For years, researchers have been searching for alternatives to halogenated flame retardants, which raise significant environmental and health concerns. One promising avenue now comes from an unexpected source: corn steep liquor. Fraunhofer researchers are extracting phytic acid, a naturally occurring, phosphorus-rich compound, from this byproduct of starch production, and turning it into an effective flame retardant for biomaterials.
Phosphorus compounds are prized in flame retardant applications because of how effectively they suppress fire. Yet phosphorus itself is a finite resource, with some estimates suggesting global reserves could run out within the next 50 to 300 years. This scarcity is driving the ScaleAmP project (see below), in which a research team is working to recover phosphorus from corn steep liquor rather than relying on mined sources. The team, comprising researchers from the Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut WKI and the Fraunhofer Institute for Applied Polymer Research IAP, is developing a flame retardant for wood-plastic composites (WPCs) and other biomaterials together with industry partners.
The phosphorus source at the heart of this work is phytic acid, also known as phytate, which occurs in large quantities in plants such as corn, wheat bran, soybeans, and rice.
"Commercial halogenated flame retardants are highly effective, but they are also toxic and environmentally harmful. To help protect the climate and meet regulatory requirements, industry is stepping up its transition to sustainable phosphorus-based flame retardants," says Matthias Bischoff, a research scientist at Fraunhofer WKI. "We are supporting this trend by using the phytic acid in corn steep liquor as an active ingredient in flame retardants and developing a cost-effective process for producing the flame retardant on a technical scale."
From Byproduct to Fire-Suppressing Material
To demonstrate the flame retardant's potential, the research partners are testing it in a wood-plastic composite — a material widely used in construction as well as in the automotive and furniture industries.
Phytic acid's high phosphorus content gives it strong potential as a flame retardant, particularly when used in the form of ammonium phytates. Under heat, the molecule forms an insulating carbon layer that cuts off the fire's oxygen supply. On its own, however, phytic acid is not effective: it requires a nitrogen source to form a synergistic compound with phosphorus, and pure phytic acid also has a very low pH that makes it incompatible with most materials.
Extracting and Purifying Phytic Acid Sustainably
One of the main technical hurdles was developing an efficient and affordable process for purifying phytic acid, given how readily it dissolves in water. Researchers at Fraunhofer IAP addressed this through a series of straightforward processing steps: by separating solids from liquids and adjusting the pH, they were able to isolate phytic acid from the proteins and organic acids that make up most of corn steep liquor. A second challenge was determining which amines pair best with phytic acid to optimize flame retardant performance — a question Bischoff and his team at Fraunhofer WKI explored by testing more than 20 different amines.
Bio-Based Performance That Rivals Conventional Products
The resulting ammonium phytates were compounded into test specimens made from WPC material. To evaluate how well different ammonium phytate formulations and ratios performed, the researchers ran standard flammability assessments, including the UL 94 flammability test and the limiting oxygen index test, comparing the results across formulations. The best-performing formulation matched the flame retardant performance of a commercially available reference product.
To date, the team has produced phytic acid at a scale of one kilogram. The next step is to scale up production to 100 kilograms, alongside efforts to draw on additional feedstocks beyond corn steep liquor — such as rice or wheat — and to refine the purification process further.
"Its potential for industrial-scale use hinges on the combination of a reliable supply, ease of processing, flame retardant performance and price," Bischoff says.
About the ScaleAmP Project
Duration: January 1, 2025 – June 30, 2026
Funded by: German Federal Ministry of Agriculture, Food and Regional Identity (BMLEH)
Project sponsor: Fachagentur Nachwachsende Rohstoffe e. V. (FNR)
Project partners:
- Cargill Deutschland GmbH (providing corn steep liquor)
- Clariant Plastics & Coatings (Deutschland) GmbH (providing reference flame retardants)
- Fraunhofer Institute for Applied Polymer Research IAP (extracting phytates from corn steep liquor)
- Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut WKI (coordinator; synthesizing and testing bio-based flame retardants)
Source: Fraunhofer WKI
