Download PDF Summer Bridge Issue on Aeronautics June 26, 2020 Volume 50 Issue 2 The articles in this issue present the scope of progress and possibility in modern aviation. Challenges are being addressed through innovative developments that will support and enhance air travel in the decades to come. Putting Out Fire...with Gasoline? A Pragmatic Path toward Clean Fuels Thursday, June 25, 2020 Author: Nicholas C. Margiewicz Renewables are in the limelight of economic models and there is much discussion about making the internal combustion engine (ICE) obsolete, perhaps with power sources such as batteries and hydrogen fuel cells. Yet ICE replacement may not be necessary. The source of most transportation emissions is combustible fuels created from fossil fuels, which are also used in sectors such as industry and agriculture. Rather than hastily retrofitting or scrapping the millions of ICE-powered vehicles that are already on the road, as part of the climate agenda—a move that would cost trillions of dollars (Sachs 2019) and potentially cost millions of poorer people their mobility—a wise, holistic investment to mitigate the effects of climate change might be as simple and cost-effective as an increase in renewables research. A carbon-free fuel to support engines powered by combustible sources such as gasoline, diesel, and propane without any major retrofits would ensure a fossil fuel–free economical and societal transition with as little risk as possible and could prevent further economic disarray in the transportation sector and in rural economies (O’Sullivan 2020). Background Over the years, technological advances and stricter, industrywide emissions standards and regulations have made internal combustion engines more efficient and less polluting (Park 2019), as have fuel formulations. Despite this, concerns remain about their emission contributions to climate change, propelling countries to push for electric vehicle use (through incentives and rebates) in preparation for bans on these engines. Mass electrification of the transportation fleet is seen as the lowest-carbon choice. But as politicians impose increasingly stringent policies on ICE-powered vehicles, there might not be enough time for battery electric vehicle (BEV) technologies to prosper to the point of functioning as well as the former. Meeting the needs of both personal mobility and personal/public health without having to sacrifice the internal combustion engine would yield the best of both worlds, despite sounding contradictory to many, as, realistically, people are expected to continue using vehicles, including ICE-powered ones, for both personal and commercial purposes for decades to come. Selected Fuel Types Fuels vary greatly in their chemical structure from gasoline to diesel to kerosene among others, but they share a common trait: they release emissions through combustion, whereas electric and fuel cell–powered vehicles release virtually none. With the transportation sector taking most of the blame for the man-made crisis of climate change, the ideal solution would be to synthesize a carbon-neutral, if not carbon-free, fuel. Octane is a gasoline additive that allows proper engine function. A higher-octane number indicates better resistance to engine knock. Renewable and fossil fuel–based sources of octane include methyl tertiary butyl ether (MTBE), benzene, toluene, ethylbenzene, xylene (BTEX), and ethanol (Stolark 2016). In 1921 General Motors discovered that tetraethyl lead was effective in mitigating engine knock, and it eventually became the preferred octane source, with low production costs compared to benzene and ethanol-based sources, until serious health concerns led to phaseout in the early 1970s. Leaded gasoline also damaged the catalytic converters intended to reduce emissions from models between 1975 and 1996, when it was banned altogether (except for use in aircraft) (Stolark 2016). Biofuels, including those made through “gasification” (which turns combustible waste into biofuel and a soil conditioner via filtering of flammable chemicals and oils from biomass, leaving behind highly refined carbon mixed with ash; Karikehalli 2019), and fuels blended with “drop-in” material such as ethanol are proven to lower but not eliminate tailpipe emissions from ICE-powered vehicles (Loyola 2019). Experiments with other transportation fuels such as ammonia are also underway. But if impacts are deemed deleterious, then these specific fuels should not be commercialized as a carbon-neutral—let alone emission-free—alternative to traditional gasoline and diesel fuel. Natural gas is not a viable solution as emissions are still released (Kusnetz 2019) and have methane as a major component (UCS 2014). Even hydrogen internal combustion engines produce emissions and are less viable than fuel cell electric vehicles (FCEVs). Hydrogen, as a primary element, has always presented difficulty with adoption for use as fuel, as incidents such as the 1937 Hindenburg crash (Lampton 2008) and hydrogen station explosions (Lambert 2019) have made the public wary. Hydrogen combusts when the volumetric ratio of hydrogen to air is as little as 4 percent. Extremely reactive, it also takes only one tenth of the amount of energy to burn similarly to gasoline, so even static electricity can trigger a violent reaction (Lampton 2008). Hydrogen presents a number of other complicating factors. Although it rapidly disperses into the atmosphere in the right conditions, any resulting flames are so faint that putting one out is difficult and dangerous as one could get burned trying to locate the fire. In addition, even small amounts of air can taint the supply in an FCEV fuel tank (Lampton 2008). And hydrogen fuel cells can produce carbon monoxide and thus make the fuel poisonous like gasoline (Service 2010). Criteria for an Ideal Fuel The ideal fuel will serve the function of both combustible fuels used for various purposes (e.g., gasoline, diesel, kerosene, heavy fuel oil) and any alternative fuel that is