Carbon Offsets: The U.S. Voluntary Market Is Growing, but Quality Assurance Poses Challenges for Market Participants

Carbon offsets--reductions of greenhouse gas emissions from an activity in one place to compensate for emissions elsewhere--are a way to address climate change by paying someone else to reduce emissions. To be credible, an offset must be additional--it must reduce emissions below the quantity emitted in a business-as-usual scenario--among other criteria. Assessing credibility is inherently challenging because it is difficult to make business-as-usual projections. Outside the U.S., offsets may be purchased on compliance markets to meet requirements to reduce emissions. In the U.S., there are no federal requirements and offsets may be purchased in the voluntary market. GAO was asked to examine (1) the scope of the U.S. voluntary carbon offset market, including the role of the federal government; (2) the extent to which mechanisms for ensuring the credibility of offsets are available and used and what, if any, related information is shared with consumers; and (3) trade-offs associated with increased oversight of the U.S. market and including offsets in climate change mitigation policies. This report is based on analysis of literature and data, interviews with stakeholders, and GAO's purchase of offsets.