Crocs, what’s actually in your shoes?

Mass balance accounting is a chain-of-custody system used to track the use of different inputs — such as fossil-based and bio-based feedstocks — through a shared production process. It is commonly used in the petrochemical industry, where raw materials are mixed together before being turned into plastics and other materials.

For example, imagine a producer uses 90% fossil fuel inputs and 10% bio-based inputs in one production batch. Physically, the outputs from that batch would each contain roughly the same ratio: around 90% fossil-based and 10% bio-based content. However, mass balance accounting allows companies to reassign that bio-based share ‘on paper’. This means one customer’s product can be credited — and marketed — with a higher percentage of bio-based content than it physically contains, while other products receive less or none.

In Crocs’ case, this means the brand can market its material as containing 25% bio-circular content if that amount has been allocated to its purchase by its supplier,  even if the actual material used in the product contains much lower amounts of bio-circular inputs — or even none at all.

This is misleading because it allows brands to profit from selling seemingly more sustainable products, while the physical composition of their products remains unchanged. The practice of mass balance — specifically free allocation or non-proportional mass balance, which is the form used by Crocs —  also makes it very difficult to verify exactly how much low-carbon content is in a material, how it was sourced and produced, and whether it has actually led to real-world emissions cuts — making its use a new, dangerous and convoluted iteration of greenwashing. 

Learn more about mass balance here. 

Crocs purchases its “bio-circular” material for their flagship foam-based material, Croslite™, from US chemical giant Dow Chemical. Croslite™ is the main material in the Classic Clog. 

Through its ENGAGE™ REN product line, Dow makes “bio-circular” elastomers by mixing bio-based feedstock, such as used cooking oil, with fossil fuel-based feedstock, then uses mass balance to freely allocate the bio-circular attributes across outputs to one specific product — in this case, the elastomers bought by Crocs and used to make their proprietary Croslite™ material that make up their Classic Clogs. 

As companies are pressured to take climate action, the use of free allocation mass balance accounting by consumer brands to make ambitious-sounding climate claims is growing. At the same time, there is growing corporate pressure on global standards bodies like the Greenhouse Gas Protocol (who set the rules for how companies measure and reduce their emissions) to integrate mass balance.

The bottom line is this: this type of mass balance accounting allows low-carbon material claims to be inflated and materials-emissions to go unaccounted for. Emissions that don’t get counted don’t get reduced. 

We cannot afford to allow mass balance to be used unscrutinized. 

There are high-integrity, credible alternatives to free allocation mass balance that trace the physical components of a material instead of just accounting. Committing to lowering their material carbon footprint using physically traceable methods ensures that Crocs’ efforts are truly leading to real-world emissions reductions and an acceleration of low-carbon solutions.