Getting It Renewable Ready

by Tom Bryan (Biodiesel Magazine) As renewable diesel producers source an array of low-quality, low-carbon inputs, they’re tapping biodiesel’s seasoned pretreatment technology providers for customized feedstock preparation solutions, both on and offsite.

From used cooking oil (UCO) and distillers corn oil (DCO) to tallow and choice white grease, these low-CI—and traditionally low-cost—byproducts of cooking, food processing and corn ethanol production are not only in ultra-high demand this summer, but on the threshold of a realignment of value and control.

Meanwhile, working behind the scenes to make these inputs feasible for renewable diesel, technology firms with decades of biodiesel pretreatment experience are applying the full weight of their feedstock and process knowledge to the creation of systems that clean up both waste and virgin oils for processing. In North America, Europe, Asia and elsewhere, companies like Desmet Ballestra, Crown Iron Works, and BDI-BioEnergy International are being tapped to design and build custom pretreatment platforms to the onerous specifications of hydrotreatment. These specialized input-cleansing regimens are new iterations of the technology and purification steps used for years in biodiesel production, but now enhanced to reduce additional key contaminants.

Friedrich (Theo Friedrich, technical sales manager for BDI) concurs, explaining that in biodiesel production, various impurities can be left in the feedstock and removed later through distillation of the final product as long as a suitable technology for the biodiesel is being used. “That doesn’t work for renewable diesel,” he says. “The hydrogenation catalysts are sensitive to several impurities, which have to be reduced to low-ppm levels to avoid catalyst poising and, in addition, other impurities like nitrogen can result in unwanted byproducts.”

One of the key differences between renewable diesel and biodiesel feedstock pretreatment is that renewable diesel hydrotreaters can take 20% free fatty acids (FFAs), and sometimes quite more depending on the hydrotreater technology, whereas traditional biodiesel transesterification processes must be fed low-FFA inputs.

Harrington (Patrick Harrington, global technical sales manager for Crown Iron Works) says most suppliers of waste fats, oils and greases are not yet accustomed to the sophisticated product analysis requirements of the renewable diesel industry. “Even a well-developed feedstock market like tallow is not typically going to give you the level of detail you need,” he says. “Certainly prior to this renewable diesel boom, they were only going to give you a spec that included FFA and color—and maybe moisture. But we now need to understand a half dozen other parameters that aren’t included.”

To fill this product characterization void, Harrington says, Crown often requests product samples from suppliers and sends them to outside analytical labs for more complete depictions of the material. READ MORE