In developed nations, energy infrastructure is largely in the background of society, providing reliable energy with little consumer awareness. Thus, it is difficult to appreciate how energy is produced from various technologies or how the climate or environmental are impacted by these technologies. Compiled below is a brief overview of lifecycle environmental impacts of coal, wind, solar, and battery technologies for the production of electricity.
The table below describes major environmental impacts over the life cycle of coal energy. It encompasses impacts from coal mining, combustion, and waste. For coal energy to contribute significantly and sustainably to power society, the greenhouse gas emissions that result from coal combustion must be prevented. There are various technologies that enable fossil fuel combustion with minimal, zero, or net negative emissions. Staged Pressurized Oxy-Combustion is one such technology specially designed for coal combustion that is currently being developed by the CCCU; we will assume SPOC technology in the coal life cycle. A brief description of SPOC technology is provided in the Discussion section.
Acid mine drainage is the pollution of water due to contact with mining activity. It is the formation and movement of acidic water containing dissolved metals. This occurs when surface water and shallow subsurface water reacts with rocks containing sulfur-bearing minerals, resulting in aqueous sulfuric acid. Metals can leach from rocks that come into contact with this acidic water. This acidic, metal-containing solution can then contaminate nearby water resources . Contaminated water resources can reach pH levels of 4, which is likely fatal to plants and animals . The mobilized metals in contaminated water can be toxic to humans and wildlife. The potential impacts on aquatic life include those on growth, behavior, and reproduction .
Mountain Top Removal requires partial or complete removal of mountain top contours to expose coal seams. The overburden (soil/rocks above seams) and interburden (soil/rocks between seams) is disposed of in adjacent valleys. There are various impacts on water resources, ecosystems, and landscapes, such as: loss of streams and water flows, elevated concentrations of ions downstream of mining operations, and degraded water quality that can be lethal to organisms . Mountain top mining can also lead to significant landscape changes, such as loss of forests and other wildlife habitats . Open pit and underground coal mining require the storage of overburden and waste rock that is removed from mining sites. These waste materials prevent other use of the occupied land and can also cause acid drainage if sulfide rocks are exposed . The mining and waste storage can also have adverse effects on surrounding landscape and habitats. In the process of washing coal to remove impurities after mining, wastes similar to those resulting from mining are produced; this waste can be dry or in slurry form, and must be stored in tailings ponds that have the possibility of leaking.
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The table below describes major environmental impacts over the life cycle of wind energy. It encompasses Rare Earth Element extraction and refining, land use, and turbine blade waste impacts. Since wind energy resources are intermittent, battery technology is required for wind energy systems to produce usefully reliable energy if no other dispatchable backup (e.g. fossil fuel, nuclear, etc.) is used to manage intermittency. As a result, the life cycle environmental impacts of wind energy include those of battery technologies.
The need for rare earth elements (REEs) used to create the strong permanent magnets for direct drive wind turbines has a significant mining environmental impact. The two main REEs required for these strong permanent magnets are Neodymium and Dysprosium . Direct drive generators allow for decreased maintenance requirements and less frictional losses (less gears/moving parts) compared to traditional gearbox drive trains paired with induction generators . Although REEs are plentiful in the Earth’s crust, they are dispersed and mixed with other elements, making extraction expensive, difficult, and environmentally damaging . Scarring of mountaintops, water/soil contamination from mining chemicals (possible downstream contamination to highly populated regions), leftover leaching ponds, and wastewater pools in Chinese chemical (topsoil and in-situ) leaching mining sites are detailed by Yale Environmental  and Earth.org . REE hard rock ores often contain radioactive material (usually in the form of uranium and thorium oxides), and the tailings (waste rock and processing chemicals) from hard rock mining are highly toxic and contain that same radioactive material. China produced ~85% of rare earth oxides and ~90% of rare earth metals, alloys, and permanent magnets in 2019 . The Bayan Obo Mine and the industrial city of Baotou, Inner Mongolia are a large source of ores and production site of REEs ; they exemplify some of the environmental risks associated with the mining and processing of REE ores with improper disposal of waste materials. Bayan Obo ore has 0.04wt% Th, and tailings have 5wt% Th , and are stored in a tailings pond near the Baotou production site  . REE extraction from ore requires many processing/smelting/refining steps and acids/alkaline/organic solvents, thus the tailings disposal pond also includes processing chemicals (e.g. total dissolved solids, ions (e.g. chloride, sulfate, fluoride, ammonium), B, Mn, Fe), and evaporation concentrates these materials . These mining impacts may be reduced if tighter environmental regulations are put in place (e.g. designated mining areas, tighter wastewater treatment, etc.) , but these changes will likely increase the cost of REEs, and these changes will take significant time to implement . China is also cracking down on illegal mining, has REE export quotas in place to limit mining demand, and has made significant progress in remediating previous REE mining damages  .
