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Abstract
One emerging problem faced by humanity as a whole is the inevitability of world natural gas and oil levels diminishing. According to BP’s Statistical Report of World Energy, oil supplies will last for only the next 55 years if we continue to use them at the same rate as we are now. This fact is important because modern society, especially in the U.S., relies heavily on oil. Without this particular source of energy, we would not be able to achieve many of the everyday activities we may take for granted. These include actions like supplying energy to power industries, heating homes, and providing fuel for transportation. In addition, The Intergovernmental Panel on Climate Change (IPCC) states carbon dioxide levels in Earth’s atmosphere will only continue to increase, regardless of the fact that carbon dioxide emissions may possibly decrease. Luckily, researchers working for the University of Tennessee and the U.S. Department of Energy found a way of turning this harmful chemical into a usable fuel source for engines and machines that produce carbon dioxide. The technique involves a catalyst of copper, carbon, and nitrogen. After applying voltage, a chemical reaction occurs to essentially reverse the combustion process with about a 63% yield of ethanol. Carbon dioxide will continue to be produced regardless, which has been proven harmful to the environment. However, converting carbon dioxide into ethanol is a two-fold success. The process reduces the global carbon footprint and produces a compound that is both more useful and less harmful. Ethanol can be used as fuel for transportation, a solvent for paints, varnishes, and perfumes, and food preservations. In this paper, we will evaluate the process and the effect of the carbon dioxide to ethanol conversion, the use of a copper-based catalyst to do so, and the practical uses for this process in everyday life.
AIR POLLUTION AND OIL LEVEL DEPLETION
With the birth of the Industrial Revolution, humanity started releasing a once scarce and toxic chemical into the atmosphere in search of electric power. It is estimated that “since the industrial revolution, about 375 billion tons of carbon have been emitted by humans into the atmosphere as carbon dioxide (CO2)” [1].
The National Aeronautics and Space Administration (NASA) claims that the average global temperature has risen by 1 degree Celsius (1.9 degrees Fahrenheit) since the 1880s and two-thirds of the rise in temperature has occurred in the last fifty years [2]. This change in global temperature has the potential to create a devastating effect on the direct balance of Earth’s complex ecosystems. Many climate change advocates and nature conservationists believe that putting this much tonnage of carbon dioxide into the atmosphere could result in a drastic negative effect on the health of the planet. To further collide with this statement, The National Academies of Science Engineering and Medicine states that not only is there strong evidence that carbon dioxide is the primary cause of global warming, but the concentration of carbon dioxide in the atmosphere has risen about 43% since the beginning of the Industrial Revolution [3]. Lastly, emitting carbon dioxide acts as a double-edged sword, while potentially harming the environment, the main source of carbon dioxide emissions is the depletion of valuable and finite resources like coal, oil, and natural gas.
It has already been stated that according to BP, at the current rate of consumption, natural gas and oil levels will only last about another half a century. In addition, coal, while being an abundant fuel source, is viewed by a majority of the population as a dirty fuel source. In response, measures have already been enacted around the world to limit or ban the use of coal as a fuel source [4]. However, it is important to understand why humanity has relied on the uses of fossil fuels and nonrenewable energy sources instead of switching to renewable resources. Thus, giving validity and importance to the reaction of recycling carbon dioxide into ethanol rather than phasing such an innovation out as part of an “old era” of power generation.
With all the staggering and worrisome figures presented above, most would ask why not switch to renewable energy sources, which is a valid question. In short, fossil fuels, while depleting at a rapid pace, are still abundant for countries that still have such resources, like the United States. On top of this, renewable resources only account for 10.7% of the total energy production in the United States. They also lack the infrastructure and raw production value to feasible and financially, in a stable manner, take over as the largest energy producer [5]. While it is certainly in the interest of climate conservation to switch to renewable energy production, doing so suddenly has the potential to cause other problems that could be more devastating and immediate, like economic and social issues. Examples of some possible issues include a large GDP, economic depressions, and the annihilation of hundreds of thousands of jobs [6]. The world’s reliance on fossil fuels such as coal and oil are too great to suddenly be cut out, and cannot change for some time, until renewable energy is considered efficient and a better alternative.
