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Ultra Low Sulfur Diesel (ULSD): the Good, the Bad, and the Rusty

Posted July 18, 2018 by Caleb Courville

You have probably heard mixed reviews about ultra low sulfur diesel (ULSD).

Some say it is great for the environment.

Others claim it causes more problems than it solves.

If you are looking for an unbiased take on what exactly is going on, you are in the right place.

Below we will cover why ULSD exists, its benefits and disadvantages vs. traditional diesel, and what you can do to protect your equipment in response to these changes.


Part 1:

ULSD: A Timeline

Clean Air Act Amendment (1990)

Congress passed the Clean Air Act in 1970 as a means to reduce harmful emissions from automobiles.

In 1990, it amended the Clean Air Act to require stricter emission reductions of:

The amendment also included, among other things, stricter tailpipe emission standards and emission testing procedures.

Concurrently, the EPA started imposing sulfur content limits in diesel fuel in an effort to specifically target sulfur oxide emissions.

Highway Diesel Program (2001)

In 2001, the EPA finalized a federally-mandated program called the 2007 Heavy-Duty Highway Diesel Program.

This program was established to further lower emissions from highway diesel engines.

Effective June 2006, the maximum sulfur limit in diesel decreased from 500 to 15 parts per million (ppm).

Chart of sulfur content (ppm) in on-road diesel overtime

This reduction marked the switch from Low Sulfur Diesel to Ultra Low Sulfur Diesel.

Clean Air Off-Road Diesel (2007)

Shortly after the highway diesel program’s inception, the EPA issued the Clean Air Non-Road Diesel – Tier 4 Final Rule.

This rule mandated sulfur reductions for off-road diesel engines, effective 2007.

Chart of sulfur content (ppm) in off-road diesel overtime

As a result, the maximum sulfur limit in off-road diesel fuel initially dropped from 3,000 to 500 ppm in 2007, and then again from 500 to 15 ppm in 2010..


Part 2:

ULSD: The Good, The Bad...

Emission Reductions

Since the 1990s, the EPA has mandated an overall 99.7% reduction in fuel sulfur content.

It has done so in order to cut diesel fuel emissions and pollution.

Sulfur oxides (SOx), specifically SO2are a threat to public health and the environment.

sulfur oxides and the threat to public health

Health concerns related to exposure from SOx include respiratory problems and lung damage.

SOx also causes environmental harm in the form of tree, plant, and stone damage, acid rain, and reduced visibility (haze).

The less sulfur content in fuel, the less polluting SOx emissions that fuel will release.

The Change in Fuel Chemistry

Reducing sulfur content greatly alters the lubricity and overall chemical composition of diesel fuel.

Refineries use severe hydrotreating to remove sulfur from diesel fuel.

Hydrotreating affects diesel fuel in the following ways:

Increases production costs

Fuel economy decreases by an estimate of 1%.

According to the EPA, severe hydrotreating increases fuel production costs by 5 to 7 cents per gallon.

However, these costs may be significantly higher depending on market, distribution, and other production factors.


Part 3:

ULSD: The Rusty

Same Tank, Different Fuels

In 2007, pollution awareness and prevention was on the rise as emission mandates came into full effect.

Since then, fuel tank corrosion damage has hit an all-time high in both gasoline and diesel fuel tanks.

ULSD fuel tankers labeled with ULSD and ethanol describing switch loading

This is because fuel hauling tanker trucks participate in something called switch loading.

For example, a truck could be hauling ethanol-based gasoline one day and ULSD the next.

ULSD causes fuel tanks to rust because of the increased water content and retention

This due to ULSD having a higher affinity to water than traditional diesel.

Water is essential for microbial growth.

However, as the EPA has confirmed, accelerated tank corrosion occurs when ULSD blends with small quantities of biofuel.

Therefore, when ULSD combines with ethanol, or other types of biofuel, even in small quantities, a problematic chain reaction occurs that not only accelerates tank corrosion but can also pose a risk to backup power systems:

ULSD problem flow chart that come from the increased microbial growth and sludge from using ULSD

Part 4:

ULSD: Problem Prevention

Addressing Low Sulfur

To combat problems with ULSD effectively, including decreased lubricity, energy density, and fuel economy, use of broad spectrum fuel additive  is considered best practice.

fuel additive can restore many of the lost properties of diesel while continually reducing emissions.

This is achieved through a fuel catalyst which allows for a more complete combustion of the fuel.

Benefits of using a fuel additive can include:

Preventing Corrosion & Downtime

As previously discussed, tanks containing ULSD have corrosion problems.

If ULSD mixed with biofuel during transportation, those problems will manifest at an accelerated rate.

To combat these issues, along with the formation of sludge, clogged filters, and downtime, you have to look at the chain of events that lead to these outcomes.

In this particular case, everything traces back to microbial growth.

Microbes that proliferate in diesel fuel love areas where water and fuel meet.

ULSD microbial growth from fuel contamination image

If you remove water, you effectively halt microbial growth along with the development of previously mentioned problems.

So how do you remove water?

You have two options:

#1 Hire a mobile fuel polishing company

A mobile fuel polishing company will bring specialized equipment to your location and filter out water, particulate, and sludge from your fuel.

Graphic depicting periodic fuel polishing with a mobile fuel polishing system

Note: Without a permanent installation, like a fuel maintenance system, it is recommended you test your fuel regularly to prevent future contamination due to condensation of new water or introduction of new fuel to the tank.

#2 Invest in a fuel maintenance system

A fuel maintenance system is a permanent installation that regularly maintains the fuel by removing water and other contaminants. These solutions run automatically.

Graphic depicting the installation of an enclosed and compact fuel maintenance system for automated fuel filtration

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