Development and transportation have been intertwined since wheels were first attached to carts over 6000 years ago. Efficient methods to move goods and people are largely responsible for the quality of life many of us enjoy today. However, these societal benefits also have a cost. Transportation accounts for about 13% of global carbon emissions. In many nations that percentage is much higher, for example in the United States transportation accounts for over one-third of US carbon emissions. Reducing transportation-related greenhouse gas emissions is a critical component of addressing global climate change.
In addition to contributing to climate change, the burning of fossil fuels contributes to air pollution. According to the World Health Organization “Significant reduction of exposure to air pollution can be achieved through lowering the concentrations of several of the most common air pollutants emitted during the combustion of fossil fuels.” Other reasons to reduce dependence on petroleum-based fuels include concerns about peak oil, energy security, and economic dependence.
Obviously, one answer is to drive less. There are many initiatives to reduce dependence on conventional vehicles. New livable community initiatives, transportation oriented development, and EcoMobility are aimed at reducing the number of vehicle miles driven. These initiatives are important, but cannot address the larger issues of moving goods and people across large distances. That is why organizations such as the Low Carbon Vehicle Partnership, and my organization, the Houston Advanced Research Center, support a wide range of sustainable transportation options.
Working on issues of sustainable transportation, I frequently get asked, “What’s going to take the place of gasoline? Which new technology will be the winner?” I’ve even been to conferences with organized debates so supporters of different technologies can argue about why theirs is the BEST low carbon fuel solution. The usual suspects in these debates are:
- Biofuels. Biofuels are attractive solutions because they mostly operate as drop-in replacements for petroleum-based fuels. They were originally hailed as a panacea, but quickly dissolved into concerns about trading food for fuel, and the carbon footprint of ethanol production. But, there is also optimism that these fuels can support sustainable energy in the developing world. Next generation biofuels such as celuosic ethanol and algael biofules are addressing these concerns, but there are questions of how quickly these technologies can be brought to scale at a competitive price. Biofuels can be used in both light duty and heavy duty vehicles.
- Electric vehicles (EVs). The momentum for electric vehicles is growing, but widespread deployment faces significant hurdles. Battery technology is improving, ranges are getting further, and there is widespread enthusiasm. The excitement even spread here to Houston, Texas (which the locals like to call “the oil capital of the world”), where NRG Energy, Inc. is launching the US’s first privately funded, comprehensive electric vehicle ecosystem. Major auto manufacturers are delivering EV automobiles today. However, battery and range concerns have limited the EVs ability to penetrate the heavy duty vehicle market.
- Natural Gas Vehicles (NGV). Recent natural gas discoveries have lowered the cost of natural gas as a fuel. Natural gas is still a fossil fuel, but the well-to-wheel lifecycle analysis shows that natural gas is still preferable to traditional petroleum fuels. It is the alternative fuel of choice for large vehicles such as transit busses and trash trucks. While conversion kits are available for passenger vehicles, major auto manufacturers are not offering natural gas cars.
- Hydrogen and Fuel Cells. There are some vehicles that have an internal combustion engine that burns hydrogen. More commonly, hydrogen is used as an energy carrier to power a fuel cell. In that way, all fuel cell vehicles are electric vehicles. Hydrogen can be created from any primary energy source, or through electrolysis using electricity and water. Prices for fuel cell technologies are falling, and may be cost competitive for some applications (e.g. replacing electric forklifts with fuel cell forklifts), but mostly are still more expensive than other options. Refueling infrastructure is also a concern. Major auto manufacturers have announced that they plan on offering fuel cell vehicles in 2015.
- Hybrid Technology. Hybrid technology is not new, but it does improve miles per gallon and reduce the need for conventional fuels. These improvements will become more marked as more plug in hybrid electric vehicles (PHEVs) and extended range electric vehicles (EREVs) enter the market. There are also opportunities for a different sort of hybrid vehicle. For example, many of the fuel cell busses that are being demonstrated today are actually hybrids – plug-in electric busses with hydrogen fuel cells. This type of hybrid bus can have significantly smaller battery packs than an all electric bus would require, but can refuel quickly and easily with hydrogen so that it can run all day.
I think the lesson in creating the hybrid vehicle is one we need to keep in mind as we create a low carbon transportation future. Instead of trying to pick a winner, remember we have a wide range of solutions. Working together to emphasize the strengths and mitigate the weakness of the various technologies, we can create a low carbon transportation future that will improve health, reduce risks, and increase quality of life.
Jennifer Ronk, Research Scientist, Houston Advanced Research Center (HARC)