Terry Bollinger wrote a comment that deserves to be a post of its own, because it could start an interesting discussion. Here it is:
The theme of “what scientists can do to help save the planet” is a good one.
I’d like to introduce a topic that concerns me greatly these days: Well-intended efforts to produce cellulosic biofuels that, if applied in non-tropical climates (read “not in Brazil”), could end up taking over huge percentages of land and water resources without necessarily truly solving the problem of replacing fossil fuels.
At present, and quite ironically, it’s not even possible to produce biofuels without using a lot of petroleum in the process. Even more ominously, there have already been cases where people who didn’t have much to begin with are going without food because biofuels have run up the prices and taken over land that should have been used to feed them. That is a very scary trend, especially this early in the biofuels game. And if people who can at least express their need are going hungry, what does that leave as the most likely fate for forests and the animals that live in them? Again, a scary trend.
So here’s the scientific part of my query: Are there other options that would make more sense for fueling the mobile part of our global infrastructure? Good rechargeable batteries obviously are part of the answer, but surely there are more possibilities.
A wild example: Is there any way a fully chemical process (versus a land-using plant base one) could use concentrated, e.g. electrical, energy from renewable sources (or perhaps nuclear, sigh) to replicate what plants do using sunlight? That is, pull CO2 from the air, add water, and generate high-energy-density hydrocarbon or carbohydrate fuels?
The point of such a wild idea would be to achieve the goal of biofuels — less use of fossil fuels — but in a way that avoids the awful environmental consequences of, in effect, using huge areas of land or water area as a very costly and inefficient way to collect renewable solar energy .
In short: Why not separate the energy collection component from the fuel-from-CO2 part, then optimize both to achieve minimal global environmental impact?
I know the answer: Because it’s really hard to do. But that doesn’t necessarily mean it’s impossible.
 Plants themselves are of course highly efficient at photosynthesis, especially some grasses. However, that’s the wrong metric; it’s like picking a gold nugget out of a ton of dross and then pretending the entire ton of dross has the value of gold. For biofuels, a realistic net cost metric would need to include how much land is used, the type of land used, what other uses of that land are being displaced (there is often a significant energy penalty when that is factored in correctly), and the average usable solar energy for the particular plants used. Under that kind of a full-cost metric, even the best cellulosic plant options amount to a very poor (and for some northern regions a potentially negative net benefit) way to collect solar energy.