Every day, millions of people handle thermal paper without a second thought. From receipts and shipping labels to tickets and medical records, these papers rely on heat-sensitive coatings to make text appear. This process involves a reaction between a colorless dye and a “developer,” producing dark text where the paper is warmed.
Despite their small size, thermal papers have a significant environmental footprint. They are produced at scale, handled daily, and often recycled, allowing their chemicals to seep into water and soil. For decades, the most common developers have been bisphenol A (BPA) and its successor, bisphenol S (BPS). Both chemicals can disrupt hormone signaling in living organisms and are frequently detected in the environment and in individuals who handle receipts regularly.
Challenges in Finding Safer Alternatives
Finding safer alternatives to bisphenols is challenging due to the need for thermal paper to remain stable, printable, and cost-effective. In 2022, the global thermal paper market was valued at approximately $4 billion and is projected to grow to about $6 billion by 2030. Regulators and manufacturers have been searching for replacements, but progress has been slow. Any alternative must react at the right temperature, remain stable during storage, mix well with other coating ingredients, and avoid background discoloration. Many proposed bio-based materials fail to meet one or more of these criteria.
A Breakthrough from Wood-Derived Materials
Scientists at EPFL, led by Jeremy Luterbacher and Harm-Anton Klok, have demonstrated that wood-derived materials can fulfill these requirements. In a study published in Science Advances, they report thermal paper coatings using lignin, a major component of wood, combined with a sensitizer derived from plant sugars.
“We have developed thermal paper formulations—commonly found in daily products like cash receipts, package labels, airline tickets, etc.—made from plant-based molecules that have very low or no toxic signatures,” Luterbacher explains. Known for his 2014 method of extracting lignin from plants without destroying it, Luterbacher’s ongoing work with lignin focuses on its potential as a color developer due to its inherent chemical groups.
Innovative Extraction and Sensitization Techniques
Isolated lignin is typically dark and chemically complex, making it unsuitable for printing. To overcome this, the researchers employed a controlled extraction method called “sequential aldehyde-assisted fractionation” to produce light-colored lignin polymers. This process reduces the presence of dark, color-absorbing groups that interfere with printing and ensures the lignin mixes well in the thermal layer—a crucial factor for proper reactivity.
To make the lignin reactive at printing temperatures, the team added a “sensitizer,” a compound that melts when heated, facilitating the interaction between the dye and developer. Instead of conventional petroleum-based sensitizers, they tested diformylxylose, a molecule derived from xylan, a sugar found in plant cell walls. The resulting mixtures were applied as thin coatings on paper and tested using controlled heating and commercial printers.
Safety and Performance Advantages
The lignin-based coatings produced clear printed images when heated, with color density values within the range required for commercial thermal paper. The coatings remained stable when stored near a window for months, and printed logos were readable after a year. While the image contrast was still lower than that of fully optimized commercial paper, the performance matched BPA-based thermal papers.
Safety tests revealed a significant advantage, as the lignin developers exhibited estrogen-like activity two to four orders of magnitude lower than BPA. The sugar-based sensitizer showed no estrogenic or toxicity profile under the tested conditions.
“The study demonstrates that safer thermal paper formulations can be made directly from non-edible biomass using simple processing steps,” the researchers noted. “While more work is needed to optimize print quality and scale-up, the results point toward receipts and labels that do their job without relying on problematic chemicals.”
Looking Ahead
The development of wood-based thermal paper represents a promising step toward safer and more sustainable alternatives in the industry. As the global market for thermal paper continues to grow, the need for environmentally friendly solutions becomes increasingly urgent. The EPFL team’s research offers a viable path forward, though further refinement and scaling will be necessary to fully replace bisphenol-based papers.
Other contributors to this pioneering research include the EPFL Polymers Laboratory and the Swiss Centre for Applied Ecotoxicology. The study, titled “Sustainable Thermal Paper Formulation Using Lignocellulosic Biomass Fractions,” was authored by Tom Nelis, Manon Rolland, Claire L. Bourmaud, Etiënne L.M. Vermeirssen, Ghezae Tekleab, Harm-Anton Klok, and Jeremy S. Luterbacher, and published in Science Advances on January 2, 2026.
