Midjourney generated image of a futuristic passenger jet covered with circuitry and sparks

How Aviation Will Decarbonize Decade By Decade Until 2100 (Part 1)

November 15, 2021November 12, 20232 years ago Michael Barnard 0 Comments

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After years of working up to it, I recently published my 3-part series on the aviation fuels of the future (part 1, part 2, part 3). I’d first asserted the likelihood that all short- and medium-haul aviation would be battery-electric four years ago as part of my overview of all transportation modes, although my opinion on long-haul was unformed. Roughly a year ago, I published about why aviation was a hard target, using a methanol fuel replacement as a basis for assessing the challenges of direct CO2 emissions, contrail-related warming, and NOx related warming, which combined make aviation worse than base fuel consumption makes apparent.

Projection of aviation energy demand by type of energy source through 2100 by author

In the more recent series, I deconstructed the arguments for hydrogen (double the cost per passenger or freight mile) and alternatives such as aluminum air fuel cells (dead on arrival), as well as the cherry-picked and illogical arguments of those arguing against battery electric. I also made the case for sustainable aviation fuels, specifically biofuels, bridging the hard to electrify long-haul segment of aviation until electrochemistry and new chemistries brought battery-electric up to a sufficient energy density to weight to cost ratio to deal with all aviation.

But I didn’t do much more than wave my hands about how long this would all take and what it would mean. Now I’ve put together version 1.0 of my projection of aviation refueling through 2100. As with all of my multi-decade projection of things like vehicle-to-grid, grid storage and hydrogen demand, this is a projection of a possible scenario by a broadly informed professional, but not a prediction. It’s informed by the degree of transformation required to actually address climate change, and awareness of a broad range of transformations under way in multiple sectors which underpin CO2e emissions.

There are several things to call out in this projection. Many were covered in the 3-part series, but I’ll summarize the main ones here.

First, aviation is unlikely to return to pre-COVID-19 levels. The efficiency and effectiveness of video conferencing and remote work has been proven across the economy, but especially in those sectors that used to be heavy fliers, and I say that as someone who used to fly weekly for business. We’ve moved a decade into the future and broken the habit of getting on planes, and corporations will no longer pay for rafts of consultants to show up Monday and fly away Thursday. Client-facing now means over video links for the vast majority of the information, sales, and consulting workforces.

Among many other data points, this was reinforced by my discussion yesterday with a former colleague who now runs the national ESG practice for Canada for one of the major consultancies. While their junior staff are itching to get back to client sites, that’s just not going to happen. Only the most important and critical deals will involve flying from now on.

Similarly, in-country travel is going to be much more favored than international travel by many more people for vacations, and that will persist. COVID-19 was the fourth epidemic in the past 20 years, following SARS, H1N1 and Ebola, and now everyone knows the consequences. COVID-19 wasn’t the last epidemic, it was just the worst epidemic since the Spanish Flu.

Aviation will rebound from COVID-19, but in my projection it will rise to below 2019 levels and remain relatively flat.

Second, electric means battery-electric, but is not limited to lithium-ion chemistries. Lithium-ion is fit for purpose for up to 19-passenger turboprops with 400 km ranges today, and the intersection of density, cost, and weight will continue to improve every year. The fast-charging technology for cars and trucks is fit for purpose for rapid recharging of electric airplanes today. The amount of manufacturing, research, and innovation underway in battery technology means that battery technologies have their own Moore’s Law equivalent, Wright’s Law. Lithium-ion is improving roughly 28% for every doubling of manufacturing capacity. But new chemistries are coming which will see significant improvements beyond that. Lithium-ion will likely prove suitable up to 100-passenger planes for 1000 kilometers, but other chemistries will take over after that.

