Our national climate goals of net zero emissions, renewable energy transition, electrified vehicle fleets, clean steel, green hydrogen, and the rest of the package focus on the ramp-up of clean energy sources and end uses. As these initiatives come to full fruition, one could envision a day when the last drop of oil is pulled from the ground, refined, and burned. After that, it’s all clean electricity running our national economy.

Although that day might be centuries away, if ever, it is realistic to think that by the second half of this century we will be shifting massively away from fossil fuels. Yet, amidst all the plans for the ramp-up of a clean energy economy, I have had a hard time finding any public or private sector plans for the ramp-down of the fossil fuel economy. So, here’s a thought experiment and some questions I’m hoping you might help me sort through.

Imagine that by 2050, or soon after, we have achieved a substantial ramp-up of clean energy systems. Electricity production is overwhelmingly from clean sources. Half of all new vehicles sold are EVs. Other transportation sectors such as marine and aviation have made great strides in adopting clean energy fuels and electric power systems. The building sector has shifted immensely away from natural gas for heating. Innovations in steel and cement manufacturing have made great strides. The list goes on, and the ramp-up trajectory is on pace for more, faster.

At the same time, the flip side of this encouraging picture is the ramp-down—the gradual but quickening weaning of the economy off of fossil fuels. Although their numbers are falling, there are still plenty of vehicles, buildings, steel plants, jets, and other important end uses relying on fossil fuels. We are in effect running two national energy systems in parallel—a fossil fuel energy system well on the way down, and a clean energy system well on its way up.

Here’s the question I’ve been puzzling with: How do we support a national fossil fuel energy system that is half the size it is today and is in decline?

For example, assuming there are still millions of internal combustion vehicles scattered all across the nation, we will still need an infrastructure and business system that produces, transports, and delivers retail gasoline and diesel all across the nation. How economical will it be to keep running a system like that—one as big in scope as it is today but with only half the total (and declining) demand? How expensive will gasoline be at the pump, especially in rural towns?

Now ask the same for all the jets, barges, buildings, cement plants, steel plants, plastic manufacturing, and other end uses still relying on oil or natural gas. If they are scattered across the nation, the fossil fuel system must remain nation-wide as well. Even if everyone is trying to get off of fossil fuels, it is not possible to do it all at once, so there is going to be a ramp-down while we ramp-up. How do we manage the ramp-down? Is there a plan, or will we just muddle through?

In particular, is there a point at which it is not feasible, either as a matter of economics or engineering, to support a nation-wide fossil fuel system as the demand ramps down but remains nation-wide? If it is not feasible, what then? Even if it is feasible in the strict sense, I imagine the fuel prices would be prohibitively expensive for many citizens and businesses unless subsidized. We are a long way off from every home and business having the option of making an easy and affordable transition to a fully-electric, clean-sourced life. Until we are, the ramp-down will impose profound transition justice concerns—what I call the other just energy transition. Will that side of the energy transition be “good to the last drop”?