Electricity generation from biomass waste is more polluting and worse for the climate than coal, according to a new study by an environmental advocacy firm.

The report, put together by the Partnership for Policy Integrity (PFPI) and delivered to the U.S. Environmental Protection Agency (EPA), concludes that biomass power plants emit more pollution than comparable coal plants or commercial waste incinerators, according to a news release from the group.

The group characterizes biomass energy as primarily generating from the burning of wood. The study, “Trees, Trash, and Toxics: How Biomass Energy Has Become the New Coal,” analyzes 88 pollution permits for biomass power plants in 25 states. The report adds that biomass power plants are subsidized by state and federal renewable energy dollars.

“The biomass power industry portrays their facilities as ‘clean,’ “ said Mary Booth, director of PFPI and author of the report. “But we found that even the newest biomass plants are allowed to pollute more than modern coal- and gas-fired plants, and that pollution from bioenergy is increasingly unregulated.”