The Spanish footwear industry research center, INESCOP, is working on the LIFE ByProtVal project to reconvert liquid and solid waste from tanneries into new retanning agents and fertilizers.

According to data published by the European Fat Processors and Renderers Association (EFPRA), European slaughterhouses slaughter around 328 million head of cattle and 6,000 million birds annually. This generates a large amount of low-risk waste called Category 3 ABP.

The Spanish Footwear Industry Research Center INESCOP, within its LIFE ByProtVal project, seeks to give these by-products a new useful life so that they return to the value chain and contribute to the circular economy. The 3.5 million tons of animal protein waste could be used as raw material to generate products for the leather industry in the form of retanning biopolymers.

One of the drawbacks in recovering this waste was the large amount of energy and water required for thermal hydrolysis. To reduce this, Inescop developed an alternative method: enzymatic hydrolysis, which has a lower environmental impact and a higher yield than the thermal process.

During the project, samples of conventionally tanned wet blue were taken and retanned to an industry standard upper leather. The tests demonstrated that the biopolymers obtained had the appropriate characteristics to be used as retanning agents.

When comparing the carbon footprints between the traditional process and the enzymatic treatment, it was confirmed that the latter reduces that footprint by half. On the other hand, the use of a protein retanning agent has better biodegradability than leather tanned with synthetic retanning agents.

Currently, the LIFE ByProtVal project is in a stage of scaling up the production process. In Soria, Spain, a pilot plant has been installed with a recovery capacity of more than 100 tons of animal by-products per year.