Today I was challenged for probably the 50th time on the subject of biofuels, which I’m bullish about. But I’m bullish about them where they make sense, and bearish where they don’t. Ground transportation? All electric. Marine shipping? Lots of electric, then biofuels. Aviation? Lots of electric, then biofuels. Note what isn’t present — hydrogen or synthetic fuels.
So why am I so strong on this? Well, it’s been a years-long process of stepping through data, chemistry, physics, economics, and publishing, then building on my findings. Let’s take a journey through time.
My first assessment was for bus transit, comparing hydrogen, diesel, and electric variants for transit close to a decade ago. What I found was that bus tests with hydrogen were failing globally even then, that green hydrogen multiplied any full lifecycle carbon debt in electricity by an unforgiving amount and that directly using electricity was lowest carbon.
In 2017 I spent some time summarizing my findings to date for different modes of transportation and the potential for hydrogen. The context then was segments where hydrogen still hadn’t proven itself to be unfit as a fuel for transportation. At the time, I suspected there might be a role in freight trains, aviation, and marine shipping. Among other things, this became a roadmap for me for assessing different transportation refueling models.
Fast forward to 2019, and Carbon Engineering, the BC-based direct air capture scheme funded by a lot of fossil fuel companies, snagged my attention with its promise of plug-compatible, synthetic transportation fuels. I published a lot of articles about the company, working up the chemical processes from scratch, reviewing the literature, and contrasting its proposed plug-compatible synthetic fuels for ground and aviation transport with alternatives such as direct electrification and SAF biofuels. That turned into a substantive published case study with a foreword by Mark Z. Jacobson.
This is the end result for aviation fuels. The NREL SAF biofuel documented was vastly lower CO2 and vastly lower cost than the Carbon Engineering equivalent, which while better from a CO2 perspective than fossil fuels was far from good, and also three times the price of existing Jet-A at the time.
The results for ground transportation were even more deeply unfavorable for Carbon Engineering (and all synthetic fuels) as it was clear even then that road freight was all going electric, and that the transition would be a lot more rapid than Carbon Engineering’s ability to scale its technology.
I asserted that Carbon Engineering’s only natural market was enhanced oil recovery on tapped-out oil wells with unmarketable natural gas supplies, and I was right, as that’s the only thing it’s apparently doing, building a couple of kilometers of 20-meter high, 3-meter thick fans in the Permian Basin with Oxy. As one of its engineers divulged at a conference I was at, the company has managed to convince the government of California and the US to give it about $250 per ton of CO2 it injects underground, despite a third of that being from burning the aforementioned natural gas, and the resulting oil emitting more CO2 than they inject. Just another CCS shell game.
Moving on into 2021 after a deep dive on grid storage, I finally engaged fully with aviation, which is one of the hard to decarbonize segments. The answer became very clear when I started looking at the physics and economics. Hydrogen wasn’t going to be it. Too expensive to operate, likely impossible to certify, and would radically diminish cargo and passenger loads. And these are hard limits of physics, not subject to technical innovation. This is very well understood stuff.
Rechargeable aluminum fuel cells wouldn’t be it either. The reaction would require absurd volumes and mass of specially prepared aluminum to be shipped to airports, then turned into a degraded form of itself in flight, and then the same absurd volumes and mass to be shipped to aluminum smelters again, and then the cycle repeating itself. The ‘fuel’ would travel vastly further than the airplane, at great expense.
Synthetic fuels built from scratch from molecules I’d already worked out with the Carbon Engineering assessment would be vastly expensive and multiply the full lifecycle CO2e of whatever electricity was used to create them, and clearly would be worse if blue hydrogen were used instead.
What did make sense was batteries and biofuels. Batteries are already fit for purpose for 4 to a couple of dozen passengers or equivalent cargo traveling a couple of hundred kilometers. Hybrid-electric turboprops with up to 100 passengers and several hundred kilometer ranges are completely viable today. And unlike hydrogen, batteries are a long way from hard limits of physics.
