BIODEGRADABLE PLASTICS USE IN AGRICULTURE, PROS AND CONS

2018 edition

Hadaly Serrano

Time periods of human history are named by the material or technology that most influences society development.  As supported by many researchers [1], it may now be considered that we are immersed in the `Plastic Age´. The continuous progress of the plastics’ multiple properties and applications has revolutionized all human fields. Nevertheless, their greatly appreciated high stability has led to a concomitant growing environmental concern with regard to their waste disposal [2].

In agriculture, the utilization of plastics for mulching is one of the most worldwide spread techniques. It consists on covering the soil surface with rolls of plastic film, leaving space to grow only the crop plants. Used for the last 50 years, it increases productivity, earliness, fruit quality, water-use efficiency and weed control. Once the crop ends, the film is to be removed. However, it is difficult to collect the mulch from the soil. Thus, due to the high stability of the mulch plastics, fragments may accumulate in the soils for decades, season after season. Even when the film is retired, it is usually not recycled but burnt or buried.

Biodegradable plastic films have arisen as an alternative to conventional polyethylene mulches, as they can be degraded in soil. Their base polymers are readily metabolized by soil microorganisms, thus biodegraded when the crop ends. However, to reach functional properties for mulching, other compounds (additives, plasticizers, dyes, etc.) are included in the mulch composition. During biodegradation, these compounds are also released to the soil, with uncertain fate. At present, the use of biodegradable mulches is growing, but studies about the consequences of the biodegradable plastic mulches long-term usage are yet scarce. In order not to compromise the future of our agroecosystems, there is an urgent need for the evaluation of the environmental impact of these new materials.

Our group studies the potential impact and ecotoxicity of biodegradable plastic mulching films. The current aim is to assess whether the accumulation of chemicals released from the biodegradable plastics can led to environmental toxicity. Special emphasis is on their effects on cultivated plants; for that, we have proposed an in vitro culture ecotoxicity test [3]. This technique is now revealing that chemicals released from some biodegradable mulches can alter development of cultivated plants. As the effects depend on the mulch composition, this information may help to choose the mulches with lower environmental impact.

Group members: Hadaly Serrano, Francisco Arnau, Lluís Martín- Closas, Ana Mª Pelacho

University of Lleida. Dpt. of Horticulture, Botany and Gardening

  1. Lewis, D. (2016) https://www.smithsonianmag.com/smart-news/are-we-living-plastic-age-180957817
  2. Kershaw, PJ. (2015) UNEP 1–38
  3. Martin-Closas, L. et al. (2014)Polym.Degrad.Stab. 108, 250–256