An In-Depth Explanation of Diesel Versus Other Fossil Fuels

The first things that spring to mind for most people when they think of diesel are semi-tractor trailers and heavy equipment. Most people associate diesel fuel with big, powerful engines that have a deep rumble and can do extraordinary things in relation to ordinary passenger cars and pickups. What isn’t as well known about diesel is that diesel also powers ships and generators and the majority of cars and light trucks in Europe. 

Even less well known about diesel is that diesel fuel is the ultimate fossil fuel. 

Most importantly, diesel fuel is cleaner than its fossil fuel counterparts like gasoline, natural gas (methane) and coal. To argue any fossil fuel is “clean” or a “clean” alternative is disingenuous, if not dangerously close to completely dishonest. Fossil fuels produce pollutants and greenhouse gases, all of them. 

On the other hand, fossil fuels are the single most important resource on the planet save land, air, and water. There is no single resource on Earth people use more universally than fossil fuels. Fossil fuels are the reason we have electricity. Fossil fuels power our vehicles. Fossil fuels heat our homes. Fossil fuels are the key ingredient to materials we cannot imagine living without like plastic, fiberglass and a huge number of polymers.  

As Innovate us explains, 

“The technological advances in the 20th century made possible the extraction of fossil fuels from the earth commercially viable. All our modern transportation and industry development process have been made possible because of the discovery and extraction of fossil fuels. More than three-quarters of the world’s energy consumption comes from fossil fuels.”

And of all the fossil fuels, diesel is the most important related to transportation. Diesel produces the most energy of transportation-related fuels, is the most stable, and the most readily available. Most importantly, diesel fuel produces fewer emissions than other transportation-related fossil fuels.

What is diesel fuel is a question most easily answered by comparing it to other fossil fuels. 

What are Fossil Fuels?

The value of a fossil fuel —  whether the fossil fuel is a liquid, solid, or a gas — is in its hydrocarbons. The combustible components of every fossil fuel are hydrocarbons. Simply, fossil fuels are hydrocarbons. Everything else in a fossil fuel — sulfur, for example — is a contaminant. Hydrocarbons have two components. As the name implies, hydrocarbons are molecular bonds between carbon and hydrogen atoms. The bond characteristics of hydrocarbon molecules and hydrocarbon chains determine fossil fuel type. 

“Hydrocarbon molecules are very common in space. Many of these molecules are small, like methane, but others are very big, involving hundreds of atoms. One of the interesting things about carbon is that it can easily make itself into long chains of carbon atoms. So it’s easy to build big molecules using carbon as a building block,” according to Quatr.us. 

Carbon’s ability to create big molecules and long chains is the reason different fossil fuels exist.

Types of Fossil Fuels

Fossil fuels come in three types: gas, solid, and liquid. The state of a fossil fuel is a product of its fuel density. Fuel density is a result of the bond characteristics, how carbon-to-hydrogen bonds fit together with respect to the number of each. The more carbon molecules in a hydrocarbon, the greater the fuel density. 

The greater the carbon-to-hydrogen ratio, the more energy a hydrocarbon produces. 

On the flip side of that coin, the greater the carbon-to-hydrogen ratio, the more carbon dioxide combustion of that particular fossil fuel produces. In other words, the more carbon in a hydrocarbon, the more pollution combustion of that hydrocarbon creates.

However, just because a fossil fuel produces less carbon dioxide during combustion does not necessarily mean that the fossil fuel is cleaner. Likewise, a fossil fuel that produces more carbon dioxide during combustion does not necessarily pollute more.

The reason being, large molecule hydrocarbons produce more energy than smaller chain hydrocarbons. That means less fuel is required to do the same amount of work. 

The Energy Density of Diesel Fuel

The energy density of diesel is one of its most valuable characteristics. There are very few fossil fuels with a higher energy density than diesel fuel. Those that have a higher energy density are either rare — meaning they are expensive — or the fuel density is so high that the fossil fuel has limited utility. 

What is Fuel Density

Even though determining the fuel density of a fossil fuel requires complex instruments and exotic formulas, the basic concept of fuel is extremely simple. Fuel density is the amount of energy a fossil fuel contains per unit of volume. With respect to diesel, fuel density is expressed as megajoules per gallon or liter. 

As Axiom.net explains, “Fuel density is the density of the fuel, commonly expressed in kilograms per cubic meter. The greater the fuel density, the greater the mass of fuel that can be stored in a given tank and the greater the mass of fuel that can be pumped for a given pump.

For example, natural gas has an incredibly low fuel density in relation to other fossil fuels. It is a cheap, impotent fossil fuel with a tremendously low energy density of 0.747 kilograms per cubic meter. That means huge volumes of methane “natural” gas are required to produce the same sum of energy as methane’s fossil fuel counterparts. 

Diesel, on the other hand, has an energy density of 836 kilograms per cubic meter. 

Comparing Fuel Density of Diesel with Gasoline, Natural Gas, and Coal Fuel Densities

Again, there are only a few fossil fuels with a higher fuel density than diesel. Fuel oil — aka, “bunker fuel” — is one example. However, the fuel density of fuel oil is so great that combusting fuel oil is extremely difficult. Fuel oil engines do not exist because it simply takes too much pressure to produce compression combustion. Kerosene — the primary component in jet fuel — also has a higher fuel density. But, there is a relatively small amount of kerosene in each barrel of crude oil which makes kerosene expensive. 