Due to the fact that carbon dioxide levels are rising to a dangerous concentration in the world’s atmosphere and the strong reliance on the world’s power production and nonrenewable energy sources, now the importance of being able to convert carbon dioxide back into a nonrenewable energy source to be used in place of oil can be seen. While it most certainly does not sound like the best-case scenario for helping the environment, this is an important technological and innovative step towards curbing the effects of fossil fuels on the environment and refilling diminishing levels of natural gases and oils until renewable energy can take over.
RECYCLING ENERGY
One of the major problems of nonrenewable resources in energy production, self-evidently, is the fact that they are nonrenewable. All non renewable sources of energy have a finiticity that, due to human consumption, are slowly being depleted. Furthermore, the Environmental Protection Agency (EPA) suggests that up to 20 percent of the potential energy out of fuel sources is wasted in the form of heat energy [7]. Tom Casten, an energy recycling business executive and corporate restructurer who is an avid advocate for a shift to recycling energy and renewable resources “We think we could make about 19 to 20 percent of U.S. electricity with heat that is currently thrown away by industry. This electricity is just as pristine as making it with a windmill or making it with a solar collector — no additional fuel, no additional pollution. Just a little bit of additional brains” [7]. Casten and other energy recyclers believe that doing so would save both companies and governments alike billions of dollars in the generation of electrical energy.
Heat waste is one of the most wasted sources of potential energy, it is estimated that a third of all energy released by resources goes unused by electrical and mechanical generators [7]. To help remedy this, many companies have found ways to turn this waste heat, usually in the form of steam or flared natural gas, to cycle back into the energy making process. This process allows for even more energy to be created. Despite this idea that could save up to 20 percent of the total energy produced, many laws and restrictions prohibit such practices, as they are deemed “too dangerous” to implement into power plants and factories. However, the facts cannot be ignored that by recycling energy created by fossil fuels businesses not only save money but increases plant efficiency as well. This is the direction that most companies that run on fossil fuels should take steps towards. These facts, lowering the overall costs of non renewables and increasing the energy output by recycling energy, are a crucial step in achieving an efficient world, however, the more interesting part is the concept.
If the concept of recycling energy is applied to a reaction that has already been complete and waste heat released, instead of an ongoing reaction, then it would be similar to turning a fossil fuel into a renewable energy resource. This concept in particular seems to be unprecedented. Fortunately, this sort of breakthrough occurred at the University of Tennessee in partnership with the Department of Energy. Researchers at the Oak Ridge National Library found a way to turn carbon dioxide, the toxic chemical now found abundantly in Earth’s atmosphere, back into ethanol, a fossil fuel that when burned, produces carbon dioxide [9]. Currently, the process is in its infancy, just having been recently developed and not efficient by any means. However, this discovery is important because it solves two problems while at the same time solving a third.
The first problem that this discovery solves is that of the diminishing oil and natural gas reserves around the world. If further research were put into developing this technology, it might just stave the possibility of oil reserves running out in the next half- century or until humanity finds a way to rely on renewable energy resources more. Secondly, it addresses the problem of high levels of carbon dioxide in our atmosphere. By using carbon dioxide as a reactant, the reaction between carbon dioxide and a metal catalyst, which will be discussed later in more detail, produces ethanol as a product in a chemical equation [9]. This removes carbon dioxide from the environment and, if again, developed properly and used in a large scale, it may slow down the effects of carbon dioxide emissions until a more concrete and reliable solution can be found.
The last problem this innovation inherently solves, without trying to, is finding a better alternative to conventional fuel sources. While ethanol is a fossil fuel, it is not a naturally occurring fossil fuel like propane or oil [10]. With this given reaction, a combustion fuel source can be made on demand without sapping from the environment while at the same time being a relatively green source of fuel. While the reaction does not have a 100 percent yield, and is largely energy inefficient, this is a crucial step in infant technology that has the potential to revolutionize the future.
