Petroleum is a fossil fuel formed from the remains of ancient marine organisms. Millions of years ago, these remains settled on the seafloor. Over time, sediment and rock piled on top of these remains. After many centuries, high pressure and heat compressed the remains into a mixture of hydrocarbons. The term petroleum usually refers to the liquid form of this mixture, which is also called crude oil or just oil. There are also gaseous forms of these hydrocarbons, called natural gas, and solid forms, called bitumen.

These petroleum forms go through a refinement process before people can use them. Once refined, petroleum products have many applications, including as fuel, as a precursor to plastic and more. Because it took millions of years to form, petroleum is a nonrenewable resource, meaning that it cannot be replaced it once it is used up.

Petroleum exists in underground reservoirs. People extract it using drilling machines, which can drill deep into the land or even under the ocean. One type of drilling, called explorational drilling, is done in areas where there are no known petroleum reserves, but where geologists suspect there might be petroleum. Developmental drilling is performed where there are known reserves. In a process called fracking, drilling operators blast water, sand and chemicals into rocks deep underground to break them apart and release petroleum.

Petroleum can be processed into gasoline to power transportation. Manufacturers also use petroleum to make many items, including tires, refrigerators, clothes, trash bags and antiseptics.

Although widely used, extraction and use of petroleum harms the environment and humans. Burning petroleum releases carbon, which increases the greenhouse gases in the atmosphere. This has contributed to the rapid climate change and global warming happening today. Burning oil accounts for around a third of the world’s carbon emissions.

While many countries have oil reserves, just four countries control more than half of them. As of the mid 2020s, Venezuela had the most oil in reserves at 303 billion barrels, followed by Saudi Arabia with 267 billion, Iran with 209 billion and Canada with 163 billion. Around a third of the world’s energy supply comes from oil. The United States, Saudi Arabia and Russia produce the most oil, while the United States, China and India consume the most oil.

Uses of Petroleum

Petroleum is a popular source of energy worldwide, particularly for transportation. Oil has high energy density compared to other sources of energy, particularly those in solid or gaseous forms. This means that smaller amounts of oil can provide the same energy as larger amounts of other fuels.

As a result, the transportation sector is heavily reliant on petroleum products, which supply more than 94% of fuel for vehicles. A lot of this fuel is gasoline, which is made from crude oil and other petroleum liquids. The transportation sector is also a major contributor to carbon emissions because of the use of oil. Experts estimate that transportation accounts for between 15% and 25% of carbon emissions worldwide each year.

Petroleum-powered products also serve as a backup to electrical power where electricity is unstable or unavailable. Power generators use diesel fuel to run and can power lights or other devices. Hospitals use generators if electricity goes out during storms or natural disasters, often saving lives, and the technology sector uses diesel generators to keep data centers up and running if other power sources go out. However, overreliance on diesel in emergencies can cause additional problems, especially when fuel access becomes a critical issue during times of emergency.

In 2022, Hurricane Fiona caused massive destruction to the U.S. territory of Puerto Rico. While some urban hospitals had working generators and access to diesel, rural clinics often did not, nor did the many citizens trying to take care of their families in their homes. There were massive lines for fuel. The disaster highlighted ongoing infrastructure issues that Puerto Ricans face after repeated hurricanes and lack of effective federal support from the United States government.

“Those of us who live in the mountains are used to having our water and electricity go out every day. Now, the whole country knows what we go through and nobody does anything,” Shamir Martinez, a resident of a rural area outside San Juan, told Reuters in 2022. This is one way that reliance on petroleum can become negative and harm marginalized communities disproportionally.

In addition to fuel, petroleum is useful for making other products, including plastics. Plastic manufacturers source chemicals called monomers—small chains of molecules—from fossil fuels to create different types of plastics. Some plastic items are essential to people’s lives, such as artificial limbs. Petroleum is also used to produce important nonplastic products like antihistamines, soft contact lenses, toothpaste and vitamin capsules. A variety of other items like crayons, skis and nail polish are also made from chemicals derived from petroleum.