-Giurco, Damien, et al. “Requirements for Minerals and Metals for 100% Renewable Scenarios.” SpringerLink, Springer, 2 Feb. 2019, https://link.springer.com/chapter/10.1007/978-3-030-05843-2_11.
-“Advanced Wind Turbine Drivetrain Trends and Opportunities.” Energy.gov, U.S. Department of Energy, 3 July 2019, https://www.energy.gov/eere/articles/advanced-wind-turbine-drivetrain-trends-and-opportunities.
-“How Rare-Earth Mining Has Devastated China's Environment.” Earth.Org - Past | Present | Future, Earth.Org, 14 July 2020, https://earth.org/rare-earth-mining-has-devastated-chinas-environment/.
-Standaert, Michael. “China Wrestles with the Toxic Aftermath of Rare Earth Mining.” Yale E360, Yale Univeristy, 2 July 2019, https://e360.yale.edu/features/china-wrestles-with-the-toxic-aftermath-of-rare-earth-mining.
-“Does China Pose a Threat to Global Rare Earth Supply Chains?” ChinaPower Project, Center for Strategic and International Studies, 12 May 2021, https://chinapower.csis.org/china-rare-earths/.
-Maughan, Tim. “The Dystopian Lake Filled by the World's Tech Lust.” BBC Future, BBC, 2 Apr. 2015, https://www.bbc.com/future/article/20150402-the-worst-place-on-earth.
-Huang, Xiang, et al. “Protecting the Environment and Public Health from Rare Earth Mining.” AGU Publications, Wiley, 1 Nov. 2016, https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016EF000424.
-“China to Step up Crackdown on Rare Earth Sector: Ministry.” Reuters, Reuters, 4 Jan. 2019, https://www.reuters.com/article/us-china-rareearths/china-to-step-up-crackdown-on-rare-earth-sector-ministry-idUSKCN1OY0R3.
The table below describes major environmental impacts over the life cycle of solar energy. It encompasses impacts from material extraction for thin-film technologies, manufacturing hazards for silicon-based panels, and waste disposal. Like wind energy, solar resources are intermittent, and battery technology is required for solar energy systems to produce usefully reliable energy if no other dispatchable backup (e.g. fossil fuel, nuclear, etc.) is used to manage intermittency. As a result, the life cycle environmental impacts of solar energy include those of battery technologies.
Material Extraction for Thin-Film PV: Thin-film PV technologies require small amounts of copper, indium, gallium, and selenium (for CIGS cells), and cadmium and tellurium (for CdTe cells) in semiconductor materials . Gallium arsenide (GaAs) cells require gallium and arsenic. These materials are mostly produced commercially as byproducts of copper, zinc, or lead mining and processing .
Manufacturing Hazards for Silicon-Based Panels: The manufacturing of traditional silicon-semiconductor photovoltaic (c-Si PV) requires the use of several hazardous chemicals, similar to those used in the general semi-conductor industry. These include hydrochloric acid, sulfuric acid, nitric acid, hydrogen fluoride, 1,1,1-trichloroethane, and acetone . Silicon dust is also commonly in the manufacturing process for c-Si PV, and are a health hazard to workers without proper protection .
-Giurco, Damien, et al. “Requirements for Minerals and Metals for 100% Renewable Scenarios.” SpringerLink, Springer, 2 Feb. 2019, https://link.springer.com/chapter/10.1007/978-3-030-05843-2_11.
-“Periodic Table.” Periodic Table – Royal Society of Chemistry, Royal Society of Chemistry, 2022, https://www.rsc.org/periodic-table.
-“Environmental Impacts of Solar Power.” Union of Concerned Scientists, Union of Concerned Scientists, 5 Mar. 2013, https://www.ucsusa.org/resources/environmental-impacts-solar-power.
The table below describes major environmental impacts across the life cycle of Lithium-Ion Batteries (LIBs). It encompasses issues with lithium and other metal extraction, and issues of waste disposal and recycling. The purpose of battery technology is to manage the intermittency of renewable energy sources (e.g. wind, solar) to enable renewables to produce energy of similar reliability to fossil fuel energy.
