Biofuel Cars were cars that ran on biofuels. They were especially common in the early 21st century.
(Note: The background section of this page uses most of the same words as Terra Futura's page on hydrogen cars to save time.)
The earliest cars were steam cars. In 1769, Nicolas-Joseph Cugnot demonstrated his steam wagon. It was slow and did not replace the horse and carriage. The first practical gasoline-powered car came out in 1886. It was designed by Gottlieb Daimler of Germany. Later, Karl Benz, also of Germany, also developed his own car. These cars were still expensive. Steam cars were still available and so were primitive electric cars. In 1908, Henry Ford, founder of the Ford Motor Company, invented the first assembly line. This made his Model T cheaper. The automobile became popular as a result. After World War I, the engine was moved to the front, closed bodies and standardized controls were part of every car. During the Great Depression, the car's body was fully closed, and fenders, wings, running boards, and headlights were integrated into the body of the car. Following World War II, there was an increase in engine power and speed limits. In 1964, the Ford Mustang came into existence. In the 1970s, the Arab oil embargo caused a trend toward increasing fuel efficiency. Independent suspension started being used. Fuel injection replaced the carburetor. Safety became a major focus. The turbocharger saw widespread use. Fuel efficiency would increase. In modern times, fuel injection was now ubiquitous. Front-wheel drive and all-wheel drive became widespread. However, in the early 21st century, it became clear that gasoline cars were producing greenhouse gas emissions that contributed to global warming. Regulations were brought about prevent this from causing a catastrophe. What would replace gasoline cars? No one knew, but diesel cars provided a possibility.
Diesel cars used a diesel engine which was invented by Rudolf Diesel in 1883. By 1898, he was a millionaire. However, it was not until the 1970s that diesel cars became increasingly common. Diesel engines had 50% efficiency, the highest of any internal combustion engine. One major problem was diesel fuel had a high sulfur content. In the developed world, technologies were commonly used that took the sulfur out. Another major problem was that the stratified charge compression ignition (SCCI) resulted in particulate matter coming out as smoke. A solution also adopted in the developed world was the diesel particulate filter which filtered out particulates. Both of these solutions made diesel engines cleaner. By the early 21st century, diesel cars were the most common car in Europe. However, they would eventually be replaced by other types of cars. These included natural gas cars.
Natural gas cars came in two versions: Compressed Natural Gas (CNG) Cars and Liquified Natural Gas (LNG) Cars. With Compressed Natural Gas, there was no need to lead foul the spark plugs because there was no lead to begin with. CNG vehicles had a lower maintenance cost. The fuel systems were sealed thus there were no spills. CNG was less likely to ignite on a hot surface. It produces very little greenhouse gas emissions and was more efficient than conventional cars, too. There was one problem. Fuel storage required a greater amount of space than in conventional cars. This was solved by Liquified Natural Gas. Liquified Natural Gas cars had all the same advantages as Compressed Natural Gas cars. LNG cars had the added advantage of fuel storage being more portable than in CNG cars. This became the most common fuel for internal combustion cars for a while before being replaced by hydrogen cars.
Hydrogen cars used Homogeneous Charge Compression Ignition (HCCI). HCCI combined the advantages of both gasoline and diesel engines. One advantage was that nitrogen oxides did not get produced. One disadvantage was that there were higher amounts of carbon monoxide and hydrocarbons emitted from the tail-pipe. It was for both of these reasons that hydrogen was used in HCCI cars. At 40% efficiency, hydrogen cars were more efficient than gasoline cars. It was faster, too. With cars becoming driverless, that was safer than ever. There was one problem. Where would the hydrogen come from? One answer was from crops.
Tech Level: 10
In the early 21st century, cars started running on biofuels. Early biofuels were made from food, especially corn. This was controversial because the price of food went up. Later biofuel cars used non-food crops. These included switch-grass which was used to make cellulosic ethanol. Algae was also used to make fuel. Even hydrogen was made using algae. Biohydrogen was the most common fuel in internal combustion cars by the 2020s. By then, all internal combustion engine cars were hybrids.