There is an overwhelming consensus that fossil fuels need to be replaced as the primary source of energy. Along with contributing to global warming, the air pollution from fossil fuels has led to increased risk of stroke, heart disease, lung cancer, and respiratory diseases (WHO, 2016). The increase of atmospheric carbon dioxide has also caused more to be dissolved in the ocean, which reacts with water molecules to form carbonic acid, gradually causing the ocean to become more acidic. Even slight changes in pH concentration can have grave impacts on the health of wildlife. However, to replace one damaging energy source with another equally damaging energy source is ill advised. As a result, it is important to consider the environmental impacts of the other options, namely the various renewable energy sources, in order to better understand how to integrate these energies.
- Production of solar releases carbon emissions
- Requires rare materials, some of which are extremely toxic and are released to the environment as they degrade (such as indium, gallium, tellurium, and cadmium, of which cadmium and tellurium are considered toxic elements)
- High land use- about 70 acres per MW produced, compared to less than 1 acre per MW for nuclear.
- Impacts wildlife, habitat fragmentation, increased erosion and water pollution, potential farmland
- High concrete and steel utilization
- Susceptible to the elements- rain, snow, clouds
The primary form of solar energy to be considered is photovoltaic cells in the form of a utility scale solar farm. Photovoltaic cells (PV cells) are generally considered to be among the more promising renewable energies as the sun produces an enormous 340 W/m2 of potentially usable power (Hanania et al., 2015) and the environmental impacts are typically understood to be insignificant. However, PV cells influence the environment in two primary ways: production and land use.
Production of PV cells is an energy intensive process which also produces greenhouse emissions. For instance, “in the case of poly- and mono-crystalline modules, the estimated emissions are 2.757–3.845 kg CO2/kWp, 5.049–5.524 kg SO2/kWp and 4.507–5.273 NOx/kWp,” (Tsoutsos et al., 2005), demonstrating that a significant amount of greenhouse gas is still produced, despite the energy being “carbon free”. Furthermore, the production of PV cells relies on certain scarce materials such as indium, gallium, tellurium, and cadmium, of which cadmium and tellurium are considered toxic elements. As the cells degrade, these will be released into the environment resulting in ecological consequences, the extent of which is unknown as few case studies have been conducted on the topic. On average, PV cells will degrade at a rate of about 0.2% to 1% per year of their initial expected output, depending on the conditions the cells is subject to (Lombardo, 2014). This means that every 25 years the cell will need to be replaced. Therefore, PV cells will need to be continuously produced to replace the degraded ones, causing a constant production of the corresponding greenhouse emissions and requiring additional scarce materials. Certainly research into safer alternative materials is advisable before PV cells are utilized on a large scale as well as increased life spans to truly reduce greenhouse emissions.
In addition, several environmental consequences result from the land use of the PV utility farms. A comparison of nuclear energy, wind energy, and PV solar energy conducted by Entergy Arkansas found that approximately 7.4 acres of PV cells are needed to produce 1 megawatt of power (Entergy). This number is assuming the PV solar panels are operating 90% efficiency for 22 hours a day, as nuclear power plants do. However, PV cells can actually operate at about 25% efficiency for roughly 8 hours a day, depending on the region, which would mean that significantly more land is required to produce this power, and even as much as 70 acres per megawatt of power produced. For reference, a megawatt of power is enough to power approximately 400 to 900 homes for a year (Bellemare, 2012). The ratio of land to power produced is a significant drawback of PV cells. The land in use could be used for farming or other more practical uses.
PV cells influence the land that they are placed on as well. For instance, the disturbance from installation and the constant shade on the ground will reduce vegetation in the area. This can lead to increased erosion, potential invasive species, and an increase in water pollution (UCS, 2013). The space required for a utility scale solar farm takes over habitat space of species and presents a barrier to gene flow via habitat fragmentation as well. One possible solution to the issue of land space is utilizing roof space of cities as well as utilizing regions that will see little environmental impact of PV cells, such as desert regions. Solar in cities would be convenient as the power produced would also be near its source load. However, the disadvantage of relying on the sun’s direct exposure limits solar’s use in cities that receive little sun.
- High land use- 60 acres per MW
- Planning ahead allows for land between turbines to be utilized for other purposes. The space between turbines also reduces some of the impacts seen in solar such as increased erosion and water pollution
- Construction, installation, and maintenance releases carbon emissions
- Land pollution, significantly taller and more conspicuous than others
- Impacts wildlife, particularly migratory birds, by affecting their flight patterns
- Spread out nature presents an advantage over solar as land animals can still move between the turbines
- Offshore wind farms present a unique approach as many of the consequences of land farms are minimized
- May impact marine life in the area, although after initial installation, could actually benefit marine animals by providing a sort of artificial reef
Wind energy is typically regarded as the other main renewable energy (besides solar) to be economically and environmentally viable as a replacement option to fossil fuels. Major utilities, such as Xcel have been investing in wind energy extensively in recent years. (Xcel Energy Inc., 2018) Similar to solar energy, the primary environmental consequences of wind energy result from production of turbines and land use. Contrary to solar energy, however, wind energy construction requires less scarce and specific materials, suggesting that wind power may be more sustainable in the long term. However, the construction process is not carbon free. The production, transportation, installation, and maintenance of wind turbines releases approximately 0.6 to 2 lb carbon dioxide per kWh, whereas coal generated electricity produce between 1.4 and 3.6 lb CO2 per kWh (UCS, 2013). Evidently, a significant amount of carbon emissions is still produced despite wind being generally regarded as a clean energy.
