Lots of people are getting excited about all the various technologies for using biofuels of one sort or another as a replacement for fossil fuels, and they may present a short-term option. But looking at the various kinds of energy production that are possible gives some insight into the best directions to promote in terms of developing long-term efficient energy production.

A study cited on EV World makes a comparison between different crop- and direct-production methods of generating energy in terms of miles per acre per year, with some eye-opening information.

At the bottom end of the scale is soybean biodiesel, which can provide only 2,400 miles per acre per year. Corn ethanol is more than six times as efficient, yielding 18,000 miles per acre per year. But because of the relatively slow rate of production from plant-based fuels, these options far fall below the productivity of directly produced energy.

The same acre can produce 10 times as much energy from wind as it can from corn ethanol, 180,000 miles per acre per year. But both corn ethanol and wind power pale in comparison with solar photovoltaic, which can produce more than 2 million miles worth of transport per acre per year.

This is not to completely dismiss biofuels out-of-hand. The cost of an acre's worth of solar PV arrays is far more than 100 times more expensive than planting an acre of corn. Many biofuels can be produced on marginal lands that are ill-suited for solar. And cellulosic ethanol can even be produced from waste, effectively making it a zero land-use fuel. And presumably the comparisons are based on sites that are optimal for each mode of generation. A site that is highly suitable for harvesting wind energy may not be a good site for growing corn, and vice versa.

The infrastructure and the existing "car parc" (the entire fleet of all vehicles in the country) is also going to take decades to turn over to the point where a significant proportion of the vehicles on the road are electric vehicles. Both a mix of energy sources and regionally appropriate choices need to be part of a comprehensive energy plan. But this offers a useful comparison that suggests where the best allocation of resources should be focused in terms of long-range planning for our energy future.

Link: EV World (chart halfway down the page)

Range Fuels has already begun building the country's first cellulosic ethanol plant in Georgia. The plant has a goal of producing 100 million gallons of ethanol per year using leftovers from Georgia's giant timber industry. Unfortunately, right now Range Fuels only has enough money to build 20 million gallons per year of capacity. The money to do that came mostly from government grants.

But now Range has announced that they've raised another $100 M from Khosla Ventures and an unnamed energy company. The injection of funds will allow range to meet it's 100 million gallon per year goal, hopefully by 2009.

Range's technology gasifies the plant cellulose using a technique created to turn coal into liquid fuel. After the gasification, turning the wood chips into ethanol is fairly trivial. Unfortunately, the process is much more expensive than the processes that turn corn into biofuel.

But the expense of the process, it turns out, is less important once corn prices start skyrocketing due to increase demands both for food and ethanol. Wood chips on the other hand are pretty much free. This is how Range hopes to make up the difference in cost, hopefully scaling up to the point where their ethanol is actually cheaper than both corn ethanol and gasoline.

$100 M definitely won't hurt their attempts to achieve this goal.

Via CNET Clean Tech