By Mike McGlothlin
Although first officially introduced in the 1980s, the term biodiesel didn’t become mainstream fuel jargon until after the turn of the century. At that time, biodiesel made huge inroads thanks to its promise of reducing America’s dependency on foreign oil, as well as being a justifiable way to reduce tailpipe emissions. Most Americans became familiar with it at the pump, where a label told the buyer a mix of biodiesel was present in the ultra low sulfur diesel (ULSD) they were putting in their tank.
But what exactly is biodiesel? Where does it come from, how is it produced, and how does it differ from conventional diesel fuel? Furthermore, outside of homegrown production and lower emissions what are the pros and cons of this renewable fuel source? To better understand biodiesel, it pays to know a thing or two about standard diesel fuel. We’ll start there in this biodiesel vs diesel comparison.
Biodiesel Pros
*Lower tailpipe emissions
*Higher lubricity
*Renewable fuel source
*Biodegradable
*Less volatile
Biodiesel Cons
*Less energy dense
*Freezes more easily
*Susceptible to mold and biological growth
Conventional Diesel Pros
*Readily available
*More affordable
*Higher energy density
*More stable in extreme heat and cold
Conventional Diesel Cons
*Higher tailpipe emissions
*Non-renewable
*Lower lubricity
What Is Diesel?
A formal biodiesel vs diesel comparison can only be conducted by first understanding where conventional diesel fuel comes from. Like gasoline, conventional diesel is a petroleum-based fossil fuel, derived from crude oil. Diesel is made up of paraffinic, napthenic, and aromatic hydrocarbons (note that paraffinic hydrocarbons being the dominant components of petroleum). The diesel fuel that’s used for transportation purposes is known as “distillate fuel” or sometimes “distillate fuel oil.” Many people mistake diesel as a byproduct of gasoline. This isn’t true. Both fuels are produced when crude oil is refined. For every 42-gallon barrel of crude, roughly 11 to 12 gallons of diesel fuel is produced.
What Is Biofuel?
Before delving into the details of biodiesel, it’s important to note that it is a type of biofuel. The biofuel family includes both biodiesel and ethanol (among others), fuels that can be produced from animal and/or oil fats, from beef or sheep tallow, from vegetable oil, and from waste cooking oil. Because of the way these fuel types are made, they are considered “renewable.” Mixtures of ethanol in gasoline (i.e. E85) and biodiesel in standard diesel fuel (example: B20) are common and can be safely run in flexible fuel vehicles (gasoline) or diesel vehicles without the need for engine or fuel system changes.
What Is Biodiesel?
As you’ve learned already, biodiesel can be produced from animal fats, oil fats, tallow, vegetable oil, and even waste cooking oil. Because it can be made using any of these renewable fuel sources, biodiesel brings with it a lower carbon footprint—although, as we’ll establish later, it is far from carbon neutral. And, thanks to lacking both sulfur and benzene (which petroleum-based diesel contains), biodiesel is biodegradable and can be reabsorbed by the environment. But despite being non-toxic and produced in a manner that differs significantly from petroleum diesel, biodiesel shares similar physical properties with conventional diesel—hence its ability to seamlessly blend with it.
Common Forms Of Biodiesel
The average consumer is most familiar with B20 and B5 blends of diesel fuel. The B20 label you see at your local filling station means that the diesel being dispense from the pump may contain as much as a 20-percent blend of biodiesel (the remaining 80-percent being standard, petroleum diesel), but no more than that. B5 blends contain 5-percent or less biodiesel, with the rest being conventional diesel. Virtually every modern, road-going diesel engine can tolerate biodiesel blends up to 20-percent, which explains the widespread use of B20. Whether it’s B5 or B20 in the tank, the performance and emissions of your average, everyday diesel truck, van, or car will be unaffected by these biodiesel blends.
Biodiesel Advantages: Renewable & Safer
Thanks to the vast field acreage in North America, where the ingredients required to produce biodiesel can readily be grown (or raised), biodiesel is a completely renewable fuel source. Unlike petroleum-based diesel, there are far fewer scarcity or international concerns associated with biodiesel. What’s more is that, in being a biodegradable fuel, biodiesel is much less dangerous for the environment in the event of a spill, and it’s also safer for those handling the
cleanup. Another standard safety feature is biodiesel’s higher flash point in relation to petroleum diesel. This means it’s less volatile, which is highly advantageous in the event of an accident.
Biodiesel Advantages (Cont.): Higher Lubricity & Cleaner-Burning
CO2 Icon. Emissions Reduction of Carbon Gas. Black Cloud of CO2 Gas. Decrease Pollution Icon. Carbon Dioxide Emissions. Vector illustration.
