Pollution on the hoof

There are also smart ways of treating or converting animal waste. Manure lagoons can be covered, capturing gases that can be used to generate power or simply be burned away (burning the gases converts most of the emissions to CO2, which is far less destructive than methane). That's the strategy being pursued by American Electric Power Co., a gigantic utility based in Columbus, Ohio, whose coal-fired power plants make it the nation's biggest emitter of carbon dioxide. This summer, the company began putting tarps on waste lagoons at farms and ranches and sending the gases they capture to flares.

American Electric is under heavy regulatory pressure. Last week, it was on the wrong end of the biggest environmental settlement in U.S. history and agreed to spend up to $4.6 billion to clean up its smokestacks. Its work on manure is part of an experiment in carbon offsets; the company anticipates that someday Congress will cap the amount of carbon dioxide that can be emitted and allow polluters to trade pollution credits. As a previous installment of this series noted, that's a less effective way to combat global warming than carbon taxes, but the American Electric example shows that it would also direct the economic might of industrial polluters toward solving off-the-beaten-path problems such as livestock waste.

Other possible solutions include providing more aid to ranchers in places like Brazil, where forests are rapidly disappearing, to make cattle operations more efficient and thus decrease the need to cut down trees. Changes in farming practices on fields used to grow livestock feed could help capture more carbon. And U.S. agricultural policy is overdue for changes. Subsidies on crops such as corn and soybeans have traditionally kept the price of meat artificially low because these are key feedstocks.

Broccoli: It's what's for dinner

Such policy shifts and new technologies would help, but probably not enough. A recent report in the Lancet led by Australian National University professor Anthony J. McMichael posits that available technologies applied universally could reduce non-carbon dioxide emissions from livestock by less than 20%. The authors advocate another, fringe approach that has long been embraced by dietitians and vegans but is a long way from going mainstream in the United States: eating less meat.