Friday, March 26, 2010

Gasoline from Sugar

It's ironic that with all the current hoopla about various alternative fuels and the electrification of personal cars--hybrids and several kinds of plug-in electric vehicles--it turns out that some of the most promising advanced energy technologies under development are designed to produce more of the same fuels that have powered cars, trucks and planes for the last century. Shell and its technology partner Virent made news this week with an announcement about their demonstration facility for turning sugar from beets or other crops into gasoline. Nor are they alone; many other companies are developing processes to turn renewable biomass into hydrocarbons, rather than the alcohols or esters that have been the principal biofuels of the last couple of decades. If any of these are successful on a scale that could compete with petroleum, it would force us to rethink our assumptions about the sustainability of what we put into our gas tanks.

The first assumption we'd need to jettison is that ethanol is good and gasoline intrinsically bad. The US and Brazil have made major commitments to using ethanol as a fuel, though from very different agricultural pathways and with very different energy, economic and emissions results. In many ways, this was making a virtue of necessity, rather than latching onto a really great fuel that had somehow been overlooked or conspired against for decades--a view you'll hear from some ethanol boosters. Unfortunately, ethanol still has all sorts of problems, even when it's made from sugar cane in the tropics using the most efficient process in the world today. Start with the fact that it's a second-rate energy carrier, delivering only 65% and 59% as much energy to the vehicle as gasoline or diesel, respectively. And while biodiesel doesn't share this drawback with ethanol, it does suffer from similar constraints on the amount that can safely be blended into fuel destined for vehicles that haven't been adapted to run on high-percentage biofuel blends.

Thanks to subsidies and mandates for its use, US ethanol consumption has expanded to the point at which we are approaching the accepted 10% limit on its inclusion in gasoline for cars not designated as Flexible Fuel Vehicles, or FFVs. The ethanol industry and its supporters have been trying to get the government to relax that limit--a move that would benefit them, but at the cost of putting more consumers' cars at risk of mechanical problems and diluting the value of what we are buying at the gas pump. No one is going to give you a discount for gasoline with 15% ethanol in it, instead of 10%, even though it will reduce your miles per gallon and thus your car's driving range by about 2%.

If the plant sugars currently being used to produce ethanol could instead be used to produce renewable gasoline and diesel fuel, it would avoid all of ethanol's compatibility and energy-content limitations, while reducing the cost of distributing fuel to service stations. Instead of having to send ethanol halfway across the country in rail cars or trucks to blending terminals, because it can't be shipped in one of the petroleum products pipelines that crisscross the nation, biogasoline would share the same highly-efficient transportation system that grew in tandem with the post-World War II expansion and dispersal of US population centers and industry. And it would do all this while emitting lower levels of greenhouse gases than petroleum-based fuels, perhaps even lower than those from corn ethanol, depending on the energy inputs required to process it. And if the sugar-to-gasoline process can be bolted onto a commercially-viable process for turning plant cellulose into sugars, biogasoline's lifecycle emissions could be reduced much further.

Now let's put this into perspective, before we conclude it sounds too good to be true. As the press release notes, Shell and Virent have a long way to go to scale up a facility making 10,000 gallons per year (gpy) of gasoline--under a barrel per day--to something that would compete with ethanol facilities producing 100 million gpy (6,500 bbl/day) or refinery units making 50,000 bbl/day. Many a process that looked good in the laboratory has failed to make that transition, which probably couldn't be accomplished in one step in any case. So, at best, this is still years away from commerciality and possibly a decade or more from wide deployment. And unless it can be easily adapted to use cellulosic feedstocks, it is subject to the same practical limitations on food crop production as current biofuels, and the same food vs. fuel competition that proved so divisive a couple of years ago, when corn prices and fuel prices had both spiked--a hardly-coincidental occurrence, considering the energy intensity of corn production.

If it does work, however, its practical advantages over ethanol are compelling, not just from the perspective of the oil industry, which would be relieved to be rid of the cost and logistical headaches ethanol has caused, but also for consumers and taxpayers. It's clear from the analysis supporting their new Renewable Fuel Standard regulations that the EPA regards biohydrocarbons as a viable alternative to current biofuels, and it just might be the pathway to ending our interminable subsidies for ethanol: 32 years and counting.

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