Human Poop To Power Mars Trips?

By Roland Piquepaille

According to a study commissioned by NASA, a crew of six astronauts would generate six tons of solid waste during a two-year trip to Mars. In "Harnessing the Power of Poop," SPACE.com says that NASA scientists have identified a bacteria, the Geobacter, found in the Potomac river in 1987, which could transform this waste into electricity. The bacteria would live in a membrane microbial fuel cell. There, they would catch electrons from human waste and produce electricity for use aboard a spacecraft or on a Martian colony. When these fuel cells pass the development stage, they would potentially be used on Earth, in our own homes, by recycling our own organic waste.

Here are some details about the bacteria and the membrane microbial fuel cell which will be used.

Geobacter microbes were first discovered in the muck of the Potomac River in 1987; they like to live in places where there's no oxygen and plenty of iron. They also have the unexpected ability to move electrons into metal. That means that under the right conditions, Geobacter microbes can both process waste and generate electricity.

Below is a photomicrograph of Geobacter metallidreducens (Credit:NASA).

The "right conditions" might be found in a new type of fuel cell--a membrane microbial fuel cell. This device is currently being developed by a NASA-funded research team led by Bruce E. Rittmann, a professor at Northwestern University.

Microbial fuel cells obtain their electrons, instead, from organic waste. The bacteria at the heart of the device feed on the waste, and, as part of their digestive process, they pull electrons from the waste material. Geobacter microbes, as well as a few other types, can be coaxed to deliver these electrons directly to a fuel cell electrode, which conducts them into a circuit -- a wire, for example. As they flow through the circuit, they generate electricity.

As we all know, human trips to Mars are still two decades away. So there is plenty of time for the development of these microbial fuel cells.

The membrane microbial fuel cell is still in the early stages of its development. Yet, if the project succeeds, we may find these devices not only in space, but also in our own homes. After all, astronauts aren't the only ones that produce organic waste.

"You have to treat the wastes anyway," points out Rittmann. "So why not make the process an energy gainer, instead of an energy loser? By producing electricity, microbial fuel cells would make the process of purifying waste streams much more economical."

For more information about the potential of this technology, this link at NASA provides an excellent list of resources, including this one about the Geobacter Project at UMass Amherst.

Source: Karen Miller, Science.NASA.gov, for SPACE.com, May 19, 2004; and various websites