Automobiles and fuel consumption

Summary: The number of cars and light trucks in the world is thought to have exceeded 1 billion around 2010, with some estimates placing the number on roads worldwide in 2022 at 1.4 billion and expected to continue to grow. These vehicles consume hundreds of billions of gallons of fuel yearly. There is a trend to develop alternative vehicles and methods of transport to reduce the use of fossil fuels.

Automobiles as industrially mass-produced vehicles have had a tremendous impact on both human daily life—economically and socially—and the natural and built environments. Since the beginning of the twentieth century, more than 2,500 companies worldwide have produced cars. In 1875, transport in France was accomplished via voiture automobile, trolleys powered by compressed air. Today, an automobile is understood to be a multitrack, non-rail-bound motor vehicle. Its main parts are an undercarriage and chassis frame, body, engine or motor including all the mechanism’s component parts (gears, battery, transmission, and so on), fuel tank, and the cabin’s interior components, which often include luxury amenities such as a radio, air conditioner, clock, and increasingly sophisticated technologies such as connections to the Internet and global positioning system (GPS) devices.

The automobile allowed a shift in residential locations, as civil engineering grew to handle the infrastructure requirements (such as highway systems), allowing the growth of the suburbs. Suburbs grew faster then their populations did, leading to lower population densities (fewer inhabitants per unit area). The decreasing population density led to higher costs for mobility and infrastructure, including underground infrastructure, which is expensive and requires regular maintenance.

Such trends have led to the criticism that cars in urban transport systems are unsustainable, pollute the air, and consume too much energy. Contributing to these problems is the fact that automobiles’ overall capacity usage is low: Only 1.5 passengers occupy each automobile, on average, causing relatively high costs per person and per mile or kilometer traveled compared to public transportation systems such as buses and subways. Concepts for sharing cars with others, including carpooling and car sharing, have been used to attempt to increase the efficiency of automobile travel. Carpooling depends on private arrangements among neighbors, friends, and colleagues to use one vehicle to (for example) commute to work. One idea to reduce automobile traffic was the institution of highway carpool-only lanes, for use only by cars carrying multiple passengers, based on the theory that such lanes would move faster than the regular flow of traffic and encourage more passengers per car. However, the results of such plans, for example in California, have been mixed. Car sharing describes the more formally organized, collaborative use of cars. Car sharing requires a public infrastructure to provide multiple persons access to cars; the first car-sharing organization was founded in Switzerland in 1948.

Conversely, since automobiles demand a high land use, they become increasingly uneconomical with higher population densities. This can be expressed in both higher costs of driving and decreased flexibility in the form of traffic jams. The problem of parking in urban areas was recognized as early as 1920, resulting in the invention of a foldable car in Germany. Many urban areas continue to struggle with parking, traffic, and other infrastructure issues, with some, such as New York City, taking steps to limit the number of automobiles on the streets.

Cars are the main reason for road construction, including all its consequences, such as deforestation, loss of natural habitat, and soil sealing. Sealed soil has a negative impact on the water balance. For example, a sealing of 50 percent of a certain area can make flooding more likely and harder to control, which in turn can cause immense damage to property, the environment, and human life.

Public costs related to automobile use also include construction and maintenance of roads and parking areas, as well as costs related to emissions and land use that are more difficult to represent. Furthermore, there are public costs related to manufacturing and waste disposal. For example, it has been estimated that the amount of water needed to produce one car is approximately 226,000 liters (nearly 60,000 gallons).

The private costs of running a car include depreciation, fuel, maintenance, repairs and part replacements, financing, insurance, parking, road tolls, taxes, vehicle inspections, and registration fees.

Market Statistics

After a decline due to the 2008 global financial crisis global production increased by 20 percent in 2010, mainly due to high demand in China, stimulating production in Europe and North America. According to International Organization of Motor Vehicle Manufacturers (OICA), approximately 57 million cars (out of a total of 80 million motor vehicles) were produced in 2021 worldwide. The main producers were China (21.4 million cars), Japan (6.6 million), India, (3.6 million) South Korea (3.1 million), Germany (3 million), and the United States (1.5 million). According to the Boston Consulting Group, in 2014 at least one-third of global demand was from emerging markets in Brazil, Russia, India, and China (the so-called BRIC nations) and in Iran and Indonesia.

The biggest producers in 2017 were Toyota (10.4 million vehicles), Volkswagen (10.3 million), Hyundai (7.2 million), General Motors (6.8 million), and Ford Motor Company (6.3 million).

