Virginia Peng, Staff Illustrator

With its eyes set on a 2035 net-zero emissions target, Yale University has turned toward carbon offsets for answers.

As carbon offsets grow in popularity, the University has also made an entrance into the market over recent years. Starting in 2020, the University retired 47,604 metric tons of carbon dioxide equivalent to reach its emissions target that was set for the University to meet in 2005. Yale has continued acquiring credits — tradable carbon-eliminating permits — for every year it fails to meet that standard. Last year, it retired 47,282 metric tons of CO2 equivalent. While its 2025 Sustainability Plan acknowledges that such offsets are stopgap measures, it anticipates that these measures will continue helping the University reach its emissions goals.

According to Amber Garrard, director of the Office of Sustainability, the University started exploring the use of offsets after setting its emissions reduction goals in 2005. Under the plan, the University aimed for a 43 percent reduction in 2005 emissions levels by 2020.

“Each year, if our annual reductions are not below our 2020 target, we retire additional offsets from our existing portfolio to maintain that commitment,” Garrard wrote in an email to the News.

Carbon offsets are purchasable certificates that allow industries to compensate for their emissions by investing in removal efforts elsewhere. Once registered and verified by third-party programs, they can be purchased as credits that are withdrawn from the market — or “retired” — following acquisition.

Kenneth Gillingham, a professor of environmental and energy economics at the School of the Environment, explained that carbon credits promise to “[reduce] emissions at a lower cost” compared to pursuing more expensive reductions initiatives. By purchasing carbon credits, industries temporarily reduce emissions as they transition toward longer-term capital investments.

Critics of carbon offsets have objected to what they say are misleading accounting practices in certain unregulated markets where carbon credits are claimed to be generated even in the absence of any real change. A study published in March by researchers from Yale and the University of California, Berkeley, found that 11 percent of all carbon offsets ever issued had overstated their climate-saving benefits.

The University’s current carbon offset portfolio has focused on projects that capture or reduce methane emissions.

As the second-most abundant greenhouse gas, methane is over 28 times more potent than CO2, though it also degrades significantly faster. Agriculture, fossil fuels and landfill waste are the largest contributors to human-caused methane emissions.

One of Yale’s six methane projects is the Laurelbrook Farm in East Canaan, which composts its manure by adding wood chips and frequently aerating it. Doing so reduces the methane emissions that would have been otherwise produced by regular anaerobic breakdown.

The University’s five other carbon offset sites are landfills.

At both the Greater Lebanon Refuse Authority Landfill and Greenville County Landfill — another two of the University’s project sites — methane reduction has involved setting the gas on fire. Per James Zendek, Lebanon Landfill’s senior staff engineer, the largest source of landfill methane comes from leachate — the wet liquid, or runoff, that flows through solid waste.

By collecting that methane, the landfill can convert the greenhouse gas into a potential energy source. Steve Pineiro, Greenville County Landfill regional operations supervisor, explained that pipes drilled throughout the landfill pile help funnel the gas to an engine for burning.

Pineiro added that the quantity of collected methane gas diminishes as the landfill ages. At its peak, methane from the Greenville County Landfill had produced enough electricity to power 2,500 homes. The site has collected 2,000 to 3,000 tons of methane annually since 2013.

According to Zendek, methane conversion to electricity produces significantly less CO2 but is not entirely emissions-free.

“[The gas] still has emissions, but they’re much, much cleaner than if you just let the gas go to the environment without running it through that layer first,” Zendek told the News.

Garrard wrote that current offset projects underwent a research and vetting process that involved faculty, staff, students and administrators across the University. The University’s five-person Carbon Offsets Program Oversight Committee worked alongside an eleven-member Carbon Offsets Working Group to evaluate project proposals, visit sites and make recommendations. Per Garrard, the process accounted for factors such as costs, permanence, campus proximity and environmental justice.

As outlined in the University’s Climate Action Strategy, carbon offsets are intended to “supplement, not replace” on-campus emissions reductions.

Gillingham said that one “downside” of offsets is “additionality” or the idea that purchasing carbon credits is not enough to prove that emissions reductions “would not have happened otherwise.” Even if investment in reforestation does lead to reduced emissions, he explained, it is impossible to ensure that the offsets were solely responsible for them.

However, Gillingham added that the offsets market is expected to continue growing. Though global demand for carbon offsets dipped in 2022, supply will likely increase through 2050. The offsets market is poised to grow from $2 billion to roughly $250 billion over the coming decades as industries seek to decarbonize.

Under the University’s current target for net-zero emissions by 2035, it will likely have to increase its reliance on offsets. Turning the campus completely carbon-free is expected to cost $1.5 billion across the next three decades.

“Based on current projections, we will need to retire significantly more offsets at that point in time to reach that target,” Garrard wrote. “As part of our larger decarbonization strategy, we will be working to reassess our approach to offsets.”

The first attempt at carbon offsetting started in 1997 after the release of the United Nations’ Kyoto Protocol.