THE BREAKTHROUGH CHEMICAL PROCESS
The topics of oil level depletion and carbon dioxide emission have sparked interest and concern among experts and nonprofessionals alike. These issues, as mentioned in the section above, have been affecting the environment in large ways such as global warming and the loss of a main source of energy. Experimenters at the University of Tennessee have discovered a process that could potentially minimize the effects of pressing issues such as depleting oil levels and excess carbon dioxide in the environment. This breakthrough involves a highly effective process for recycling ethanol into carbon dioxide through utilization of an electrochemical process. The scientists at the University of Tennessee developed this process with small spikes of metal-based catalysts in order to produce ethanol from carbon dioxide.
This breakthrough is important because it provides a partial resolution to two separate issues. The first benefit of recycling carbon dioxide into ethanol is that the levels of carbon dioxide in the environment are reduced. As mentioned earlier, excess carbon dioxide in the environment is a pressing issue and is strongly correlated to negative impacts such as significant warming of the atmosphere and a buildup of greenhouse gases. Adam Rondinone, the lead author of the published study from the University of Tennessee, states “We’re taking carbon dioxide, a waste product of combustion, and we are pushing that combustion reaction backward with very high selectivity to a useful fuel” [9]. Along with mentioning the first benefit, Rondinone’s statement touches upon the second benefit of the newly discovered process as well. This second benefit is the fact that the recycling process produces ethanol. As a clean and renewable fuel, the production of ethanol is better for the environment. For example, ethanol produces a smaller amount of emissions when burned than a normal fuel source, such as gasoline.
As defined by AEN (Alternative Energy News), “ethanol is a biofuel that can successfully replace gasoline and diesel in the future to reduce the level of harmful emissions of the vehicles with internal combustion engines” [10]. In fact, flex fuels composed of ethanol are already being implemented in other countries, such as Brazil, China, Canada and the European Union, as an alternative to gasoline [11]. Any fuel that contains ethanol contributes to lower levels of emissions. Furthermore, the more ethanol in the fuel, the more clean and powerful it is. According to Magda Savin from AEN, “today, almost all vehicles can run on fuel that contains up to ten percent ethanol” [10]. In addition, ethanol can be used as a solvent for paints, varnishes, and perfumes. It is also commonly implemented in the process of preserving foods and beverages.This means that advances in technology regarding ethanol production, like the breakthrough discussed, can be directly integrated into daily life to impact society in a positive way.
A surprising aspect of the breakthrough discovered at the University of Tennessee is that the technology was not created intentionally. The team at Oak Ridge National Library (ORNL) was studying catalysts based on nanoscience when they decided to conduct an experiment involving the arrangement of atoms to create a catalyst. The group of scientists however did not expect their experiment to result in the production of ethanol. In fact, the team did not expect the reaction to result in a production of any chemical [12]. Rondinone states in the ORNL report, “We discovered somewhat by accident that this material worked. We were trying to study the first step of a proposed reaction when we realized that the catalyst was doing the entire reaction on its own” [9]. A large surprise for the team was the fact that the catalyst that they developed held the power to essentially utilize a waste product to reverse the combustion process and produce a useable fuel.
The way that the reaction proceeds is based off of steps involving the unique structure based off of nanoscience techniques. This structure allows the reaction to be started from the electric fields produced. The initial reaction that follows converts the carbon dioxide into carbon monoxide. The carbon monoxide then becomes a reactant that can be utilized in the rest of the steps to result in the production of ethanol [12]. This technique may seem rather short for such a complicated reaction. This is due to the fact that upon solidifying the process, the scientists from the University of Tennessee “wanted to minimize diversions down the wrong pathway and keep all the products moving together toward this final outcome, which is the alcohol” [12]. This works in the scientists’ favor because when chemical reaction has multiple steps, every step has the potential to branch off into different directions that may not be beneficial to the outcome. According to the Oak Ridge National Library Reporter, electrochemical reactions like this normally result in a mixture of separate products in small quantities [9]. The scientists were able to produce this result with the help of their unique catalyst.
