There is nothing worse than opening your tank to discover your diesel fuel is contaminated with “algae“. If this fuel were ever to be used, it could wreak havoc on your fuel filters and consequentially your engine.

In acknowledging this, you may be asking yourself, "how do I get rid of this “algae” and prevent it for good?"

Luckily, we have some answers to those very questions. In this article, we’ll explain what the “algae” really is, where it comes from, common methods to combat it, and best practices to keep it at bay.

Understanding the "Algae" Problem

In order to properly address this fuel contamination issue, we must first understand what it is we are trying to combat and where it is that it comes from.

A Common Misnomer

For decades, it has been a common misconception that the dark sludge forming in your fuel tank is actually “algae”. As a result, many still refer to it as such today. In reality, what you are actually witnessing is an over-proliferation of microbes in the fuel.

How do we know this?

For starters, your fuel tank is far too dark to harbor any known species of algae. These plant organisms need sufficient sunlight to survive.

On the other hand, it is well documented that there is no shortage of microbes dwelling in diesel fuel.

The problem of microbial contamination originates when water present in the diesel separates into a distinct layer below the fuel. This is commonly referred to as "phase separation". At this point in the process, you may begin to notice a dark layer forming in the fuel.

Another term often used to refer to this form of fuel contamination is the “diesel bug”.

The interface between the diesel fuel and the water creates the perfect breeding ground for various bacteria and fungi to thrive. The microbes will live and proliferate in the water while consuming the hydrocarbons from the diesel fuel above.

In time, the accumulation of microbes will form visible biomass (rag layer) between the water and diesel fuel. By-products and dead cells from the growing microbial communities also fall towards the bottom of the tank to create a viscous sludge.

The Effects of Microbial Growth

When churned up, the sludge by-product of microbial contamination can clog any engine filter with ease.

A clogged engine filter, especially one clogged at a time of importance, can cause serious problems.

For example, data centers relying on diesel generators for backup power may experience unexpected downtime due to clogged filters. This can result in costs of hundreds to tens of thousands of dollars a minute while unplanned maintenance is being carried out.

On a smaller scale, clogged filters on many marine vessels such as boats and yachts can often leave their operators stranded on the water.

“The diesel bug may start on a microscopic level, but it is clear it can lead to macroscopic consequences.”

Common Solutions for the "Diesel Bug"

There are a lot of opinions on how to best prevent “algae”/microbial proliferation in the fuel.

Some will push for the use of biocides which use hazardous chemicals to kill the microbes directly.

Others prefer fuel additives designed to prevent phase separation from happening.

At AXI International, we understand that neither of these solutions is perfect, but recognize they embody two valid methodologies for controlling microbial growth in diesel fuel.

You can either kill them directly or prevent the very conditions they need to thrive.

Biocides

Although initially effective, biocides are not the end-all solution to microbial growth and sludge formation.

Placing health, safety, and environmental concerns aside, frequent use of biocides can create resistant microbes that no longer die upon application.

This is due to the fact that it is nearly impossible to completely sterilize diesel fuel. As a result, the surviving microbes, through means of natural selection, will exhibit increasingly resistant traits that eventually render the biocides ineffective.

Best Practices for Microbial Contamination

If microbial growth has progressed to a point that it is noticeable, no treatment already mentioned will effectively remove or break up the sludge already formed in the tank.

Removing Microbial Sludge

In order to remove sludge from the fuel, you will have to employ the use of a mobile fuel polishing service or system.

Mobile fuel polishing systems work by circulating the fuel out of the tank for filtration.

These systems are designed to effectively remove both large and small contaminants like particulates and sludge while also helping to prevent future microbial contamination through the removal of water.

Unfortunately, a single fuel polishing serve will not prevent microbial growth indefinitely. Water will find its way back into the tank through means of refueling and condensation formation. If fuel polishing is your preferred method of prevention, prepare to schedule multiple servicings throughout the year.

Preventing Microbial Growth

In some cases, fuel additives that pull water up into the fuel by means of an emulsifier can be an appropriate response to stifle microbial growth.

The additives work by addressing the problem at its source. Without phase-separated water, microbes cannot over-proliferate in the fuel.

In time, the emulsified water can exit the fuel tank as it is fed into the engine alongside the fuel and vaporized out the exhaust.

Preventative Solutions for Tier-4 Engines

For applications involving Tier-4 compliant engines, water emulsifiers are not a recommended solution as they will only create additional problems. This is because Tier 4 engines have a High-Pressure Common Rail (HPCR) system that feeds the fuel into the combustion chamber at extremely high pressures with very little tolerance for anything other than the fuel itself.

Emulsified water, being much larger than the 2-4 micron injector openings, can cause abrasive wear and eventual failure of the injector tips. Due to this reality, Tier 4 engines require a much more technical solution.

