Spring 2013 Magazine

The Brain

Carbon Calculator

Eric Masanet uses mathematical models to understand carbon emissions and find solutions for reducing them


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Eric Masanet

As the ninth-largest economy in the world, California has the muscle to influence opinions beyond its borders. So it’s no surprise that all eyes are on the Golden State as it implements a relatively new approach to combating greenhouse gas emissions: letting companies buy and sell the right to pollute.

Under California’s “cap-and-trade” program—the most expansive of its kind in the country—state regulators place a cap on the amount of carbon that oil refineries, power plants, and large factories may emit per unit of production. The cap decreases over time to rein in emissions. Companies that exceed the legal limit face a choice: clean up or buy extra allowances from companies that have some to spare.

Under California’s 'cap-and-trade' program, state regulators place a cap on the amount of carbon emission per unit of production.It sounds simple, but assigning carbon emissions to individual products is anything but. “Assigning emissions is an especially complex problem in the manufacturing sector, where one facility can produce a lot of different products,” says Eric Masanet (MS ’96), associate professor of mechanical engineering and of chemical and biological engineering at McCormick. “To distribute carbon allowances fairly across an industry, we need to account for these differences in product outputs within an industry, as well as differences in their production processes.”

For the past year Masanet, Northwestern postdoctoral researcher Mike Walker, and partners from the University of California, Berkeley, and the Dutch consulting firm Ecofys have been working to design mathematical approaches to help the California Air Resources Board, the regulatory agency overseeing cap-and-trade, make credible, mathematically sound decisions about carbon allowances across California’s many industrial plants.

Masanet is focusing on California’s food processing industries, which include large companies like Morningstar, Frito-Lay, and Gallo, that can have massive operations that are complicated to analyze. In the tomato processing industry, for instance, numerous products, from ketchup to diced tomatoes to sauce, are made from one raw commodity. Any formula regulators use to assign carbon allowances must take all the products into account.

“Regulators can’t just say to a tomato processing plant, ‘You can emit X grams of carbon dioxide for each tomato you process,’ because the emission levels are different for each product,” Masanet says. “Our goal is to accurately assign emissions to a broad range of products—providing a calculation method to regulators so they can fairly distribute allowances and drive change across an industry.”

Driving change is the goal of all of Masanet’s work. He often employs life-cycle analysis to study the environmental impacts of the entire life cycle of a product, from manufacturing to consumption to disposal. By quantifying the energy usage, emissions, and environmental effects of current and potential technologies and behaviors, life-cycle analysis informs smarter manufacturing processes and policies.

“From a sustainability perspective, my research seeks to determine where we are today, where we could be, and the steps we can take to get there,” Masanet says. “Putting numbers on potential reduction opportunities is an important first step in designing policy, as these numbers illuminate where design can make a difference, where manufacturing can make a difference, and so on.”

Whether comparing the carbon footprints of tomato products or researching the life cycle of computer equipment, Masanet is supplying the cold, hard facts that have been lacking in his field. “You frequently hear that a product or process is ‘green,’ but it takes good data to determine whether that’s true,” Masanet says. “People want to know if they should use paper or plastic, cloth diapers or disposable. While the answer might seem obvious, it actually depends on a lot of factors, and we don’t know the answer until we do these detailed analyses.”

Researchers like Masanet are beginning to close that knowledge gap by making sustainability research available not just through publications but also through open-source models that others can adapt and reuse. Masanet currently has been funded to develop two open-source models: one, funded by Google and in collaboration with Lawrence Berkeley National Laboratory, to quantify the energy efficiency benefits of cloud computing, and another, funded by the National Science Foundation, to minimize the environmental footprints of complex manufacturing supply chains. “The idea is to leave something behind so that other researchers can help move the field forward,” he says.

Masanet’s big-picture analyses are also helping to guide economic decisions. In a project for the US Department of Energy, Masanet and his collaborators are assessing the societal and economic benefits of nextgeneration manufacturing process technologies in the United States.

“We think industries like nanotechnology, clean energy technologies, and additive manufacturing might create jobs, reduce carbon emissions, and be a boon for our economy, but putting numbers to these claims is incredibly important,” Masanet says. “There are thousands of technologies the government could invest in. Having hard numbers on the potential benefits of each technology helps in decision making.”

After only a year at McCormick, Masanet has already added three sustainability courses to the curriculum, including Life-Cycle Analysis and Sustainable Manufacturing Systems. In addition, he is working on a new project, funded by McCormick’s Walter P. Murphy Society, that would enable Northwestern students to provide no-cost life-cycle sustainability audits to local manufacturers.

“Sustainability improvements are vital for a clean planet and a healthy economy, but they’re not going to happen on their own,” Masanet says. “We need to change behavior, change mindsets, realign incentives. It’s going to take bright students getting trained in these areas and going out and making it happen, and Northwestern is making a big commitment to doing that.”

By: Sarah Ostman