Hydrothermal carbonization of pectin side streams into functional biochar

Overview

This solution offers a pathway to valorize pectin-production side streams by converting them into a functional, carbon-rich biochar through hydrothermal carbonization (HTC). The process directly handles wet, high-moisture residues (typically 75–85% moisture), eliminating the energy-intensive drying step required by conventional pyrolysis. HTC at 180–280°C in water produces a carbon-enriched solid with increased fixed carbon and heating value, as well as a nutrient-rich aqueous co-product containing sugars, organic acids, and minerals.

The biochar is intended for use as a soil amendment and as a phosphate/nutrient adsorbent. Pectin-rich chars from comparable fruit residues have shown strong nutrient and phosphate binding—among the highest reported for this class of materials—making this approach particularly attractive for nutrient recovery and environmental applications.

Technical specifications

Process:

• Hydrothermal carbonization in water at 180–280°C
• Typical biochar yields of 50–70% (dry basis)
• Direct processing of wet feedstock with no drying step
• Residence times starting at 15 minutes, optimized to target biochar yield, fixed carbon, and heating value

Characterization:

• Feedstock and biochar analyzed by FTIR, SEM, TGA, BET, XRD, and Raman
• Proximate and ultimate analysis to track carbon enrichment and fuel properties
• Phosphate adsorption testing to evaluate nutrient-binding performance
• Lab-scale soil-amendment testing where feasible

Co-product:

• Aqueous phase assessed as a potential fertilizer input, containing recoverable sugars, organic acids, and minerals

Technology readiness level

The technology is at the bench-scale validation stage. A previous study has validated HTC on similar fruit residues such as apple and grape pomace, demonstrating increased fixed carbon and heating value after treatment. The current program will generate feedstock-specific data for pectin side streams through a 12-month validation plan: feedstock characterization, bench-scale HTC trials, biochar characterization and adsorption testing, and a techno-economic scale-up assessment. HTC equipment and characterization capabilities are already available, supporting rapid optimization and a clear path toward pilot integration.