Michigan tightens manure-spreading rules for large animal farms

Michigan’s environmental regulator has introduced new restrictions on how the state’s largest livestock operations manage millions of tons of manure, prompting a sharp divide between environmental groups and agricultural producers.

The Michigan Department of Environment, Great Lakes and Energy (EGLE) has issued updated conditions for Concentrated Animal Feeding Operations, or CAFOs, which collectively house most of the state’s dairy cows, hogs, poultry and turkeys. These facilities generate an estimated 40 million to 60 million tons of solid waste and about 4 billion gallons of liquid waste annually, far exceeding the volume produced by the state’s human population.

Winter spreading ban

A key provision in Director Philip Roos’s recent opinion prohibits CAFOs from spreading manure or liquid waste on fields from Jan. 1 through March 19. Sales of manure to third parties during the same period are also banned. Regulators argue that winter applications on frozen or snow-covered ground lead to runoff, contributing to elevated levels of E. coli and phosphorus in rivers and lakes, including waterways that feed western Lake Erie.

The directive follows years of litigation over tightened CAFO permit conditions first introduced in 2020. Farmer groups challenged the rules both administratively and in court, but the Michigan Supreme Court upheld EGLE’s authority to impose permit requirements aimed at preventing water pollution.

In January, an administrative law judge found that CAFOs contribute to nutrient and bacterial contamination, supporting revisions to the state’s 2015 permit. Roos said the judge’s removal of certain March restrictions was based on “convenience to farmers,” not scientific evidence, and reinstated tighter limits.

Environmental and industry response

Environmental advocates welcomed the decision. Katie Garvey, senior attorney with the Environmental Law and Policy Center, said winter spreading offers “no agronomic purpose” and results in waste remaining on frozen ground until thaw conditions cause runoff.

Agricultural groups criticized the ruling as excessive. Andy Kok, general counsel for the Michigan Farm Bureau, said producers already operate under a “zero impact” standard and argued that additional reporting and operational limits will not improve water quality but will increase regulatory burdens.

Calls for targeted enforcement

The Citizens Research Council of Michigan questioned whether broad restrictions are the most effective way to address pollution. The group’s October report suggested that expanded monitoring would help regulators distinguish between typical operators and those contributing disproportionately to water-quality violations.

Michigan has been operating under a statewide Total Maximum Daily Load plan for E. coli since 2019. Environmental groups say the strengthened permitting framework should be used to address CAFO contributions more directly. “The sooner these protections get put in place, the sooner we can start to see improvements,” Garvey said.