History

The wheel was invented around 4,000 BCE. Carriages, driven by human muscular power—pulled, carried, or operated by means of treadwheels—began to be developed around 400 BCE. As early as 100 BCE Heron of Alexandria invented a prototype of a steam engine.

In the Renaissance diverse vehicles such as treadwheel wagons and sail wagons were introduced. A sail wagon constructed by the Dutch mathematician Simon Stevin in 1600 was able to transport up to thirty persons using wind energy. Also in the Netherlands, Christiaan Huygens built a reciprocating engine powered by black powder in 1674, now considered the prototype of a combustion engine. During the 19th century, there were many experiments with steam engines. François Isaac de Rivaz, for example, constructed a vehicle with a combustion engine fueled with hydrogen in 1802. One year later, the so-called London steam carriage, a stagecoach with a steam engine, was introduced, but at that time it proved too expensive. However, already in 1828 a steam-powered bus shuttled between London and Bath in England. The Sentinel was a steam truck built at the beginning of the 20th century.

The first, although ineffective, electric car was built in 1839 by Robert Anderson. Later, in the 1860s, the so-called Hippomobile, a vehicle driven by a hydrogen-gas-fueled internal combustion engine, was invented by Étienne Lenoir and made a tour from Paris to Joinville-le-Pont. At the same time, Nikolaus Otto developed the four-stroke-cycle internal combustion engine, which was patented in 1876. The modern car was introduced by Karl Benz, patented in 1886, and followed by other, independently developed, versions by Gottlieb Daimler and Wilhelm Maybach in Germany and Siegfried Marcus in Austria. Benz and Daimler established their own companies to mass-produce cars. The first diesel motor was constructed by Rudolf Diesel in 1897. Shortly thereafter, in 1898, the first speed record was set by Gaston de Chasseloup-Laubat, driving an electric car at 39.23 miles per hour; this record was beat in 1901, again by an electric car, reaching more than 62 miles per hour. By 1900, in North America there were more than four thousand automobiles produced by seventy-five producers, including steam cars, electric cars, and cars with Otto engines.

Eventually, internal combustion engines fueled by gasoline (petrol) became the leading motor types, because gasoline was abundantly available at a reasonable price and offered, thanks to its higher energy density, a long-distance range and high speed. At the beginning of the twentieth century, many technological innovations followed, including front-wheel drive, four-wheel drive, disc brakes, hydraulic brakes, rotary engines, radial ply tires, and windshield wipers.

In 1913 Henry Ford introduced automobiles that were mass-produced using an assembly line, allowing a reasonable retail price that many people could hope to afford. In Germany, assembly-line production was started by Opel in 1924. Two years later, Benz and Daimler merged into the Daimler-Benz-AG. The automatic gearbox was introduced in 1940. By 1951, the first car offering servo steering by default was produced by DaimlerChrysler. Since 1967 Otto engines with electronic fuel-injection systems have been produced. During the 1970s General Motors developed the catalytic converter for Otto engines. Mercedes introduced an electronic antilock braking system (ABS brake) in the late 1970s, followed by airbags in 1980 and electronic stability control (ESC) in 1995.

In 1984 modern natural-gas-powered cars were introduced to the market, followed by hybrid vehicles in 1997. Further research continues to take place regarding automotive engineering (steer-by-wire, brake-by-wire), drive mechanisms and engines (fuel cells, hybrid motors, electric cars), safety, entertainment, satnav, integration of recyclable materials, and driverless cars.

Alternative Engines

Electric cars can offer significant fuel economy. For example, the Nissan Leaf was rated at 34 kilowatt-hours per 100 miles and the Chevrolet Volt at 36 kilowatt-hours per 100 miles. This enables mobility with very low environmental impact from exhaust gases. The production of electrical power based on fossil fuels (such as coal) emitted about 0.855 pounds of carbon dioxide (CO₂) per kilowatt-hour in the US in 2021. Studies have shown that, assuming electric cars would be powered with conventional power, not green power from renewable resources, the indirect carbon dioxide emissions of electric vehicles would still be drastically lower than gasoline cars.

