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  • Writer's pictureRon Kotrba

Fabricating a Future for Biodiesel

The SME Dublin crew recently manufactured a second tanker of biodiesel made from brown grease at its new 5 mgy facility owned by Smisson-Mathis Energy and built by Tactical Fabrication. (Photo: Smisson-Mathis Energy LLC)

With prices for cleaner feedstocks through the roof, Tactical Fabrication and Smisson-Mathis Energy have forged an all-inclusive, turnkey model for biodiesel production based on the least desirable and lowest-cost materials. After years of development, they are now ready to roll it out to the world.

One might consider Frankie Mathis, owner of Tactical Fabrication LLC, a soothsayer of sorts. Sure, he is a successful business owner with decades of metal-fabrication experience. More recently, in the past 10 years, Mathis has delved head first into designing, engineering and building biodiesel plants and the processes that make them work. But years ago, he saw what few others could foresee and began developing a business model around that vision. Now, he and his crews at Tactical Fabrication and Smisson-Mathis Energy are ready for the world to take notice.

In 2015, when Mathis began the early feedstock-investigation work that would eventually culminate in SME Dublin LLC—a 5-million-gallon-per-year (mgy) biodiesel facility in Dublin, Georgia, owned by Smisson-Mathis Energy, a joint venture between Tactical Fabrication and The Smisson Group of Macon, Georgia—he did so with two of the dirtiest, least desirable, most problematic and lowest-cost materials in mind: brown grease from restaurant grease traps; and FOG, or fats, oils and greases from sewage and wastewater-treatment plants. Used cooking oil prices might have been high then, but no one could have foreseen the rapid growth in renewable diesel and sustainable aviation fuel (SAF) projects coming years later, and the extreme demand on “cleaner” feedstocks and the upward pricing pressure that comes along with it. Now, with cash bids for soybean oil surpassing 90 cents a pound, inedible tallow at 80 cents and choice white grease at 75 cents—making the feedstock costs alone for a gallon of biobased diesel from these three materials range from $5.60 to nearly $7 a gallon—this groundwork Mathis laid years ago to produce on-spec fuel from materials some outfits still have to pay to get rid of was nothing short of brilliant.

But it’s not just the sophisticated ability to process these low-quality, high-sulfur materials into on-spec methyl esters that makes the SME Dublin showcase plant stand out. Mathis and his teams at Tactical Fabrication and Smisson-Mathis Energy have developed an alpha-omega strategic model to roll out to industry that encompasses feedstock origination, collection, cleanup, plant staffing, processing, and selling. This is the definition of a turnkey operation.

“We want to partner with companies that offer biodiesel plants,” Mathis tells Biobased Diesel™. “We want to provide technology like we have in our SME Dublin plant. We supply the feedstock, the technology, staffing—we can come in and make a whole new ecosystem with harvesting feedstock, turning it into fuel, and actually selling it. We’re a one-stop shop. We’ve done it all. For a plant buyer, it’d be just a matter of handing the keys over to them.”

In April, SME Dublin produced its second tanker of biodiesel from brown grease. “The brown grease came from a local collector in Atlanta,” Mathis says. “We are presently working with other collectors that only land apply their grease so as not to affect the brown-grease market.”


To better understand how Tactical Fabrication and Smisson-Mathis Energy designed, engineered, erected, staffed and operates the SME Dublin facility, it is essential to first review their field experience. When Smisson-Mathis Energy was formed half a decade ago, Trip Smisson brought his entrepreneurial skills and experience to the joint venture, while Mathis contributed all of his biodiesel knowledge to the relationship.

Nearly 10 years ago, Tactical Fabrication began working with the Novozymes enzymatic biodiesel process at Viesel Fuel in Florida. At the time, in 2013, only three companies in the world were using enzymes for biodiesel production. “The first 100 reactions were the challenge,” Mathis says. “No. 100 was celebrated. When we had 1,000 successful reactions, it was just business as usual. We now had solid reactions with waste vegetable oil, and with brown grease and FOG.”

