For two centuries, the world has relied on fossil fuels to power our homes, travel, and industry. But with the greenhouse gases emitted by these fuels causing potentially catastrophic global heating and contributing to pollution that’s detrimental to our health and ecosystems, the world is transitioning to cleaner sources of energy. So, what is the cleanest sources of energy?
Renewables like wind and solar power harness natural forces to produce electricity and don’t generate any direct greenhouse gas emissions as they do so. Does that make them 0% clean?
Unfortunately, no. You also must consider the total carbon footprint across the technology’s full lifecycle. For example, the carbon footprint of solar power must account for the emissions associated with the material that makes up the photovoltaic (PV) panels, its transportation and assembly, and the construction and maintenance of solar farms.
Our World in Data has compared the lifetime carbon emissions of eight major energy sources, drawing on data from the IPCC and the scientific journal Nature. The footprints are measured as emissions of CO2-equivalents per gigawatt-hour of electricity over the lifecycle of the power plant. A gigawatt-hour is equal to the annual electricity consumption of 160 people living in the EU:
As you can see, no energy source is entirely free of carbon impact. But even including their raw materials and construction, renewables produce just a fraction of the greenhouse gases that coal, oil, and natural gas do. Even nuclear power plants, which require vast construction projects, yield very little carbon for the amount of energy they produce.
In addition to global heating, you should also consider the other environmental impacts of an energy source, including air and water pollution; damage to public health, wildlife, and ecosystems; and the creation of potentially toxic waste.
You should also consider the likelihood, or risk, of these various impacts. For example, while the radiation from a nuclear power station can have catastrophic impacts on the surrounding land and water, the likelihood of its release is incredibly low given all the safety precautions taken at plants.
In 2017, a group of scientists published a paper weighing up the impact of electricity generation by renewables, nuclear, and fossil fuels on human health and ecosystems. They considered the environmental effects associated with the production, operation and dismantling of these facilities and the production, transport and combustion of their fuels.
While no energy system was found to be without adverse environmental side effects, “the magnitude of difference in pollution between fossil and some renewable energy options is stunning,” the researchers wrote. For instance, the entire process of manufacturing, installing, and operating solar PV panels produces less pollution than just mining and delivering coal to a coal fired-power station – before the coal is even ignited.
Wind and solar farms do have impacts on their local environment, but they can be minimised by careful site selection and planning. Additionally, technological advances have already dramatically reduced the energy and materials required to produce solar PV panels and wind turbines.
Not all renewables are created equal, however. The dams of hydroelectric plants can cause serious ecological issues through habitat destruction.
Meanwhile, biomass – typically wood – releases CO2 and other pollutants into the atmosphere when it’s burned to generate power. Biomass advocates argue that trees draw CO2 from the atmosphere as they grow, making biomass technically carbon neutral. However, the need to fuel biomass plants with wood chips has led to the destruction of forests and other habitats and their replacement with monoculture plantations.
Nuclear projects also have good risk profiles and little impact on the wider environment, despite scare stories about radiation, the scientists found.
“The findings of our work should put to rest residual myths about adverse health and ecosystem impacts associated with the high energy use and material requirements of producing and installing solar and wind power plants and put in perspective the health impacts associated with ionizing radiation from nuclear power,” the scientists concluded.
Ultimately, there is no single energy source that will power our planet in the future. Instead, wind, solar, and nuclear will work in tandem to generate much cleaner power.