Carbon Offsets vs RECs: What's the Difference?

Did you know that Williams College is involved in two types of carbon markets? 

First, our investments in carbon offset arrangements allow us to compensate for the college’s carbon emissions by financially supporting projects that reduce or remove greenhouse gas emissions elsewhere. The Campus Environmental Advisory Committee (CEAC) developed a set of carbon offset recommendations during the academic years 2017/18 and 2018/19 which facilitated the college’s first offset purchases in 2020 from projects including clean cookstoves in Honduras (Proyecto Mirador), biogas digesters and clean cookstoves in China, rooftop solar panels providing DC electricity to households in India, and turning pig waste into compost in Brazil. With the help of the offset purchases, we were able to ‘neutralize’ our emissions, while continuing to pursue actions on multiple fronts to reduce and eliminate sources of carbon emissions in our operations or to replace them with renewables. 

Second, Williams is also purchasing renewable energy certificates (RECs), which represent the environmental attributes of renewable electricity generation per megawatt-hour delivered to the power grid or offtaker from a particular source. The environmental attributes include information about the type of renewable energy source, where it is located and when it was generated as well as an emissions profile of the electricity generating source and a unique identification number. This information allows RECs to be sold with and without the associated electricity, thereby creating a market that can promote the addition of new renewable energy generating capacity and that allows the buyer to make certain claims about their use of green electricity, even if the ‘green electrons’ did not directly power their activities. The Farmington Solar Project is a great example of how the college purchases both electricity and RECs (aka bundled RECs) and thereby reduces its own carbon emissions while stimulating development of new renewables and supporting New England farmers.

Both carbon offsets and RECs serve as part of the college’s commitment to achieving carbon neutrality.