Circular Economy & Materials
By-product synergy
The practice of turning one facility's wastes into another's raw materials through organised networks — the operational core of industrial symbiosis.
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A process, developed and promoted by the US Business Council for Sustainable Development, that brings clusters of facilities together to create closed-loop systems in which one facility's wastes — materials, energy, water or by-products — become another's inputs. Unlike static waste exchanges, BPS is an active, facilitated matching process; unlike eco-industrial parks, it works with existing co-located industry rather than purpose-built sites.
References
BPS definition and closed-loop mechanics; US BCSD network locations; active-process vs waste-exchange and eco-industrial-park distinctions; Frosch & Gallopoulos 1989 lineage.
Kalundborg (Denmark, since 1970s) as the canonical symbiosis example.
Overview
What it means
By-product synergy operationalises industrial ecology — the field named by Frosch and Gallopoulos in 1989 — at facility level: a facilitated process inventories participants' under-valued streams and engineers exchanges (gypsum to wallboard, fly ash to cement, waste heat to district energy, CO₂ to greenhouses). US BCSD ran networks in Chicago, the Gulf Coast, Kansas City and the Pacific Northwest.
The exemplar remains Kalundborg, Denmark, where industrial symbiosis has operated since the 1970s. The concept differs from general "industrial symbiosis" mainly as a branded, methodised implementation of the same principle.
How it is used
Facilitators (industry councils, consultancies, public agencies) run synergy networks; circular-economy programmes and eco-industrial-park standards cite BPS methods; digital platforms now attempt the matching at scale.
Why it matters
By-product synergy demonstrates that much "waste" is a logistics and information problem, not a materials problem — and that solving it cuts disposal costs, virgin inputs and emissions simultaneously.
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