All energy sources affect health, environment, climate, and economy to different extents. These are important factors that must be considered when assessing the energy mix of the future. Renewables have clear challenges that are best solved in combination with other energy sources such as nuclear power and gas power with carbon storage.
These are the numbers we have used to calculate the footprint of the energy sources. In some cases, the sources provide ranges. We have then used median- or average values provided by the sources.
UPDATE 10.1.21: Costs for renewables have been updated with 2020 figures from the IEA (for renewables, IEA uses numbers collected by IRENA, but may differ due to different calculations). Note that these figures assume a carbon tax of 30 USD / tonne CO2. Instead of using "Low stability", we have decided to use the term "Not operating" to better reflect that the percentage time that the power plants are not operating due to aspects such as absence of wind or sun, as well as other reasons.
This is simply 100% minus the capacity factor.
The capacity factor has been updated with actual 2019 numbers from Statista, with the exception of fossil fuels and biomass where we have used the IEA's 2020 assumptions of 85% capacity factor.
IEA has chosen to do so because the fuel is always available, allowing the power plants to theoretically operate as needed. Costs for solar and wind power do not reflect system-lcoe (need for backup), which will lead to significantly increased costs with a high share (> 10-20%) in the energy mix. Long-term operation of nuclear power (LTO) has not been taken into account, which will significantly reduce costs. With a 20-year extension of existing nuclear power plants, this type of energy will be the cheapest according to the IEA.
|Emissions tonn CO2eq/TWh||97000||4000||6000||98000||4000||820000||715000||490000|
|Land use in m2/kW||7142,9||543,5||150,8||12500,0||4,2||7,4||5,1||2,1|
|Materials use i tonnes/TWh||14068||10260||16457||235410||930||124019||87168||77877|
|Critical metals in kilos/TWh||6,40||529,88||81,82||8,92||19,89||8,92||8,92||8,92|
|Costs in $/MWh||47||56||85||62||77,5||58,6||58,6||46,3|
|Not operating (100% - capacity factor)||57,2 %||62,6 %||73,9 %||50,7 %||7,4 %||46,0 %||41.4 %||42,4 %|
|Solid waste in tonnes/TWh excl. CO2eq||14068||10260||16457||21080||932,5||81725||1184||581|
|Share of total energy consumption in %||2,7 %||0,8 %||0,4 %||7,1 %||1,7 %||27,9 %||34,5 %||24,5 %|
A real green shift is about more than climate
A real green shift is about sustainable change in a more climate and environmentally friendly direction, and means that growth and development are happening within nature's tolerability limits. A discussion of the energy mix of the future therefore requires a total understanding of the impact each energy source has on health, environment, climate and economy. A focus on greenhouse gas emissions is of course very important, but the UN is also clear on that loss of nature is as great a threat to humanity as climate change. At the same time, the UN Sustainability Goal No. 7 states that everyone shall have access to reliable, sustainable and modern energy at an affordable price. For political decisions, other factors than climate must be included in the overall picture so that the health, environmental and economic consequences are minimized. It is possible to achieve the goal with a balanced energy mix, but not with renewables alone.
In three articles I have presented and discussed eight different parameters that together provide a total picture of the footprint for different energy sources. The results will surprise many, and certainly create debate. That is needed.
Greenhouse gas emissions: Greenhouse gas emissions are to many the most important parameter, where fossil fuels account for 95%, and where coal power is the worst. Hydropower and biomass have challenges, with higher emissions than, for example, gas power with carbon storage. For hydropower, the emissions are due to a combination of need for concrete and formation of methane gas from the decay of organic matter in man-made reservoirs. Although biomass is currently considered climate neutral, it takes time from combustion to new uptake of CO2, for forests up to 120 years. Nuclear, solar and wind power have the lowest emissions.
Mortality: Nuclear power has a bad reputation but is as safe as solar and wind power. Hydropower and biomass cause a great deal more deaths per energy unit, but this pales in comparison to fossil fuels which causes by far most deaths, mainly due to premature death caused by air pollution, and where coal causes the most deaths. This is due to the release of hazardous particles, sulphur dioxide and nitrogen oxides in connection with the burning of fossil fuels. Emissions of particles and nitrogen oxides are also a problem for biomass.
Material consumption: Biomass has by far the material consumption, closely followed by fossil energy sources. This is due to the fuel itself, of which large quantities are required. While these are renewable for biomass, this is not the case for fossil fuels. Apart from the fuel, solar, wind and hydropower has by far the highest material throughput. This is due to the low power density of renewables, which means that more or larger power plants are needed to produce the same amount of energy as fossil and nuclear power plants. This is problematic due to increased demand for mining and power-intensive heavy industry. Nuclear power has by far the lowest material use of all energy sources.
Critical metals: The shift to renewables depends on enough materials being available to build the power plants. Modern wind power plants currently have a very high consumption of the rare earth metal neodymium, which are on EU's list of critical raw materials. A strong growth of wind power, especially offshore where this consumption is highest, therefore requires solving this challenge. Solar power plants also have a relatively high consumption of critical metals, in addition to large amounts of silver.
