I’d like to explore a bit about the future of transportation. Our transportation system uses oil. Or maybe it’s better to say it is oil. Currently we get over 95% of the energy used for transportation of all kinds from oil. This is going to have to change. What are our options?
Just as a breakdown, let’s look at the energy inputs today:
- Cars, trucks: Oil
- Buses: Oil, Natural gas, Electricity
- Planes: Oil
- Trains: Oil, Electricity
Buses and trains that use electricity are indirectly using, for the most part, natural gas and coal, which provide the vast majority of our electricity. This sort of dependency on fossil fuels—setting aside climate change for the moment—would be okay, if there weren’t an issue with the availability of these fuels, particularly liquid fuels.
Choke points and common remedies.
As we face near-term oil peaking and depletion, the availability of oil, and thus transportation fuels, is going to steadily decrease in the near future. Having a transport system so dependent upon a single energy source is a huge vulnerability.
In recent years industry and politicians alike have hailed natural gas as a clean alternative to oil. The source of natural gas is the recently-popular approach of hydraulic fracturing in which underground rock is broken apart under high pressure to release natural gas trapped inside. But the problems with this miracle alternative are numerous. First, the obvious environmental impacts are horrendous as documented in the must-watch documentary Gasland. Second, but less obvious, are the indirect impacts including the fact that fracking may leak so much natural gas that the process is worse than using coal from a climate perspective. Third, natural gas drilling, like a lot of things these days, is driven in part by a speculative bubble, in which Wall Street favors “booked reserves” (natural gas that can be claimed to be under the ground at some well) rather than whether those booked reserves are profitable, leading to perverse incentives in which companies will drill unproductive wells to book reserves (here’s a bit more from an oil/gas industry veteran). Fourth, there may simply be not enough natural gas there to be a viable alternative in the long term. This study goes through many of the infrequently-discussed issues with natural gas.
So, if natural gas isn’t the answer, what is? Well often people discuss electric cars as an “alternative”. However, electricity has to be generated in some way, and currently we get over 85% of our electricity from fossil fuels or nuclear, neither of which are long term options. Setting aside the limits of switching to alternatives for generation (the issues of which are discussed in David Fridley’s great article on the Nine Challenges of Alternative Energy), we’d still have to produce and sell enough electric cars to make a dent. Recent reports say 1/3 of car sales will be electric by 2020. The problem is such reports don’t discuss that sales are not the same as the base of cars actually being used (and they ignore trucks and other vehicles). Nor do they discuss the limits of rare earth elements, or economic issues relating to peak oil—but let’s ignore that for now. With roughly 800 million internal-combustion engine vehicles out there, and with meager goals in industrialized countries of having at most a couple of million electric cars on the road by 2020, it’s clear that even in a decade we’ll be far away from the electric car future so often seen as an answer.
So it seems we’re stuck with the installed base of cars and trucks and planes and trains for now. And they run on liquid fuels. So the next best bet is to devise an alternative source of liquid fuel: biofuel. Today we produce a fair amount of corn ethanol that’s used as a gasoline additive, but it yields zero net energy, meaning that it takes roughly as much energy in inputs as it yields as a fuel once produced (its inputs are natural gas for fertilizer and the oil-powered agriculture system to grow the corn, for processing corn into ethanol, and for transporting the ethanol to distribution points). Making ethanol from sugarcane, as they do in Brazil, is more efficient, though it still doesn’t scale to the levels it’d need to in order to power all our vehicles. Bioengineered algae is under development as a third generation biofuel, but it’s still not viable, and even if it were, it would require vast areas of land for production.
Since our rail system is largely diesel (and inter-city rail is sparse and poorly maintained), the much-needed transition to using rail isn’t happening at the rate we need. And it’s unlikely we’re going to switch to using wood-gas cars anytime soon.
Maybe instead of doing what we do, let’s do different things, or fewer things, or smaller things. Maybe it isn’t a great idea to hurl a ton of metal using ancient stored sunlight in order to move a person that weighs a tenth of that. Maybe we should stop thinking about ways to run all our cars on some new alternative fuel source or technology, and instead think about other options for meeting our transportation needs.
In the not-so-distant future, air travel and long-distance road trips are likely to be luxuries that very few people will be able to afford. We will need to look to other options.
When looking at transportation alternatives, we should consider their efficiency in moving people or cargo. This graph (from MacKay’s excellent book Sustainable Energy – Without the Hot Air) shows how efficient various modes of transport are in terms of person-miles per gallon of gasoline:
As it shows, bicycling and walking are the most efficient ways of getting around, though electric trains are also very efficient. We’re all going to be doing a lot more walking and/or biking. It’s also important to enact bike and pedestrian friendly civic design policies, and though I think in the long run these are inevitable, the sooner the better.
It’s absolutely essential we invest more in both long-distance high speed rail but just as importantly local and regional electric metro / light rail, but these are long-term, large-scale projects that at the moment there seems to be little appetite for either at the federal or state level.
Within cities today’s diesel-based bus systems can be retrofitted in many ways. A good option is to electrify bus systems, but to make using them more speedy, we can dedicate lanes on the road for buses.
There aren’t many good options for air travel – no energy source that we know of has the energy density of oil. So we’re stuck with using oil for planes, though I think it’s likely that since we won’t ever really run out of oil (though it will become prohibitively expensive), planes will still be used by those who can afford them and for essential services. Aviation might be the best application of limited algae-based biofuel production. Finally, for those on a coast or along a navigable waterway, a sailboat might not be a bad option (Orlov has written extensively about this).