Thus far, much of the interest in cellulosic ethanol has focused on the development of enzymes to promote fermentation, rather than on the provision of the crop waste or non-food crops that would be converted into fuel. An article in Monday's San Francisco Chronicle focused on the activity at the "upstream" end of this future value chain. Even if the comparison to a "Spindletop" of cellulose is hyperbole at this point, it's intriguing to consider the risks that these developers are taking on, as they push to develop and plant new energy crops in advance of the full commercialization of the process they are intended to feed.
When I first ran across the research into methods of turning cellulose into ethanol a few years ago, the Department of Energy folks who were promoting it were targeting "corn stover", the waste from corn ethanol production, as their likely initial feedstock. That still probably makes sense, since this material will already have been harvested and collected in the course of producing the feed for current-generation ethanol plants. It's not hard to imagine first and second generation facilities operating side by side, until the cellulosic process becomes cheap enough to displace the grain-based version--if ever. However, others are looking beyond corn stover to switch grass and the miscanthus hybrid mentioned in the Chronicle. The allure of this tall, rapidly growing "superweed" is understandable, although those pioneering this energy crop will have to manage two key issues.
First, they must find alternative outlets for their production, in case of delays in making cellulosic ethanol processing fully operational. That probably means lining up biopower plants to consume their biomass. This sector, which involves firing or co-firing smallish thermal power plants with wood and other biomass, has been a modest success, despite receiving much less publicity than wind or solar power. The key hurdle involved would be proximity, given the economics of transporting low-density fuels long distances.
The other issue concerns real or perceived hazard to other crops. Even if the ultimate variety of miscanthus chosen for energy cropping doesn't involve genetic modification, there's a long history in this country of foreign plants that have gotten out of control or failed to work out as intended. In California brittle, messy Eucalyptus trees were introduced from Australia as wind breaks. I'm particularly attuned to this example, since one of these ill-considered trees dropped a 9-ton limb on our house when I was growing up. The southern experience of kudzu is probably even more relevant to miscanthus.
Whatever the ultimate feedstock limit on biofuel production, it's clear that that limit will be much higher if it is based on a wide variety of hardy, low-input energy crops, rather than on a few food crops. Once the cellulosic ethanol process has been fully demonstrated at an industrial scale and the cost of its enzymes falls sufficiently to make it competitive with corn ethanol, its ultimate success will depend on the availability of high-quality, low-cost biomass. Outside the corn belt, that will mean dedicated energy crops such as miscanthus and switchgrass, if their commercial risks can be managed successfully. Perhaps the players in the different segments of this nascent value chain should start considering vertical integration or alliances.