GLOBAL WARMING: COWS OR CARS? - MEAT: A Benign Extravagance - page 204

a pathetic 50 grams. Horses, which are not ruminants, but can digest grass thanks to their
long colon, are reported as averaging 18 kg of methane, so if we decided to get rid of cows
because of their methane emissions, we perhaps ought to dispense with horses as well. 36
But once again, as with nitrous oxide, before coming to any conclusions about the envir-
onmental impact of these grass eating animals, we need to examine the opportunity costs
of eliminating beef and dairy from our diets.
Without beef, sheep and dairy protein, we would need to consume an extra 25 per cent
of our current production of grains, pulses and vegetables to compensate. The IPCC estim-
ates that plant crops produce 17 per cent of current man-made methane emissions, exactly
half of the amount emitted by livestock, so in theory this would increase correspondingly,
eating into the methane savings made by getting rid of our ruminants.
However most of this (ten out of the 17 per cent) comes from rice grown in paddy fields,
which produce methane, like natural wetlands. Twenty years ago most analysts were of the
view that global rice cultivation produced more methane than the beef and dairy industries,
for approximately the same global total of protein (though this generated less media interest
than cows, probably because rice neither farts nor belches). 37 But in recent years, estimates
for the amount of methane from rice have reduced by about half. According to M Khalil
and M Shearer, this is because China over the last two decades has reduced its annual meth-
ane emissions from rice from 30 million tonnes per year to ten million tonnes, mainly by
replacing organic fertilizer with mineral fertilizers. 38 This raises the question of what has
happened to its organic fertilizers, particularly since the amount of available manure must
have risen enormously in China over the last 20 years. Have some of these methane emis-
sions been transferred from the rice sector to the animal sector through inefficient recycling
of nutrients? Or do they appear as nitrous oxide emissions through the application of ma-
nure to dryland crops? Khalil and Shearer don't say, although they do acknowledge that the
chemically fertilized rice is probably emitting more nitrous oxide.
Even after these improvements in rice performance, each kilo of rice now is said to gen-
erate about 100 grams of methane, while a kilo of milk from a productive dairy cow gener-
ates about 13 to 26 grams of methane (so rice pudding is to be avoided). 39 Since the protein
content of milk is about a third of that of rice, weight for weight, and the energy about a
tenth, the milk provides somewhat more protein per unit of methane than the rice, but less
energy. There would not be a lot to be gained by eliminating dairy production and repla-
cing it by rice cultivation. However this is unlikely to happen to any great extent, because
most of the countries which produce a lot of milk do not grow much rice, and the main rice
eating countries are not great milk producers, preferring pigs and poultry - the exception
being India. If beans, nuts and dryland grains were the main substitutes for beef and dairy,
the methane emissions they generated would be relatively small.