not considered carbon-neutral (e.g., natural gas/CNG). Depending on its energy density and formulation, the fuel may be more efficient, while vehicle power may decrease, remain the same, or even increase. To function most like gasoline and diesel fuel, for example, the energy density to beat is 44–46 megajoules per kilogram (MJ/kg) and 42–46 MJ/kg, respectively (table 1). Table 1 Such a fuel might allow ICE-powered vehicles to circumvent taxes and bans because emissions would be substantially, if not completely, eliminated. It would make reaching the desired 350 parts per million (ppm) CO2 and the ambitious 1.5°C global warming threshold of the Paris Climate Agreement by 2050 more feasible, and even make it possible to achieve both goals much sooner. In the United States, this would eliminate the potential problem of Transportation and Climate Initiative states losing business to nonparticipating states, while still supporting ICE-powered vehicles (Schoenberg 2019). It would also nullify artificial price hikes on these vehicles due to their emissions, making personal mobility more accessible to those of lower incomes. A formulation that supports older cars that were designed to run on leaded gasoline and are vulnerable to even the slightest amount of ethanol in modern gasoline (including E10) is also reasonable. Lead substitutes exist as additives for these vehicles (Redex 2019), along with ethanol fuel filters (CAR Magazine 2018), ethanol-free gasoline that can be ordered online (Siegel 2018), and replacement parts to minimize effects on their engines. Without them, old leaded fuel–dependent vehicles would have gone to the scrapyard by the millions—a fate that ICE-powered vehicles may face in the near future, except the few that are donated to museums. Potential Fuel Alternatives CO2 Use Although CO2 is one of the main greenhouse gases contributing to climate change, as a raw material it allows fuel to be far less polluting than traditional gasoline made of petroleum from oil refineries. Emissions-to-fuel technologies are a step closer to achieving carbon-neutral fuel. Carbon Engineering, based in Squamish, British Columbia, utilizes a direct air capture system to create synthetic gas (syngas) by capturing CO2 from the atmosphere and, with just water and hydrogen, forms a pipeline-ready gas (Conca 2019). A similar process involves carbon mixing with H2 generated from photoelectrolysis of water, which yields methane and water, before producing electricity through a combustion system that releases these emissions before recycling them (Hashimoto 2018). However, processes that use less, if any, water must be seriously considered so as not to burden the world’s water supplies (Rosa et al. 2020). Furthermore, MIT postdoc Sahag Voskian and chemical engineering professor T. Alan Hatton have developed a device to capture carbon at any concentration, even below the 400 ppm naturally found in the atmosphere, allowing for virtual elimination of the element in the air (Chandler 2019). It is a stack of large electrochemical plates resembling a battery that takes in CO2 as polyanthroquinone-coated electrodes charge as the compound is attracted to them; the reverse reaction occurs once the battery is discharged. A prototypical battery, it is expected to be cost-effective over time and make it even easier to remove emissions (Chandler 2019). Although it might be argued that it may already be “too late” to commercialize these fuels (which were all but ignored for decades), for society to continue to function as normal, it really is “better late than never.” British sports car manufacturer McLaren, which plans to hybridize its lineup by the middle of the decade, has expressed interest in developing a synthetic fuel. COO Jens Ludman pointed out that the technology for developing syngas from solar energy exists and has potential to be used in ICEs with little modification (Hood 2020). He also acknowledged that some emissions would be present but would end up producing as much lifetime emissions as batteries, including those from production (Hood 2020). According to a Bosch (2017) study, benefits from the commercialization of such fuel include not only allowing older vehicles with ICE technologies to stay on the road (coexisting with BEVs), but also reducing treatment costs, and the same applies with hybrid car ownership costs after 160,000 kilometers (99,419 miles). In addition, the existing filling station infrastructure can remain in use. Although the relatively new technology will be expensive at first, Bosch predicts that average costs will eventually plummet to between €1.00/liter ($1.08/gallon) and €1.40 ($1.52)—cheaper than gasoline (Bosch 2017). “Power-to-X” technologies could see other forms of energy, including electricity, helping to advance progress toward “green gasoline” that can take the form of other fuels such as diesel and kerosene. Also using CO2 as a base, Chemieanlagenbau Chemnitz (2019) and Mitsubishi Hitachi Power Systems GmbH constructed a complete process chain using hydroelectric power generation. Photosynthesis, Catalysis Another benchmark is an “artificial leaf” created by the University of Cambridge (2019). Inspired by the natural process of photosynthesis, a device consisting of two light absorbers and a cobalt catalyst is submerged underwater, where one absorber (BiVO4) produces oxygen with a reaction from the catalyst via exposure to a blue light while the other (perovskite, CaTiO3) uses another chemical reaction to dilute CO2 to produce carbon monoxide and hydrogen (Jasi 2019). Even though this promises a sustainable liquid fuel alternative produced with a much cleaner process, environmental concerns are sparked by the use of carbon monoxide. Also, while it can still be used on rainy and/or cloudy days (University of Cambridge 2019) it does not match the energy density of natural gas, but there is room for improvement (Satherley 2019). Low-cost molybdenum nanoparticle catalysts have been developed by chemists at the University