All-gas biofuel plant in Chiclana, Spain (Photo: All-gas)

Humans are a lot like cars.

No, seriously--in order to make us work, we need fuel. That fuel is our food, which we metabolize in order to function, and anything not required by the body we produce as waste. Sounds familiar, right?

Conveniently, that waste can then also be used to fuel our cars, albeit after a few more processes have taken place. That's what is happening in one Spanish town right now, where sewage from the town's residents is being used to produce a green biofuel.

While our bodies might be done with certain substances after we've used them in our body's chemical processes, bacteria in our dung (and the dung of other creatures, for that matter) can produce useful byproducts such as methane, or to fertilize algae used to create biofuel.

The latter is what Spanish firm All-gas is doing in the town of Chiclana, Reuters reports.

A facility just outside the town uses the waste water and southern Spanish sunlight to grow algae, then used to produce biofuel.

It's a small part of Spain's $15.7 million plans to research algae-based biofuel, in an effort to pursue alternative energies and reduce the country's dependence on imported oil.

With Spain in the midst of record unemployment and huge budget deficits, the cost-effectiveness of the process is of high priority. Luckily, All-gas says its biofuel project is over $2.6 million cheaper to set up and run than a conventional sewage plant, and is gaining plenty of interest from several small towns in Spain.

At the moment, the small existing plant is still in early stages, having harvested its first algae crop last month. By 2015, the plant aims for 3 tons of annual production from 10 hectares of land, enough to fuel around 200 cars or 10 city garbage trucks per year. It won't be replacing regular petroleum products for some time then, but as a low-cost and low-carbon alternative to fueling a city fleet on regular gasoline, it still has its place.

The plans are small at the moment, but with enough land and interest from other cities there's little to stop the project expanding further.

And the best thing is, local residents need do no more than remember to flush...