With all the waste that comes in, GENeco must process it to get the bio-gas out. First they strain out all the sands and other grits, along with plastics, polymers and, as GENeco's recycling manager so casually points out, contraceptives. From there the waste undergoes bacterial anaerobic digestion for two weeks. This process breaks the waste down into a gas and solid. The gas is mostly methane and partially CO2. The solid will be used as a fertilizer, as it is still extremely nutrient-rich.
Now, you might think all this digestion would use up a lot of energy, but processing all the waste actually produces more energy than it uses. The facility is completely carbon neutral, and one day could run on the energy it produces. This is a position that many other energy sources have not accomplished yet. In fact, the site produces about 35 Gigawatt-hours per year, or enough to send McFly back to the future almost 29 times.
So why did GENeco pick the VW Beetle? When asking kids about the project, they suggested that they use the VW bug because the process of collecting all the methane depended on many little bugs to digest the waste. Pretty clever. We just aren't sure if a convertible was the best idea.
The car works just like a CNG car. There are two tanks in the rear that store about 23 liters of methane. The pressure of the tanks run at 200 bar, but when going into the engine, pressure is reduced to 2 bars.
The Bio-Beetle still uses gasoline to start, but only runs on it for about 30 seconds until the car has warmed up. Once ready, a controller automatically switches to methane and you're riding purely on what amounts to the magic toots of science.
Looking further to the future. GENeco plans to digest even more materials, including those plastics and polymers. This would cut down the amount of time needed to produce bio-gas and could also improve yields.