Surfers hate it, kids love talking about it, it smells, but it does have its uses: a by-product of treated sewage is sewage sludge. In the UK sewage used to be dumped out to sea, causing pollution to our beaches and marine life. EU legislation put a stop to this: however many other countries still continue this practice. Through the process of digestion and incineration, sewage produces a biogas that can be used to generate energy. Bacteria within the sewage break down the solid biomass content and reduce smells. Sewage gas is a mixture of methane, carbon dioxide, hydrogen sulphide, nitrogen and hydrogen. The proportion of methane content in sewage varies considerably, making it highly volatile and therefore difficult to deal with. History Point: In the 1930's sewage gas was used to power public transport systems in some German cities, including Essen and Munich. Hardly surprising when the organic waste from one person can produce 30-35 litres of fermentation gas per day!
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