SENATORS PATTED themselves on the back last week after passing a wide-ranging energy bill, a feat that seems amazing given the partisanship on Capitol Hill and the deep divisions between the parties on fossil fuels in particular. But the hype was too good to be true: The bill has at least one glaring flaw that must be changed before President Obama considers signing it.

There is a lot to like in the bill and the process that led to its passage. Lawmakers put aside major points of contention and moved forward with items they could agree on — or at least live with. The bill authorizes hefty increases in the energy research budget. It includes programs to make buildings more energy-efficient. It would harden the electrical system against cyberattacks and make the grid more capable of taking on new sources of renewable power. The bill would also speed approvals of natural gas export facilities, which will not please some environmentalists but is nevertheless a net positive step. In return, the bill gives environmentalists a permanent reauthorization of the Land and Water Conservation Fund, which directs federal oil and gas royalties toward preserving natural landscapes.

But the bill also would command the Environmental Protection Agency to “recognize biomass” — that is, plant matter such as wood harvested from forests — “as a renewable energy source” because of its “carbon-neutrality.” This is a rank example of Congress legislating science rather than allowing agency experts to make determinations based on facts, and the results could be very bad for the environment.

Burning wood produces carbon dioxide emissions; the case for treating biomass energy as carbon-neutral is that, as plants grow back, they recapture carbon dioxide from the air. Yet burning biomass releases a lot of CO2 into the atmosphere all at once, and plant regrowth takes time. Meanwhile, scientists warn that the planet could reach climate tipping points soon. This alone is reason not to treat biomass and, say, wind energy as equivalent.

Moreover, trees will continue growing, sequestering carbon dioxide all along, if they are not harvested for energy, which calls into question the net carbon benefits of chopping them down and growing new ones. Using wood for electricity also means that other industries, such as paper, might have to get their raw materials from other places, which could end up increasing deforestation. The country cannot get much electricity out of biomass, anyway. Tim Searchinger, a Princeton University researcher, calculates that obtaining 4 percent of the country’s electricity from biomass would require 74 percent of its timber harvest.

Biomass advocates respond that the product is better than fossil fuels. That might be so, but it is not an excuse to treat biomass like any other renewable.

Sixty-five experts, including Mr. Searchinger, warned senators in February against including the biomass language in the bill, predicting that it would “promote deforestation in the U.S. and elsewhere and make climate change much worse.” Lawmakers should have listened to these experts and left the science to the EPA. They have one more chance when they merge the Senate and House versions of the bill.