Nanogirl: How green are your greens?

By making a few simple food substitutions, the environmental impact of the food we eat could be significantly reduced. Photo / 123RF

It’s no surprise a diet rich in fruit, grains and veges is kindest to the planet but the first comprehensive carbon footprint league table for fresh foods will tell us just how green our greens (and meat) are.

Vegetarians have often argued that their diet is more environmentally friendly than the diets of omnivores.

It makes sense; if we feed plants to animals and then eat those animals, we will use more resources and produce more greenhouse gases than if we just ate the plants to start with.

Food labelling has enabled us to see how many calories and what nutrients a beef burger has compared to a veggie burger, but what about food labelling to compare their environmental impact?

Research just published in the Journal of Cleaner Production compiled the first comprehensive carbon footprint league table for fresh foods.

The researchers reviewed 369 published studies that provided 1718 global warming potential values for 168 varieties of fresh produce including vegetables, fruit, dairy products, staples, meat, chicken and fish from around the world.

As expected, they found that fruits, grains and vegetables had the lowest impact on the environment, followed by nuts and pulses.

When it came to meat - chicken, pork and fish offered the greenest options with moderate carbon footprints.

In New Zealand, cattle have been the focus when it comes to climate impact and for a good reason.

Beef and dairy products had the highest environmental cost of the foods studied with lamb not far behind. This is because the digestive system of ruminants such as cows and sheep consist of a four-chambered stomach which digests plants by fermentation.

The fermentation produces methane as a byproduct which is a greenhouse gas with around 20 times the heat-trapping ability of carbon dioxide. At almost one-third of New Zealand's total greenhouse gas emissions, the release of ruminant livestock methane is our largest single contributor.

For the New Zealand produced food analysed in the study, 1kg of greenhouse gas emissions approximately equals: 4 New Zealand Kiwi fruit, 24 New Zealand apples, 60g New Zealand lamb, 888ml New Zealand milk, 100g New Zealand cheese.

In foods not produced in New Zealand 1kg of greenhouse gas emissions approximately equals: 2.6kg oats, 1kg lentils, 1.2kg peanuts, 4 eggs, 270g chicken, 44g Australian beef.

The study included details on whether foods had been farmed, the farming style and the country of production. From this, one thing became clear - not all lamb chops, tomatoes or fish are created equal.

The researchers hope that this new list will help consumers to calculate the environmental impact of the fresh food that they buy so shoppers can quantifiably see the impact that their food choices could have on the environment.

With summer around the corner and barbecue season about to begin, many of us won't want to give up our summer steaks and sausages completely.

A study of Australian diets found that the average family of four produces a weekly carbon dioxide emission of around 115.8kg from their food shop alone. Using the data from this new table, the substitution of beef and lamb for chicken and fish in their weekly shop resulted in a 30 per cent reduction in the food greenhouse gas produced by the family.

By matching their weekly protein intake with a plant and fish based diet the family produced a 52 per cent reduction in their food greenhouse gas emission.

In New Zealand agriculture produces 48 per cent of our total greenhouse gas emissions. This new research shows that by making just a few simple weekly food substitutions, the environmental impact of the food we eat could be significantly reduced.

With a growing consciousness around eating in a more planet-friendly way, restaurants could use this information to create more sustainable recipes and perhaps the menus of the future will contain a low carbon footprint option.