of Southern California for Carbon Recycling International’s George Olah Plant in Iceland, which captures emissions from the nearby Svartsengi Power Station. The catalysts mix with the emissions to perform chemical reactions similar to those in combustion, such as splitting carbon-oxygen bonds to form a “carbon-neutral” hydrocarbon fuel (Oberhaus 2020). Synthetic fuels that are part of the oxymethylene ethers group are being assessed on a single-cylinder testbed in trials done by the Technical University of Munich, funded by the German Federal Ministry of Economics, under the XME Diesel project (Wilkes 2020). Results showed that because the fuel has a lower calorific value than traditional diesel, more must be put into the engine to achieve the same performance, and so the injectors had to be modified. Pollutants are nevertheless cut to the point of meeting current Euro 6 standards, giving cars retired from European roads because of increasing taxes and failed emissions tests a second life back on the roads (Meinecke 2018). Hydrogen While hydrogen alone is unsuitable for traditional internal combustion engines without modifications (as discussed above), it can be used as a base in synthetic fuel, and demand is expected to skyrocket thanks to Canada-based Proton Technologies’ Hygienic Earth Energy concept (Collins 2020). At existing oil fields (operational, abandoned, or defunct), air and/or oxygen is channeled into the reservoir or coal bed where hydrocarbons are ignited, and when the fire’s temperature exceeds 500°C (932°F), injected steam and/or water vapor reacts with the hydrocarbons, creating the syngas. Additional water would spark yet another reaction that releases even more CO2 and hydrogen—without impurities (including CO2), as patented palladium-alloy membranes allow only the hydrogen through a metal lattice. Hydrogen could be produced for as little as 10¢–50¢ per kilogram. Even green hydrogen—which is split from water molecules and also consists of oxygen with renewable energy, costing $2.50–$6.80 right now—would cost $1.40/kg and 80¢/kg by 2030 and 2050, respectively (Collins 2020). Research All these methods can close the global carbon cycle, with carbon capture/emissions reduction as the first line of defense. However, prevention of both environmental problems and a backlash requires further progress, research, and innovation for a truly “carbon-neutral” fuel, so these solutions, which all use CO2 as a base, are not yet viable in the long run. Researchers at McGill University and the European Space Agency have developed a fuel designed for external combustion engines that is made of various metal powders such as aluminum, lithium, magnesium, silicon, and zinc (similar materials are already used for rocket fuel) (Hellemans 2015). Although metals have the advantages of easily recyclable outputs (iron oxide) and a much higher energy density than hydrogen and batteries, they should not be entirely relied on to cancel out emissions because of concerns about heavy metal poisoning and toxicity for wildlife, soil, and water (symptoms vary by type of metal; Tchounwou et al. 2012). Beyond the Automobile The scope of proposed alternative fuels should not be limited to automobiles. The aviation industry has its own complicated emissions elimination problem. JetBlue’s plan to become carbon-neutral by June 2020, aside from through carbon-offsetting projects, is to use a sustainable aviation fuel for flights departing from San Francisco International Airport (Stevens 2020). Widespread implementation of such fuel would mean a much cleaner and safer tourism industry. An example of a sustainable aviation fuel option is a synthetic fuel pioneered by Dutch company Urban Crossovers, with CO2 sourced by Swiss environmental company Climeworks (which can also sequester the compound underground) (Beard 2019). Another is fuel that uses power-to-X technologies to create a water-based kerosene also using carbon capture for formulation. The latter was pioneered in Germany in 1925 and was intended to be used by Hitler’s Luftwaffe (Stevens 2020), in response to an oil embargo during the Great Depression. The agricultural and industrial sectors can also benefit from these proposed fuels. Current postharvest processing and marketing made possible from efficient mechanization cannot be considered environmentally friendly if ICE-powered machinery is used. Conclusion Once new alternative fuels are produced and commercialized to the point of being affordable, they can easily be applied to all types of ICE-powered transport (Sachs 2019), allowing for more resilient energy supplies (Prentiss 2019) and clean economic growth. Such innovation is proof that emissions elimination does not need to be prohibitively expensive in the long run, and that it will not be necessary to scrap millions of ICE-powered vehicles, whether they run perfectly or not. In the near future, greenhouse emissions will no longer be treated as the root of all evil, but as a valuable economic commodity when captured and/or filtered quickly enough, kickstarting the next gold rush out of thin air. References Beard S. 2019. 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The Transportation and Climate Initiative is a regional collaboration of 12 Northeast and Mid-Atlantic states (Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Virginia) and the District of Columbia that seeks to improve transportation, develop the clean energy economy, and reduce carbon emissions from the transportation sector.  Before turning to the use of the new alternative fuels, owners of existing ICE-powered vehicles would clean out deposits accumulated in their engines. This process might involve special equipment that electrolyzes water to split H2O molecules into oxyhydrogen to initiate a chemical reaction that strips the deposits so that they are expelled through pressure from the exhaust system. About the Author:Nick Margiewicz just completed his junior year at North Port High School in Sarasota County, Florida.