CIRCU-PECT: cascade valorization of spent pectin-production side streams

Overview

CIRCU-PECT is a cascade valorization process that transforms wet spent biomass from pectin production—citrus peel and apple pomace—into valuable, reusable products instead of a disposal stream. The process mechanically dewaters, screens, and refines these variable wet side streams into separate functional components.

The press liquor is processed through membrane filtration to recover residual pectin, sugars, acids, and mineral salts. The remaining fibrous solid is graded into distinct qualities: long fibers for molded-fiber packaging and paper additives; shorter fibers for biocomposite filler; and fine fractions for biochar. Non-conforming fractions are routed into biochar-assisted anaerobic digestion, which counteracts the well-known inhibitory effect of citrus limonene on methane-producing organisms and increases biogas yield.

All unit operations—pressing, membrane separation, refining, pyrolysis, and digestion—are commercially mature, allowing the cascade to be implemented as a modular addition to existing processing plants with little pretret for the wet biomass. The approach focuses on non-food industrial markets, which simplifies regulatory requirements and removes the need for disposal-only end routes.

Technical specifications

Key technical features:

• Mechanical dewatering, screening, and refining separate wet residue into press liquor and graded fibers
• Membrane filtration recovers residual pectin, sugars, acids, and mineral salts
• Long fibers are suitable for molded-fiber packaging and paper additives; short fibers are suitable for biocomposites
• Fines are converted to biochar for anaerobic digestion co-treatment
• Biochar-assisted digestion mitigates citrus limonene inhibition and boosts methane yields
• Existing equipment types (ollers, membrane filtration, refiners, pyrolysis/digestion) are used, lowering development risk

Validation evidence to date:

• Green extraction already demonstrates 20–28% pectin recovery from citrus/apple residues
• Specialty-paper routes from residual fibers show high economic indicators (NPV above €240,000 and IRR > 100%)
• Biochar co-treatment reduces lag time and increases methane yield in citrus residues

Technology readiness level

The integrated cascade is currently at the proof-of-concept stage; the individual unit operations are commercially available, but their end-to-end integration and optimization for this feedstock have not yet been completed.

Development validation is planned in stages: feedstock characterization and dewatering installation (months 1–4); recovery of residual pectin and sugars through membrane filtration and pilot molded-fiber/paper production (months 4–12); biocomposite filler formulation from fine fibers (months 8–16); biochar production and co-digestion trials (months 12–20); and a full techno-economic, life-cycle, and regulatory review (months 19–24). This roadmap is expected to take the integrated process to TRL 6–7 and readiness for full-scale industrial rollout.