A year later, Tactical Fabrication built a continuous system with Desmet Ballestra, Novozymes and Viesel Fuel. “This system was truly continuous, as one drop of oil produced one drop of fuel,” Mathis says. The 2-liter-per-minute system operated for one year.

In the ensuing years, used cooking oil prices were shooting up and, eventually, the federal $1-per-gallon tax credit went away. “UCO was not an option for biodiesel production,” Mathis says. Starting in 2015, Tactical Fabrication was presented with FOG and brown grease from the local wastewater-treatment plant to see if that oil could be converted into biodiesel.

“We were able to successfully achieve making the FOG and brown grease into biodiesel,” Mathis says. “The biodiesel spec for sulfur was 500 parts per million (ppm). Brown grease biodiesel could be blended. The biodiesel pathway was approved by the EPA. It was 2017 when the spec on sulfur was decreased to 15 ppm. The blending option went away.”

Tactical Fabrication, along with its then-newly formed joint venture Smisson-Mathis Energy, began distilling the sulfur out of biodiesel, hoping to get the level low enough for blending. “We succeeded in getting the sulfur to 50 ppm simply,” he says. “With six months of research, we cracked the mystery and got to 5 ppm of sulfur in the finished fuel, opening the door for pure brown-grease biodiesel.”

In 2018, Tactical Fabrication and Smisson-Mathis Energy started creating pilot units, the biggest one capable of processing 40 liters per minute. Construction on the 5 mgy SME Dublin plant in Georgia began in 2019.

SME Dublin was finished being built last September and its first tanker of biodiesel from brown grease went out in October. Then came a delay.

An aerial shot of the 5 mgy SME Dublin biodiesel plant in Georgia. (Photo: Smisson-Mathis Energy LLC)


“Since Covid, brown grease has changed,” Mathis says. “We were taking in feedstock from brokers, and they had considerable amounts of industrial waste in the grease. With some tankers, nearly 30 percent of the grease would not convert into biodiesel. We were sitting on 250,000 gallons worth of feedstock that we brought in, which had so much loss in it, so much material other than free fatty acids or triglycerides.”

The result of this unfortunate occurrence was the company had to empty all its tanks and hand pick collectors from which it could accept grease. “We had to revamp everything after we started,” Mathis says.

Although he says he’s not quite sure why or how Covid changed the brown-grease market, Mathis says he never experienced this issue prior to the pandemic. But after Covid, any brokers from whom he bought brown grease had varying fractions of this “Covid oil” in it.

Bo Munk, a technical consultant for Tactical Fabrication and SME Dublin, has a theory. “Once Covid hit, these places were excessively cleaning,” he says. This, he poses, would deposit more cleaning product in the brown grease and potentially cause the issue. “Another theory,” Mathis adds, “is it just sat for two years.”

After several months of regrouping, SME Dublin processed its second on-spec load of biodiesel from brown grease this spring.

“Before, we were making fuel with what we could get,” Munk says. “Now, we’re making it with what we want.”

SME Dublin doesn’t go to brokers for its brown grease anymore. “They charge $4 a gallon for brown grease,” Mathis says. “That business model makes money, but not as much as ours, thanks to the brown-grease collectors we work with.”

He says those from whom SME Dublin gets its brown grease do not collect grease to sell. Rather, they collect it for land applications or landfills. “Those are the collectors we are working with, which gets us very near zero cost for the feedstock. For instance, in Dublin, every drop collected was land-applied in Georgia.”

Once the biodiesel plant is steadily running, SME Dublin will get paid to “dispose” of that material. “We still have to dispose of the water and solids, but thankfully the city of Dublin is working with us to develop infrastructure inside their city to help us,” Mathis says.

As far as FOG from wastewater treatment facilities is concerned, Tactical Fabrication has spent almost a decade working to develop a sustainable and environmentally beneficial solution. It began with a pilot project that involved developing the best way to harvest the grease directly from the wastewater-treatment plants. Enter its FOG Harvester.

Using commercially available equipment, the FOG Harvester separates the water, solids and oils on site so the water can remain at the treatment plant, the solids can be used for anaerobic digestion, and the oils are suitable for biodiesel production.