Lithium ion batteries (LiBs) are an integral part of ensuring reliability in an electricity grid with high renewable penetration. The majority of lithium today is extracted from hard rock ores (e.g. spodumene) or salt brines . The general process of extracting lithium from hard rock ore is detailed by . Pollutants such as overburden/waste rock, ore tailings, and other process chemicals (e.g. sulfuric acid for leaching) are produced and must be disposed of. Hazardous wastes (e.g. tailings and chemicals) are typically disposed of in tailings ponds. In most industrialized countries, these ponds are required to be lined to prevent leaching . Brine extraction is performed by pumping brine into ponds, concentrating the salts (which contain Mn, K, borax, and Li) through evaporation, and then chemically extracting lithium . This is a very water intensive process, requiring approximately 500,000 gallons of water per tonne of lithium. South America’s “Lithium Triangle” (Chile, Bolivia, and Argentina) contains approximately 52% of global lithium reserves and approximately 56% of global resources . It is also an extremely arid region; in the Salar de Atacama of Chile, ~65% of water in the region is used for lithium mining activities . There is potential for chemicals (e.g. HCl used in processing) to leak from evaporation pools and contaminate water and soil . For more information on lithium extraction processes, see . There are a variety of LiB chemistries, but common components include Co, Ni, Mn, Al, and graphite . Virgin sourcing of these materials requires hard rock mining that can lead to soil/water contamination from waste rock, tailings, and acid mine drainage (more mining impact details in , , ). Extracting and refining these virgin materials will also result in waste material and chemicals.
-Bolton, Robin. “Lithium Mining Is Booming - Here's How to Manage Its Impact.” Greenbiz, Greenbiz, 11 Aug. 2021, https://www.greenbiz.com/article/lithium-mining-booming-heres-how-manage-its-impact.
-Burba, John L. “Assessing the Environmental Impact of Spodumene Mining and Processing.” Innovation News Network, Innovation News Network, 18 Aug. 2021,
-Katwala, Amit. “The Spiralling Environmental Cost of Our Lithium Battery Addiction.” WIRED UK, Wired, 5 Aug. 2018, https://www.wired.co.uk/article/lithium-batteries-environment-impact.
-“Mineral Commodity Summaries 2022.” USGS Publications Warehouse, USGS, 31 Jan. 2022, https://pubs.usgs.gov/periodicals/mcs2022/mcs2022.pdf.
-Bell, Terence. “What Are the Basics of Commercial Lithium Production?” ThoughtCo, ThoughtCo, 21 Aug. 2020, https://www.thoughtco.com/lithium-production-2340123.
-Pagliaro, Mario, and Francesco Meneguzzo. “Lithium Battery Reusing and Recycling: A Circular Economy Insight.” Heliyon, Elsevier, 15 June 2019,
-“How Can Metal Mining Impact the Environment?” American Geosciences Institute, American Geosciences Institute, 2022,
-“Mining 101.” Earthworks, Earthworks, 2019, https://earthworks.org/issues/mining/.
-“Environmental Risks of Mining.” Environmental Risks of Mining, Massachusetts Institute of Technology, https://web.mit.edu/12.000/www/m2016/finalwebsite/problems/mining.html.
The magnitude of required land use are significantly greater for renewable technologies (wind, solar) than that of conventional and fuel-based technologies (coal, gas, nuclear). The differences in magnitude of land use can be shown by comparing the amount of land the U.S. devotes to each of its major energy technologies per unit of primary energy supplied by that technology. Based on an analysis of U.S. energy land allocations by Bloomberg and a U.S. primary energy supply breakdown by the U.S. Energy Information Administration (Bloomberg analysis released in 2021, EIA data for year 2019), the land required per unit energy (in million acres per quadrillion BTU) was calculated for fossil fuels, nuclear, wind, and solar:
Based on the analysis above, wind and solar technologies respectively require about 48x and 9x the land area required by coal to produce the same amount of primary energy. Natural gas and nuclear require 2.46x and 0.52x the amount of land that coal requires per unit of energy output. Note that this analysis only addresses the magnitude of land use and not how each technology impacts the environment; for details on how land is impacted by each technology, refer to the Life Cycle Analysis tables. For breakdowns of current U.S. energy land allocations, see . It is important to note that the Bloomberg analysis  includes supply of all energy, including heating, transportation, and manufacturing. For breakdowns of U.S. primary energy supply by source, see . The land intensity calculations assume that the Bloomberg land use data and the EIA energy supply data are representative of the U.S. energy system at the same point in time; since the reports both involve data that is around the 2019-2021 time range, we will neglect any changes in U.S. energy infrastructure within that time period.
