This is interesting, it suggests that a herd of 200 cows produces as much greenhouse gas as driving a family car 3,000 miles. Dr Andy Thorpe of Portsmouth University said that 200 cows expel as much methane annually as the equivalent carbon dioxide emissions of a car burning 21,400 litres of petrol. He also says that whilst CO2 emissions have increased by 31% in the past 250 year, methane emissions have increased by 149%. Apparently methane has a greater warming effect than CO2 and also has a longer lifetime in the atmosphere as well as being responsible for a fifth of global warming since 1750. Around 55 to 70 per cent of methane comes from the farming of animals such as cows, sheep and goats which produce methane as they digest food. It makes me wonder what are the methane emissions of the human population? I suppose we could eat less meat and more vegetables but would that mean that we produce more methane?