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4 feedstock pretreatment adsorbents tested, 1 works

Test results were released in the latest edition of Biodiesel Tech Notes from the University of Idaho's Biodiesel Education Program.
By Ron Kotrba | November 02, 2011

University of Idaho environmental science student Emily Shimada and Jon Van Gerpen, head of the University of Idaho’s Biodiesel Education Program, tested four feedstock pretreatment adsorbent additives for their effectiveness in removing free fatty acids. Test results were released in the latest edition of Biodiesel Tech Notes from the university’s Biodiesel Education Program.

The document notes that commercial food frying operations use adsorbents to remove FFAs from fryer oil, including Magnesol 600R—not to be confused with Magnesol’s D-SOL product used to wash biodiesel on the backend of the process. In addition to Magnesol 600R, the other additives tested on oils with between 1 percent and 5 percent FFAs were X-Tend, a commercial frying oil purifier manufactured by Selecto Scientific in Suwannee, Ga.; Super Bio-Z, a zeolite manufactured by JNS Ranch Co. in Rathdrum, Idaho; and Montmorillonite K-10, a bentonite clay made by Acros Organics in New Jersey.

The four adsorbents were tested on chicken fat with 3.8 FFAs at concentration levels of 0.5 percent, 1 percent, 2 percent and 3 percent, although the 3 percent Magnesol concentration results were dropped because it was unable to be filtered.

The adsorbents were mixed with the chicken fat and stirred for 20 minutes at 60 degrees Celsius, then poured through a celite filter on top of a 0.7 micron glass fiber filter.

Post filtration the material was tested for FFAs, water, calcium, magnesium and phosphorus (the other impurities were tested for to see if the additives removed anything other than FFAs). In addition, the resulting materials were transesterified into biodiesel, water washed and run through the cold soak filtration test to see if those additives used in feedstock pretreatment could help improve those results.

With the goal of reducing FFA concentration from 3.8 percent down to at or near 1 percent, the results showed that the only adsorbent out of the four able to significantly reduce FFAs was Magnesol 600R. At 2 percent additive concentration, the Magnesol 600R reduced FFAs from 3.8 percent to around 1.24 percent.

Van Gerpen and Shimada then tested the Magnesol product with a blend of chicken fat and vegetable oil with an FFA concentration of 1.45 percent, and all concentrations of the 600R product reduced the FFAs to below 1 percent.

The researchers note that none of the products had an effect on cold soak filtration time when tested on water-washed biodiesel produced from the treated feedstock.

Regarding the other impurities tested for, they note that the bentonite clay reduced calcium, magnesium and phosphorus in the feedstock at all concentration levels. X-Tend reduced all of those as well in all concentrations, except for magnesium at the 0.5 percent additive level. However, both Magnesol and Zeolite increased calcium and magnesium levels, and Zeolite also increased phosphorus amounts at the 0.5 percent treatment level.

The researchers conclude by saying, “Magnesol 600R appears to be a low-cost, viable solution for reducing FFA levels of 4 percent and below." When bought in bulk, the cost works out to about 5 cents per gallon per percent FFA reduction.