Neal Williams and Jim O’Neil
- Feb 2
- 3 min read

Reducing Impurities in Renewable Diesel Production

Mineral solutions for feedstock-pretreatment process efficiencies.

Renewable diesel is a key component in decarbonizing the transportation sector and reducing global reliance on fossil fuels. High market demand and environmental policies are pushing biofuel producers to use more waste-based feedstocks. However, lower-quality feedstocks can negatively impact production throughput and performance.

Before heavily contaminated oils can be converted into fuel, they need to be refined, typically using a filtration media for solids removal. Imerys, a global leader in specialty minerals, has developed tailor-made renewable diesel filtration solutions based on an in-depth understanding of the manufacturing process and business constraints of the biofuel industry. The product lines of filterable adsorbents, and diatomaceous earth (DE) and perlite filter aids, help producers utilize a wider range of feedstock—including “dirtier” fats and oils—needed to meet rapidly growing demand as renewable diesel and sustainable aviation fuel become the fuels of the future for road and aviation transportation.

A Varied, Extensive Portfolio

Imerys filter aids have the flexibility to remove contaminants with the widest range of permeability available. Celite, the DE filter-aid product line, is derived from the remains of microscopic fossilized algae. Imerys is the global leader in diatomite production, mining from freshwater and saltwater deposits in California, Washington and Mexico. Harborlite, the perlite filter-aid product line, is produced at numerous expansion plants located across North America. Expanded perlite particles are precisely milled to the desired particle-size distribution to filter a wide array of contaminants with a high solids-holding capacity. Perlite is between 30 percent and 50 percent lighter in density, therefore reducing waste-disposal costs. With more than a century of production experience and technical expertise, the Imerys filtration team can assist plant operators and their engineering support teams to optimize their filtration-system performance.

Cynersorb eliminates poor filtration functionality of current adsorbents by starting with a filter aid and then adding proprietary surface engineering. The DE substrate is used for solid-liquid separation, trapping colloidal contaminants within its micropores. This 3D network is also used as a substrate to hold a high-surface area, reactive silica-gel layer, which adsorbs soluble contaminants. Finally, this silica gel is used to carry chelating chemistry that reacts with the remaining contaminants, transforming them into filterable or adsorbable species.

More liquid can be filtered through Cynersorb, allowing the reduction of current filter aids and increasing production capacity. Internal voids also trap particulate contaminants so fast flow is maintained even with very cloudy rendered fats or used cooking oils (UCO). It is more effective at breaking down soaps, phospholipids, trace metals and polar contaminants than current solutions. Cynersorb works synergistically with bleaching earth, allowing a significant reduction of bleaching-earth loads while reducing oil loss.

Proven Solutions for Common Feedstocks

As biofuel production grows, so does competition for feedstock. Producers are drawn towards lower-quality feedstocks, either due to their more favorable carbon-intensity (CI) values or lack of availability. The increasing use of UCO and waste animal fats as feedstocks pose challenges in terms of higher levels of soaps or phospholipids, glycerol and trace metals that need to be removed as part of the refining process. Imerys has performed extensive internal and external testing and worked with customers to understand the pretreatment requirements for specific feedstock blends, including pilot trials conducted by Mohammad Shahin Alam, head of the fats and oils program at Texas A&M University.

Results of a beef-tallow case study showed that Cynersorb reduced phosphorus to 1.4 parts per million (ppm) and metals to below detectable limits, bringing the feedstock within renewable diesel requirements for hydrotreating. The synergic adsorption of phosphorus by blending bleaching earth with Cynersorb brings production efficiencies. A blend of 0.4 percent bleaching earth and 0.1 percent Cynersorb performed better than either adsorbent individually, with more than 90 percent phosphorus removal. The higher permeability added to the body feed opens the filter cake to improve flow rate in addition to improving contaminant removal.

Improved filtration with Cynersorb (Source: Imerys)

A case study of distillers corn oil (DCO) showed that Cynersorb removed metals content to 5 ppm and phosphorus to below 1 ppm. Free fatty acid levels were not reduced, so there was no yield loss. Again, blending Cynersorb with bleaching earth showed a synergistic removal of phosphorus and metals with improved filtration. Cynersorb enhances the performance of bleaching earth with faster flow rates and higher yields, reducing filter cycles and waste.

Cost Reductions Achieved with Imerys Minerals

Some larger plants could see a six- to seven-figure cost avoidance by using our adsorbent and filter-aid technology to remove impurities, reduce waste disposal, increase cycle lengths and lower powder-dosing rates. We work closely with customers to help identify new solutions to problems that have yet to happen. Imerys’ proven track record and innovation are core to our reputation. If you’d like to discuss how we can help you increase filtration capacity, reduce your filtration costs or improve your product quality further, please reach out.

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