I continue to bolster my argument - whatever problems we have with biofuels (and they are numerous) the one problem we won't have is a lack of source material.
Latest example: a company has devised a plasma reactor that takes used tires, whips them up to about 30,000 degrees (fahrenheit, celcius, does it matter?) and thus dissociates the carbon, oxygen, and hydrogen into separate gases. The reactor then cools the gas, and reacts it through a catalyst in to ethanol.
That 30,000 degrees sounds like it would cost a lot, in terms of electricity. But ionized plasmas are well-understood, and you can buy plasma torches commercially. The company's press release (yes, grain of salt) says that the output should be at least 4x as much as the energy input.
In the 1970s, the Soviet experimented with a coal-fueled plasma reactor for electricity generation. It was hugely expensive in terms of capital, but had zero particulate emissions and was extremely efficient. So this isn't really buck rogers stuff.
I'm not certain, but it looks to me like this kind of reactor could potentially take almost any kind of carbon-rich waste (plastics, biomass, garbage, dried sewage) and convert it to ethanol. As a bonus, the reaction doesn't need a direct source of natural gas, like conventional ethanol. The ionizing plasma just needs a supply of electrical power, meaning we can potentially power this renewably.
It's nice to think of a future where our cities don't emit massive amounts of solid waste, to be buried in the ground or dumped in to our watersheds. We could potentially scale up technology like this to produce ethanol not just from our current flow of garbage, but our massive garbage reserves as well.
Inevitably, however, our civlization will reach a point where we begin depleting our garbage reserves, a point I will call "Peak Garbage." (Alternately, "Dymaxion's Peak.") We will then need to either massively increase our investment in garbage exploration and production, find alternate sources of garbage and sewage, or dramatically constrain our consumption of garbage. Are we ready for this earth-shaking era in human history?
(Story via Energy Blog & Green Car Congress.)