Tools of industrial metabolism

The problem with approaching circular economy as an industrial ecologist

Haas et al. describe circular economy in terms of two material flows: 1) the recirculation of materials within the socioeconomic system, and 2) those biological materials that re-integrate with ecological cycles once outputted from the socioeconomic system. In comparison, other definitions of circular economy place more emphasis on material flows that are “restorative” and “regenerative” i.e. there is a prioritization of how the socioeconomic system can steward the environmental systems upon which it depends. The omission of this stewardship perspective from Haas et al.’s working definition of circular economy affects the objectives and strategies used. For example, there is more of an emphasis on recycling, reuse, and the use of biological materials over non-biological materials instead of a consideration of how the socioeconomic system can be made to operate more like and in cooperation with the environmental system.

Another consequence of Haas et al.’s definition is in choice of methodology:  the authors apply a sociometabolic approach to assess the circularity of global material flows. The authors construct a material flow analysis (MFA) for the EU and for the world, and the way in which the MFA allows them to calculate indicators for circularity that reflect their working definition. For example, the indicator “recycling as percent of materials processed” enables an evaluation of circular economy’s first material flow, and another indicator “biodegradable flows as percentage of materials processed” reflects the second material flow.

The potential strengths of the MFA methodology and the indicators used are that there is 1) consideration of how stock growth diminishes circularity by “trapping” resources, 2) promotion of “eco-design” that contributes to overall reduction of EOL waste that can’t be recycled, and 3) a recognition that the use of fossil fuels for energetic use represents a nearly 100% conversion of this material flow from materials processed to irreversible and irrecoverable emissions. The potential weaknesses of this methodology are that there is 1) no consideration regarding the quality of outputs to the environment which results in a radical overestimate of the compatibility of socioeconomic system biological outputs with ecological cycles, and 2) a misdirected prioritization of recycling and understanding the barriers to recycling.

The authors discuss potential barriers to recycling, which include:

  1. Recovered EOL material is less than total processed material demand;
  2. EOL material has been degraded, and there are (sometimes) significant energy and economic requirements to recover this material; and
  3. The material used in stock remains in the socioeconomic system such that there is a time lag created by stock lifetimes.

Point 2 above is reminiscent of the discussion in the first Ayres’ reading, Haas et al. reflect on how in some instances, recycling is technically feasible but not economically viable, but they then consider an additional environmental cost of recycling which is the consumption of energy. How is the trade-off between energy consumption and “circularizing” material flows considered?

While there is thoughtful discussion concerning recycling, there is no consideration of the “development context.” As an example, the indicator, “Waste rock as share of PM,” is much lower for EU-27 than the world because the EU-27 imports processed metal ore rather than doing more local metal extraction. Is it misleading to exclude these material flows from the EU-27 analysis when the EU-27 is the agent providing the economic motivation for this material flow? It’s as if non-circularity could be outsourced.

In conclusion, the industrial metabolism approach to circular economy seems inadequate, and I’m left asking: what are other frameworks that could be and have been used to assess the circularity of global material flows?


Haas, W., Krausmann, F., Wiedenhofer, D., & Heinz, M. (2015). How circular is the global economy? An assessment of material flows, waste production, and recycling in the European Union and the world in 2005. Journal of Industrial Ecology, 19(5), 765-777.

Ayres, R. U. (1994). Chapter 1 Industrial metabolism: Theory and policy, Chapter 1 in Industrial Metabolism: Restructuring for sustainable development, Ayres, R. U., & Simonis, U.E., ed. Available at