As I discussed with Heart Aerospace founder and CEO Anders Forslund, batteries are simply an engineering compromise space today, with sufficient energy density by mass available at higher price points. The slope for battery energy density increases over price is steep and will remain so for a long time. As I discussed with a global consulting firm’s representative this week when they engaged me for my opinion on redox flow technologies for data center backups (that’s a separate topic I’ll address, as it’s something I’ve worked through as well), the speed of maturation of electrochemistry and materials with the advent of machine learning characterization assessments and automated testing has shrunk innovation cycles from decades to years.
And for the rest of aviation, the question becomes whether the radically lower CO2e emissions are sufficient. The answer is that yes they are as an intermediate compromise, when combined with operational changes to substantially diminish contrail formation. Mark Z. Jacobson and I spoke of this in 2020, and at that time he thought hydrogen was required. I’m satisfied it won’t work now, but haven’t circled back to have the followup discussion with Jacobson yet. SAF biofuels turn out to be much cleaner burning than fossil Jet-A, and at some point there must be a compromise.
Of course, that still left trains, and perhaps some lingering questions about long-haul road freight. But there empirical reality reared its head. China’s 500,000 electric buses, 400,000 electric trucks, and 40,000 km of high-speed, electrified, grid-tied freight and passenger rail built since 2007, Europe’s massive amount of electrified freight rail, and the German state of Baden-Württemberg’s strong assertion that it wouldn’t bother with hydrogen for rail anymore as it was three times as expensive battery and grid-tied locomotion made it clear that arguments against electrifying road and rail freight were specious, or so narrowly tied up in local politics as to be worth ignoring.
Rail is already the least carbon-intensive form of ground transportation, already diesel-electric hybrid, easy to tie to caternary overhead electricity, easy to add TEUs full of batteries swapped out in transshipment terminals to, and already generating electricity from dynamic braking that could be turned into regenerative braking. Yes, all ground transportation would be grid-tied or battery-electric in a few decades. That’s just a question of time.
But there was still the question of carrying capacity of biofuels for aviation. And so, I needed to understand both aviation passenger and cargo demand and resultant energy demand from aviation sufficiently well to be able to project electrification and SAF biofuel replacement curves into the future. Demand will not rise nearly as rapidly or as the aviation industry expects, and battery-electric will start with regional air mobility and expand upward in range and capabilities for decades, until, in my assessment, it will be capable of delivering passengers across the Pacific by 2070 or so. It will still take until around 2100 for most jets that burn things to age out and be replaced by modern airframes powered by the miracles of battery electrochemistries.
But what does that mean for SAF biofuel demand? Having the actual energy requirements, it was relatively trivial to use OSTI’s calculations for land-area required for energy from stalk cellulosic biofuels. If memory serves, Damon Vander Lind, formerly chief engineer of Google Makani’s airborne wind energy technology and then Kittyhawk’s urban air mobility electric vertical takeoff and landing aircraft (two spaces I’ve assessed closely as well), and now running Magpie, an aerospace startup which is intending to enable long-haul, battery-electric, conventional takeoff and landing aircraft, provided me with the link to the calculator as we were discussing our relative opinions last year.
What was the result? Diverting about 50% of current corn, wheat, and rice stalks to stalk cellulosic processing and then into ethanol to SAF biofuels was sufficient to meet global peak demand for all of commercial and generation aviation. No food required. No new land required. Just dual-crop for food and fuel. And, of course, as we continue to move calorie-stripping subsistence farmers off of the land and into more useful livelihoods, switch grass on semi-arable land is completely reasonable as well, and about 3% of global land mass would supply all SAF biofuels for peak aviation demand. Having spoken to a biofuels expert as well last year, it’s likely that grain stalks will mostly be used because they are already waste in fields where machines are doing collection, while switch grass is basically massive prairies that would have be harvested.