Utilizing wind energy requires much greater land use than solar energy, on account of the massive size of the wind turbines. On average, approximately 60 acres of land are utilized to produce 1 megawatt of power, significantly more land than solar energy (Entergy). However, this is due to the spread of the turbines to ensure rotors do not collide; typically the turbines are spaced 5 to 10 rotor lengths apart. Considering strictly the land occupied by the turbines, the actual work per land use rate is about 1 megawatt per acre of land.(UCS, 2013) Furthermore, the spread out nature of the wind turbines allows for the remaining land to be used for other purposes, such as livestock grazing, farming, etc., a benefit that solar energy does not provide as the PV cells occupy most of the land area in use. In contrast to solar cells, wind turbines are significantly taller and louder. The noise pollution can significantly impact the behavior of nearby animals, and the height of the turbines has been shown to interfere with birds and bats, resulting in deaths and altered flight patterns. (UCS, 2013) Research is currently being conducted as to how to avoid this impact on flight animals. However, the visual disturbances caused by the turbines can decrease public favorability of wind energy in areas near populated regions. Further research is being conducted on offshore wind farms, which provide several benefits, such as reduced impact of noise pollution, less land use, and less interference with birds and other flying wildlife. However, these types of wind farms will likely impact marine life, although not necessarily negatively. Some research has indicated that the base of the turbines may serve as artificial reefs and benefit the nearby aquatic ecosystem.(UCS, 2013) Several offshore wind farms are being planned in the United States. (Drouin, 2018)
- Land use- damming river leads to flooding of surrounding area to create reservoir
- Impacts nutrient content and quality of the water, both in reservoir and downstream from the dam
- Colder water, less oxygenated, increased pollutants
- Impacts wildlife, primarily fish in the water
- Threat of downstream life dying if water isn’t released appropriately, either by drying up or drowning through too little or too much water release
- High concrete and steel use
Hydroelectric energy involves damming a river to create a reservoir, and using the water’s kinetic energy to turn turbines and generate electricity. However, it is important to note that not all of the consequences of building dams can be attributed directly to hydroelectric power, as there are many other reasons for building dams besides electricity generation. The most obvious consequence is the impact of the turbines on the aquatic life, such as fish getting caught in turbines, fish being unable to travel downstream, etc. However, several systems have been designed to reduce these complications, such as fish ladders and intake screens (UCS, 2013). Dams generally restrict water flow, which can have profound impacts on the water itself. For instance, areas downstream can dry up if the water isn’t released appropriately, which will kill the aquatic life in the area, and may negatively impact vegetation relying on the river as a water source as well. In addition, the water from the reservoir tends to be colder, lower in oxygen than normal river water, and has altered silt loads, which can harm aquatic life downstream that rely on specific river water characteristics.(EiA, 2017). Aerating turbines are one way of ensuring the water is properly oxygenated as well as circulating the water to ensure colder and warmer sections mix, but further increase energy usage and operating costs of the dam.
In addition to the wildlife impacts, hydroelectric energy also produces carbon dioxide emissions. While the amount produced does vary depending on the size of the reservoir and the climate the river is in, the emissions are not insignificant. It is estimated that for construction and normal operations of a hydroelectric plant, approximately 0.5 lb CO2/kWh are produced, as compared to the 1.4 to 3.6 lb CO2/kWh produced by from coal-generated electricity.
