Canned and pouched wet pet food appears to be nearly seven times as bad for the environment as commercial dry food.
Calorie for calorie, the production of wet food for dogs and cats creates 690 per cent more greenhouse gas emissions than making dry kibble does, because of the higher animal protein content. For a 10-kilogram dog eating wet food, this could mean an annual carbon “pawprint” roughly equal to the human footprint with regards to food consumption, says Márcio Brunetto at Sao Paulo University in Brazil.
“Our study demonstrates that the production of pet food in Brazil has an important environmental impact and this is certainly similar in other countries,” he says.
Pet populations are on the rise worldwide, with current estimates of at least 133 million cats and 156 million dogs in total in the top three countries – the US, China and Brazil – alone. Because food production in general accounts for 26 per cent of global greenhouse emissions, Brunetto and his colleagues wondered how the production of pet foods in particular affected the planet.
They analysed the proportions of ingredients in nearly 940 kinds of Brazilian cat and dog foods designed for healthy adult animals, including commercial dry foods, commercial wet foods, commercial “homemade” foods (professionally prepared blends using ingredients meant for human consumption) and homemade foods based on recipes available online.
To understand the environmental impact of each kind of food, they looked at the 212 ingredients used in total across all the products and used existing databases to work out the environmental effects of their production. This included greenhouse gas emissions, land use, sulphur and phosphate emissions and the use of fresh water.
Then, the researchers calculated these effects per 1000 kilocalories of food.
They found that an average 10-kilogram dog on a dry-food diet would be responsible for about 830 kilograms of CO2 equivalent per year – roughly 12.4 per cent of that of an average Brazilian citizen, says Brunetto. But if that same dog were on a wet-food diet, it would be associated with annual CO2-equivalent emissions of about 6500 kilograms. If all Brazilian dogs were fed wet food, their diets could represent almost 25 per cent of the total emissions for Brazil, he says.
The difference in water content doesn’t explain the gap between the environmental impacts of dry and wet food, says Brunetto, because the researchers compared values based on dry matter. Rather, it was the variation in the kinds of ingredients, including the amount of animal protein, which affected the results.
The environmental impact of homemade meals, which the researchers also investigated, was between that of wet and dry food, says Brunetto.
The findings add to our knowledge about how pet management can affect the environment – an issue that “should not be ignored”, says Peter Alexander at the University of Edinburgh, UK. But he thinks the numbers in the study don’t look plausible. “I think they’re too high, because we’re talking mostly about byproducts,” he says.
Byproducts such as blood and offal can have an economic value and use even if they aren’t fit for human consumption, but this doesn’t mean they have the same environmental impact as prize cuts of meat, he says.
Pet food manufacturers could consider reducing animals’ carbon footprints by experimenting with alternative protein sources such as mealworms, says Brunetto. “We [need to] create new strategies, since we run the risk of reaching a time when we – pets and humans – compete for the same food,” he says.
The study didn’t look at the environmental effects of packaging.
Journal reference: Scientific Reports, DOI: 10.1038/s41598-022-22631-0
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