Last week, freshman Democratic Rep. Alexandria Ocasio-Cortez released the text of her long awaited Green New Deal, a proposal that would radically reshape the American economy, by mandating widespread adoption of net zero greenhouse gas emissions by 2030. To some, this is already a nearly impossible goal. For many leading environmentalist groups, however, the net zero emissions language doesn’t go far enough.

The difference between net zero and renewable might seem subtle, but for environmentalist groups, it could end up being a major breaking point between the green dream and achievable policy.

Net zero emissions, on the other hand, implies generation methods like biomass power, which creates carbon emissions through combustion that are then mitigated by the growth of the plant-based fuel. Carbon capture is one of the key technologies that could be used in net zero generation, because successful emissions capture could allow for the continued use of conventional fuels such as natural gas and coal. Renewable generation, on the other hand, is energy produced by sources that are naturally replenished, such as wind and solar.

Although carbon capture is seen as one of the most market-friendly ways to mitigate the effects of fossil fuel consumption, green groups are banding together to resist subsidizing it.

“In addition to excluding fossil fuels, any definition of renewable energy must also exclude all combustion-based power generation, nuclear, biomass energy, large scale hydro and waste-to-energy technologies,” reads an open letter sent to Congress from 626 green groups in January. The letter laid out their vision of what a Green New Deal should look like.

The signatories, including Greenpeace, the League of Women Voters of the United States, and dozens of local and regional environmental groups, want to stop all fossil fuel leasing and extraction, while expanding public transportation in order to fully phase out private vehicles.

The trouble is, the text of the Green New Deal released by Ocasio-Cortez falls short of this proposal. Two states (California and Hawaii) as well as the District of Columbia, have already established renewable energy standards that would require a full transition to renewable energy.

As currently drafted, Ocasio-Cortez’s plan would allow for similar technologies. This is simply an acknowledgement of reality, say those working in energy policy.

“There is simply no way to realistically to ramp-up all that electricity unless nuclear power (which currently produces 20% of electricity), is built out as well,” William Murray, manager of the energy policy team at R Street Institute, tells InsideSources. “Nor is battery storage technology mature enough yet to work in tandem with wind and natural gas to balance the grid. In 10 years it will be, but not now.”

Murray sees carbon capture as “a good idea whose time has come.” Carbon capture technology would allow the U.S. to continue to use conventional generation sources while also decreasing overall emissions. Supporters of carbon capture see it as a bridge technology, helping to keep the lights on while less expensive renewable generation methods are developed.

Carbon capture includes technologies that capture carbon emissions and pump them underground or using these captured emissions to manufacture other products. Either approach means that greenhouse gases are being taken out of the air. What makes environmentalists concerned is that these gases were released into the atmosphere to be begin with.

Environmentalist groups are wary of embracing carbon capture out of fears that it would both retard the transition away from fossil fuels and also fail to protect those communities most vulnerable to the effects of climate change.

“Net Zero emissions, which equate carbon emission offsets and technology investments with real emissions reductions at source, would only exacerbate existing pollution burdens on frontline communities,” Angela Adrar, executive director of the national Climate Justice Alliance wrote to Grist, saying that these communities were being used as “sacrifice zones.”

Major environmentalist groups including Greenpeace,, and the League of Conservation Voters welcomed the Green New Deal when it was announced, but see it as a starting point. Their true goal is a zero carbon economy, which goes further than what Ocasio-Cortez’s bill proposes.

“The fossil fuel industry will not transition willingly and on its own to life-sustaining, renewable practices, because it is determined to trash our planet for its profit no matter the cost,” said Greenpeace USA Climate Director Janet Redman. “We must make every effort to phase out fossil fuels at the same time as we promote renewable energy if we’re going to make it.”

The trouble is that it is difficult to reach 100 percent renewable energy while maintaining reliability. Countries like Iceland, Costa Rica, and Norway, who have made significant strides toward 100 percent renewable power, did so by relying on natural resources like geothermal and hydro power. But not all U.S. cities are conveniently located atop an active volcano complex like Iceland.

Follow Erin on Twitter.