Just how much energy goes into a sports utility vehicle versus a hybrid vehicle? GREET can tell you exactly.

There are spreadsheets and then there are spreadsheets. Taking up 15 megabytes of hard disk space and with 28 separate tabs, Argonne National Laboratory’s publicly available GREET (Greenhouse Gases, Regulated Emissions and Energy Use in Transportation) model can answer just about any question that a company, government agency or academic researcher has about greenhouse gas emissions and energy consumption of vehicles powered by everything from Brazilian sugarcane to hydrogen fuel cells. For any given vehicle technology and fuel system, GREET separately calculates the energy consumption by energy type; the emissions of greenhouse gases, including carbon dioxide, methane and nitrous oxide; and the outputs of six critical pollutants, including nitrogen oxides and soot.

In the last two years, project leader Michael Wang and his five-person team have updated GREET to model even the energy it takes to produce a vehicle’s fuel and get it to the pump; how much energy is used in driving the vehicle; and how much energy is required to manufacture the vehicle and recycle or dispose it at the end of its cycle. “That gives a real comprehensive life-cycle approach to looking at conventional and advanced vehicles,” said team member Andrew Burnham.

Wang, who hails from China, began this massive spreadsheet model in 1995. Upon earning his doctorate in environmental science at the University of California-Davis and joining Argonne, in DuPage County, Illinois, he wanted to compare conventional vehicle impacts with electric vehicles. “But that’s like comparing apples to oranges,” said Wang. “It’s easy to measure the emissions of a gasoline-powered combustion engine as it rumbles away, but looking at only the quiet whirr of an electric motor may not show its true impact on the environment. Its electricity, which is generated at a power plant far from where the vehicle was operated, has to be taken into account.”

Consequently, Wang’s model asks, how was that power generated? Was it produced in a coal-fired plant in Arkansas or at a wind-energy farm in California? How was it transported to the electric wall outlet? How much energy did it take to produce the aluminum used in the car’s engine? While Wang initially made his calculations by hand, he soon realized he could build a spreadsheet that would make this task easier for him and, ultimately, the transportation community.

The project took off just as the federally sponsored Partnership for a New Generation of Vehicles— collaborative research between National Laboratories—federal agencies and major automakers on how to bring highly fuel-efficient cars to the marketplace, got rolling in the early 1990s. The partnership impelled people to think about fuel-cycle analysis.

Today, GREET can simulate more than 82 vehicle-fuel combinations. It has more than 9,000 registered users worldwide. To address technology improvements, GREET simulates fuel production pathways and vehicle systems over a period from 1990 to 2020 in five-year intervals. Since the biggest challenge is acquiring accurate data, Wang is constantly tinkering with parameters. Most recently, his team used survey data just released from the Energy Information Administration to update his efficiency estimates for petroleum refining operations.

Just as Wang realized that a vehicle’s impact can extend beyond its tailpipe, researchers began challenging how far those impacts spiral out. For instance, when corn is grown on a farm recently cleared of native vegetation, this land-use change and its direct impact on greenhouse gas emissions are relatively easy to calculate. More contentious is how farming in the United States might indirectly affect greenhouse gas emissions in international economic channels. If the United States exports less corn, or U.S. corn prices increase, some maintain that other countries may expand their corn-growing operations.

Wang and his group at Argonne are still grappling with the issue, and working with other organizations to address the indirect effects of large-scale biofuels production with economic general equilibrium models. But more comprehensive models will be needed to take into account the supply and demand of agricultural commodities, land-use patterns and global land availability.