For example, a 2010 Swedish study calculated the nutrient content and number of nutrients per serving of several beverages in relation to the greenhouse gas emissions associated with their production, manufacturing, packaging and transportation. Milk rated very highly, with a high nutrient density index per equivalent carbon emission of 53.8 per 99 grams greenhouse gas emission. Soy drinks and red wine, by comparison, have a nutrient density index of 7.6 per 30 grams and 1.2 per 204 grams of emissions, respectively.
Van Amburgh has also found in a not yet published study that carbon dioxide and methane emissions from byproducts included in animal feed are considerably lower when fed to dairy cattle than when incinerated.
Byproducts most often used in the American dairy industry include distillers' grains from ethanol production, citrus pulp from juice production, almond and soybean hulls, soybean meal, cottonseed, extracted canola meal and even baked goods and candy.
Their inclusion in animal feed not only helps the environment, but can boost nutrients and enhance yield and provide an economic opportunity for the byproducts that in many cases greatly reduces the cost of food to the consumer, Van Amburgh said.
"Because of the microbial fermentation digestion process that occurs in the cow's rumen, the byproducts are digested in a manner that can positively enhance the nutrient supply," he said. "For example, candy byproduct provides sugar and the end product of the fermentation produces the substrate necessary for milk sugar production, so fed in moderation, candy can enhance milk yield with no ill effects on the milk composition or quality."