-Merrill, Dave. “The U.S. Will Need a Lot of Land for a Zero-Carbon Economy.” Bloomberg.com, Bloomberg, 29 Apr. 2021, https://www.bloomberg.com/graphics/2021-energy-land-use-economy/.
-“U.S. Energy Information Administration - EIA - Independent Statistics and Analysis.” U.S. Energy Information Administration (EIA) - Data, https://www.eia.gov/totalenergy/data/browser/index.php?tbl=T01.02#/?f=A.
SPOC is a combustion technology with inherent carbon capture capabilities currently being developed by the CCCU. It is designed to avoid many of the issues present in traditional, post-combustion carbon capture operations, which are often a retrofitted “patch” on existing fossil fuel plants. Some of the issues SPOC avoids include: significantly less than 100% capture rates, high capture costs and energy penalties that make CCS economically uncompetitive, and the use of toxic scrubber chemicals for capture.
Instead of removing relatively dilute CO2 from flue gas using hazardous scrubbing chemicals, SPOC technology creates a flue gas stream with a majority composition of CO2 and removes pollutants and impurities from the CO2 stream. The key features of SPOC that enable this operation are oxy-combustion and elevated operation pressure.
Oxy-combustion is the burning of fuel in high purity oxygen and recycled flue gas instead of air, resulting in flue gas composed primarily of CO2 and with reduced NOx levels (due to lack of N2). Elevated operation pressure reduces the O2 requirement for complete burnout of coal, reduces the volume of gases in the system (and thus the size and cost of system components), enables harnessing and usage of latent heat (phase change heat) of water in the flue gas, and enables easier removal of NOx and SOx from the flue gas. The high operating pressure results in an increased dew point temperature of water, enabling the moisture in the high temperature flue gas to transition from the gas to the liquid phase. The heat energy released from this phase transition can then be harnessed and used to pre-heat the water used in the steam cycle, thereby increasing the efficiency of the plant. The high pressure also enables significant percentages of the NOx and SOx in the flue gas to be absorbed by water; the Direct Contact Cooler (DCC) both cools and removes NOx and SOx the flue gas by washing it with cooling water, eliminating the need for other NOx and SOx emissions control techniques. The flue gas leaving the DCC is high purity CO2, which is then sent to the compression and purification unit (CPU) for purification to utilization (e.g. enhanced oil recovery) or sequestration grade. The integrated CO2 capture strategy of SPOC enables higher capture rates (without toxic scrubber chemicals) while incurring a much smaller energy penalty on the plant than traditional, post-combustion capture, which relies on repeated heating and cooling of a CO2 absorbent to pull relatively dilute CO2 from the flue gas, on top of the requirement for NOx, SOx, and other pollutant removal. SPOC is also capable of efficiently cofiring biomass, which enables net carbon negative operation.
SPOC’s staged combustors (multiple compact combustors connected in series-parallel) enhance efficiency by decreasing the amount of flue gas recycle required to maintain optimal heat flux from the combustors to the turbine steam. The modular design also enhances flexibility without compromising efficiency, as individual combustors can be shut down in times of low demand to allow the others to maintain full (optimal) capacity and efficiency. Flexibility is particularly important for reliably supplying variable demand without large reductions in efficiency (a.k.a increase in cost). Liquid Oxygen Storage (LOS) further enhances flexibility; the air separation unit (ASU) can increase output in times of low electricity demand and decrease output in times of high electricity demand to enable the combustors to continue operating at optimal capacity. The SPOC system is designed to efficiently handle variable demand, enabling the production of cheap, reliable energy; it also can help to mitigate supply intermittency in electricity grids with high variable renewable energy (VRE) penetration.
For more details, see: Axelbaum, Richard L. Washington University in St. Louis, St. Louis, MO, 2019, Modular Pressurized Coal Combustion for Flexible Generation, https://netl.doe.gov/sites/default/files/2020-02/Modular-Staged-Pressurized-Oxy-combustion-Power-Plant-System-Washington-University-in-St.-Louis.pdf. Accessed 9 Mar. 2022.