UTILIZING A METAL-BASED CATALYST
Catalysts, in general, are beneficial to reactions because they allow a reaction to proceed at a quicker and more efficient pace. They do this by lowering the activation energy required to initiate the chemical reaction. Lower activation energy is accomplished by increasing the frequency of collisions between the reactants. However, this process does not affect the physical or chemical properties, nor the thermodynamics of the reaction [13].
Transition metals serve as great catalysts compared to other elements and molecules on the periodic table. The reason for this phenomenon is that transition metals, depending on the nature of the reaction, can lend or withdraw electrons from the reactants [7]. In addition, transition metals can vary their oxidation states and form complexes with the reactants. A few of the most common transition metals used as catalysts include cobalt, tin, silver, gold, iron, and the most popular platinum [7]. The problem with many of these metals, including platinum, is the high price. When considering price, copper is much easier to obtain.
Furthermore, copper in particular is an excellent catalyst for this specific experiment. According to Deyanda Flint from Georgia State University, “transition metals must have d-electrons (electrons in the third subshell of the atom) to spare, and they have variable and interchangeable oxidation states”
[14]. This requirement make copper perfect for the reaction. Copper has multiple oxidation states including Cu²⁺ and Cu³⁺. Furthermore, copper has an incomplete d-orbital which enables it to exchange electrons and form chemical bonds easily [14].
The technology utilized by the team of scientists from the University of Tennessee in the recycling of carbon dioxide into ethanol involves a catalyst made of carbon, nitrogen and copper [12]. By incorporating nano-scientific techniques, “the carbon and nitrogen particles are arranged into tiny, sharp spikes, like little lightning rods, with copper nanoparticles imbedded among them” [12]. These spikes allow the reaction to begin with the energy from the strong electric fields that they generate. When the coating is added to carbon dioxide, water and electricity, the reaction yields ethanol, in fact, on average the reaction produces a 63 percent yield of ethanol. With respect to carbon dioxide, sixteen percent of the molecules are converted to either methane or carbon monoxide [12].
Overall, the catalyst holds a special property from its nanoscale structure. Most importantly, the structure consists of the copper nanoparticles that are embedded within the carbon spikes [9]. This approach of nanotexture has an advantage in comparison to other approaches because the production of the catalyst is not as expensive as others. In most electrochemical conversions of carbon dioxide, metals such as platinum, silver, iron, tin, and gold have been utilized. Instead of using an expensive or uncommon metal, copper is used to avoid unnecessary costs. In addition, copper is capable of converting carbon dioxide into more than thirty different products through electrochemical processes. Some of these products include carbon monoxide, formic acid, methane, ethane, and ethylene [15]. In addition, the technique discovered by the researchers at the University of Tennessee is able to operate at room temperature in water. As reported by the Oak Ridge National Library, “Given the technique’s reliance on low-cost materials and an ability to operate at room temperature in water, the researchers believe the approach could be scaled up for industrially relevant applications. For instance, the process could be used to store excess electricity generated from variable power sources such as wind and solar” [9].
MOVING FORWARD WITH THIS DISCOVERY
This discovery is a promising option for decreasing the concentration of carbon dioxide that is being released into our atmosphere. Considering the low cost and obtainable experimental conditions of the process, the researchers at the Oak Ridge National Laboratory feel that the process can be increased in order to achieve a number of larger scale industrial applications. For example, Rondinone states that this process can be used to “store excess electricity generated from variable power sources such as wind and solar”. In addition, a process like the one described would “allow you to consume extra electricity when it’s available to make and store ethanol” [9]. The original researchers from the University of Tennessee have plans to optimize and refine their work to improve the process’s rate, as well as the properties and behavior while converting the carbon dioxide into ethanol with the help of their catalyst.
