Wisconsin wastewater utility generates first U.S. carbon credits for watershed-based compliance

Madison Metropolitan Sewerage District has pioneered the generation of verified carbon credits through its Yahara WINS initiative, linking watershed conservation to greenhouse gas emission reductions and water quality compliance.

March 13, 2026

2 min read

still waters of the Yahara River in Stoughton, Wisconsin

Madison Metropolitan Sewerage District has become the first utility in the United States to generate verified carbon credits tied to watershed-based water quality compliance through its Yahara WINS initiative.

The project produced 24,143 verified carbon credits in January for avoided greenhouse gas emissions associated with choosing watershed conservation instead of constructing additional treatment infrastructure at the district’s Nine Springs Wastewater Treatment Plant. Each credit represents one metric ton of carbon dioxide equivalent avoided.

Launched in 2017, the Yahara WINS (Watershed Integration Network System) program allows the utility to meet phosphorus limits under the Clean Water Act through watershed-based conservation practices rather than constructing a new tertiary treatment facility. The 20-year initiative is projected to avoid about 73,463 metric tons of carbon dioxide equivalent emissions between 2017 and 2036.

“WINS proves watershed conservation can be a smarter path to compliance,” said Ecosystem Services Manager at the District Martye Griffin in a press release. “Verified carbon credits in avoided greenhouse gas emissions add another measurable benefit. This is a model that other utilities can replicate to help offset the cost of Clean Water Act obligations and support climate goals.”

The credits were verified by Sustainability Science and issued through Regen Registry. Boulder, Colorado-based Virridy developed the carbon accounting methodology used to quantify emissions reductions and manages credit sales.

“Carbon markets have focused on forestry and renewable energy,” said CEO of Virridy Evan Thomas in a press release. “This shows they can work for water infrastructure decisions, giving utilities a new tool.”

Initial buyers include the Water Environment Federation, which purchased 1,000 credits and named the utility a climate partner of WEFTEC 2026, and Mortenson. The credits are expected to generate roughly $270,000 in revenue for the district through 2036.

Yahara WINS works with municipalities, farmers and conservation groups across the 536-square-mile Yahara River watershed in Wisconsin to reduce phosphorus runoff using practices such as cover crops, stream buffers and streambank stabilization.