Yale Scientists Explore Yard Waste's Environmental Impact

Yale Scientists Explore Yard Waste’s Environmental Impact

According to a new study from Yale University, one of the sneakiest carbon culprits could be waiting for you at the curb. The study, directed by Yuan Yao, an assistant professor of industrial ecology and sustainable systems at the School of Environment, analyzed the ecological impact of urban tree debris and the outcomes of various disposal strategies. According to the research, avoiding the landfill entirely for tree trimmings can greatly cut down on greenhouse gas production.

Rather than sending them to landfills or having them burned, Yao argued in an article for the News that “there is a great need to divert urban tree wastes to valuable utilization.” Utilizing a methodology known as Life Cycle Assessment, the study’s authors determined how much of an impact reusing, repurposing, and recycling organic materials actually have on the environment. From “poor usage” means like landfills to “optimal utilization” methods like biochar production, they explored a variety of routes to discover that even “fair utilization” methods like incineration may reduce carbon emissions by about 115 megatons.

Wood chips and mulch are good ways to deal with downed trees, but Yao argued that turning them into long-lasting wood products would be even more effective in minimizing their impact on the environment. Postdoctoral researcher and study co-author Kai Lan remarked, “Our study indicates the potential benefits of applying circular economy principles to biomass waste in the urban context to potentially deal with climate change.”

Even though it has by about a third since 1990, the United States still sends around 10.5 million tonnes of yard debris to landfills annually. Even though cities aren’t frequently blamed for a lot of tree trash, they nonetheless leave a substantial imprint. Twenty-five million oven dry metric tonnes of leaves and twenty million metric tonnes of trees are discarded each year from the United States urban forest. That’s about 20 megatons of carbon mass and minerals that, if allowed in landfills, might eventually make their way into the air or water supply.

New York, Atlanta, Boston, Chicago, and Philadelphia would benefit the most from reducing their global warming potential by diverting urban tree trash. Based on their research, the team estimates that between 127.4 and 251.8 megatons of annual carbon dioxide emissions might be prevented if all tree waste were “fully used” by being turned into timber, woodchips, or compost. Furthermore, it would yearly remove between 93.9 and 192.7 kilotons of nitrogen from water sources.

However, the best waste treatment practices may differ from one state to the next. Due to geographical differences, certain areas would do better with strategies designed specifically for the indigenous flora. Using dead leaves as compost or mulch is the most effective way to reduce carbon emissions in the Northeast, which is home to many dense deciduous forests. Conversely, places like California would benefit the most from reducing their global warming potential by reusing lumber.

However, many municipalities anticipate that implementing these conclusions will be a time-consuming endeavor. The study acknowledges the obstacles to fully realizing the potential of urban yard trash, including illicit dumping and a lack of municipal services and infrastructure.


Joint efforts from people, governments, and communities are required to effectively recycle tree debris. As Colleen Murphy-Dunning, head of the Urban Resources Initiative and lecturer in urban and community forestry at the School of the Environment stated, there are many more trees on private property than there are on public land. To implement the principles of the circular economy in urban forests, it will be necessary to educate not only the public works department but also private landowners on proper tree debris disposal practices.

The furniture sector is beginning to adapt to the shift. Room & Board and Brick + Board are just two of the newer businesses that have sprung up over the past decade that turn recycled wood from downed trees into stylish furniture.

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Meanwhile, companies like CityBench have been collecting trees from all across New Haven to turn them into new furniture and home decor items. CityBench was founded by Zeb Esselstyn, who was motivated to do so after hearing that “35-40% of hardwood lumber that is used each year could be replaced if you just tapped into the urban forest.” Together with his sibling, he has crafted thousands of pieces of furniture from reclaimed urban oak since 2009.

About 29,000 trees line the streets of New Haven.

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