Gas wins | Runner up: Nuclear
Waste and pollution risks are different. Waste is a byproduct for which there is no use. Pollution, by contrast, is something created during a process that poses a risk either to people or to the environment. All energy sources create waste, but not all energy sources create equal amounts or types of waste. The Better Energy Strategy helps us choose energy sources that minimize waste and enable us to recycle waste whenever possible.
Natural gas produces the least amount of nonrecyclable waste, and solar panels and wind turbines produce the most.
The process of extracting and processing natural gas produces wastewater containing some chemicals and pollutants. That wastewater is usually reused onsite, but some is disposed of through a practice known as underground injection which places the polluted water where it can no longer be accessed or used.
Wind turbine blades can't be recycled, so they end up in landfills. Each turbine blade is over 165 feet (50m) long and is made from toxic materials. In the US alone, about 32,000 blades will be thrown away from 2020 through 2024. If investment in wind power continues to grow, tens of thousands of blades will eventually enter the waste stream.
Solar power poses the biggest pollution risk from waste disposal. Solar panels last only about 25 years, and recycling them is expensive. As a result only about 10% of solar panels get recycled, and the rest end up in landfills. The number of US solar panels due to retire by 2030 would cover about 3,000 American football fields, and solar panel waste is estimated to reach 78 million tons by 2050—the equivalent of throwing away 60 million Honda Civics. Governments fear groundwater contamination from discarded solar panels because each one is composed of toxic materials like gallium arsenide, tellurium, silver, crystalline silicon, lead, cadmium and other heavy metals.
Nuclear plants produce 300 times less waste than solar plants. That waste takes the form of spent nuclear fuel. Contrary to what you may have seen on The Simpsons, spent nuclear fuel is solid (not glowing green liquid). It consists of metal tubes containing small pellets of uranium.
Uranium pellets are an extremely dense energy source. Ten of them store enough energy to power an average US household for a year. The pellets are placed in steel tubes which are gathered into bundles and loaded into the reactor. After the fuel has been in use for a few years, it’s removed from the reactor and placed into water to cool for another five years. After that it’s placed inside concrete and steel containers, which are stored in rows next to the reactor.
Spent nuclear fuel requires care and attention to ensure it’s safely contained, but among the kinds of waste I’ve discussed, it poses the least risk of pollution for two reasons. First, nuclear plants generate a small amount of waste compared to other energy sources. Second, it’s the only energy source that prevents waste from going into the environment. All the nuclear fuel ever generated in the U.S. after 60 years is safely contained and can fit on a single football field stacked less than 10 yards high.
Radioactivity is the main concern associated with spent nuclear fuel. Yet there's never been a single recorded case of a human dying or being harmed from exposure to civilian nuclear waste. In addition, radioactivity diminishes with time. About 40 years after a fuel bundle is decommissioned, the heat and radioactivity of the fuel bundle will have fallen by over 99%.
In addition, nuclear waste can be recycled. Spent nuclear fuel coming out of large nuclear plants retains more than 90% of its potential energy. That spent fuel can be used by some small nuclear plants. These small plants can recycle both the fuel from large nuclear plants and their own fuel multiple times. There’s enough energy in spent nuclear fuel to power the US for 150 years. Fuel recycling reduces the volume of waste that requires long-term storage and hence reduces the cost of long-term storage.