- High and low level radioactive waste
- Can be extremely toxic and fatal to plants and animals, with a large decay time period
- Remains in environment for very long periods of time and can contaminate food and water sources
- Thermal pollution from water cooled reactors
- Synergistic effect on water pollutants
- Impacts wildlife living in the water that require specific temperature ranges
- High steel and concrete use
- Water cooled reactors require access to water as well as land, though significantly less land than renewable energy sources
Nuclear energy, while not technically classified as a renewable energy, does present another option with which fossil fuels can be replaced. The primary impact of nuclear energy is radioactive waste. Current nuclear fission designs rely on isotopes of elements such as uranium and plutonium. The waste from the nuclear reactors can be radioactive, and therefore potentially harmful to human health, as well as the health of other living animals. Contrary to popular belief, not all nuclear waste is extremely harmful and toxic. As noted earlier, waste can be classified as low-level or high-level, indicating its radioactivity and the time required to reach safe levels (EIA, 2017). In addition, most of the waste produced (by volume) is low-level waste. Highly radioactive waste will generally remain unsafe and toxic for thousands of years, and as a result presents a unique complication, that is, what should be done with the waste, a topic already explored in this paper. With that being said, nuclear waste is among the most strictly monitored and enforced wastes of any of the various energy sources. Nuclear meltdowns and spills can have severe consequences for the surrounding environment. Radiation can lead to cancer by causing free radicals in the body and destroying the bonds in molecules, thereby destroying cells and tissues within the body. In addition, this radiation can take decades to decrease to safe levels, rendering the region uninhabitable. Food and water contaminated also will not be safe to consume. While these consequences are of great concern, such disasters are rare, as a result of the many different safety measures and security protocols put in place to reduce the likelihood of meltdowns. Furthermore, as demonstrated in a comparison of the Chernobyl disaster to the Fukushima disaster, government policies and food safety campaigns can have a significant impact on the impact of a disaster (Steinhauser et al., 2014).
In addition to the radioactive products of nuclear energy, another product is heat, an environmental consequence shared by certain fossil fuel plants. Most nuclear reactors in use presently rely on water for cooling. This water is then pumped into nearby rivers and bodies of water, thereby leading to thermal pollution (Jaffer, 2011). Increased water temperature has a synergistic effect on toxins and water contaminants, causing the toxicity of the water to increase with increasing temperature (Langford, 1990). Increased temperature can also influence the wild life living in the water. Many organisms have narrow temperature ranges in which they can thrive or even survive. Altering the temperatures of the rivers, lakes, etc. can greatly impact the composition of living organisms within the body of water. This could influence the ecological balance of the ecosystem. Modern nuclear reactor designs have attempted to reduce such impacts by considering alternative cooling methods to water as well as alternate fuel sources that can produce less radioactive waste.
While nuclear energy does not technically produce greenhouse emissions in its production of energy, the building of reactors does indeed release carbon dioxide from use of concrete and steel. For instance, an EPR nuclear reactor producing 1600 MW of power, requires 40,000 tons of steel and 200,000 tons of concrete. Factoring in the lifetime of the reactor, about 60 years, with an 80% efficiency rate for 7000 hours a year, approximately 1 TWh of energy is produced for every 300 tons of concrete used.(Comby, 2007) In comparison, wind energy produces 1 TWh for every 18,900 tons of concrete used, roughly 60 times the amount of concrete and 50 times the amount of steel.(Comby, 2007) Current worldwide production of PV cells requires 1.2 million metric tons of concrete and steel each year, which amounts to approximately 423 tons of concrete and steel per TWh over the lifespan of current worldwide PV cells in place (assuming 17% efficiency, 6 hours a day, for 25 years).(NREL, 2004) Concrete is actually a major contributor of carbon emissions, annually accounting for between 2 and 5% of total annual emissions for a total of about 38.2 gigatonnes of CO2 over the last 80 years (Leung, 2009). However, it also worth noting that concrete will actually reabsorb much of the CO2 it releases as it begins to cure over time (Leung, 2009). On average a ton of concrete and cement produces about 0.88 tons of CO2 emissions, which amounts to 264 tons of CO2 per TWh of power released for the construction of a nuclear and 16,632 tons of CO2 per TWh from wind turbines, and 372 tons of CO2 from concrete in use of PV cell construction. (Leung, 2009)(Vaughan, 2017) PV cells require significantly less steel and concrete than wind, but both renewables require more than nuclear energy, and have shorter lifespans overall. Certainly the excess use of materials raises an environmental concern, as the manufacturing of steel and concrete produce carbon emissions as well. Furthermore, the mining of such materials increases the environmental impact of each of these energies. Utilization of more steel and concrete is significant environmentally but also raises an economic concern as well. In comparison to solar and wind energy, nuclear energy requires far less land. Arkansas Nuclear One nuclear plant produces approximately 1.63 MW of power per acre of land used, a significantly more efficient and energy dense system than any of the renewable energies considered.
Each of the various renewable replacements (solar PV, wind, hydro) for fossil fuel energy possess potential. With that being said, it is inadvisable to switch from one energy source, due to environmental concerns, to another energy source, which also produces significant environmental issues. Instead, nuclear seems to be a proficient energy source for meeting current energy demands while fossil fuels are phased out, until the various environmental consequences of the renewable energies have been further explored and efforts have been made to correct such consequences.
Each of the various potential renewable replacements for fossil fuel energy possess potential. With that being said, it is inadvisable to switch from one energy source, due to environmental concerns, to another energy source, which also produces significant environmental issues. Instead, nuclear seems to be a proficient energy source for meeting current energy demands while fossil fuels are phased out, until the various environmental consequences of the renewable energies have been further explored and efforts have been made to correct such consequences.
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