There are two basic types of digester, batch digesters and continuous digesters. Natural gas contains about 80% methane, with a heating value of around 1000 BTU per cubic foot (35 BTU per litre).įiltering biogas, or 'scrubbing' it, can remove the carbon dioxide and the other impurities, raising the BTU. Its heating value is around 600 BTU per cubic foot (21 BTU per litre).

Anyway, you won't get impaludism from making biogas because it all happens inside a closed digester.īiogas usually contains about 55-65% methane, 30-35% carbon dioxide, and some hydrogen, nitrogen and other impurities. Before they drained their swamps, the English were prone to malaria (previously called 'the ague', often mentioned in Shakespeare), and to a disease called impaludism, defined in The Lancet 120 years ago as the general state of morbidity afflicting people who lived too close to a bog, characterised by frequent fevers, enlargement of the spleen and other ailments. Methane is also called marsh-gas it's what will-o'-the-wisps are made of, the ghostly lights sometimes seen flickering over marshes at night, the source of much mediaeval fear and superstition, and not without cause. Landfills and tips that leak methane are a major contributor to human-caused global warming.īut you won't be releasing any biogas into the atmosphere, and when you burn it, the only emissions are carbon dioxide and water vapour. Making and using biogas is part of the natural cycle, and it doesn't contribute to global warming. For a detailed explanation of this, see 'Greenhouse gases and global warming'. But, also like carbon dioxide, the methane produced in the natural cycle of growth and decay is climate-neutral. Like carbon dioxide, methane is a greenhouse gas in fact it's 23 times worse than carbon dioxide. Natural gas is indeed natural, in the same way that petroleum is natural, and, like petroleum, it's a fossil fuel it's heavily processed, its production depends on fossil fuel inputs every step of the way, and it contributes to global warming. Chemically they're the same, but that's where the resemblance ends. The 'natural gas' piped to millions of consumers in North America, Europe and elsewhere is also methane, though it's purer than biogas.

Classics on organic growing, soil and health (full text online)īiogas, or methane, is a clean-burning, 'green' fuel used for heating and cooking, transport and power generation and you can make it yourself.

Design biogas plant pdf viewer