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Dairy prepares to turn manure into renewable diesel

Progressive Dairyman Editor Walt Cooley Published on 06 February 2014

Just five years shy of their family dairy’s 100-year anniversary, dairymen brothers Bruce and Brad Scott of San Jacinto, California, faced a most terrible “what if” situation.

State water quality regulators informed the Scotts that within five years they could no longer apply any manure – in liquid or solid form – to their adjacent farm ground.



The officials claimed that their dairy manure, and that from 26 other dairies in the valley just over the mountains from Los Angeles, California, was adding too much salt to the area’s groundwater. Officials gave them three alternatives: move the manure, move the dairy or go out of business.

Hauling manure wasn’t cost-effective. And relocating the dairy would have jeopardized the family’s nearly century-old creamery 50 miles away in Chino, California, where all of the 1,100-cow dairy’s milk is processed into world-renowned frozen yogurt, locally distributed fluid milk and other soft dairy products.

The brothers didn’t want to shutter the two family businesses. So they fought back, although quietly and behind-the-scenes, for themselves and their neighbors.

“I personally promised the regional water quality control board that I would come back in five years with a deliverable solution that I was proud of or I would not be back to renew my permit,” Bruce Scott recalls of the tenuous situation in 2007.

The clock was ticking. The days to their 2012 deadline were short.


Bruce and others first set out to identify the number of livestock units in the valley, the amount of manure they produced and where that manure was being applied. Their goal: Prove that they weren’t the only ones contributing to the groundwater’s salt-loading problem.

“The problem was we didn’t know what the real problem was,” he says. “It had never been identified or even quantified.”

Without knowing the real cause of the saltier groundwater, regulators had settled on stricter regulations. They banned the discharge of manure unless it had “zero total dissolved solids.” That means it must be cleaner than bottled water before applied to a field.

“In most watersheds, you’re dealing with nitrogen or phosphorus impairments, and those are uniquely identifiable,” Bruce says. “Total dissolved solids means mitigating just about the entire chemistry chart.”

Bruce and his allies used money collected from a regional milk assessment to hire a full-time executive director, Pat Bolt, and fund the overhead of their infant organization for the first year. The group would later become a non-profit organization, known as the Western Riverside County Ag Coalition, and seek grant funds to continue studying the valley’s salt-loading issues.

Over the next several years, Bruce and his group would publish several scientific papers about nutrient management and leaching mitigation. They also created an integrated regional dairy management plan.


“We had many pats on the back for our accomplishments,” Bruce recalls.

However, in the back of his mind, Bruce wasn’t convinced it would be enough to get his family’s permit renewed. He knew regulators would want them to have implemented something new, not just prove what he was already doing was working.

In 2010, the Scott Brothers met Steve McCorkle, an engineer with experience in the oil and gas industry. McCorkle had overseen oil and gas exploration activities in some of the most remote places on earth, including desert locations in the Middle East with no access to energy or water for hundreds of miles. Those activities began with using early waste extractions from oil and gas drilling in order to create energy and clean water for those operating the exploration.

“Even to find non-renewable energy, you need to create some renewable energy,” McCorkle says of what he learned from those experiences.

McCorkle wanted to use his expertise to create renewable energy from a non-food source that was considered a waste. His idea was to take this non-food source and convert it into energy with pyrolysis gasification, in other words thermally decompose it in the absence of air, and then liquefy it into renewable diesel.

He says there is a historical precedence for using this method, known as the Fischer-Tropsch process, to make transportation fuels. It is named after the two German scientists who developed it for use in converting coal into diesel to fuel German military vehicles in World War II.

McCorkle’s gasifier is not a digester; in fact, it produces very little methane or carbon dioxide gases because the feedstock is thermally decomposed without the introduction of air or oxygen. But in order for the process to work, the feedstock needs to be high in energy or BTUs. McCorkle believed dairy manure might be just the right feedstock. That’s because its most potentially polluting elements of dairy manure also contained the highest BTU values.

Bruce convinced his family to listen to McCorkle’s ideas. They had already studied all the existing manure processing systems and found they would be ineffective at meeting their valley’s new zero total dissolved solids regulations or would be inadmissible for use due to their valley’s air quality regulations.

