Natural Gas Vs Diesel: Which Pollutes More?

Natural gas and diesel are two energy sources that are widely used across the world. While natural gas is often marketed as a clean energy source, it is a fossil fuel that contributes to climate change and air and water pollution. On the other hand, diesel engines are known for their high levels of toxic emissions, which have been found to be detrimental to human health and the environment. With both energy sources having a significant impact on the planet, it is important to understand which of the two causes more pollution.

Diesel vs Natural Gas Pollution

Natural gas is a fossil fuel that contributes to climate change

Natural gas is a fossil fuel, composed of ancient plant material deposited in an oxygen-poor environment and cooked over millions of years by heat from the Earth. It is found in geologic formations, such as shale, sandstone, and other types of sedimentary rock. Natural gas deposits are often located by geologists using seismic surveys on land and in the ocean to find the right places to drill wells.

Natural gas is a major contributor to air pollution, water pollution, and climate change. It has been given the misleading moniker of being "natural", which gives the public a false impression of being safe for the environment. The term "natural gas" was popularized in the 19th century when it was vying with electricity to become America's stove fuel of choice.

Natural gas is produced by compressing it to less than 1% of its volume at standard atmospheric pressure. It is then stored in a compressed gaseous state in vehicles, which provides adequate driving range. The two forms of natural gas currently used in vehicles are compressed natural gas (CNG) and liquefied natural gas (LNG). LNG is produced by purifying and super-cooling natural gas to turn it into a liquid, which removes most of the extraneous compounds.

To extract natural gas from rock formations, energy companies use hydraulic fracturing, or fracking, which involves pumping a mixture of water, sand, and chemicals into the rock under high pressure. This breaks up the rock, allowing the gas to flow out of the pores and into wells. While natural gas is a significant contributor to climate change, it is important to note that other fossil fuels, such as diesel, also have a significant impact on the environment and human health.

Natural gas extraction methods can cause earthquakes

Diesel cars emit more nitrogen oxides (NOx) and fine particulate matter like carbonaceous PM and SOAs. Older diesel engine designs produce emission levels that exceed current standards. However, newer engines feature particulate filters that reduce emissions by capturing polluting particles in exhaust gases. Diesel fuel produces more carbon dioxide (CO2) per gallon, but fuel efficiency means it emits less CO2 per mile. Diesel engines can operate for 30 years or more, and millions of older, dirtier engines are still in use.

Emissions from diesel engines contribute to the production of ground-level ozone, which damages crops, trees, and other vegetation. They also produce acid rain, which affects soil, lakes, and streams and enters the human food chain via water, produce, meat, and fish. These emissions also contribute to property damage and reduced visibility.

Gasoline, on the other hand, often includes fuel additives called octane boosters, which create pollutants when burned. Octane boosters usually contain aromatic hydrocarbons, which are toxic to humans and can cause various health problems when inhaled.

Now, to address the question of whether natural gas extraction methods can cause earthquakes, the answer is yes. A comprehensive study by the National Research Council has confirmed that fracking can cause earthquakes. However, the number of earthquakes linked to fracking operations is relatively small compared to those induced by conventional oil and natural gas extraction. The greatest risk of earthquakes due to fracking comes from pumping wastewater from those operations back into deep sandstone formations for permanent disposal, as this can increase subsurface pressure and the likelihood of encountering a fault.

It is worth noting that the lack of standardized data and industry best practices for minimizing earthquake risk in underground injection work has been a concern for federal and state regulatory agencies. While most induced earthquakes are small, some have reached significant magnitudes, such as the M3.6 earthquake in Oklahoma, which was induced by hydraulic fracturing.

Diesel cars produce more carbon dioxide per gallon

Diesel cars have been at the centre of controversy due to the amount of toxic emissions they produce. A 2017 study indicates that diesel cars produce more carbon dioxide (CO2) per gallon than gasoline cars. However, due to their fuel efficiency, diesel cars emit less CO2 per mile. Diesel engines are "lean-burn", meaning they use less fuel and more air to get the same performance as a petrol engine.

While diesel fuel contains slightly more carbon (2.68 kg CO2/litre) than petrol (2.31 kg CO2/litre), diesel cars' overall CO2 emissions tend to be lower. Gasoline cars are the only type that produces carbon monoxide, a toxic pollutant that diesel cars do not emit. Diesel cars also produce less carbonaceous particulate matter pollution than gasoline cars.

However, diesel cars emit more nitrogen oxides (NOx) and fine particulate matter like carbonaceous PM and SOAs. Older diesel engine designs produce emission levels that exceed current standards, but newer engines feature particulate filters that reduce emissions by capturing polluting particles in exhaust gases. These filters tend to clog up when used mainly for urban driving and require regular maintenance.

The promotion of diesel cars as a more environmentally friendly option has been criticised. Some governments are planning to discourage their use or even ban them from urban areas due to the health and environmental risks associated with diesel emissions.

Diesel exhaust is harmful to human health

Furthermore, diesel exhaust particles can act as adjuvants to allergens, increasing the sensitization response and potentially contributing to the allergy pandemic. Epidemiological studies have also demonstrated a link between diesel exhaust exposure and various adverse health outcomes, including mortality, chronic bronchitis, respiratory tract infections, ischaemic heart disease, and stroke.

The impact of diesel exhaust on human health is so significant that the United States Environmental Protection Agency (EPA) has implemented regulations to reduce diesel emissions and improve air quality. The Diesel Emissions Reduction Act (DERA) Program was created to promote diesel emission reductions and address the negative consequences of diesel exhaust on human health, the environment, and the global climate.

While newer diesel engine models have lower emission levels than older ones, it is important to continue implementing strategies to reduce diesel emissions further and mitigate their harmful effects on human health.

Diesel engines produce nitrogen oxides

The health and environmental implications of nitrogen oxide emissions from diesel engines are significant. Nitrogen dioxide (NO2), a component of NOx, is a major pollutant and a contributor to smog formation. It has harmful effects on human health, particularly the respiratory system. Long-term exposure to NO2 has been linked to respiratory and cardiovascular issues, children's respiratory symptoms, and lung function problems. Additionally, NOx emissions contribute to the production of ground-level ozone, which damages crops, trees, and other vegetation. It also leads to the formation of acid rain, impacting soil, water sources, and the human food chain.

To address the issue of NOx emissions from diesel engines, various methods have been developed. Selective Catalytic Reduction (SCR) is commonly used in diesel vehicle exhausts to convert NOx into harmless nitrogen and water. However, due to its expense, it is not widely used in smaller, cheaper vehicles. Selective Non-Catalytic Reduction (SNCR) is another method that involves injecting urea or ammonia into the exhaust to reduce NOx levels without the need for a catalyst. On an industrial scale, exhaust gases can be treated with chemicals such as sodium hydroxide or hydrogen peroxide to remove NOx.

While newer diesel engine models have lower emission levels than older ones, the impact of diesel engines on pollution is still a cause for concern. The longevity of diesel engines, with some operating for 30 years or more, means that older, dirtier engines are still in use. This has led to initiatives such as the Diesel Emissions Reduction Act (DERA) in the US, which provides funding for projects aimed at reducing diesel emissions from existing engines.

In summary, diesel engines produce nitrogen oxides (NOx) through the combustion process, and the high levels of NOx emissions have detrimental effects on human health and the environment. While methods exist to reduce NOx, the continued use of older diesel engines contributes to pollution. Efforts to mitigate these emissions and improve air quality are ongoing.

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