One of the main concerns over all-electric vehicles is their limited range on a single charge, but ever-improving batteries and other technologies can help minimize this issue. For example, Tesla Motors produced an electric roadster in 2009 that offered almost the same comfort and capacity as gas-powered cars regarding speed and a distance range of 248.5 miles. Its energy use was 17.7 kilowatt-hours per 100 miles. The long-distance range was made possible through high-quality batteries. The storage of electrical energy is subject to further research, because in order to provide the power for long-distance ranges and more comfortable cars, batteries must be large and heavy whereas for medium-sized cars they can be smaller but need to be recharged more often. In the latter case, several hours are required to charge the battery. Other technologies have been explored to get around these limitations. Electric cars equipped with photovoltaic cells could be commercially developed, though batteries remain a necessary concern in the absence of constant sunlight. A special type of electric car powered by hydrogen converted into electrical power by a fuel cell has been produced and even sold commercially, though the technology remains expensive and faces challenges such as the costs of installing appropriate refueling infrastructure.

The advantage of hybrid cars is the ability to switch between a gas-fueled internal combustion engine and an electric motor. At partial loads, the electric motor drives the car, thus reducing the burning of the fossil fuel and its accompanying exhaust gases. Such vehicles can get better gas mileage and produce lower emissions than gas-only vehicles but are not constrained by the range and refueling issues of fully electric or hydrogen automobiles.

In 2022, CNN reported that, according to Kelley Blue Book, electric vehicles contributed to 5.6 percent of all auto sales in 2021, up from 1.4 percent in 2019. The increase in sales was attributed to both a rise in supply and demand, as well as a reduction in the overall cost of an electric vehicle when compared to just a few years earlier.

Calculating Energy Use

Besides taking solely the operating distance into account to calculate energy consumption, it is important to determine the gas consumption per transported net load and distance. This method is used to compare the energy consumption of different vehicles, or transporting options. For example, if a truck spends 14.9 gallons of diesel fuel per 100 miles to transport a freight of 20 tons, the truck uses 0.07 gallon per 100 kilograms per 100 miles. If a fully occupied car, spending 3.2 gallons of diesel for the same distance to transport 500 kilograms (including passengers and luggage), the car needs 0.64 gallon per 100 kilograms per 100 miles. Although spending more fuel, the truck has the better energy balance.

Measures to Reduce Gas Consumption

A car’s energy balance can be affected not only by technological advances but also by the design of a car with respect to the rules of physics and the manner in which the car is driven.

From the standpoint of physics, a technological challenge is the reduction of resistance and friction, including flow resistance, inner resistance, rolling resistance, and inertia.

Flow resistance is reduced by an aerodynamic body design, covered wheel houses, smooth surfaces, narrow tires, and cameras instead of wing mirrors, as well as the reduction of the cross-section area that faces airflow. The minimization of inner resistance requires a low-viscosity oil to reduce friction loss in the motor, efficient gears, brakes with low friction, and efficient idling and start-stop systems. Rolling resistance, which is the drag on the vehicle incurred as tires roll on a flat surface and encounter friction, is reduced in light cars, in which wheel bearings can also be optimized. Finally, whenever speed changes, inertia is directly proportional to the vehicle’s mass (expressed as weight); lighter cars with smaller engines have a lower mass and thus can more easily overcome inertial resistance and work more efficiently at even speeds.

Generally, the efficiency of an automobile is defined by the efficiency of its conversion of chemical and/or electrical energy into mechanical energy. The main difficulty regarding combustion engines is that they work most efficiently at full loads and less effectively at partial loads, resulting into higher fuel consumption (lower efficiency) at lower loads. This can be mitigated through optimal gear ratios and improvement of the engine efficiency at partial loads. Electric motors work at partial load significantly more efficiently than do combustion engines. Moreover, the high demand for comfort, including air conditioning and entertainment devices, daylighting and other safety features, increases the energy use, leading to debate over the appropriate balance between fuel efficiency and desirable features.

Regulations

Based on a 2008 ruling by the California Air Resources Board (CARB), and strengthened by Governor Jerry Brown in March 2012, California mandated that 15 percent of major automaker vehicles sold annually in the state must be zero-emission vehicles (ZEVs) or near-zero-emission vehicles by 2025. A 2022 law later set the stage to ban all gas-powered vehicles in California by 2035. About one dozen other states have adopted CARB rulings; the US Environmental Protection Agency (EPA) also selectively adopts some CARB standards. ZEVs must be able to cover a certain distance without any emissions at all.

In Europe, the enhanced environmentally friendly vehicle (EEV) standard, limiting CO₂ emissions in new vehicles to 120 grams per kilometer, was originally set to be achieved by 2012 and then, in view of the world economic crisis, pushed back to 2015. It has motivated further research and development.

