Carbon pawprint: is man’s best friend the planet’s enemy? In a 2017 study, Okin estimated that the 160M domestic cats and dogs in the US were responsible for between 25-30% of the environmental impact of meat consumed in the country. That’s 64M tonnes of C02, equivalent to the annual emissions of 13M cars. Kelly Swanson, a professor in animal nutrition, disputes the findings of that study, saying the calculations were based on “a lot of inaccurate assumptions”. Geography also plays a part in this, as a 20-40 pound dog in the Netherlands will produce 4.2-17 tonnes in its lifetime. But the same dog in China would only produce 1.5-9.9 tonnes.