When McCorkle told the family about his system, one of which was already in operation as a pilot project to treat dairy slurry at a public utility agency operating in the most strict air quality district, he said it could process their liquid manure to zero total dissolved solids while producing both ashen and liquid fertilizers for their crops and renewable diesel or electricity for on-farm use and off-farm sales. They were all intrigued.

Thinking it was too good to be true, Bruce’s mechanical mind looked for a catch.

When he told others of McCorkle’s system, they too were dubious at first. Purifying wastewater? Making diesel from manure solids? Few impacts on air quality? Yeah, right, they would say. One high-ranking NRCS official in California offered for a team of engineers and experts – 30 of them – to scrutinize the system.

“ ‘Where’s the skunk in the room on this?’ ” Bruce recalls the official asking him. “I told him I hadn’t found it yet and that’s why I kept pursuing it.”

The report came back with a thumbs up from all the reviewers. Later on, the same NRCS official would see to it that EQUIP funding rules were amended to permit the Scott brothers to apply for funding under the federal program to assist with their initial investment costs.

Meanwhile, being sympathetic to the punitive nature of the regulations the Scott brothers faced and the dairy’s other sustainability efforts, which include solar power generation, McCorkle committed to help the Scott brothers. He also wanted to prove that his company, Ag Waste Solutions (AWS), could operate its technology full-time under California’s regulations, arguably the strictest on the planet.

“I knew if we could do it here, we could do it anywhere,” McCorkle says.

But time was almost up.

In 2012, Bruce and his family presented McCorkle’s idea to local regulators as part of their permit renewal application. They hadn’t yet started any construction.

“They told us that we’d studied the problem wonderfully but that we hadn’t implemented anything,” Bruce says of their 2012 permit review.

Environmental groups and regulators were lining up in opposition to their permit renewal. But because McCorkle’s other pilot project just so happened to be operating in the same air quality district, the committee renewed the dairy’s permit for another five years with the stipulation that they incorporate McCorkle’s technology and prove by the next permit application it was mitigating the dairy’s manure nutrient discharge and meeting the valley’s zero total dissolved solids regulation.

“It’s been quite a game to find out how to weave in between these contradictory regulatory mandates,” Bruce says.

With the help of two grants, AWS investment and a 50 percent equity stake in the project themselves, the Scotts are moving forward toward making renewable diesel this year. McCorkle says he hopes the Scott Brothers Dairy project will prove to other farmers and interested investors that the project can run commercially 24-7 in the harsh dairy environment.

“We have combined a waste water treatment facility and a refinery into a modular, portable, farm-scale system that can be permitted anywhere,” McCorkle says.

Watch a video tour of Scott Brothers Dairy.

The dairy’s new multi-stage system first separates the high-BTU manure solids from the dairy’s liquid manure effluent. McCorkle says the first stage should remove 98 percent of the total suspended solids and 40 percent of the dissolved solids, making a good irrigation water for most farms.

The extracted water will then be further purified to remove the other 2 percent of suspended solids and the remaining dissolved solids, making the water potable or suitable for irrigation at Scott Brothers Dairy. The manure solids will then be fed to the pyrolysis gasifier.

That system can consume 1 ton of moist manure per hour and produce about 200 pounds of nutrient-rich ash and liquid fertilizer and anywhere from 15 to 35 gallons of renewable diesel, depending on feedstock characteristics.

(The diesel production at Scott Brothers will be less than this due to the limited size of the diesel production system funded by the grant in the first phase of the project. By 2015, excess gas produced will be used to generate electricity as part of the second phase of the project.)

“Renewable diesel is one of the cleanest burning diesels on earth because it has no sulfur emissions,” McCorkle says of the system’s final product. “This will be the first dairy in the U.S. and possibly the world to be producing it.”

The Scott brothers plan for their new system to be in operation this year.

“I don’t believe that responsible sustainability involves shipping your problem to someone else’s backyard,” Bruce says. “I see a very clear direction to a solution to our unique situation and have pushed back against all the obstacles. I even convinced my family to literally bet the farm on this project as our future direction.” PD

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