3. Biogas Upgrading
After cleaning, biogas can be converted to a variety of biofuels.
3.1. Natural Gas
Injecting purified biogas into natural gas pipeline has become a common practice. According to the US pipeline specifications, natural gas pipeline injection typically contains CO2, water vapour, H2S and O2 at less than 3%, 112 mg/m3, 350 mg/m3 and 1 ppm, respectively. Low concentration of water vapour and H2S is essential to avoid condensation and corrosion. Under certain conditions, long distance pipelines have to be heated, or the gas which is to be transported has to be preheated. Otherwise the temperature would fall below the dew point, because the gas temperature drops in the pipeline and corrosive condensate would develop. In the United ...