And it’s worth pointing out that this is one of about eight major SAF biofuel pathways. A lot of them use waste food biomass, especially vegetable and animals fats, to shorten the pathway from light hydrocarbons to heavier kerosene equivalents. The world is absurdly big, and we have absurd amounts of biological calories we can use in a mostly virtuous cycle without anyone going hungry.
That last, by the way, is a nonsense meme that doesn’t stand up to the slightest scrutiny. Even biofuels made from corn ears had exactly zero impacts on global provision of calories to people. We produce vastly more than humanity requires, and waste absurd amounts of it. We have a distribution and economics problem, not a calorie problem.
And so to the last major fuel demand area — marine shipping.
Similar to efforts for aviation, I projected all marine tonnage, distance, and energy demands for global inland, nearshore, and marine shipping, including all efficiency demands and assessing all fuel alternatives through 2100. That required assembling a unified dataset for the three, working through different modes, looking at variances in cargo types and assessing most of the different efficiency levers that that were available to be pulled.
A big data point was that 40% of all deepwater shipping was of bulk coal, oil, and gas, and that’s all going away. That’s 40% of the hardest problem, gone with the disappearance of fossil fuels. Some of that will likely be replaced with biofuel shipping, but with massive electrification of all modes of transportation, a lot less mass and volume of biofuels are going to be shipped than the absurd amount of fossil fuels we ship annually today.
And another 15% of bulk shipping is raw iron ore, usually heading to the same ports coal is going to, a supply chain and processing requirement that’s going to change. A lot more steel will be made from scrap steel in electric steel minimills. A much greater percentage of iron ore will be processed locally into hot briquetted iron or steel with green hydrogen or direct electrical reduction. Container shipping up, yes, but bulk shipping declining radically.
And the results were clear there too. Battery-electric was completely fit for purpose for all inland shipping and roughly two-thirds of nearshore shipping. Putting batteries in shipping containers that could be used on trains or ships, charged at transshipment ports, and loaded onto trains or ships as needed is a trivial extension of existing container logistics. That left a portion of nearshore shipping and the declining segment of deepwater shipping that required biofuels.
And that amount was less than the amount required for peak aviation demand, which would consume quite a bit less than than half of waste biomass and grain stalks available. Total biofuels demand for aviation and marine shipping, in other words, were well under current agricultural and biomass feedstock volumes.
But what about the damages of agriculture, many ask. It’s high-carbon too, they cry. Ammonia-based fertilizers degrade into high global warming potential NOx after applications to fields, and phosphate fertilizer creates massive algal blooms in water it runs into.
And they are right, but that’s a set of problems we have an increasing set of solutions for. Low-tillage agriculture preserves both short term soil carbon and the long-term glomalin carbon sequestration pathway. Expanding precision agriculture requires cheap computers, GPS, and limited farm equipment automation to radically reduce fertilizer (and pesticide and herbicide) use. Moving calorie stripping subsistence farmers off of the land and into useful occupations in urban areas frees up semi-arable land and eliminates the typically high-fertilizer use practices there. And finally agrigenetics is coming up with great new tricks, with Pivot Bio’s tweaked nitrogen-fixing microbes that are the energizer bunny of fertilizers, don’t produce multiples of CO2 as they are made, don’t turn into high GWP NOx, and are as easy to make as brewer’s yeast. As agriculture becomes more virtuous, so do biofuels.
It took a few years, a lot of publication, some corrections from kind (and unkind) strangers who in many cases have become regular collaborators, rebuilding my brain so that I could approximate being a chemical process engineer, stuffing a rather absurd amount of different domains into my wetware, working through snarls of energy unit conversions and building outsized spreadsheet models, but my opinion is solidly based.
Biofuels are fit for purpose, and we have a lot more resources for them than the requirements. Arguments against them are mostly specious, biased, or based on very stale data.
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