Circular Metrics for Bio-materials
How do we quantify the circularity of regenerative biological materials in a way that enables their evaluation alongside non-biological materials fairly and comparatively?
The circular bio-economy is a very significant component of the circular economy.
Regeneratively sourced materials also stand to play an ever more prominent role as we start to tackle widespread dispersive uses of persistent synthetic materials - such as those that have led to the current ocean plastics crisis.
Photo by Dustan Woodhouse on Unsplash
The sustainable extraction of natural resources from the environment isn't without its challenges however and so understanding the circularity of biological materials is therefore vital if the industry is to ensure the effective deployment of the circular bio-economy.
In 2019 I led a project with members of the Ellen MacArthur Foundations CE100 group of leading circular economy organisations to incorporate biological material flows into the Material Circularity Indicator (MCI) methodology that we originally published together in 2015, during my time at Granta Design. You can read more about that project in my previous post, here.
Neglecting to incorporate biological material flows into the methodology might be considered by many to be a significant oversight. Biological materials, after all, have many intrinsic advantages from the perspective of the circular economy. Materials like timber, hemp, cotton and kelp typically have great properties and a lower embodied carbon, their growth usually removing CO2 from the atmosphere.
When products made from biological materials reach the end of their lifecycles, the constituents can be readily reincorporated back into natural material flows using well-established biological systems. These natural nutrient cycles have existed for as long as life on earth has. Indeed, the model that the circular economy represents, in which materials are cycled through flows, without waste, but instead with end-of-life materials becoming 'nutrients' for future products has been modelled closely on how biological systems handle materials in nature.
The reality of the initial project, however, was that we had a relatively small budget and a limited time in which to develop the methodology. The team also felt it essential to prioritise the 'abiotic' or human-made materials that most of our customers and partners were using in their products across the aerospace, automotive, medical devices and energy sectors.
The 'Butterfly diagram', often used to describe the separation of biological and non-biological material flows in the circular economy does, however, have both sides and I had looked for the right opportunity to 'circle-back' and complete this missing part of the methodology.
Circular Economy Butterfly diagram, Ellen MacArthur Foundation
The opportunity arose at the CE100 Acceleration workshop in Oakland, California, in 2018. The Ellen MacArthur Foundation enables co-projects between members of the CE100 at these events, and I decided to pitch an update of the methodology to the other members. There was a positive response, and over the following year, I assembled and led an incredible team of circular economy thought leaders to expand on the original work.
The team itself comprised circular economy leaders from DS Smith, DuPont, Eastman, Essity, Gispen, IKEA, Natureworks, Oregon Department of Environmental Quality, Scion Research, StopWaste, TetraPak, UPM Raflatac, and the US Green Building Council. Due to the wide geographical spread of the team, we mostly worked on the project remotely, holding online sessions and offline reviews, eventually every week.
Given that the circular economy model has evolved from natural material flows, you would think that they would be easier to incorporate into the metric than human-made materials. Overall, however, the methodology had to assess natural materials on a like-for-like basis with materials such as metals, synthetic plastics, composites, and ceramics.
We also had to resolve several previously contentious issues:
Conceptual separation.
Many of the drivers for biological materials in the circular economy are either environmental or ecological. The Materials Circularity Indicator (MCI), is not, however, an environmental or ecological metric - as I discussed in my previous post.
The principal argument behind this separation is the objective of being able to understand the trade-offs between making a product or system more circular, and the economic, environmental and social effects that we hope to manifest through the circular economy approach. If we mingle the concept of 'circularity' and the impacts we hope to achieve through a 'circular economy system', the user ceases to be able to identify the trade-offs that exist and can no longer optimise their model for maximum impact.
This conceptual separation is something that we had identified in the original MCI project. After explaining this to the new team, we unanimously agreed on the benefits of this separation. However, we still found that we had to constantly sanity check our thinking to ensure that we were not unnecessarily incorporating factors already embodied, or better suited to other types of indicator.
Crossing the wings of the butterfly diagram.
A perceived complication was the need to handle materials that started life as a biological nutrient but were changed, through chemistry, to behave and resemble synthetic or petrochemical materials.
From the perspective of the butterfly diagram, these materials would start on one side and move to the other, often not behaving exactly like either.
Photo by Ian Parker on Unsplash
For example, some bio-plastics, although sourced from grown materials, subsequently behave like conventional petrochemical polymers, and do not degrade safely in the environment in a manner that aligns with the biological cycles of the circular economy. There are, of course, others that do decompose safely in the natural environment, and still, others that will only safely breakdown in industrial composting.
However, the original Materials Circularity Indicator evaluated the inflow of materials to the product as a separate component to the calculation from the outflow of materials from the product, permitting us to consider inflow and outflow independently, which is a significant advantage to the approach and allowed us to easily overcome this issue.
Regenerative sourcing.
The extraction of biological materials from the environment represents a flow of nutrients from the production area to the area of use. How should the approach promote the continued viability of producing regions and prevent over-extraction of resources? Should all biologically sourced materials be automatically considered circular?
We all agreed that this shouldn't be the case. A core objective of the circular economy for biological materials is regeneration. As an extreme example, if one were to cut down an entire forest to make toilet paper, this would not be circular. The ability of the ecosystem to regenerate would be lost, essential symbiotic relationships would become disrupted or destroyed, and the value of the biological system would be degraded - even if the forest was immediately replanted.