Land use: Biomass has the highest area need for the energy produced. To cover a significant share of energy consumption with biomass, large land area is thus required. But hydro, wind and solar power are also area intensive. Renewable energy sources are simply not very efficient compared to fossil fules, which requires far less acreage. However, only modern gas-fired power plants can match nuclear power plants in terms of efficient land use.
Costs: Hydropower and modern gas-fired power plants currently have the lowest costs distributed over the life of power plants, and are followed by wind power. Although solar panels are becoming increasingly cheaper in price, the energy source is still more expensive than the alternatives. This will gradually change, but if the need for backup is included, eg. battery storage, then solar and wind power will still be more expensive than other energy sources. Nuclear power is struggling with high costs due to lack of standardization and high safety and waste management requirements.
Stability: An indicator of stability is the capacity factor that shows how much power is delivered relative to the maximum installed capacity. It is admittingly not a perfect parameter as delivered power is dependent on marked needs but serves the purpose of a general guidance. Oil power plants are less efficient than alternatives and thus not commonly used today. Electrification of the transport sector and heating will therefore be important contributions to reduced oil consumption. Solar and wind power have very low stability due to seasonal variations and varying access to wind and sun. Demands for higher stability lead to increased costs and increased land use, which is a challenge for large-scale development of solar and wind power plants. By far the most stable energy source is nuclear power plants.
Fixed waste: Disregarding emissions to air (greenhouse gases, SO2,NOx), the largest amount of waste originates from the combustion of coal and biomass, which produces large amounts of ash. Although much is recovered, much is hazardous. Nuclear power produces very small amounts of waste, but it is radioactive and requires extensive safety measures related to removal and storage. Disregarding combustion waste, solar, wind and hydropower generate the most waste. This is related to the removal of materials in connection with the shutdown of power plants at the end of their lifetime. Most of the waste is concrete, steel and glass, but parts are potentially dangerous. Solar power makes use of potentially harmful cadmium and lead that can leak into the underground, while wind turbines contain high amounts of potentially hazardous chromium. In addition, the turbine blades consist of non-degradable composite material, and have shelling of microplastics during operation. Due to the low power density, the amount of hazardous waste from renewables will be far greater than from nuclear power. What in the future will cost most lives is uncertain, and the opinions about hazardous waste are often guided by the individual person's perception of the worst possible outcome. As such, the parameter is often binary by being accepted or not.
Overall, nuclear power is superior to other energy sources
Looking at all the factors and weighting them equally (which is not necessarily correct), nuclear power outperforms alternative energy sources, with cost and hazardous waste as the most negative. Not surprisingly, coal has the highest footprint with the highest mortality rates, most waste, high material consumption and the highest emissions of greenhouse gases. There is simply not much good to say about coal other than that there is a lot of it and electricity prices are decent enough. Gas power comes out better than renewables even with significant greenhouse gas emissions. Gas power with carbon storage will therefore have a lower total footprint than renewables, and lower greenhouse gas emissions than both biomass and hydropower.
Of renewable energy sources, solar power currently has the lowest total footprint but struggles with unstable electricity delivery, high costs and much waste. Biomass has the highest footprint due to large fuel consumption and high area need, in addition to producing a lot of ash waste and harmful emissions to air. Hydropower has significant land need, high material requirements, as well as relatively high greenhouse gas emissions. Wind power has low stability and must solve the challenge of high consumption of critical metals. Achieving this, wind power will have the lowest total footprint of all renewable energy sources.
If emissions are weighted four times higher than the other factors, nuclear power remains the best option, while oil joins coal as the worst options. Gas power still comes out better than biomass, even without carbon storage.
The importance of the individual parameters will in part be subjective. Many believe that greenhouse gas emissions are the most important, while others are most concerned with the natural interventions. Since each individual will have their own opinions on what matters most, a website has been established, https://energy.glex.no/footprint/, where readers can make their own assessments and interactively see the results of their choices. There, interested readers can also find the source material that forms the basis of the analyses and, if desired, more information.
This work has looked at parameters that can be quantified. There are other aspects that may be as important, but that are not easily quantified, and therefore are not included in this study. Fear is such a parameter, eg. the fear of future consequences of improper handling of waste. The same applies to visual pollution, the value of unspoiled nature, as well as the danger of the extinction of animal and plant species. These are qualitative aspects that our politicians must consider, together with fact-based knowledge of our energy sources, when decisions are to be made.
It is not about either or
It is not possible to deliver energy without negative consequences. It is all about finding a balance that is acceptable and providing the lowest possible total footprint. No single energy source can solve the climate challenge alone, and a power mix consisting only of renewables will, in addition to having practical and economic challenges, bring unnecessarily large negative consequences for nature and the environment. A constructive climate debate therefore requires an understanding of each energy source's impact on climate, environment, health and economy. Hopefully, the work I have done, with good help from geophysics student Wouter Bell Gravendeel, and documented in four different articles, can contribute in the right direction.