What is new is the fact that the polyolefin—in this case, PE—will be formulated in such a way, that it becomes biodegradable. My first thought was: here we go again. Why spend research funds, time and effort on finding ways for non-degradable plastics to degrade, instead of, for example, setting up collection and thermal or mechanical recycling programs? Why not put those same efforts to work to develop films with the requisite properties that are produced from biodegradable, bio-based plastics?
According to Repsol, the first product to be developed using the new technology will be mulching films designed to degrade in due course into biomass with minute quantities of water and CO2. Microorganisms that naturally occur in the ground are said to activate this process of biodegradation. As a result, it will no longer be necessary to remove the film after the crop has been harvested, the company claims. The new biodegradable polyethylene is therefore intended to complement the existing system of agricultural plastic waste management, “ruling out any negative environmental impact that may occur from residues of conventional films that could ensue from its withdrawal.”
Repsol moreover emphasizes that these new biodegradable mulching films will in all respects retain the required functionalities of conventional polyethylene films, i.e., temperature stabilization, preventing weed germination and preserving soil moisture and nutrients, reducing water and fertilizer usage. Furthermore, the films made with the material have the same mechanical properties as conventional films; consequently they can be processed with standard machinery and laid in the field in the conventional way.
The company provides no further detail on how biodegradability of the material is achieved, beyond stating that it is collaborating with AESL, a company known for its Enzymoplast technology. According to the AESL website, the use of Enzymoplast in a 4-10% concentration will render polyethylene 100% biodegradable and compostable. In addition, AESL is at great pains on its website to point out that its technology is different from so-called oxo-biodegradable products, which as was recently shown in a University of Michigan study, not to actually biodegrade in soil. Unlike oxo-biodegradable plastics, not only do AESL’s enzyme-mediated plastics not contain any heavy metal salts, they are compliant both with EN13432 and ASTM D 6400, says AESL. However, materials incorporating Enzymoplast will not be eligible for OK Compost certification or to bear the Seedling Logo, as these, according to AESL, are reserved for bio-based products only.
The latter, however, is not actually completely true: as a study published in May, 2014 by the Belgian research lab OWS points out, “many fossil based products are certified in line with EN 13432 or the international counterparts and do carry the OK Compost and/or Seedling logo.” Moreover, the composting standard ASTM D6400 is a standardized laboratory protocol, designed to evaluate biodegradation in controlled, industrial composting facilities, not to simulate farm field conditions. The OWS study is extremely skeptical about the biodegradability of enzyme-mediated plastics, and questions the validity of the claims made by AESL. In fact, on a scale of 10, the report rates the reliability of the claims with a 2.
As agriculture is a strategic applications area for Repsol, it is not hard to understand the company’s interest in developing biodegradable solutions aimed at providing more convenience for end users. Whether or not enzyme-mediated technology is the way to go, however, remains to be seen. The product will have to prove itself in practice.
It will have the chance to do so: Repsol says it will soon be adding the biodegradable polyethylene grades for mulch film to its portfolio, together with other solutions for different agricultural applications for agriculture, including covers for greenhouses and small tunnels, silage, thermal blankets, shading nets, raffia, waterproofing of reservoirs, irrigation piping, fruit and vegetable packaging.
We shall see.