Few people think about what happens to the peel, pulp, and rind left over once fruit becomes orange juice. But that waste stream is industrial in scale. A widely cited 2014 paper, "Limonene: a versatile chemical of the bioeconomy," published in the Royal Society of Chemistry journal Chemical Communications, drew renewed scientific attention to the many industrial applications of d-limonene, the oil responsible for the characteristic smell of citrus peel, and a compound scientists have long known can be extracted from citrus waste. Food-grade d-limonene isolated from citrus waste already reaches 96 percent purity, a level pure enough for commercial use without further processing, notable for a compound still mostly obtained from agricultural waste.
Citrus waste itself is a significant by-product of Florida's juice industry. According to Biomass Magazine, the state's citrus processing produces up to five million tons of citrus waste annually, much of it dried and fed to cattle at reduced cost, or simply discarded.