Fuels

The most common fuel is gasoline (petrol) as composed for internal combustion Otto engines. That includes all spark-ignition engines, compared to compression-ignition engines, which are fueled by diesel.

Special mixtures are used for racing fuels. Since 1993 in Europe, Formula One racing fuels must fulfill European Union (EU) fuel regulations. Prior to adoption of this standard racing fuels contained many toxic substances. Unlike standard gasoline, which is calculated in fuel value per liter, racing fuels are calculated in fuel value per kilogram.

Because fossil fuel resources are limited, the development of alternative propulsion technologies and alternative fuels is imperative. During World War II about 500,000 automobiles in Germany were modified to drive on wood gas.

Compressed natural gas (CNG) and liquefied petroleum gas (LPG) are both applicable for use in Otto engines, providing a high knock resistance with research octane numbers (RONs) of between 105 and 130. LPG is a mixture of butane and propane, liquefied at relatively low pressures. Depending on market forces liquefied natural gas (LNG) and CNG can be much cheaper than gasoline while emitting 25 percent less CO₂ and dramatically fewer air pollutants. While methane can be produced from biogas or wood gas, propane and butane are by-products of petroleum refining.

Alternative Fuels for Combustion Engines

Alternative fuels are thought to provide more sustainable energy sources—but to allow standard use, more research is required regarding efficiency of combustion, storage, and safety. Hydrogen as a fuel for Otto engines holds potential because of its high octane number, and ease of ignition. More research regarding storage, however, is still required.

Diesel engines can be fueled with vegetable oil instead of diesel, but vegetable oil fuels have a tendency to gum and become viscous upon cooling. Attempts to reduce these problems have resulted in the development of biodiesel.

Ethanol as a fuel is produced by fermentation, using such starch sources as wheat, corn, sugarcane, and other crops. Traditionally it has been used as an agent mixed with gasoline. So-called flexible fuel vehicles, or flex-fuel vehicles, have been driven with a mixture of 85 percent ethanol and 15 percent super. To reduce the competition with agricultural food production, cellulose from a variety of nonfood sources is being developed as a source of ethanol.

Most of the foregoing alternatives do not offer all benefits of classic gasoline for internal combustion engines. Criteria that are considered in choosing alternative fuels include distance range; maximum engine performance; stability of stored energy; acceptable refueling procedures regarding time, safety, and efficiency; the safety of passengers; and the environmental benefits or risks.

Emissions, Health, and the Environment

Exhaust emissions of automobiles contribute about 20 percent of worldwide CO₂ emissions, thus boosting the greenhouse effect. Motor vehicle emissions also contain a variety of toxic substances, such as benzol (benzene), toluol (toluene), and xylol (xylenes). Together with particulate matter, nitrogen oxides, and exhaust gases from industrial plants, these emissions form smog in urban (and increasingly suburban and rural) areas, which are responsible for a number of health hazards.

The addition of tetraethyl lead (TEL) to gasoline as an anti-knocking agent between 1923 and 1995 resulted in some fatal exposures to lead in the form of car exhaust from millions of automobiles worldwide. TEL contaminated air, soil, and water. In the 1970s, for example, the annual gasoline consumption in the United States included about 200,000 tons of lead. Since 2000 leaded petrol has been banned in the EU, and several member states completed phaseouts prior to that date. In the United States, leaded gasoline was phased out upon an initiative of the Environmental Protection Agency (EPA) based on the Clean Air Act of 1970. The TEL phaseout took place between 1976 and 1986. By the year 2000 more than 50 nations had removed leaded gasoline from their markets. Nonetheless, TEL gasoline is still sold in many developing countries.

Diverse volatile organic compounds (VOCs) react with oxides of nitrogen (NO_x) and, in the presence of ultraviolet (UV) radiation (sunlight), form ozone. Ozone in the stratosphere forms the important UV-protective ozone layer, but ozone near or at the Earth’s surface is classified as smog and has a strong effect on the respiratory system. Ground-level ozone affects not only human health but also plant growth, causing millions of dollars in lost crops annually. A 2005 EPA report noted that automobiles and trucks contribute about 26 percent of all nationwide VOC emissions. An additional 19 percent originate from nonroad equipment, such as gasoline and diesel stations, from fuel evaporation.

