Bernie Sanders just dropped his version of what a Green New Deal would look like if he becomes president — and it looks incredibly ambitious. The proposed set of federal policies aims to simultaneously avert a climate crisis while building up a green economy that protects workers and vulnerable communities.

At $16.3 trillion spent over 15 years, Sanders’ climate deal is by far the priciest of all the Democratic candidates left in the primary race. It’s also arguably the most progressive — pushing for the US to have a carbon-free economy by 2050. The senator from Vermont also set a 2030 benchmark goal of reaching 100 percent renewable energy in the country’s two most carbon-intensive industries, transportation and the power sector, by investing in solar, wind, and geothermal power. Sanders’ plan would also declare climate change a national emergency, bring the US back on board with the Paris climate agreement, and commit $200 billion in funding to help developing nations cut their emissions and adapt to the effects of climate change.

Sanders’ climate deal is by far the priciest of all the Democratic candidates

According to the United Nations’ international panel of scientists, in order to prevent the worst effects of climate change, the world needs to become carbon neutral by midcentury. That goal allows countries to continue emitting planet-warming gases, as long as they’re removing the same amount from the atmosphere. It’s considered a more realistic approach to keeping the planet from warming beyond the crucial tipping point identified by United Nations scientists, especially since we’re not on track to meet goals set in the Paris climate agreement as it is. Sanders’ aims are more ambitious, because unlike the United Nations and other presidential hopefuls, he’s looking to fully stop burning fossil fuels, and isn’t relying on commonly discussed alternatives to reach his objective.

“To get to our goal of 100 percent sustainable energy, we will not rely on any false solutions like nuclear, geoengineering, carbon capture and sequestration, or trash incinerators,” Sanders writes in the almost 14,000-word manifesto.

“we will not rely on any false solutions like nuclear, geoengineering, carbon capture and sequestration”

Sanders is the first candidate to explicitly lay out those measures in his plan for a Green New Deal. When Representative Alexandria Ocasio-Cortez (D-NY) and Senator Ed Markey (D-MA) introduced a resolution for a Green New Deal in February this year, both lawmakers skirted the issue — leaving nuclear energy and carbon capture on the table.

Nuclear energy, geoengineering, and carbon capture are all controversial. Nuclear energy opponents worry about its safety and what to do about nuclear waste. Geoengineering, or using technology to manipulate the climate, is still unproven. Carbon capture technologies, which take carbon dioxide out of the atmosphere, are really expensive and nascent, too. And critics say that reliance on these measures doesn’t address the concerns of communities living near power plants, pipelines, fossil fuel deposits, uranium mines, and toxic dumps.

The question that remains is whether Sanders could actually achieve his lofty aims. First, it comes with a mammoth $16.3 trillion price tag. Rival Joe Biden’s climate proposal is just $1.7 trillion. And even though Sanders has put his foot down on nuclear energy, carbon capture, and geoengineering, not even all environmentalists are on board.

“We need to have every option on the table”

“We need to have every option on the table,” Joshua Freed, vice president for clean energy at the Democratic think tank Third Way, told The New York Times. “The Sanders plan appears to be big, but it’s not serious.”

Freed’s concerns allude to larger tensions between progressives and moderates within the Democratic party, as others hope that Sanders’ moonshot will push policy toward bolder climate measures. Adrien Salazar, climate campaign strategist at progressive think tank Demos, tells The Verge. “A move to get the US fully decarbonized by 2050 shifts the narrative, that’s a new standard for what is actually bold and ambitious.”