Commercial wet food diets for dogs have almost seven times the climate impact of dry food diets, according to a new analysis. For cats, too, the environmental impact of wet food is greater than that of dry food, the analysis reveals.
The study is part of a growing body of research highlighting the environmental impact of pets.
Several past studies have calculated the environmental or climate impact of pet diets, but these all used hypothetical diets or dry diets only. The new study takes a broader and more empirical approach.
A team of researchers in Brazil gathered information on the ingredients found in 618 types of dog food and 320 types of cat food. The diets included commercial foods sold by major pet food retailers in the country as well as recipes for homemade diets found online.
Brazil has a population of 52.2 million dogs and 22.1 million cats. Other countries with a preponderance of pets include the United States, with 76.8 million dogs and 58.4 million cats, and China, with 27.4 million dogs and 53.1 million cats.
The researchers used ingredient label information to estimate the percentages of each ingredient with the help of a standard software package. This enabled them to calculate the nutritional and caloric content of the various diets, as well as the environmental impacts: greenhouse gas emissions, land use, water use, sulfur dioxide emissions (which are related to acidification), and phosphate emissions (which are related to eutrophication).
Dry diets are the most calorie-dense, while wet and homemade diets provide more protein, the researchers report in the journal Scientific Reports. For both dogs and cats, wet diets have the highest environmental impacts and dry diets the lowest, with homemade diets generally in between.
The basic problem is that cats and dogs are carnivores, and diets high in animal ingredients have correspondingly large carbon and other environmental footprints.
Most of the protein in pet food is of animal origin. In dry diets, about 45% of calories come from animal ingredients, while in wet diets the figure is almost 90%, the researchers found.
For dog diets, all of the environmental impact variables studied were lower for dry diets. For cat diets, the dry diets were lower in terms of climate, land use, and phosphorus impacts.
A 10-kilogram dog eating 540 calories a day would be responsible for 828 kilograms of carbon emissions yearly on a dry diet or more than 6,541 kilograms yearly on a wet diet, the researchers calculated. The carbon footprint of the dry diet works out to 12.4% of the average per-capita carbon footprint in Brazil and that of the dry diet is a whopping 97.8%. In other words, a dog fed a diet of commercial wet food could have a carbon footprint almost equivalent to that of the average Brazilian person.
The climate impact of feeding the entire canine population of Brazil adds up to between 0.04 and 0.34 gigatons of carbon emissions per year, or 2.9% to 24.6% of the country’s entire estimated emissions.
One mitigating factor: some of the ingredients in pet food are byproducts, and pets are sometimes fed table scraps. In other words, they eat food that would otherwise go to waste.
Still, it’s worth thinking about potential strategies to reduce the environmental impact of pet diets, the researchers argue. Existing dry food diets are more sustainable than wet food diets, but wet food diets are healthier for some individual dogs and cats.
One way to make pet food more sustainable overall is to make sure it doesn’t contain excess nutrients. (“All types of diets included in the present study provided more protein and fat than recommended for dogs and cats,” the researchers note.)
Pet foods could be formulated with plant-based protein, but this might require adding synthetic amino acids to meet the nutritional requirements of dogs and cats. Or pet diets could make use of sources of animal protein with smaller environmental impacts, such as chicken, pork, or even insects, the researchers say.
Source: Pedrinelli V. et al. “Environmental impact of diets for dogs and cats.” Scientific Reports 2022.
Image: Ed Schipul via Flickr.