is 95% carbon dioxide. Sunlight powers the reactor, and the system incorporates astronauts' greywater – used water coming for example from a bathroom sink or shower. 

The 'photoelectrochemical' system in the reactor is capable of splitting water molecules into hydrogen and oxygen, and uses the hydrogen together with carbon dioxide to create methane. Since the greywater would also be detoxified in the process, the system would double as a waste recycling method.

"This activity represents a significant leap forward in space exploration and sustainable carbon dioxide conversion technologies," explains Elena Garcia, Tekniker's lead for the project. "Unlike prior technologies, our reactor addresses both carbon dioxide reduction and greywater treatment simultaneously, enhancing sustainable mission planning."

The HISRU project ('Photoelectrochemical system for CO2 reduction to produce fuels and sewage treatment') was submitted through the Open Space Innovation Platform (OSIP) and implemented by the Discovery element of ESA's Basic Activities.

Mars' otherworldly conditions

Since the researchers are developing this system to be employed on Mars, they need to take into account the Red Planet's environment. Because of its distance from the Sun and a relatively dusty atmosphere, Mars gets less than half the sunlight Earth does – this means that any solar-powered technologies destined for the planet need to be adjusted to these conditions.

Besides consisting mainly of carbon dioxide, the air on Mars is also extremely thin – martian air pressure is less than 1% of the air pressure we experience on Earth. To make sure the reactor will function in these conditions, the team tested their prototype in a machine simulating the martian environment.

Development continues

The researchers have delivered their results in a final presentation at ESA's ESTEC technical centre in the Netherlands. "This activity shows the potential of the HISRU technology to reduce carbon dioxide for the production of oxygen and methane from greywater both on Mars and Earth," says Jean-Christophe Berton, OSIP call initiator and ESA's lead for the project.

At the moment, several improvements are required to increase the energy efficiency and reduce the overall environmental impact for terrestrial applications. While the technology seems promising for Mars exploration, it requires further improvements at system level to meet operational requirements.

"Support and funding from ESA Discovery via OSIP have been fundamental to enabling this innovative approach. ESA has supported us along the way, from the essential preliminary studies through manufacturing to assembly and testing," says Elena.

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