We concluded that to be considered circular as an input, natural materials would need to be grown regeneratively. There is currently no definitive mapping of what regenerative production means from the context of the circular model, and our team didn't set out to resolve this particular question. There are of course a variety of schemes, such as FSC for timber, that might be appropriate. Still, these schemes have typically been screened against traditional sustainability objectives and not explicitly tested against delivering the requirements of a circular bio-economy, and this is perhaps, therefore, a future area of focus. For lack of such a suitable scheme, the definition we chose for regenerative or 'sustained production' as we called it was:
'...extraction that does not reduce the capacity for future production of that material below its present capacity and also does not reduce the natural capital of the associated or dependent indigenous ecosystems.'
Perhaps interestingly, the focus on the regeneration of natural capital and indigenous ecosystems may not preclude the unlimited extraction of non-indigenous or invasive species.
For the methodology then, materials that are traceable to a regeneratively managed source can be counted as being entirely circular as inputs for products. This level of circularity is effectively the same as that for reuse in the methodology, excepting of course any manufacturing or production losses that are not managed in a circular manner.
If a regeneratively sourced material is blended with one that isn't or one that can't be verified, the circularity is reduced, effectively by a rule of mixtures. The ability to blend regenerative and non-regenerative/unknown sources in the calculation is essential as not all supply chains are transparent down to the batch level that would otherwise be needed to reflect a degree of input circularity. In this case, the user may instead use an average industry figure, for example, to represent the level of regenerative production prevalent in the region of origin instead. The driver to enhance traceability and increase regenerative production persists, however, as this may serve to set one product aside as being more circular than others.
The methodology highlights that organisations will need to implement robust systems supporting traceability and transparency to claim regenerative sourcing as part of their circularity approach. After some reflection, although this requirement might be considered potentially cumbersome, greater transparency and traceability will also undoubtedly be in the mindset of any company taking the circular economy seriously.
Systems for managing traceability and providence are already evolving rapidly. We will likely see the more significant application of blockchain-based methods such as those deployed by Bumble Bee Foods and SAP (see video below) to ensure robust traceable links to regenerative production are verifiable.
The need for regeneratively sourced input materials is also significant for several of the end-of-life scenarios, as I’ll discuss next.
Regenerative Cycles
Just as a regenerative origin for a biological material supports material circularity, the destination of the material after each use, or at the ultimate end of life of the product also needs to minimise linear materials extraction, and support the regeneration of natural capital and indigenous ecosystems.
There are however more options to consider:
Reuse, remanufacturing and recycling, were already covered by the original methodology and apply to both biological and non-biological materials alike. Reuse is considered essentially 100% circular, excepting any product losses. Remanufacturing is almost as good as reuse, with a perhaps marginal reduction in circularity to reflect any materials needed to restore the product to service. Recycling efficiency determines the circularity of recycling as an option. Some polymers and alloys have meagre recycling rates, other materials (cardboard, for example) have much higher recycling rates. Recycling efficiency is, of course, both product and region-specific, and using such specific data is encouraged, as it will provide a more realistic assessment.
Domestic or industrial composting only applies to biological materials. In the interests of supporting regenerative flows, the organic material would need to be free from any human-made materials that might reduce the regenerative ability of the composting output (e.g. digestate). This requirement doesn't shut the door entirely to materials that are inert or benign but it would likely exclude many synthetic coatings and toxic preservatives. Circularity can then be claimed if the nutrients in the outputs (digestates, liquids and gases) are made available for subsequent regenerative production. This requirement deliberately shuts the door to landfill and other linear disposal routes for nutrients that would divert value from regenerative biological material flows.
Energy recovery, by incineration or pyrolysis for example, isn't part of the circular economy for human-made materials but is an entirely linear end-of-life option that permanently removes materials from use, destroying residual value and requiring additional linear extraction to replace them. It is perhaps unsurprising then that this was one of the more contentious topics. Biological materials grow using CO2 from the atmosphere, and organic ashes can likewise form a useful source of nutrients for some soils. A natural carbon cycle exists that, some of us argued, should form part of the circular economy for biological materials. Through careful consultation within the team and with the Ellen MacArthur Foundation, we agreed on a set of requirements that would need to be met for energy recovery to be included as a circular option for biological materials, these were:
Other end-of-life options, besides landfill, must have been exhausted.
The material must be from a biological source.
The biological material must be demonstrably from a source of sustained production (i.e. regeneratively produced).
The biological material must be uncontaminated by technical materials - except where these are demonstrably inert and non-toxic.
Energy recovery must be optimised, and the energy usefully employed to displace non-renewable alternatives.
The by-products of the energy recovery must themselves be biologically beneficial and must not be detrimental to the ecosystems to which they are introduced.
(Materials Circularity Indicator Methodology, Ellen MacArthur Foundation, 2019)
If this set of requirements is fulfilled and can be verified, then some circularity can be claimed - based on the efficiency of the energy recovery process and the carbon content of the material (which is typically 45-50%). Circularity only applies to the mass of material fulfilling the requirements, again with a rule of mixture applying to any blend.
The inclusion of this route may be particularly pertinent to some bio-plastics that lack a suitable end of life option. Where bio-plastics can't be recycled or reused, and where the feedstock originates from a regenerative source, energy recovery may be a permissible circular option as an alternative to the linear models of landfill or ending up as litter in the ocean.
Where then does biogas sit in this model? In my opinion, if it is possible to demonstrate that the above criteria have been fulfilled, then energy recovery from biogas can also be considered circular.
A promising future for the circular bio-economy
It has been great to have had the opportunity to plug the gap in the original methodology and to have now a quantitative approach that works for both human-made and grown materials alike. My sincere thanks to the Ellen MacArthur Foundation and to the members of the team that worked on this project for their awesome support and contributions.
To my knowledge, none of the main users of the MCI method has implemented this update yet, but I plan to implement a simple tool over the coming weeks that will allow you to try this approach out - watch this space!