Mostly true: “40 percent less CO₂ emissions for a vegan diet compared to eating meat and dairy products”
According to an article published by the European energy company Vattenfall on their website referring to the German Environment Agency, “A vegan diet produces around 40 percent less CO₂ emissions […] compared to someone who eats meat and dairy products.” The claim turns out to be mostly true. The Vattenfall article mentions neither a date…