Another emission is carbon monoxide, a colorless, odorless, and tasteless gas, which is very toxic; when breathed, it causes asphyxia (oxygen deficiency in the blood). In the United States, 27 percent of greenhouse gas emissions were caused by transportation in 2022.

In 1997 the EPA enforced the National Ambient Air Quality Standards for particulate matter (PM). PM comprises the smallest particles of all airborne particulates. The mean 24-hour value of PM₁₀, which are particles of 10 micrometers or smaller, may exceed 150 micrometers per square meter at most once per year (in the European Union the standard is 50 micrometers per square meter). The mean value for PM_2.5 is 15 micrometers per square meter.

Road traffic is a major contributor of PM emissions, due to carbon-particulate matter emissions, tire particles, and abrasion particles from brakes on asphalt. Because of their size, these particles can penetrate deep into the lungs upon inhalation and there create a high risk for developing asthma and lung cancer.

Bibliography

"Autos and Fuels." OICA. International Organization of Motor Vehicle Manufacturers, 2016. Web. 13 May. 2016.

Bastian-Pinto, Carlos, et al. “Valuing the Switching Flexibility of the Ethanol-Gas Flex Fuel Car.” Annals of Operations Research 176 (2010).

"Carbon Pollution from Transportation." United States Environmental Protection Agency, 19 May 2022, www.epa.gov/transportation-air-pollution-and-climate-change/carbon-pollution-transportation. Accessed 20 Jan. 2023.

"Electric Vehicle Myths." United States Environmental Protection Agency, 22 Dec. 2022, www.epa.gov/greenvehicles/electric-vehicle-myths. Accessed 20 Jan. 2023.

European Commission, Directorate-General for Energy and Transport. Promoting Biofuels in Europe: Securing a Cleaner Future for Transport. Luxembourg: Office for Official Publications of the European Communities, 2004.

Ferreira, Alex Luiz, et al. “Flex Cars and the Alcohol Price.” Energy Economics 31 (2009).

Goettemoeller, Jeffrey, and Adrian Goettemoeller. Sustainable Ethanol: Biofuels, Biorefineries, Cellulosic Biomass, Flex-Fuel Vehicles, and Sustainable Farming for Energy Independence. Maryville, MO: Prairie Oak, 2007.

Gupta, Ram B., and Ayhan Demirbas. Gasoline, Diesel, and Ethanol Biofuels From Grasses and Plants. New York: Cambridge University Press, 2010.

International Energy Agency. “Biofuels for Transport: An International Perspective.” Paris: Organisation for Economic Co-operation and Development/International Energy Agency, 2004. http://www.iea.org/press/pressdetail.asp?PRESS‗REL‗ID=127.

Nag, Ahindra. Biofuels Refining and Performance. New York: McGraw-Hill, 2007.

National Energy Technology Laboratory. Zero Emission Power Generation Technology Development. Morgantown, WV: National Energy Technology Laboratory, 2005.

Plant, Jeremy F., Van R. Johnston, and Cristina E. Ciocirlan. Handbook of Transportation Policy and Administration. Boca Raton, FL: CRC Press, 2007.

Tiseo, Ian. "CO Emissions from Transportation in the U.S. 1990-2021, by Source." Statista, 11 Jul. 2022, www.statista.com/statistics/999680/us-carbon-monoxide-emissions-from-storage-and-transport/. Accessed 20 Jan. 2023.

Valdes-Dapena, Peter. "Electric Vehicle Sales Hit a Tipping Point in 2022." CNN Business, 27 Dec. 2022, www.cnn.com/2022/12/27/business/electric-vehicle-tipping-point/index.html. Accessed 20 Jan. 2023.

"World Motor Vehicle Production." International Organization of Motor Vehicle Manufacturers, www.oica.net/wp-content/uploads/World-Ranking-of-Manufacturers-1.pdf. Accessed 20 Jan. 2023.

Worldwatch Institute. Biofuels for Transport. London: Earthscan, 2007.

Zachariadis, Theodoros I. Cars and Carbon: Automobiles and European Climate Policy in a Global Context. New York: Springer, 2012.

Zhao, Fuquan, ed. Technologies for Near-Zero-Emission Gasoline-Powered Vehicles. Warrendale, PA: SAE International, 2007.

"2021 Production Statistics." International Organization of Motor Vehicle Manufacturers, www.oica.net/category/production-statistics/2021-statistics/. Accessed 20 Jan. 2023.