Smisson-Mathis Energy and SME Dublin are working with enough companies in Georgia alone to satisfy the feedstock requirements of its 5 mgy plant. “We’ve done the footwork in Georgia,” Mathis says. “Everything that’s transportable in Georgia to Dublin, we are working. The most important thing is that, through our collection services, we ensure the best-quality feedstock from the worst feedstock possible. What we are trying to avoid, and the reason we’re working with grease-trap collectors directly, is so we don’t get caught up in the firestorm of feedstock prices skyrocketing. We can control all avenues.”

Crew members guide the tanker truck into position. (Photo: Smisson-Mathis Energy LLC)

Process Technology

The 5 mgy enzymatic biodiesel production facility in Dublin utilizes a batch process, “as there will be a learning curve with this new feedstock, and getting consistent feedstock will take some time,” Mathis says.

Munk says in a sort of tongue-in-cheek way that he has been building the relationship with Novozymes over the past 36 years, as his uncle is the one who developed the enzymes used for biodiesel production. “We have a great relationship with Novozymes, it’s not exclusive but we are a preferred engineering partner,” Munk says. “We know how to make their enzymes work with brown grease. It’s extremely important for us to use our experience to tweak the reactor function with brown grease. It’s not rocket science, but once you get it, you have to be able to do it again and again. The enzymes are robust, but you need to understand the enzymatic process. There are good and bad sides. It’s very different than traditional biodiesel processing. Brown grease is very high in free fatty acids (FFA), which is different than working with glycerides.”

With very little glycerin bound up in glycerides, the end result yields very little free glycerin. “Maybe a half a percent, but we’re not looking to harvest that,” Munk says.

The enzymes convert 95 percent of the FFA into methyl esters, so SME Dublin uses Purolite resins to react the remaining 5 percent FFA into biodiesel on the back end of the process. “We do that rather than caustic washing it out and creating a loss,” Mathis says.

The distillation unit is critical to getting the biodiesel made from high-sulfur feedstock such as brown grease down to acceptable, ultra-low levels below 15 ppm. The distillation process was developed completely in-house by Tactical Fabrication.

“It took four different units and six months to work out, but now we can consistently remove sulfur down to 10 ppm,” Mathis says. “It was the development of this distillation system that made this whole approach work.”

SME Dublin is currently selling its distillation bottoms to a company out of Atlanta.

The plant is equipped with the software foundation to eventually make it fully automated, including process monitoring. John Tucker, an automation specialist with Industrial South, is helping to automate the facility and develop an autopilot system for the reactions. Process reactions can be monitored through unique flow meters, so if any adjustments are needed, the PLC can make those while SME Dublin builds its knowledge base.

“Through five or six different sensors and a program we’ve written, we can tell how the fuel is doing,” Tucker says. “In the future, we’ll be able to make a chart of what additional chemicals might be needed in the reactor to rectify any potential problems. Basically, I can be in any country in the world and start and run this plant. It’ll be 100 percent automated. People who are there will monitor it, but the system is totally automated. When we get to that point, you don’t need very many people to operate the plant. We’re trying to take the human element out of all these complicated reactions.”

Vision Attained

Tactical Fabrication and Smisson-Mathis Energy have been on a yearslong journey—and they have reached the vision created years ago to build full-size biodiesel plants using FOG captured in sewer systems and brown grease from restaurant grease traps. “We have expanded along the way, specifically in feedstock procurement, where we not only have an in-depth understanding of the market and technologies, but also a network of companies ready to make trap grease a solution to climate change—nothing more, nothing less,” Mathis says, adding that inquiries about the technology or a plant build should be directed to SME Dublin’s plant manager, Sean Fulghum.

“With Smisson-Mathis Energy, Tactical Fabrication has designed, fabricated, constructed and commissioned the first biodiesel plant,” Mathis reiterates. “As a natural next step, we need to partner with global forces to move this technology out to the world—so trap grease becomes a thing of the past, globally.”

Author: Ron Kotrba

Editor, Biobased Diesel™




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