We burn in a year's time, an amount of fossil fuel that took about a million years to lay down.
So at the maximum we have about 400 years worth of fossil fuel to burn, probably much less than that. But that gives you some idea of how rapidly we are depleting this natural resource.
But a bigger problem is, that as we take this carbon from underground in its solid form and we burn it we add oxygen to it, and this makes carbon dioxide which goes up into the atmosphere. Now were taking carbon from below ground and weâ??re putting it into the atmosphere. And in the atmosphere, it traps heat. Thatâ??s the basis for the greenhouse effect.
Now if we were to take wood from a forest and burn it in our stoves to get the heat or in our furnaces to create electricity. The carbon from that tree would go back up into the atmosphere, and then it would go back into the plants. We take a tree away from the forest, another tree appears. So we're simply cycling carbon in place. That's different from taking carbon from below ground and adding it to the atmosphere. With carbon from below ground we're making a net increase in the atmospheric co2, with carbon from trees, we're not making a net increase in the carbon in the atmosphere. , we're simply cycling it in place.
There are a lot of trees and grasses. How much of those would we need to replace a certain major fraction of the energy that we get from burning fossil fuel? That's a big question. And how could we go about doing that? And when we get to that question, we very quickly come to the next question which is, "Well, which one of these species will respond most rapidly to CO2 and grow back? Which one of them is the most efficient at taking carbon dioxide from the atmosphere putting it into wood and letting us then extract the energy from the wood?" That question we donâ??t know the answer to yet.
In part we don't know the answer because we do not really understand fully the range of responses of plants to high CO2. We don't understand the mechanisms whereby different species respond differently to increasing carbon dioxide. So to my way of thinking this is one of the great unsolved problems that we're faced with that we have to address in the future if weâ??re going to use the biosphere to help us solve the problem of global warming. And I don't see any way around it. We have to use the biosphere and everything else we can think of to replace energy from fossil fuels.