Mass Balance Approach

Quick Overview

The mass balance approach allows bio-based and recycled feedstocks to be tracked through complex chemical supply chains without physical segregation. A certified percentage of renewable input is allocated to specific output products, enabling drop-in bio-based plastics using existing infrastructure.

What is Mass Balance?

The mass balance approach is a chain-of-custody model used to track the flow of sustainable feedstocks through complex production systems where bio-based, recycled, and fossil inputs are physically mixed in the same reactors, crackers, and pipelines.

Rather than physically tracking individual molecules from bio-feedstock to final product, mass balance allocates a percentage of sustainable input to a corresponding percentage of output. If a steam cracker processes 10% bio-naphtha and 90% fossil naphtha, up to 10% of the output (ethylene, propylene) can be sold as “bio-attributed.”

Why It Matters

The mass balance approach solves a critical infrastructure problem: investing in dedicated bio-based production lines for bulk chemicals is economically unfeasible at scale. Instead, existing petrochemical crackers can process bio-naphtha (from residues, tall oil, waste) alongside fossil inputs, with the sustainable portion allocated to premium products.

This enables the production of drop-in bio-based polyolefins (Bio-PE, Bio-PP) chemically identical to their fossil counterparts, without requiring separate production facilities.

Certification

The three major certification schemes:

• ISCC PLUS (International Sustainability and Carbon Certification) — most widely adopted
• RSB (Roundtable on Sustainable Biomaterials) — stricter criteria, preferred by NGOs
• REDcert2 — focused on European biofuel and biogas markets

Criticism

Environmental groups argue mass balance can be misleading, as the product itself is chemically identical to fossil-based plastic — no actual bio-carbon may be present in a given polymer chain. The approach is seen as a transitional solution while dedicated bio-based production scales.

Key Players

BASF, SABIC, Borealis, and others now produce mass-balanced chemicals. The approach is essential for meeting Scope 3 emission reduction targets and EU recycled content mandates.