In part 1 of this series, I introduced the problems facing changing airline fuels to low-carbon models, both the perverse effectiveness and convenience of jet fuel and the challenge of certifying airlines, and dealt with the reality that hydrogen requires losing 20% of revenue and increasing fuel costs to 50% of total operating expenses. In part 2, I dealt with Wright’s head-scratcher notion of using aluminum air fuel cells to get around hydrogen’s failures, along with a sideline of why the people dismissing battery-electric airplanes are not to be trusted. In this final part, it’s time for biofuels, and why they are fit for purpose and scalable.
While I’m bullish on battery-electric for short-haul aviation this decade and medium-haul aviation in the 2030s, I’m not bullish on batteries for long-haul for the next few decades, but am after that. And we have to reduce long-haul aviation emissions sooner rather than later, so at least an interim solution is required. That’s where biofuels come into play.
Aviation Biofuels Exist, And They Are Low Carbon & Reasonably Priced
Certified aviation biofuels have been available for over a decade, and routes have been flown with them. They are an existing solution that’s plug-compatible with existing engines. There’s no need to bet on a non-existent technology or to create soon-to-be-stranded supply chains.
Under a 2016 NREL case study, they have a fraction of the CO2 emissions of either fossil fuel jet fuel or synthetic jet fuel (when the synthetic jet fuel is given substantial benefits of the doubt). The heavy lifting of getting carbon and hydrogen out of the air and water, and their tight molecular bonds is done by plants. The transformation into fuels is done by distillation and some post-processing.
Lots Of Biofuels Can Be & Are Manufactured
Biofuels are created today in very large volumes around the world. They are already approaching 2 million barrels of oil a day equivalent globally. This is a scaled technology with strong supply chains.
Biofuel production continues to improve. First generation technologies have radically lowered CO2 emissions in their lifecycle. Second generation stalk cellulose biofuels have been in operation commercially since 2014 and are expanding. This means dual cropping for calories, with corn ears, for example, going to animals or humans, and stalks and leaves going to airplanes.
The carbon debt of agriculture is going to reduce substantially with the shift to low-tillage agriculture, agrigenetic fixing of nitrogen with soil microbes, and most nitrogen-based fertilizers disappearing, a must do for addressing climate change. As a result, the carbon debt full lifecycle of biofuels is going to shrink even further.
Agriculture continues to improve in efficiency, as long as we get climate change under control. As a recent study pointed out, we’ve had substantial advances in agricultural efficiency, but we’ve lost 21% of them to climate change.
Among other things, agriculture continues to sensibly consolidate under highly efficient and increasingly large agribusiness with higher and higher automation, and business models more amenable to regulatory and market carrots and sticks. More and subsistence farms on semi-arable land are disappearing and the land is becoming more available for regreening and renewable energy. And, of course, wind turbines fit among agricultural crops and in grazing areas with close to zero actual impact. Land use for biofuels competing with renewables is much less of a concern than most people realize or project. One nice thing is that we’ll get all of the land currently used for fossil fuel extraction and processing back, which Mark Z. Jacobson’s team points out is more than the land required for their scenario of 100% renewables.
Existing Demand For Biofuels Is Going To Disappear
From a demand perspective, most of the use of biofuels is going to evaporate as virtually everything it’s used for today electrifies. No fuels of any sort will be burned for ground transportation, short- and medium-haul aviation, short- and medium-haul shipping, or heating in the future.
All biofuels will be used for the hardest to electrify segments of the economy, and that’s long-haul shipping and aviation. Demand will grow, but not nearly as much as many assume. No more wasteful pork barreling with ethanol schemes for cars and trucks.
While long-haul aviation will persist, it’s not going to be as prevalent. COVID-19 shifted us a decade forward into video conferencing and digital signatures for business, academia, and conferences. The habit of long-haul flying for business people has been broken, and many won’t return. The habit of companies buying consulting services from road warriors expecting to see SAP deployment consultants on site has been broken, and many won’t want more than the absolute minimum back. The business community has adapted to much lower costs of business, and business people have adapted to spending a lot less time traveling. And regardless of anything else, the cost of long-haul flying is going to go up, although not as much as the silliness of hydrogen or aluminum would drive it. Until the energy density of rechargeable batteries is there, the cost of long-haul flights will be higher, driving down demand.
I had projected a few years ago that only 3-4% of all fuel demand might persist after transportation electrification globally, but that is likely to be lower. The bridge from 2 million barrels of oil a day to the much smaller requirement is manageable. As a note, I had described long-haul aviation and shipping at the time as a niche where hydrogen had not proved itself to be a bad choice, which is to say I hadn’t done sufficient analysis to rule it out yet. Now I have.
The combination of technical advancement, reasonable supply, and diminishing total demand leads me to believe that biofuels will be the dominant long-haul aviation fuel.
This isn’t perfect. Contrails and their warming have to be dealt with through operational adjustments, but modeling shows that can be done by flying a few hundred meters lower altitude with substantial improvements. And any fuel burning in the atmosphere creates NOX, with the attendant warming and pollution concerns. But low-carbon biofuels and relatively straightforward flight operation changes can eliminate close to two-thirds of long-haul related warming, and obviously in this model the short- and medium-haul emissions disappear entirely. This should suffice until electrochemistry catches up to kerosene energy densities.
And that’s the way discussions of aviation fueling alternatives go. Completely unworkable, absurdly optimistic assumptions are made about far future potential costs of non-existent fuel supply chains for hydrogen and things like aluminum. The completely reasonable movement of lithium ion and related chemistries to a reasonable density today for 19-passenger planes with 250-mile ranges at a reasonable weight and price point, and the projection forward to higher densities, lower costs, and lower weights are ignored.
Hydrogen and other alternative fuel advocates use radically different goal posts for their preferred technologies than for battery-electric. Investors and policy makers should be aware and beware.
Appreciate CleanTechnica’s originality? Consider becoming a CleanTechnica Member, Supporter, Technician, or Ambassador — or a patron on Patreon.