However, other researchers are skeptical of the results and of whether the process can be repeated in another laboratory [16]. Admittedly, the chemical reaction in which one goes from carbon dioxide directly to ethanol with just a single catalyst is very difficult, but these researchers at Oak Ridge National Laboratory have found a catalyst that on a nanoscale allows them to get the precise results they want [9]. Not only will this process impact the reduction of fuel emissions positively, it could “be used to store excess energy from wind and solar electricity generation” [16]. The future of this innovation is scaling it to industrial level because the impact can be felt the most if the individuals or corporations contributing to the problem on the largest scale, remove themselves from the issue by improving their footprint. Even achieving a theoretical rate of zero fossil fuel emissions is not going to be enough to sufficiently reverse the damage done to our environment over the past more than 50 years by fossil fuel emissions of greenhouse gases. This chemical discovery is very new and there is quite a bit left unexplored or researched, so a level of skepticism is to be expected.
FURTHER STEPS TOWARD EFFICIENCY
Carbon dioxide is a heat-trapping greenhouse gas that has been tied to climate change and global warming. Though there are other contributing factors like methane, nitrous oxide, and CFCs, carbon dioxide is definitely a factor that humans have a large hand in contributing to. A report by the IPCC stated their findings that concluded that there is about a “95 percent probability that human activities over the past 50 years have warmed our planet” [17]. Climate change has been attributed to the “greenhouse effect,” which can be defined as the warming from the heat that is trapped by the atmosphere. Earth has a natural greenhouse effect but the additional greenhouse gases in our atmosphere have affected the Earth’s climate and water levels. On average, we have seen higher temperatures and, as a result, more evaporation and precipitation in some areas and contrasting increased dryness and risk of droughts in other areas. The global temperature has increased by 1.9 degrees Fahrenheit since 1880 and eighteen of the 19 warmest years have occurred since 2001 [17]. As the problem worsens, we will see the higher temperatures warming the ocean, melting glaciers and icebergs, which will lead to higher sea levels.
Ethanol as a fuel source has been seen as a promising alternative to fossil fuels. In Brazil, there has been a “large-scale program for using ethanol as fuel” [18]. Ethanol is associated with “green energy” and the concept of energy sources that reduce greenhouse gas emissions. In Brazil, ethanol was derived from sugarcane and gasoline (24 percent ethanol and 76 percent gasoline) [18]. However, in the US, ethanol is commonly used as an additive to gasoline to increase its oxygen content. Pure ethanol is rarely used as fuel for transportation; the most popular use of ethanol comes in a blend called E85, which is 85 percent ethanol and 15 percent gasoline. However, to judge ethanol’s position as a renewable fuel one must analyze is ecological footprint within its production and emissions. Focusing on the US, the process of manufacturing and distributing ethanol has a positive effect on carbon dioxide emissions, but there are drawbacks.
In the US, the greatest concern with turning to using ethanol in higher concentrations in gas blends for fuel is the impact growing a crop like corn in huge quantities has on the environment. Since the manufacturing of ethanol uses a large quantity of corn, corn causes soil erosion and reduces biodiversity [18]. Using a chemical process to produce ethanol alleviates this problem; a clean way of producing ethanol that has an added effect of reducing carbon dioxide emissions is the solution to the only problem present in increasing the use of ethanol. Increasing the ethanol in gas blends would increase gas mileage, cut carbon emissions and air pollution from fuel, and reduce the need for toxic additives in gasoline. Increasing the ethanol in gas blends would increase gas mileage, cut carbon emissions and air pollution from fuel, and reduce the need for toxic additives in gasoline [19]. According to a team at Argonne National Laboratory, “ethanol today results in 37 percent less carbon pollution per mile than gasoline” [19].
At this point, we may ask what can be done, considering the best time to do something about fossil fuel emissions would have been 20 years ago. However, the next best time would be right now. Research from climate scientists has concluded that “we need to reduce [fossil fuel] emissions by about 4 percent a year, going to zero emissions, or even negative emissions…” [20]. There are solutions like wind, solar, and nuclear energy that are just not solving the problem fast enough. The net zero emissions approach is not yielding results fast enough; solutions are needed that will reverse fossil fuel emissions to negative emissions. That’s where a process like the one being discussed comes in. The benefits of a process like this being utilized on large scales will affect Earth’s future. A turn towards sustainability and environmentally conscious practices will make all of the difference in the fight against climate change and global warming.
Source: Youness El Fouih, Chakib Bouallou
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