Third, battery-electric and biofuels are only going to start making a noticeable dent in aviation fuel toward the middle of the 2030s. This is a hard sector to decarbonize, and significant transformation and development is required to achieve these targets. For example, in my piece articulating the case for biofuels, one of the transformations that will occur is the elimination of wasteful use of biofuels in easier to electrify sectors. The 2 million barrels a day currently going into cars and trucks today needs to be repurposed as all ground transportation electrifies.

The economic intersection of battery energy density, weight, and cost is sufficient for 400-600 km range planes with 4-19 passengers today, and that will grow substantially with each passing decade, but it’s insufficient for the majority of current flights right now. And, of course, battery-electric passenger planes need to be manufactured and certified, something companies like Heart Aerospace and Electron Aviation are working hard at.

Fourth, I’ve put a line in for it, but sharp eyes will note that hydrogen is going to be providing zero energy for aviation. I see no future for it based on the assessment of massive increases of costs and the need to use hydrogen for much more useful decarbonization purposes. There is no value for hydrogen as a fuel compared to alternatives, and our current hydrogen use is a massive carbon emissions problem.

Fifth, SAF biofuels will only grow as a source through 2060, when I project that energy densities of batteries will be sufficient for 80% of flights, and a sufficient number of battery electric airplanes will be replacing the current fleets. After that, it starts diminishing rapidly as fuel burning turboprops and turbofans retire. Biofuels for aviation are only a 40-year growth market and after that they will diminish. Of course, agricultural lobbies will work to extend this, and may very well pervert or at least defer rational decision making.

Sixth, battery electric barrels of oil equivalent is arrived at by using a blended efficiency factor for current aviation between the remarkable 55% of high-altitude turbofans at cruise, and the much lower efficiency of internal combustion turboprops operating at lower levels. I use that to determine the gigajoules required, then use the very high efficiency factory for electric motors to gross it up to the MWh required for similar distances. In other words, it’s the normalized energy used per distance flown that becomes the electricity figure. This seems defensible to me, and conservative.

Finally, many deep analysts have issues with this perspective. People seemingly close to current SAF results have disagreed with my earlier analysis. Others deeper into batteries have disagreed with my perspectives on aluminum air fuel cells, albeit on what appear to be technicalities and some lack of a systems engineering perspectives. People invested in hydrogen for their various reasons disagree with this analysis of course. Professor Mark Z. Jacobson disagrees with the earlier biofuels portion of the analysis, although the time perspective and CO2e perspective still might shift his opinion.

Electric, yes, but biofuels for aviation are hardly any better than jet fuel. They are combustion fuels that pollute with NOx, Has, CO, CH4, and emit black and brown carbon, the 2nd-leading cause of global warming, create contrails just like jet fuel, and hardly reduce CO2.

— Mark Z. Jacobson (@mzjacobson) November 10, 2021

So do consider this to be one of many potential scenarios. It is imperfect.

One of the things I looked at while preparing this scenario was a set of market analyses projecting aviation fuel growth. To say I found them remarkably lacking in reality, context, and usefulness would be to deeply understate how silly I thought they were. There was no recognition of the state change that COVID-19 had brought, the projections were clearly based on projecting history in a straight line into the radically altered future, they ignored the requirement for aviation to deal with climate change, and they ignored the battery-electric and biofuel revolutions sweeping up to replace petroleum-sourced kerosene fuels.

For commodities traders, businesses, strategists, and policy makers, I would recommend being very leery of most of the market analyses currently in the space. Anyone invested in hydrogen aviation startups such as ZeroAvia and Wright Electric should be considering their exit very carefully, as there is still hype to ride, but no upside due to the laws of thermodynamics and economics. Obviously anyone considering investing in aviation fuel alternatives should avoid hydrogen pathways as well, beyond hype-oriented speculative investments lasting at most 5-6 years.

And so, that’s part 1 of the projection through 2100. In part 2, I’ll deal with the all important results of the shift, the reduction in CO2e emissions. That includes not only direct CO2, but as I noted in the assessment of the challenges of aviation, contrails and NOx projections as well.

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