ABOARD THE DREDGE BUTCHER, OFF THE LOUISIANA COAST — All day and all night, this ship off a knob of Louisiana at Alligator Bend sucks up silt from the floor of Lake Borgne and pumps it through a half-mile of fat steel pipe. At the other end, a slurry gushes noisily out into what was until recently a stretch of open water. New land is rising here, forming mud flats that will soon be covered with waving spartina grass.

This is the unglamorous, mucky — and, to be honest, smelly — work that goes into restoring the fragile marshlands that help protect southern Louisiana from hurricanes and that provide a haven for wildlife.

What is most interesting about this project, however, is who is paying the bills. While the state government has developed a detailed master plan for wetlands restoration in the region, and money has been promised from the federal government and the BP settlement of the 2010 oil spill, this project is getting its funding from a private equity firm. The company, Ecosystem Investment Partners, intends to profit from its good works by selling environmental restoration credits to private developers and government agencies like the Army Corps of Engineers, which need them to offset environmental damage done by their projects.