BY PANOS PREVEDOUROS PHD – Furthering the efforts of recycling, re-use and sustainability, Bristol, UK water and sewer company has developed infrastructure to produce methane-based biogas from sewage waste, clean it from its high content of CO2 and fuel cars with it.
Compressed Natural Gas is not new as a fuel for vehicles. Just to name a few, Athens, Rome, Seattle-Tacoma and Seoul use GNG in all or most of their public transit bus fleets. Australia has tens of thousands of private cars powered by CNG or LPG, which is liquefied petroleum gas.
The main sources are, as their name implies, Natural Gas and Petroleum Gas. A third source of methane is organic matter decomposition (which actually created natural gas in the strata of the earth over the millennia.)
Renewable sources of organic matter include biomass, food waste and … poop. Sludge, the accumulation of solids at waste treatment plants, is often problematic even for cities like Honolulu which has two Waste-to-Energy facilities, so it typically up in the landfill. (Honolulu had a contract to develop fertilized pellets from it, but the venture was not successful.)
The dumping of thousands of tons of sludge is, of course, a lose-lose situation because of the loss of land and the loss of an energy source at the same time. Bristol’s Wessex Water has developed and biogas and demonstrated the Bio-Bug, which other than a simple modification to the fuel supply and storage system remains a conventional Bug with the original engine (and in most similar applications the car is switchable on-the-fly between gasoline and methane/propane/butane.)