Fueling Our Transportation Future

John Heywood

Some one-third of our primary energy consumption is used to transport people and goods. So transportation is an important research area in our developing MIT Energy Initiative. The scale of our transportation systems is vast: some 800 million vehicles in use in the world today and projections suggest there will be 2 billion vehicles by 2050. Almost 100 years of continuous development have fine-tuned the fuels, propulsion systems, vehicle technologies, and use patterns to match our economic and social contexts. Petroleum-based fuels, and internal combustion engines on land and water, and gas turbines in aircraft, dominate. In the developed world, at least, most of us like the services our transportation systems provide. But it is becoming ever clearer that the energy requirements and environmental impacts of our transportation systems will have to be drastically reduced.

MIT, with its strong engineering core, is a place where realism based on quantitative assessments really matters. The numbers that define transportation impacts are truly daunting. How then can we be optimistic about meeting these energy and environmental challenges? What should the breadth and scope of our transportation energy research agenda be, if we are to make progress? What issues should we analyze and then explain to the broader community?

Let’s be clear about the challenge: is it feasible to achieve, say, a factor of four reduction in energy consumed per vehicle so that over the next few decades we can offset the anticipated growth in number of vehicles?

Personal and public transportation, and freight, all pose major challenges. Here, I will focus on light-duty vehicles – cars, pick-ups, SUVs, and minivans – to illustrate what the agenda should include. We can reduce fuel consumption by improving vehicle technology, by reducing vehicle weight, by driving less as well as less aggressively, by finding new sources of energy, by making both technology and behavioral changes. To illustrate the potential of working on a broad set of improvement factors, consider the cumulative impact that several of them could have if each achieves a 20% fuel consumption reduction. Each 20% reduction would reduce fuel consumption to 0.8 of what it was originally. Now 0.8 multiplied together six times yields 0.26, which is close to one-quarter or a factor of four reduction. Thus to offset the anticipated growth in number of vehicles, we will need to achieve substantive fuel consumption reductions through many different steps that include technology improvements, finding substitutes for petroleum, and changes in driver and user behavior.

The table lists twelve different areas where reductions in vehicle energy consumption and greenhouse gas emissions are potentially feasible. They are divided into two categories. In the first category, each action has the potential for affecting the entire in-use vehicle fleet. For example, raising fuel taxes to replenish our Highway Trust Fund so that it can adequately maintain our roads would reduce everyone’s mileage. If ethanol from biomass steadily builds up in volume and displaces gasoline, then fleet petroleum consumption will go down.

The second category lists opportunities where fuel consumption and emissions could be reduced through improvements and changes in new vehicle technology. Some of these areas offer substantial reduction potential, but would evolve more slowly since the impact only occurs as new vehicles with improved or different technology are produced and enter the in-use fleet. The last two on this list – hydrogen and fuel cells, and electricity and advanced battery technology – would be radical changes. These are being explored and developed because of their potential to “fuel” major parts of our transportation system with low greenhouse gas emissions if the hydrogen or electrical energy can be produced without releasing CO2.

This list of opportunities (and others no doubt could be added) identifies the broad dimensions of a research agenda focused on reducing transportation energy consumption. For many of us at MIT, carrying out research on parts of this agenda will be our professional responsibility. However, all of us should view this agenda as a set of opportunities where we can contribute as individuals. Each of us can drive less aggressively, choose vehicles that consume less fuel next time we buy or rent one, and be more thoughtful about how much we drive. In the end it will be the sum of all our individual contributions – both professional and personal – that will make a difference. Somehow, we will have to find effective ways to get off our current path of steadily rising transportation energy consumption.

	Back to top
	Send your comments