For Tier-4 engines, automated fuel maintenance systems are the best approach to prevent “algae”/microbial growth in diesel fuel. Fuel maintenance systems are permanent installations that work on a programmed schedule to regularly pull fuel from the tank to filter out contaminants.

Unlike fuel polishing systems, fuel maintenance systems are better at maintaining the fuel as opposed to reactively restoring it from a highly contaminated state.

By the same effect of fuel polishing systems, fuel maintenance systems prevent “algae“/microbial growth through the removal of water.

You have probably heard mixed reviews about Ultra Low Sulfur Diesel (ULSD). Some say it is great for the environment while others claim it causes more problems than it solves. If you are looking for an unbiased take on the ins and outs of ultra-low sulfur diesel, you are in the right place.

Below we cover why ultra-low sulfur diesel exists, its benefits and disadvantages vs. traditional diesel, and what you can do to protect your vehicle or equipment from any negative side-effects of ULSD.

Why Does Ultra Low Sulfur Diesel Exist?

In a nutshell, Ultra Low Sulfur Diesel (ULSD) was created in response to a number of regulatory actions aimed at reducing diesel fuel emissions.

Clean Air Act Amendment (1990):

In 1970, Congress passed the Clean Air Act as a means to reduce harmful emissions from automobiles. The Clean Air Act was later amended in 1990, requiring stricter emission reductions of hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matter.

Concurrently, the EPA started imposing sulfur content limits on diesel fuel in an effort to help buses and trucks become compliant with other emission standards coming into effect that year.

The primary motivator for reducing overall emissions was to mitigate the harmful health and environmental effects caused by fossil fuel 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 decrease emissions by enabling the use of advanced emission control technologies for new highway diesel engines. Although effective, these technologies were found to be easily damaged by sulfur, requiring serious sulfur reductions in diesel fuel in order for them to be used. Effective June 2006, the maximum sulfur limit in diesel was slashed from 500 to 15 parts per million (ppm).

This reduction officially marked the switch from low sulfur diesel (500 ppm) to ultra-low sulfur diesel (15 ppm).

Clean Air Off-Road Diesel Rule (2004):

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.

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

The Pros & Cons of Ultra Low Sulfur Diesel

The intended effect of lowering sulfur content in diesel fuel has led to many positives that can be derived from the large reductions in harmful emissions. Unfortunately, to achieve reduced sulfur levels, the fuel must first be processed. This processing has led to some less than desirable side effects due to the changes it makes to the fuel’s chemistry. Whether the benefit of reducing emissions outweighs the negative side effects of ultra-low sulfur diesel is a judgment we will leave for you to make.

The Good: Emission Reductions

Since the 90s, EPA mandates have resulted in a 99.7% reduction of sulfur content in diesel fuel. This reduction is directly responsible for a decrease in sulfur dioxide (SO₂) emissions which, alone, have been a major contributor to serious health and environmental issues.

Health concerns related to sulfur dioxide (SO₂) exposure include respiratory problems and lung damage. Tree, plant, and stone damage, acid rain, and haze are some of the environmental effects of sulfur dioxide (SO₂) emissions. 

Sulfur reduction in diesel fuel has also enabled the use of advanced emission control devices in modern diesel engines. These devices have been able to reduce nitrogen oxide and particulate matter emissions by 90% and 95% respectively. Nitrogen oxide and particulate matter have both been found to contribute to serious health problems such as premature mortality, aggravation of respiratory and cardiovascular disease, aggravation of existing asthma, acute respiratory symptoms, chronic bronchitis, and decreased lung function. In addition to these issues, NOx and particulate matter emissions are suspected to be carcinogenic and contribute to the development of lung cancer.

In 2004, it was estimated that heavy-duty trucks and buses were responsible for about 1/3 of all nitrogen oxide and particulate matter emissions. By reducing emissions from these popular modes of transport, it can become apparently clear that the benefits of ultra-low sulfur diesel lie in the betterment of both public health and the surrounding environment.

The Bad: Changes in Fuel Chemistry

Removing sulfur contents from diesel fuel has been shown to greatly alter the lubricity and overall chemical composition of the fuel. Refineries use severe hydrotreating to remove sulfur. This is a process that also happens to decrease diesel’s natural lubricity, lower energy density (fuel economy), and increases overall production costs.

While hydrotreating does increase the fuel’s cetane level, most of the side effects of hydrotreating are less than desirable. The fuel economy of ultra-low sulfur diesel is estimated to decrease by 1% and, according to the EPA, severe hydrotreating also increases fuel production costs by 5 to 7 cents per gallon. However, these costs may be significantly higher depending on the market, distribution, and other production factors. Lower fuel lubricity is known to contribute to increased engine wear which can also increase maintenance and repair costs for equipment that consume ultra-low sulfur diesel.

