Most developed nations are now promising to go carbon neutral by 2050. Implementing those pledges will require daunting sacrifices and staggering costs. President Biden has promised to spend $500 billion annually on climate mitigation, the equivalent of $1,500 per American per year. Most U.S. voters are not willing to pay that personally. A survey by The Washington Post showed that more than half the population was unwilling to pay even $24 for climate mitigation.

Setting aside the political obstacles, there are significant technical challenges to reaching zero carbon. For starters, absent a change in our support for nuclear power and emissions of carbon capture, we don’t have enough land for the new alternative energy sources required to achieve carbon neutrality.

The U.S. uses 81 million acres to power its economy today, and unfortunately, renewables require a lot more space than carbon fuels. Our current energy land use footprint is the size of Iowa and Missouri combined. Two-thirds of that is devoted to transportation fuels, primarily corn ethanol. About a third of America’s corn and soy crops go to biofuels, which use more land than all other power sources combined but provide just 5% of the nation’s energy. Those 81 million acres include: farming for biofuels (52 million), hydropower (9 million), solar and wind farms (7 million), oil and gas pipelines (5 million), power lines (5 million), oil and gas drilling (3 million), coal mining and storage (0.6 million), nuclear plants (0.2 million), and fossil fuel plants (0.15 million).

A December 2020 study by Princeton University’s Net-Zero America Project mapped several pathways to reaching carbon neutrality by 2050. Each path has unique land-use challenges, from sitting hundreds of new nuclear reactors to finding homes for a million wind turbines.

The most land-intensive case in the study eliminates fossil and nuclear plants by 2050. Wind and solar provide 98% of electric power and at least 50% of all new cars are EV’s. In this model wind and solar need to provide 4X the electric power of the current U.S. grid. To achieve that, energy land use would quadruple to accommodate 250 million acres of added wind and 17 million acres of solar. Wind farms would occupy an area equivalent to Arkansas, Iowa, Kansas, Missouri, Nebraska and Oklahoma. Notably, the non-battery alternatives for the grid storage this high-renewable model needs are still experimental.

Is there enough land available for 250 million acres of new wind farms? The answer is a qualified maybe, according to estimates from the Department of Agriculture. The contiguous U.S. includes 654 million acres of pasture and 391 million acres of farmland. In many instances wind turbines can be incorporated into those areas if the landowners agree to sign up for royalty deals. The challenge is many locations are not windy enough to be economic. Princeton’s study assumes 11% of 2050 power could come from offshore wind farms, with modest land use. Up to 3% could also come from rooftop solar with no new land requirement. In sunnier places rooftop solar could generate 74% of electricity, according to the U.S. National Renewable Energy Laboratory (located in Colorado).

Another scenario relies less on wind and solar, but instead requires building hundreds of nuclear plants and natural gas plants outfitted with systems to capture carbon emissions. Wind and solar development need only continue at the current pace, while carbon-capture and nuclear infrastructure expand rapidly. Nuclear supplies 50% of our carbon free energy today.

In this model wind and solar generate 44% of electricity by 2050, while 50% would come from nuclear and natural gas plants with carbon-capture. We would either need to build 250 big nuclear plants, or thousands of smaller reactors like the designs being tested by Terrapower and NuScale Power. Natural gas and nuclear plants are compact, but permitting new plants still presents serious challenges. While no one wants a power plant in their backyard, some people don’t want nuclear power on the planet.

Capping emissions at natural gas plants also creates land use challenges. It requires a network of pipelines and storage facilities that would occupy an estimated 500,000 acres, and the technology is also nascent. Princeton’s study estimates it will take $100 billion in private and public investment in CO2 capture demonstration projects to enable commercialization at industrial scale.

New electric transmission lines represent a land-use constraint in every carbon neutrality scenario. Under the Net Zero America Project’s high-renewable scenario transmission capacity would need to more than triple or else wind and solar projects would be stranded. The politics surrounding new transmission lines are not encouraging. In 2011, President Obama created new policy incentives to speed the permitting of five Western transmission projects. Only one is under construction today. Three still face permitting delays. The fifth was canceled.

Hyperbole is the native tongue of politics. Leaders employ soaring rhetoric to cajole, inspire and create the illusion of momentum. Zero Carbon 2050 pledges fit snugly into this pattern of over-promising and under-delivering. Inspiring as these pledges may be, the probability of success seems more remote than putting a man on the moon was in 1962 when JFK inaugurated the space race.