However, like the production and burning of oil, plastic has harmful environmental effects. Because they decompose extremely slowly, discarded plastics fill up oceans and landfills, harming wildlife. Plastics break down into smaller pieces called microplastics, which can be found all over the planet, even in remote environments. Toxins from plastics and microplastics leach into the environment and build up in animal bodies, including humans, potentially causing negative health effects.

Drilling for Petroleum

Drilling petroleum also harms the environment. The drilling process starts with finding oil reserves. Companies find reserves by conducting seismic tests, which make extremely loud noises that disturb wildlife. For example, these sounds can interrupt sea creatures that use sound to find mates and hunt, such as whales, and can even cause them to lose their hearing.

To drill on land, workers must clear the area for industrial use, destroying habitats. Oil wells are holes that are drilled and then used to bring petroleum to the surface. The construction of an oil well, including construction of any roads through an animal’s habitat, can cause migration patterns to change. This happened in the Murchison Falls National Park in Uganda, where experts have noted that animals like elephants are avoiding the oil pipeline that runs through the park, resulting in disrupted mating and foraging patterns.

After drilling begins, wells can leak oil and gas into the environment. In the short term, this can kill animals. Damage from petroleum leaks can affect ecosystems for decades. This is the case with the Deepwater Horizon oil spill that happened in 2010. Scientists have recorded that the effects of the spill, which killed tens of thousands of sea turtles and birds and trillions of fish hatchlings when it happened, are still apparent on the seabed, noting that the area around the drill has little life compared to surrounding areas.

Drilling is a major contributor to climate change worldwide. Because petroleum products are made up of mostly carbon and hydrogen, they emit carbon when burned, which mixes with the oxygen in the air to make carbon dioxide. Adding excess carbon dioxide, a heat-trapping gas, to the atmosphere contributes to climate change. The process of extracting petroleum-based products alone creates about 5.1 billion tons of greenhouse emissions, or about 15% of the world’s total emissions.

Drilling for petroleum products also poses risks to human health. Working in petroleum extraction is dangerous, with people dying in explosions and from contact injuries. Some estimates say that more than two workers in oil fields die per month in the U.S. state of Texas. In West Texas where oil production is the main industry, an unexpected source of job-related deaths are road fatalities. Workers who are tired and stressed from working long hours get into car crashes because of the pressure to move the product around the area as quickly as possible. Many of the people working in oil fields in Texas are Latin American and recent immigrants, both traditionally marginalized communities in the United States and disproportionally affected by the danger of working in the industry.

People do not need to be petroleum workers to experience negative health impacts. Pollution from fracking can leach into water or release into the air, and long-term exposure can contribute to health problems in humans. Research has shown that fracking releases toxins that may cause cancer, and other research has shown that older adults have a higher chance of premature death if they live near certain types of oil and gas development sites.

Additionally, access to petroleum can impact human and civil rights, often affecting already marginalized communities the most. Research in the United States has found that historically marginalized groups like Black people, Latin American people and people experiencing poverty are more likely to live near oil and gas wells, exposing them to negative health impacts.

Indigenous people have also needed to fight to protect their ancestral homelands from the environmental harms of drilling. In the Amazon, Indigenous activists like Luene Karipuna of the Karipuna people are advocating to stop the Brazilian national oil company Petrobras from drilling near fishing areas. The company argues that the drilling will not affect Indigenous groups, but Indigenous leaders like Karipuna say their rights are being trampled because Petrobras did not consult them, and Indigenous groups never approved the company’s drilling license.

On a larger scale, demand for oil can lead to restrictive governments and conflicts between countries. Some experts say petrostates, or countries heavily reliant on oil and natural gas production, are often less democratic than countries with more diverse income streams. These experts consider Russia, Iran and Venezuela examples of petrostates with more authoritarian governments. Control of oil production often leads to conflict or war. One example is the U.S. military strikes against Venezuela and removal of former President Nicholas Maduro in 2026, which allowed the United States to gain control of the Venezuelan oil reserves.

Because petroleum is a nonrenewable resource, it is likely that humans will eventually run out of usable oil. Experts say humans will run out of extractable oil in about the 2050s or 2070s. Some refute that number, arguing that developing new technology could allow oil extraction from new places, or that as people switch over to renewable energy, the existing oil supply will last longer. Regardless, oil and other petroleum-based fuels are finite resources.

