An Innovative, Green Cascade Protocol for Grape Stalk Valorization with Process Intensification Technologies

What if grape stalks—the leftover stems from winemaking—could be transformed into valuable green chemicals? A new cascade protocol uses ultrasound and microwaves to turn this waste into a treasure trove of bio-based compounds.

Grape stalks, the often-discarded residue of winemaking, are getting a second life in the lab. Researchers have developed a sustainable, circular process that extracts valuable compounds from this biomass, starting with lignin and moving on to cellulose. The protocol is a model of green chemistry, relying on enabling technologies like ultrasound and microwaves to save energy and reduce environmental impact.

First, ultrasound-assisted extraction (UAE) at 40 kHz and 200 W, combined with natural deep eutectic solvents (NaDESs), breaks down the lignin in grape stalks. This step not only isolates lignin but also produces a polyphenol-rich liquid fraction, highlighting the potential for bioactive compounds. Among the NaDESs tested, a combination of choline chloride and levulinic acid (ChLevA) stood out, achieving over 70% delignification.

After delignification, the cellulose-rich residue is treated with a flash microwave-assisted process, yielding an impressive 85% levulinic acid—a top-value biobased platform chemical. Remarkably, this levulinic acid can be recycled to regenerate ChLevA, enabling another delignification cycle. This cascade approach promises a full valorization of grape stalks, turning waste into a renewable resource for the bio-economy.

Key Points

• Ultrasound + NaDESs achieve >70% delignification of grape stalks.
• Flash microwave process yields 85% levulinic acid from cellulose.
• Cascade protocol enables full valorization via circular recycling.