Years ago, there was a bumper sticker, "Trees are America's Renewable Resource." And yes, you can regenerate a harvestable forest in 20 years or so: a nanosecond compared to the millions of years necessary to create fossil fuels.
However, and it's a BIG however—biofuels such as timber or scrap wood, or for that matter, corn-based ethanol, are for the most part not sustainable. They are far from carbon-neutral, and in fact generate large amounts of carbon and other pollutants. Think about it: coal and oil are fossilized carbon that originated from plants and animals; wood and corn haven't fossilized the carbon, but they are very much carbon-based life forms, and we add a lot of carbon back into the air when we burn them.
So the effect of these fuels on climate change is negative: they push us more in the direction we DON'T want to go.
Add to that such effects as habitat destruction from clear-cutting, food shortages resulting from diversion of protein crops into energy that powers machines instead of humans and animals, and toxicity from burning chemically treated wood scraps, and it's pretty clear that this path isn't sustainable.
Are there biofuel technologies that actually are sustainable? Maybe. <a href="http://www.google.com/search?q=q+microbe+technology&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a">The Q microbe</a> certainly seems to have promise. As a non-scientist, I leave that answer to those who know more than me.
In the meantime, let's focus on those technologies that clearly ARE sustainable. <a href="http://rmi.org/">Amory Lovins of the Rocky Mountain Institute</a> estimates that we could easily save 70 to 80 percent of our energy by simply designing for maximum energy utilization and eliminating the considerable waste of our present systems. Beyond that, truly sustainable technologies such as small-scale solar, wind, and hydro generated at or very near the point of use hold out a lot more promise than either biomass plants or centralized coal, oil, and nuclear.