With the exception of bunker fuel and exotic fossil fuels, diesel has a higher energy density than almost all other fossil fuels. With the exception of anthracite coal, the world’s most valuable; diesel has a higher fuel density than every other type of coal. There is not a gas-state fossil fuel with a higher fuel density than diesel. Of the liquid fossil fuels, again, only bunker fuel has a higher energy density. 

What Does Energy Density Mean with Respect to the Practical Use of a Fossil Fuel?

One consequence of fuel density is fuel economy. The greater the fuel density of a fuel, the better “gas” mileage a vehicle will have. Comparing the fuel efficiency of a diesel powered vehicle with a gasoline-powered vehicle of comparable size illustrates the significant difference between the fuel density of diesel and other fossil fuels. 

The fuel density of conventional diesel is 836 kilograms per meter cubed. The fuel density of conventional gasoline is 744 kg/m3.  While the difference in density is only 11 percent, the difference in fuel economy is much greater. 

A diesel engine gets between 25 and 35 percent better fuel economy than a gasoline engine of comparable size.  According to the U.S. Department of Energy:

“Diesel engines are more fuel-efficient and have more low-end torque than similar-sized gasoline engines, and diesel fuel contains roughly 10% to 15% more energy than gasoline. So, diesel vehicles can often go about 20% to 35% farther on a gallon of fuel than their gasoline counterparts. Plus, today’s diesel vehicles are much improved over diesel of the past.”

To get a rough idea of just how significant 30 percent is, a gasoline-powered vehicle that gets 35 miles per gallon gets 15 miles to a gallon less than a comparable diesel-powered vehicle. The diesel-powered vehicle will get 50 miles per gallon. 

The same can be said for other types of fossil fuels. The fact that they have considerably lower fuel densities than diesel means that significantly more of each fuel is necessary to produce the same amount. For example, the energy content of natural gas that is 95 percent methane is a minuscule 0.747 kilograms of per cubic meter. That is more than a thousand times less than that of even gasoline. In other words, massive amounts of natural gas are necessary to produce the same amount of fuel in a gallon of diesel.

Coal is much closer to diesel with respect to fuel density, though it is not equal. And, coal has issues that other fossil fuels do not. It is easily the dirtiest fossil fuel with respect to combustion emissions. 

Life Cycle Emissions of Diesel

Emissions are as much a part of the answer to what is diesel question as hydrocarbons and fuel density. The emissions from diesel fuel are much, much less than those from gasoline, natural gas, and coal. But, it is not always easy to see that diesel is the most environmentally friendly fossil fuel. The reason it is not common knowledge that diesel produces fewer emissions and pollutes less than other fossil fuels is that, often, only combustion emissions are cited by those claiming other fuels are cleaner.

It is true that diesel produces more combustion emissions on a volume scale — gallons, liters, cubic meters, etc. — than gasoline and natural gas. But, using combustion emissions per gallon — or any other volume measurement for that matter — is of little to no value. Not only is using combustion emissions per unit of volume of no value, it is misleading to the point of being wholesale dishonest.

According to the U.S. Department of Energy, diesel fuel produces 22.38 pounds of CO2 per gallon. Gasoline only produces 19.64 pounds of carbon dioxide per gallon. By taking the numbers at face value, it appears that gasoline produces fewer emissions than diesel. But again, gasoline gets 30 percent less miles per gallon. 

So, while diesel produces 12 percent more carbon dioxide per gallon, it actually produces less carbon dioxide over an equal amount of distance, 21 percent less emissions to be exact. That is to say, while diesel produces more emissions per gallon, since 30 percent less is required to travel the same distance, the amount of emission produced on a volume scale is irrelevant. 

Far more relevant to the clean-vs-dirty-fuels comparison than emissions per gallon or liter is the amount of emissions produced per mile or per hour of operation. 

Increasing Fuel Efficiency and Reducing Emissions of Diesel with Technology

One of the most valuable traits of diesel fuel, high energy density, is also its biggest drawback. 

The denser a fuel, the more difficult it is to oxygenate the hydrocarbon molecules in that fuel in order to generate combustion. Large molecule hydrocarbons tend to bind together in clusters as a result of the positive and negative charges they carry. Hydrocarbon clusters do not easily bond with oxygen and the result is an incomplete burn.

However, technologies exist that can make diesel fuel more uniform by breaking up the clusters that occur naturally. The Rentar Fuel Catalyst, for example, neutralizes the charge that binds hydrocarbon molecules together in clusters. The result is a homogeneous diesel fuel. When diesel fuel is homogeneous, the hydrocarbon molecules oxygenated and oxygenated hydrocarbon molecules combust more completely. 

In other words, even though diesel is already arguably the most productive fossil fuel, with the use of combustion increasing technologies, diesel produces even more energy. And equally important, a more complete combustion reduces emissions. 

The Rentar Fuel Catalyst increases fuel efficiency by between 3 and 8 percent on over the road vehicles. Mounted on off-road heavy equipment, the Rentar can increase fuel economy by up to 12 percent. For generators, the increase in fuel economy is often over 12 percent and on furnaces and boilers, fuel efficiency can reach increase rates of 30 percent. 

Equally if not more importantly, the Rentar Fuel Catalyst reduces black smoke by up to 44 percent. The Rentar reduces greenhouse gases by up to  19.2 percent and cancer-causing volatile organics by anywhere from 16.7 percent to 58.7 percent, depending on the volatile organic type. The Rentar reduces elemental and organic carbons by up to  35 percent.

The answer to the question what is diesel fuel is simple. Diesel fuel is the single most valuable fuel type of the single most valuable energy resource — fossil fuels — we have. 

With the Rentar Fuel Catalyst, diesel becomes even more valuable.