Strategies for detecting ecotoxicological effects of biodegradable polymers in agricultural applications

Abstract

Biodegradable is the long awaited and highly accepted property for materials (polymers) used in agricultural applications. Methods for determining biodegradability and material disintegration are established and already in use for routine analysis. Methods for analysing ecotoxic effects caused by biodegradable materials are neither established nor in routine use. In the past, biotests have been developed and optimised solely for investigations of single chemicals. Such tests are applicable even if they are not validated for the detection of undesired ecotoxicological effects deriving from biodegradation of polymers in soil. Since the biodegradation process does have an influence on the physical, chemical and biological status of the soil matrix, both biotests and chemical analysis are required in many cases. Theory, background data from method development and some results are presented.

Analysis of long-term degradation behaviour of polyethylene mulching films with pro-oxidants under real cultivation and soil burial conditions

“…Scott and Gilead 1995, Karlsson et al 1997, Arnaud et al 1994, Corti et al 2012). On the other hand, contradictory results have also been reported in the literature, while biodegradability of such materials in real soil conditions is strongly disputed (Kyrikou and Briassoulis 2007, Feuilloley 2004, Fritz 2003.…”

“…In addition to the biodegradable and compostable agricultural plastics, mulching films of controlled degradation have also been introduced and used in agricultural applications (Kyrikou and Briassoulis 2007;Feuilloley 2004;Fritz 2003;Scott and Gilead 1995;Karlsson et al 1997;Scott et al 1999). The most widely used approach to induce oxodegradation in polyethylene is the use of special additives known as prooxidants (mainly carbonyl groups and metals blended with many ingredients, like cobalt acetylacetonate, nickel or ferrous dithiocarbamate, magnesium stearate, or carboxylate- Kyrikou and Briassoulis 2007).…”

Vegetal fiber‐based biocomposites: Which stakes for food packaging applications?

“…But a downside to their extensive use is often their intrinsic reactivity and thus lower inertia than most conventional petrochemical‐based plastics. For example, to overcome the poor moisture barrier properties of starch materials, commercial water‐resistant starch‐based bioplastics are produced by using fine molecular blends of biodegradable synthetic polyesters (e.g., polycaprolactone (PCL) or polybutyrate adipate terephthalate (PBAT)), which form the continuous phase (and give the water resistance), gelatinized starch (up to 40–60%), and compatibilizers . On the other hand, microbial polyesters such as polyhydroxyalkanoates (PHA), which are produced by bacterial fermentation and constitute a reserve of carbon and energy within the microorganisms, display huge advantages such as their excellent barrier properties and water resistance, but are currently available at a cost that remains high (between 2 and 5 €/kg) .…”

Degradation in soil behavior of artificially aged polyethylene films with pro‐oxidants

“…The use of specialized pro-oxidants as additives in polyethylene films, results in acceleration of the breakdown of polyethylene exposed to UV and/or heat, to very small fragments (these materials are known as fragmentable). Several publications, 3,[11][12][13][14][15][16] question the biodegradability of the oxo-degradable film fragments. 6,7 Pro-oxidant additives, usually transition metals, present in the polyolefin backbone catalyze chain scission producing free radicals.…”

“…[8][9][10] Unfortunately, as described by Narayan, 11 the introduction of some of the oxo-degradable materials in the market is also associated with "a growing number of misleading, deceptive and scientifically unsubstantiated biodegradability claims proliferating in the marketplace". Several publications, 3,[11][12][13][14][15][16] question the biodegradability of the oxo-degradable film fragments. There is no adequate evidence to support the complete consumption of these fragments by the microorganisms that inhabit natural environments within a reasonable time frame.…”