Easing Depletion

In "Hot, Flat, and Crowded" by Thomas L. Friedman, he says that global warming is a man-made mistake, caused by "our vastly increased emissions of carbon dioxide and other greenhouse gases from the burning of fossil fuels such as coal and oil, as well as from deforestation, large-scale cattle-grazing, agriculture, and industrialization."
As kind of a reflex I read through these topics a second time and tried to think of ways to solve them, but I got hung up. We can make power with a combination of solar cells, wind power, wave power, nuclear power, and more, instead of burning coal and oil. Within a few years we'll have compressed-air-powered cars and electric cars, so we'll use a lot less oil, as long as people are motivated to make the switch. For deforestation, we can't really solve that. I don't see the world using less wood any time soon. All we can really do is plant more trees, which we really should do. Large-scale cattle-grazing was the most puzzling one to me. The gases emitted are mainly methane and carbon dioxide from their digestive systems. Methane in the atmosphere traps heat 21 times more efficiently than CO2 traps heat. I had an idea that if a lot of cows were in a warehouse, their gas would float to the ceiling, and there could be chimney-type openings in the ceiling with torches that would burn the methane. This may sound far-fetched to you. But methane, when combusted, turns into CO2 and H2O (CH4 + O2 --> H2O + CO2), or carbon dioxide and water vapor. The drawback to putting a bunch of cows in a warehouse is that it would most likely be inhumane, and it's not worth abusing animals to break down methane, so I couldn't solve this one. As far as agriculture, we need it to live. All we can do there is streamline our current processes, if possible. For industrialization, all we can do is make more efficient machines powered on more efficient energy.