History of Petroleum Use

Use of petroleum products goes back to the ancient world. Civilizations like the Sumerians and the Babylonians recorded that crude oil was seeping out of the ground. This phenomenon happens because oil reserves can seep up through openings in the earth. Having learned that crude oil and bitumen were waterproof and could glue things together, people from these civilizations used petroleum products in construction as mortar.

Later societies found more uses for petroleum. In the Sichuan Valley of China, people in ancient times burned natural gas deposits to heat brine and produce salt. In North America, Indigenous people, such as the Chumash Nation, used bitumen to seal and waterproof their canoes. Around the 7th century, a Persian alchemist known as Al-Razi discovered how to make kerosene from petroleum, which scientists later developed for use in lamps.

During the Industrial Revolution, demand for petroleum increased dramatically. In 1859, Edwin Drake built the first drilled oil well in the U.S. town of Titusville, Pennsylvania. This well, and others that came later, were able to reach oil that was formerly inaccessible. Previously, people dug oil wells by hand, but this well used new cable technology to drill.

Drilling the seabed followed soon after drilling on land. The first offshore well was built off the end of a pier in the U.S. town of Summerland, California, and started producing oil in 1897. Today, offshore oil and gas rigs are huge structures, almost like small cities, that contain living quarters for hundreds of workers as well as space for equipment and storage. They can drill wells at depths of 3.2 kilometers (2 miles). Once all the oil has been extracted, the wells are meant to be plugged to avoid environmental contamination, then abandoned.

The invention of offshore drilling has left an impact on marine ecosystems. One positive is that ocean wildlife like sponges and corals have populated some abandoned rigs, turning them into reefs that support other aquatic life. Countries like Malaysia have encouraged this practice as a way to revitalize their oceans. However, if oil and gas companies don’t plug their wells adequately or delay plugging for years, the wells release harmful toxins into the water and air. Research also shows that offshore wells can emit much higher levels of methane than abandoned land-based wells.

While oil and other fossil fuels spurred the Industrial Revolution, their use created massive amounts of pollution, marking the start of human-influenced climate change on Earth.

Replacements for Petroleum Products

Due to the environmental and human cost of relying on petroleum products for fuel, scientists are developing less harmful replacements. One of these replacements is bio-oil made from biomass, or organic waste materials. Agricultural waste, forestry waste and waste from urban settings can all be used to produce bio-oil, which can then be used as biofuel.

Biofuels can be combined with petroleum products to give them more power. This is the case with ethanol, a type of alcohol derived from corn that is frequently mixed with gasoline for cars. Another example is biodiesel, which is made from soybean oil and petroleum diesel. A different biofuel called renewable diesel—chemically similar to petroleum diesel but made from plant oils—can be used in vehicles without being blended with petroleum products.

Scientists have also developed a renewable natural gas from biomass. When biomass breaks down and decays, it releases gases. Scientists can harvest and refine these gases to use for generating electricity.

There are also ways to decrease reliance on diesel generators. Implementing solar power, including solar microgrids, could fill the role previously filled by generators in emergencies. Solar microgrids use solar panels to gather energy, so their use would be unaffected by fuel shortages in an emergency. After Hurricane Fiona in 2022, while much of the island was without power, some areas of Puerto Rico had access to microgrids. People on the microgrids avoided having to wait in long lines, hoping to buy fuel to run generators during power outages after the hurricane.

Scientists are also developing bio-replacements for petroleum in asphalt. Traditional asphalt uses bitumen, but bio-asphalt uses plant-based bio-oils instead. In addition to being better for the environment, some research has shown that bio-asphalt might function better than traditional asphalt at high and low temperatures.

In addition to innovation, international cooperation is key for phasing out petroleum and other fossil fuels. In 2023, countries attending the United Nations Climate Change Conference agreed to transition away from fossil fuels and invest in renewable energy to cut emissions by 43% by 2030. Actions like the Fossil Fuel Treaty Initiative bring together stakeholders across multiple countries to advocate for teamwork across the world’s nations and create more legal instruments to hold countries accountable to their climate-related pledges. Many stakeholders across the world are working on this goal, but it will take monumental effort to decrease and eventually end the reliance on petroleum products.