In direct comparison to ULSD, biodiesel boasts notably higher lubricity. This is because oxygen is present in the molecules that form the chemical makeup of biodiesel. The major benefit here is that the diesel injection system and the diesel engine as whole will live a longer service life. Then there are the environmental impacts, where biodiesel shines once more. According to the U.S. Environmental Protection Agency (EPA), more than 10-percent less carbon monoxide (CO) and 10-percent lower diesel particulate matter (PM) is produced when burning biodiesel as opposed to standard diesel fuel. And according to the Department of Energy and Agriculture, biodiesel can also reduce carbon dioxide (CO2) emissions by 78-percent as compared to conventional, petroleum-based diesel.
Biodiesel Disadvantage #1: Less Energy Dense
With any alternative fuel source, there is inevitably going to be a trade-off. For biodiesel, its shortcoming is its lower energy density when compared to petroleum-based diesel. This lower energy density can result in reduced fuel economy, lower horsepower and torque output, and it can even effect engine start-up. The negative effects from running light biodiesel blends such as the aforementioned 80/20 diesel to biodiesel (B20) are only marginally noticeable, at best. However, diesel blends with higher concentrations of biodiesel can and usually do hinder a diesel engines’ efficiency, performance, and overall functionality significantly. It’s important to remember that most diesel engines aren’t designed to run on high concentrations of biodiesel.
Biodiesel Disadvantage #2: Lower Stability In Extreme Temperatures
Be it extreme heat or extreme cold, biodiesel is less stable than standard diesel. In freezing conditions, biodiesel’s cold filter plugging point (CFPP)—though it can vary from fuel to fuel—is much lower than conventional diesel and will gel up much sooner. This is one of the primary reasons B20 is the maximum biodiesel blend offered at gas stations. On the opposite end of the spectrum, biodiesel is susceptible to mold and other biological growth, especially when stored. Whether it be frigid cold or excessively hot, it pays to properly treat your biodiesel blend with a reputable fuel additive, as various winter and long-term storage additives exist.
Common Misconception: Biodiesel Is Carbon-Neutral
Biodiesel is often referred to as a carbon-neutral fuel, which is to say that production of the fuel nets no carbon output of CO2 (again, carbon dioxide) into the atmosphere. In reality, that’s far from accurate. The fertilizer used to grow the crops required to produce biodiesel releases CO2, and further CO2 emissions are generated during the oil extraction process. Then, when the fuel is being refined, during drying, and throughout the time it’s being transported, unknown amounts of CO2 are released as well. Of course, it goes without saying that the crops needed for making biodiesel can drain resources (or add strain) to vital food supplies.
Conventional Diesel’s Key Advantages
On energy density, temperature stability, affordability, and availability, fossil-fuel based diesel fuel bests biodiesel in virtually every measurable way. Petroleum-based diesel’s roughly 138,000 BTU rating (vs. approximately 120,000 BTUs for biodiesel) translates into better mpg and peak performance. Its more favorable CFPP (between 10 and 15-degrees F for most winter blends) means it’s better-suited for equipment used in wintry conditions. Its high availability correlates to being able to find conventional diesel at virtually every other gas station in the U.S. (55-percent of all gas stations carry it). And finally, the cost of commercially available, standard diesel is almost always cheaper.
Diesel’s Disadvantages
Lower lubricity, higher emissions, and being a non-renewable fuel highlight the list of drawbacks associated with conventional diesel. When ULSD became the standard fuel in the U.S. (it was phased in between 2006 and 2010), its lower sulfur rating led to reduced lubricity being present in the fuel, which many believe served to decrease the service life of countless LSD (low sulfur diesel) era engines. As for cleanliness, biodiesel’s more eco-friendly hydrocarbon makeup (and its lack of sulfur altogether) make fossil fuel diesel the bigger polluter of the two. And unlike biodiesel, petroleum-based diesel is a non-replenishable, non-renewable fuel source. Once all the crude is gone, it’s gone.
Which Fuel Is Better?
A loaded question, but one that many folks are likely to ask. Depending on your specific needs, or your requirements for a particular piece of equipment, engine, or vehicle, either conventional diesel or biodiesel could be the right choice for you. From a practicality standpoint, petroleum-based diesel is more convenient, easier to get, and cheaper while biodiesel is generally more expensive and harder to find at the present time. For most, the use of B20 or B5 pump diesel has and continues to suffice as a sound all-around option for fuel. With it you get lower tailpipe emissions without paying a noticeable fuel economy (or performance) penalty, a fuel that can remain stable in extreme weather conditions, and diesel that came from both fossil and renewable sources.
