Maryland lets pollution cutters sell credits to polluters that must comply

Cleaning up the Chesapeake Bay means cutting nitrogen, phosphorus and sediment, but the cost of doing so differs enormously between a wastewater plant and a farm on the same river.

Maryland made the pollutants tradable: only certified credits can be used against a load or wasteland allocation or an NPDES permit, and any trade must occur within the same trading region.

To generate a credit a source must prove a reduction below its baseline, have it certified and logged on the registry, and follow rules on public funding and trade ratios, so the credit a buyer purchases is a verified, quantified reduction rather than a promise.

The result is flexible compliance: a plant faces its real marginal cost and can pay a cheaper source to reduce more, so the same total cut costs less, while local water-quality standards still apply to every buyer.