The Rusty: Corrosive Effects of ULSD

In 2007, pollution awareness and prevention were on the rise as emission mandates came into full effect. Since then, tank corrosion has hit an all-time high for both gasoline and diesel storage. A recent study suggests this may be symptomatic of fuel tankers participating in switch loading where tanker trucks might transport ethanol-based gasoline one day only to haul ultra-low sulfur diesel the next.

Alone, ultra-low sulfur diesel has a higher affinity to water than traditional diesel. Water is known to be one of the main contributors to tank corrosion while also fostering rapid microbial growth in diesel. It has been shown that mixing ULSD with small amounts of biofuel, such as ethanol, may accelerate tank corrosion. This is due to the microbes in the diesel fuel digesting trace amounts of ethanol, creating high-enough levels of acetic acid to cause significant corrosion of the surrounding tank.

In conclusion, the benefits of ultra-low sulfur diesel are undeniably noble but, as with many significant changes, there will always be trade-offs to consider.

Fortunately, there are a number of products and technologies created to help mitigate the undesirable side effects of ULSD.

Preventing Problems Caused by ULSD

There may be several issues created from the processing of Ultra Low Sulfur Diesel (ULSD) but almost none of them are unable to be addressed through the adoption of new fuel technologies and products.

Addressing Reduced Lubricity & Fuel Economy

As previously mentioned, hydrotreating diesel fuel to remove sulfur does reduce overall lubricity and energy density (fuel economy). To effectively address these problems, one can adopt a fuel additive, possibly addressing both issues with a single bottle. Using a fuel additive does require the individual to regularly dose their fuel supply upon fill-up, but the benefit they receive from doing may exceed that of simply restoring what was lost during the hydrotreating process.

Much like the supplement industry, there is no shortage of fuel additive offerings on the market. Some of these options work quite effectively while others are simply well-marketed “snake oil”. When looking to adopt a fuel additive we strongly encourage you do your own research before putting your hard earn dollars to the test.

AXI International provides a line of broad-spectrum fuel additives, all of which feature a broad set of benefits in addition to increasing fuel lubricity and improving fuel economy. In many cases, it has been shown that our AFC fuel additives have more than paid for themselves with fuel efficiency gains alone. This is mainly achieved with a fuel catalyst which enables a more complete combustion of the fuel, burning more fuel for power in the engine and sending less unburnt fuel out the exhaust. To learn more about our fuel additives click here. If you would like to discuss our additive offerings with one of our experts, fill out the form here.

Preventing Corrosion & Unplanned Downtime

Accelerated tank corrosion is no doubt a serious issue, especially for companies storing large volumes of Ultra Low Sulfur Diesel (ULSD) for backup power applications. ULSD’s high affinity to water and the practice of fuel switching are two factors contributing to this alarming problem. Luckily, there is a solution to this in the form of regular fuel filtration.

Water in diesel fuel has long been an issue leading to tank corrosion and rampant microbial growth (“the diesel bug”).

When microbes proliferate in the fuel, they begin to produce a sludge byproduct that prematurely clogs onboard filters of connected equipment like backup power generators. The clogging of these filters can lead to unplanned maintenance and downtime, a serious issue for mission-critical facilities. In addition to producing sludge, these microbes will break down trace amounts of biofuels, producing acetic acid. This acid, alongside water, contributes to accelerated tank corrosion.

By regularly filtering water out of the fuel, one can prevent accelerated tank corrosion from occurring. Without water, microbial contamination cannot occur, and without microbial contamination, acetic acid cannot be produced from the trace amounts of biofuel often found in ultra-low sulfur diesel.

So one may ask, how is it that water continually finds its way into the fuel and how do I regularly filter water out of the fuel?

To answer the first question, water is always present in fuel to some degree. This presence is usually higher in ultra-low sulfur diesel and biofuels due to their chemistry. Through tank condensation, water is continually reintroduced into the fuel supply as warm days turn into cooler nights. To answer the second question, you generally have two options to filter contaminants, such as water, out of your fuel supply:

Option #1: Periodic Fuel Polishing

One can purchase a mobile fuel polishing cart or hire a service to bring specialized equipment to filter your fuel supply. This service is usually done in a reactive manner as regular fuel testing is carried out to detect if water or microbial contaminants have reached a certain level to justify the servicing.

Although effective, this option is not recommended for mission-critical and backup power applications due to its reactive nature. A lapse in fuel testing or filtration can easily lead to fuel contamination issues outside of tank corrosion such as sludge and particulate accumulation.

Option #2: Automated Fuel Filtration

One can also purchase and install a fuel maintenance system to automatically filter the attached fuel supply on a scheduled basis.

This option requires minimal involvement outside of periodic filter changes on the installed fuel filtration system. Regular fuel filtration is considered a best practice as it ensures the fuel remains free of water and other damaging contaminants, protecting your tank and the attached equipment from the shortcomings of ultra low sulfur diesel and newer biofuels.