Controlling the Emissions of Charbroiled Burgers

UC Riverside is helping the South Coast Air Quality Management District find ways to reduce the particulate matter emitted by commercial cookers

Commercial under-fired charbroilers emit a large amount of particulate matter into the air we breathe. PHOTO BY PETER PHUN

Riverside, Calif. — When you think of air pollution, you automatically think of diesel engine fumes, smoke stacks from industrial plants and machine exhaust. You don’t think of a charbroiled hamburger.

Researchers at the University of California, Riverside, however, have confirmed previous findings that commercial under-fired charbroilers cooking hamburgers emit a large amount of particulate matter into the air we breathe.

“Emissions from cooking hamburgers on commercial charbroilers are a very significant uncontrolled source of directly-emitted particulate matter… if left uncontrolled they emit more than twice than all of the heavy-duty diesel trucks,” said Bill Welch, principal development engineer for the study. “For comparison, the average diesel-engine truck on the road today would have to drive 10 miles on the freeway to put out the same mass of particles as a single charbroiled hamburger patty.”

“Commercial cooking is the largest source of directly emitted particulate pollution in the Southland,” said Barry Wallerstein, executive officer for the South Coast Air Quality Management District (AQMD).  “However, all truck emissions are responsible for far more pollution and health risks than charbroilers.”

Trucks are not only a significant source of directly emitted PM2.5, but also the No. 1 source of NOx (nitrogen oxide) emissions in our region, Wallerstein said.  NOx emissions form both ground-level ozone and PM2.5 (particulate matter) in the atmosphere.

“When you consider both the directly-emitted PM2.5 from trucks, as well their NOx emissions that form particulate matter in the atmosphere, trucks are responsible for nearly three times the amount of PM2.5 pollution than that emitted by all commercial charbroilers,” he said.

In addition to contributing to particulate matter, it is also known that diesel exhaust is carcinogenic.  Diesel particulate matter is responsible for the overwhelming majority of cancer risk from air pollution, Wallerstein said.

Bill Welch

Bill Welch is the principal development engineer for the study. PHOTO BY PETER PHUN

Funded by AQMD, UC Riverside’s Center for Environmental Research and Technology (CE-CERT) is now testing existing control technologies for under-fired charbroilers supplied by five vendors. Welch and his team, in conjunction with AQMD, developed the protocol for testing emissions.

Although commercial cooking equipment generates grease, smoke, heat, water vapor, and combustion products, AQMD’s existing charbroiler regulation only addresses so-called chain-driven charbroilers, which are far outnumbered by under-fired units. If technologies being tested at CE-CERT prove feasible and cost-effective, AQMD could require emission reductions from under-fired charbroilers. However, AQMD will only adopt such a regulation if it is needed to supplement existing control measures to achieve federal health-based standards for particulate matter, Wallerstein said.

Past research has established that for every 1,000 pounds of meat cooked, 33 pounds (or 3 percent of the weight of each hamburger) goes into the atmosphere in the form of particulate matter.

Stanley Tong, an environmental engineer who works with EPA in San Francisco, says there is a higher concentration of commercial charbroilers in the Los Angeles area because of the higher density of population. “There are a lot of emissions going out that’s not being controlled,” Tong said. “So the goal is, how do we find the technology that’s cost-effective and that works?”

It’s not that easy. Welch, who has been running CE-CERT emissions tests since 1994, says he’s tested emissions from engines, boats, ships, and weed whackers. “This [commercial charbroiling] is by far the most complicated,” said Welch. “It’s really difficult to generate the emissions as well as test it. Initially I tried going out to restaurants and measuring the emissions there, but every time we went out we got a different result,” he explained. At CE-CERT’s test lab, everything is standardized, from the temperature of the meat to the temperature of the grill.

CE-CERT has also tested emissions from chicken, steak, hamburger, cookies and pizza, and one thing is clear: “By far the worst offender is the open under-fired charbroiler,” he said. “Each 1/3-pound hamburger cooked by the open under-fired charbroiler will emit 5 grams of particles; that same hamburger fried on a griddle will put out less than 10 percent of that — less than half a gram. It’s the same hamburger, but the way you cook it is critical. ”

Burgers that UCR students don’t eat get donated to a food bank in Redlands. PHOTO BY PETER PHUN

The testing obviously involves cooking a lot of hamburger patties — but just how much are we talking about? Prior to this year, CE-CERT, which is part of the Bourns College of Engineering, had cooked 4 tons of hamburgers. Since May, Welch and his team have cooked 4,000 1/3-pound patties. He is quick to note that they don’t go to waste. “With students they’re very popular,” Welch says. “But what the students don’t eat we donate to a place called the Inland Harvest, a regional food bank committed to feeding homeless shelters.”

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