WetEV
Well-known member
GRA said:"Lamb has the greatest impact, generating 39.3 kg (86.4 lbs) of carbon dioxide equivalents (CO2e) for each kilo eaten – about 50 percent more than beef. While beef and lamb generate comparable amounts of methane and require similar quantities of feed, lamb generates more emissions per kilo in part because it produces less edible meat relative to the sheep’s live weight. Since just one percent of the meat consumed by Americans is lamb, however, it contributes very little to overall U.S. greenhouse gas emissions."
As someone that enjoys pasture raised lamb and goat as well, I was shocked. I'm slightly dubious that cattle and sheep are that similar. I remember reading the reverse in a journal many years ago. I'm under the impression that not all ruminates are the same, and that diets the animals eat can make more than a factor of two difference in methane production. A bit of poking around in journals show that overgrazing increases methane production:
http://rd.springer.com/article/10.1007%2Fs11284-006-0191-9" onclick="window.open(this.href);return false;
http://www.tandfonline.com/doi/abs/10.1080/00288233.2005.9513671#.U-EqiPJ0ysE" onclick="window.open(this.href);return false;
The source below gives the range for the USA as range cattle seem to be near 54 kg/head/year. Sheep are near 8 kg/head/year for the USA as an average. Note that older animals are much higher methane producers.
http://rd.springer.com/content/pdf/10.1007%2Fs10584-008-9506-x.pdf" onclick="window.open(this.href);return false;
For a rough calculation, a 500 kg on the hoof steer seems to dress out to yield approx. 250 kg of meat, and a 60 kg lamb dresses out to about 30 kg. So a naive calculation might be: 4.5 kg of meat per kg/head/year of methane per calf, and 3.75 kg of meat per kg/head/year for lamb. Slightly worse.
That simplistic calculation doesn't everything into account. As lambs per ewe is about 1.5 or more, and as calves per cow is about one or less, the ratio of lambs to total sheep is higher than for calves to total cattle. Also, calves are usually slaughtered at older ages, so they have more time to release more methane. Taking this into account, it looks to me like the correct ratio is more like 6 kg of lamb per kg of methane, rather better.
Taking all this into account, grass feed beef seems to be higher in methane per kg of meat than grass feed lamb, but I'm not an expert on this. Have I missed anything important?