As the Halloween season draws near, the excitement of trick-or-treating and the prospect of a trove of fun-sized chocolate bars take center stage. However, what often goes unnoticed is the staggering number of cocoa pods harvested each year to satisfy our collective sweet tooth. While the cocoa beans and pulp are transformed into chocolate, the husks of these pods are typically discarded. In a significant breakthrough, researchers have now revealed that cocoa pod husks possess the potential to serve as a valuable raw material for flame retardants.
Every year, an estimated 24 million tons of cocoa pod husks are generated as waste. Although these husks have been explored as a source of carbohydrates and sugars, their composition also includes lignin, a robust lipid polymer commonly found in woody plants. Lignin offers a renewable alternative to certain substances traditionally derived from petroleum, such as flame retardants.
While previous efforts to produce lignin have predominantly focused on hardwood trees, some scientists have successfully processed other plant materials that would otherwise be discarded, such as rice husks and pomegranate peels. Inspired by these successes, Nicholas J. Westwood and his team embarked on a mission to assess whether high-quality lignin could be extracted from cocoa pod husks and to explore its potential for creating valuable and practical materials.
The researchers initiated their study by obtaining cocoa husks and grinding them into a fine powder. A thorough rinsing process removed fatty residues, and the powdered husks were subjected to the butanosolv process, a standard method for lignin extraction, involving boiling in a mixture of butanol and acid. Subsequently, they confirmed the high quality and purity of the isolated lignin, with no traces of carbohydrates or other impurities.
In the next phase, the research team conducted a series of three chemical modifications to the pure lignin biopolymer, imparting flame-retardant properties. They integrated 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), a fire suppressant molecule, into the lignin polymer’s structure.
Experimental results revealed that when the modified lignin was subjected to heat, it charred without combustion, indicating its potential as a flame retardant. The researchers acknowledge the importance of conducting human safety tests, which are planned for the next phase of testing. Looking ahead, the team aims to optimize the properties of their cocoa pod husk-based flame-retardant materials, a remarkable step towards sustainability and innovation in material science.