Gates, p.115
A chicken has to eat two calories worth of grain to give one calorie of poultry.
A pig eats three times as many calories as we vet when we eat it.
Cows have the highest ratio: 6 calories of feed for every calorie of beef.
The wealthier the people of the world get, they eat more calories, especially more meat and dairy. Producing more meat and dairy requires growing more food for the livestock.
p.121
In the US, 40 percent of food is wasted. When wasted food rots, it produces methane with warming equivalent to 3.3 billion tons of CO2 annually.
p.122 << It’s been estimated that if we couldn’t make synthetic fertilizer, the world’s population would be 40 to 50 percent smaller than it is. >>
p.124 << Finally, after the fertilizer is applied to the soil, much of the nitrogen that it contains never gets absorbed by the plant. In fact, worldwide, crops take up less than half the nitrogen applied to farm fields. The rest runs off into ground or surface waters, causing pollution, or escapes into the air in the form of nitrous oxide — which, you may recall, has 265 times the global warming potential of carbon dioxide. All told, fertilizers were responsible for roughly 1.3 billion tons of greenhouse gas emissions in 2010, and the number will probably rise to 1.7 billion tons by mid-century. >>