Planes

There are obviously different types of planes. I am going to focus on jets that take jet fuel because air travel in jet planes is the most common type of air travel.

Aviation is the one area where there is no alternative to liquid fuels on the horizon.

Aviation is extremely sensitive to weight, more so than vehicles. Space is also important. In any case, electric motors would only work with propellors, not jet engines. Therefore, what we are realistically looking at is replacing fossil fuel with synthetic fuel. This works with existing jet engines.

As I mentioned in the technology overview, while there is no problem reusing waste CO₂ from existing industrial and biological processes, this has a ceiling now and we want to reduce waste CO₂, so this ceiling will come down. So, for synthetic fuel production to scale, we are looking at getting CO₂ from the air in a process called direct air capture (DAC).

On that basis, let's work through some cost numbers. There is limited synthetic fuel production and even less with DAC. As production scales, we can expect costs to come down.

I am calculating the cost of synthetic fuel production with DAC myself, based on various other costs. I have looked up reputable sources for those costs which are linked in the table below. Where there is a range, I am taking the lower figure. I feel that this is justified since we would try to improve on the best pilot, rather than the worst. The currency conversions are at the time of writing, so they could be different by the time you read this page.

So, the difference in CO₂ cost between DAC and Cement is $0.79386.

We take a typical kerosine component C₁₂H₂₆. This is normal practice and they are all similar, anyway. For C₁₂H₂₆, 84.71% of the weight comes from carbon (based on a carbon atom being 12 times the weight of a hydrogen atom). And for each Kg of carbon, we need 3.667 Kg of CO₂ (based on oxygen atoms being heavier than carbon atoms by a third). Multiplying this together, we need 3.106Kg of CO₂ for each 1Kg of C₁₂H₂₆. This brings the cost difference of the CO₂ to $2.465.

Thus we arrive at a total cost of approximately AU$ 5.52 per Kg for electrolysis+DAC jet fuel.

Please note: I made a good faith effort to give you a reasonably accurate price. Of course, there are limitations and inaccuracies. In particular, electricity prices vary by country and that could make some difference, though hopefully in Australia's favour as we have abundant wind and sunshine.

The difference with regular jet fuel is $2.94/Kg.

Note that there are only pilot projects for DAC. We can expect the cost to come down significantly when DAC scales. This article in Science Direct states:

"Current costs range from $600 to $1,000 per ton of CO₂, but with increased deployment and supportive policies, these costs could fall to $150-$200 per ton over the next 5-10 years."

My apologies for so much mathematics. But I couldn't find a single figure for electrosys+DAC jet fuel. And I felt I needed to justify the numbers.

At this stage, synthetic kerosine with DAC is too expensive to mandate more than a small percentage.

So, I propose: An immediate legislated target of Australian made electrolysis+DAC jet fuel of 2% and a more relaxed target of an additional 2% for electrolysis jet fuel where waste CO₂ may be used. The additional 2% could be imported but only on ships which use green fuels. Shortfall charges would apply. The targets would definitely apply to domestic flights and also to refueling of international flights. I'll leave it for somebody else to figure out rules for ensuring that international operators don't just avoid or minimise refueling in Australia.

These initial targets are modest and will not cause a dramatic increase in fuel costs. The term "shortfall charge" is a term already in use to describe the amount payable when environmental targets aren't met. It's not a tax because the intent is that the targets are met and it's not a fine because the targets can't be met immediately. In the case of Australian made electrolysis+DAC jet fuel, it obvious that the targets can't be met immediately since the plants to make it don't exist. Nevertheless, the incentive should exist immediately. The shortfall charges must be at least as big as the difference in cost between fossil jet fuel and green jet fuel.

Of course, these targets need to be increased over time until jet fuel is fully renewable.

My motivation with these targets, apart from obviously incentivating the move away from fossil fuels, is to see Australia at the forefront of this emerging technology. This is an area where we have a natural advantage of sun and wind which would allow us to not only be self-sufficient but also remain an energy exporter in a post fossil fuel world.