On a recent tour of NREL‘s Biomass reserch lab, I learned about a new (to me) way to make biofuel. Plant and animal oils and fats can used in conventional petroleum refineries to make diesel and jet fuel. This idea has actually been around since the 1990s, when it was first demonstrated on a pilot scale.
Most of my readers are probably well aware of efforts to cultivate microalgae as a source of oil for biodiesel. This is to biodiesel production what cellulosic ethanol technology is to ethanol production: an up-and-coming technology that has the potential to increase the level of production to where it can actually provide a significant volume of fuel relative to our transportation needs (corn ethanol and biodiesel from conventional crops and waste oil both fall far short on this measure.)
Green diesel and jet fuel address two major problems for biofuels:
- Biofuels lack an existing distribution infrastructure (they must be moved around by train, and even if it were possible to use existing pipelines, they do not lead to where most biofuel is currently produced.) Conventional refineries, naturally, are already integrated in the existing infrastructure.
- Ethanol has a lower energy density than gasoline (about 30% less), and I know of no way to convert biomass into a high enough energy density fuel to power jet aircraft. This process produces jet fuel, neatly dealing with that problem, and holding out the hope eventually reaching a 100% transport (we’d still have to massively increase efficiency to reduce consumption to a sustainable level.)
Oil refiners are interested because bio-based oils contain little or no sulfur, and removing sulfur from diesel is an increasingly expensive process as more stringent standards go into effect. In fact, regulation for ultra-low sulfur diesel is partly behind the recent price rise in diesel vs. conventional gasoline. It used to always be cheaper than gas, but now it is more expensive.