When you think about ways to pare down your carbon footprint, certain things come to mind. You could ditch the electric water heater and go solar instead. Alternatively, you might forgo the flight to Europe and subscribe to GreenPower. Less well-known is the sizeable contribution of food purchases to each individual’s total greenhouse emissions in the form of carbon dioxide, methane, nitrous oxide and fluorocarbons.

Fortunately there are ways to modify our diets to cut back on these gases and help tackle a range of other environmental issues. In the UK, Canada and Sweden, consumers are now able to make use of carbon labels on food products as a means of cutting their carbon footprints. They will probably be arriving in Australia, too, when enough people demand them.

Meat, dairy and some alternatives

Among items in the shopping basket, animal foods are responsible for some of the highest emissions, and an average family’s meat consumption can contribute more to global warming than the manufacture and running of a four-wheel-drive vehicle. The UN Food and Agriculture Organization’s 2006 report Livestock’s Long Shadow estimates that the rearing of livestock produces 18 per cent of the world’s greenhouse emissions, more than all transport sectors combined.

As meat products go, from a greenhouse perspective beef is the biggest emitter, followed by pork, with chicken the least of the three. Another major meat-related issue is its sometimes huge water footprint. Professor Wayne Meyer of the University of Adelaide has estimated the “embodied water” for one kilo of Australian beef at 50,000–100,000 litres. Among dairy products, cheese is the most greenhouse-intensive, with milk the least.

Feedlots, which are widely used for raising Australian beef, chicken and pork, have a sizeable ecological footprint of their own. Their large appetite for grain feeds consumes land, energy, water and chemicals, while the fertiliser use causes extra emissions of nitrous oxide, a greenhouse gas with about 310 times the global warming potential (GWP) of CO2. The wastes generated can present a huge disposal headache and may emit the toxic gases hydrogen sulphide and ammonia.

For those who still like the idea of eating a steak, grass-fed beef has the advantage of cutting out the animal feed. Unfortunately, the benefits are not so clear-cut, as grass-fed cattle emit significantly higher quantities of methane, a greenhouse gas with a GWP of 21. An Australian study released early this year indicates that overall greenhouse emissions from grass-fed beef are higher than feedlot beef, although it omitted the huge potential for carbon sequestration on beef pastures, which some believe would tip the balance back towards the grass-fed camp.

Also, cattle should eat grass instead of grain. When they are fed corn in feedlots they require extra antibiotics and can experience a sensation similar to heartburn due to the acidity of corn and feedlot bloat, which is caused when the rumen (part of the cow’s digestive system) fills with gas that cannot be released. This has the potential to suffocate the animal.