Cascade Valorisation of Lemon-Processing Residues (Part I): Current Trends in Green Extraction Technologies and High-Value Bioactive Recovery

Every year, the citrus industry throws away up to 32 million tonnes of waste—yet hidden in those peels and seeds are goldmines of bioactive compounds. Could lemon waste be the next sustainable treasure trove?

The global citrus industry produces a staggering 15–32 million tonnes of waste annually, and lemon processing alone leaves behind peels, seeds, and pomace that make up 45–55% of the fruit's mass. But these leftovers are far from useless—they are packed with high-value bioactive compounds waiting to be unlocked. This review, the first of a two-part series, dives into green extraction technologies that can turn this waste into wealth. By analyzing 847 scientific papers from 2003 to 2025, the authors map out the uneven composition of lemon fractions and propose a hierarchy of valuable products: from essential oils and pectin to polyphenols, seed oils, citric acid, enzymes, and even nanocrystalline cellulose. Four sustainable methods take center stage: ultrasound, microwave, supercritical CO2, and enzyme-assisted extraction. Compared to conventional techniques, these green methods boost yields by 16–112%, slash processing times by 89–98%, and cut energy use by up to 95%. Yet, the path isn't without hurdles—current research is fragmented, focusing on single products without solid economic assessments or industrial-scale tests. The solution? Integrated cascade biorefineries that use sequential green extractions to maximize value from every lemon scrap, paving the way for a circular economy.

Key Points

• Lemon waste is 45–55% of fruit mass, rich in bioactives.
• Green extraction boosts yields 16–112%, cuts energy 95%.
• Integrated cascade biorefineries turn waste into revenue streams.