Environment

Wood-Fired Pizza May Taste Good, but It's Also Wrecking the Environment

New studies examine the environmental impact of restaurants using wood-burning ovens.

pizza
Photo Credit: Kurman Communications/Flickr CC

For millennia, people have been baking flat bread and topping it with various ingredients. Today we call it pizza, though the word was first documented in the year 997 in Gaeta, a city in central Italy. At that time, pizza was baked in wood-burning stoves. Eventually, gas and electric ovens took over, being cheaper and easier to maintain.

In recent years, the wood-fired oven has made a resurgence around the globe, along with the increasing popularity of gourmet pizza; specifically, authentic Neapolitan pizza, which has specific rules for its creation, including the requirement of a domed, wood-fired oven.

While pizza lovers around the world have rejoiced at the chewy crusts and unique smoky flavor only wood can confer, there is a terrible downside: the negative environmental impact of all this burning wood. And wood-fired pizza isn’t the only culprit; steakhouses that use wood-burning ovens are also contributing to an increase in air pollution and global-warming greenhouse gases.

In a study published in the journal Atmospheric Environment, researchers looked at the impact of wood-burning stoves in Sao Paulo, Brazil, known for its churrascarias, or barbecue-style steakhouses (there are some 500 of them), as well as some 8,000 pizza parlors, some so massive they can seat 600 people at a time. Every single day, the city's pizza parlors produce nearly a million pizzas. That's a lot of burnt wood.

But it’s not just emissions scientists are worried about when it comes to wood-burning ovens: Deforestation is also a problem.

“There are more than 7.5 hectares [about 19 acres] of eucalyptus forest being burned every month by [Sao Paulo’s] pizzerias and steakhouses,” said Prashant Kumar, the study’s lead author, a professor of civil and environmental engineering at the University of Surrey in Guildford, England. “A total of over 307,000 tons of wood is burned each year in pizzerias.”

He adds, “This is significant enough of a threat to be of real concern to the environment negating the positive effect on the environment that compulsory green biofuel policy has on vehicles.” That policy means that Sao Paulo’s drivers fill their gas tanks with a biofuel made up of soy-based diesel, sugarcane ethanol and gasohol (a mix of 75 percent gasoline and 25 percent ethanol).

However, some scientists counter that biofuels actually have no “positive effect.” According to a recent study conducted at the University of Michigan Energy Institute, biofuels are actually worse than gasoline in terms of climate impact. The researchers found that running an American-made car or truck with corn-based ethanol would have produced more CO2 emissions than a vehicle using gasoline during the eight-year period that was assessed.

While vehicle pollution remains a top concern for Sao Paolo and the rest of the world’s urban centers (data collected by the United Nations suggest that cities produce around 70 percent of global greenhouse-gas emissions), the contribution of burning wood in these cities has not been considered, though it has a measurable negative impact.

"Once in the air, the emitted pollutants can undergo complex physical and chemical processes to form harmful secondary pollutants such as ozone and secondary aerosol,” said study co-author Yang Zhang from the North Carolina State University.

"It became evident from our work that despite there not being the same high level of pollutants from vehicles in the city as other megacities, there had not been much consideration of some of the unaccounted sources of emissions,” said Dr. Kumar. “These include wood burning in thousands of pizza shops or domestic waste burning."

Of course, driving your car and eating a wood-fired pizza aren’t nearly on the same level when it comes to your carbon footprint. In the U.S., cars and trucks are responsible for almost 20 percent of the nation’s total emissions, with each gallon of gas pumping some 24 pounds of carbon dioxide and other greenhouse gases into the atmosphere. But if current gastronomic and population trends continue, nations may have to start tracking all the wood that’s being burned by restaurants.

"Although the huge number of passenger vehicles and diesel trucks are the dominant contributor to particle emissions, at least we understand the impact that this is having on the environment and can factor in solutions,” said Kumar’s colleague and study co-author, Maria de Fatima from the University of Sao Paulo. “The important contributions to particle emissions gained from burning of wood and the seasonal burning of sugarcane plantations need to be accounted in future studies as they are also significant contributors as a pollutant."

Some big cities are aggressively tackling this problem. In New York, Mayor Bill de Blasio has backed a new piece of legislation that would require pizzerias to install air filters on both wood- and coal-fired ovens to reduce their greenhouse gas emissions and particulate matter that increases air pollution. If passed, the city's pizza shops will have to comply by 2020.

So until your city adopts similar legislation, if you simply must have wood-fired pizza, consider leaving the car at home. That way, you can help offset your culinary emissions—and walk off the calories, too.

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