Soot, the byproduct of burned organic materials like biomass, carbon and hydrocarbons, can convert solar energy into heat. Researchers have created flat pellets and coatings made from soot from burned wood, pet coke and other hydrocarbons. To utilize the coating the team engineered Solar stoves that can be heated up to 400 degrees Fahrenheit. The cost to produce the stove is $150, but the new coating powering it is only about $1.00 per square meter. The coating could be used in large heaters or boilers to dry large quantities of industrial products. Drying is one of the most energy-intensive and costly industrial processes.
https://uh.edu/news-events/stories/2022-news-articles/april-2022/04272022-solar-stoves.php