Division of Environment and Natural Resources

DGRADE - Constraints to degradation of biodegradable plastics in terrestrial systems

Active Last updated: 15.03.2021
End: dec 2022
Start: jan 2020

There is an increasing interest in plastics, both as a resource and as a pollutant. Climate change and environmental concerns have boosted the development of biodegradable plastics, spanning from disposable food containers to waste bags and agricultural mulch films. But how fast do these products degrade in Nordic soils and waste streams?

Status Active
Start - end date 01.01.2020 - 31.12.2022
Project manager Claire Coutris
Division Division of Environment and Natural Resources
Department Bioresources and Recycling Technologies
Partners NIBIO, NORSUS, Green Dot Norway, SIMAS IKS, Norsk Landbruksrådgiving, Agri Råd.
Total budget 6480000
Funding source Norwegian Research Council and Handelens Miljøfond (Grant number 303560)

There is an increasing interest in plastics, both as a resource and as a pollutant. Although a lot of emphasis is placed on recycling, the use of recycled plastics is still low in Europe. In this context, climate change and environmental concerns have boosted the development of various types of biodegradable plastics.

The use of biodegradable plastics spans from disposable containers for food/drink, serviceware and wipes, via waste bags for food waste collected for biogas production, to agricultural films used to cover soil during vegetable production. Waste and recycling companies are poorly prepared for such a transition, as is the public, which struggles in keeping a profusion of products and their waste separation apart. In addition, biodegradable plastics may not degrade so quickly and completely that the products disappear in nature, and the label may encourage people think otherwise, enhancing littering.

Plastic types.png
In DGRADE, we are investigating biodegradable polymers, which can be fossil-based or bio-based. A biodegradable polymer is a material designed to undergo a significant change in its chemical structure (broken chemical bonds of the macromolecules), as a result of biological activity and under specific environmental conditions.

Non-degradable bio-based polymers (such as bio-PET, bio-PE, etc.) are outside the scope of this project. The ambiguous term "bioplastics" should be avoided, as the prefix "bio" doesn't indicate whether it stands for biodegradable or bio-based.​​​​

Our three main objectives

  • Firstly, we want to know how fast biodegradable mulch films used in agriculture are degraded in cold climatic regions like Norway. There is public concern that degradation may not occur fast enough, and that macro- and microplastics could accumulate in soils.
  • Secondly, we want to describe the fate of biodegradable plastics, such as compostable waste bags, glasses and cutlery, during composting. It is important to verify that the intended end-of-life treatments are not a source of plastics to the environment.
  • Finally, we want to describe the environmental costs/benefits of biodegradable plastics and provide a life-cycle perspective in both agriculture and waste streams.

Ultimately, the project will help providing the recycling and composting sector with the information needed to make sound decisions on questions regarding these materials, and provide farmers with advice on which type of biodegradable plastic products to use for specific purposes and conditions.

Work packages

WP English.png
Work packages in DGRADE: WP1 Project management (NIBIO), WP2 Degradation in soil (NIBIO, with support from NLR and Agri Råd), WP3 Degradation in waste streams (NIBIO, with support from SIMAS), WP4 Life cycle analysis (NORSUS, with support from GDN and SIMAS), WP5 Dissemination (All)

 

Publications in the project

Abstract

There is an increasing interest in plastics, both as a resource and as a pollutant. In Europe, 25.8 million tons of plastic waste are generated each year, and their effects on climate, economy, human and environmental health are major challenges that society needs to address. Although a lot of emphasis is placed on recycling, the use of recycled plastics is still low in the EU. In this context, climate change and environmental concerns have boosted the development of various types of biodegradable plastics. The use of biodegradable plastics spans from disposable containers for food/drink, serviceware and wipes, via waste bags for organic waste collected for biogas production, to agricultural films used to cover soil during vegetable production. However, biodegradable plastics are rarely degraded so quickly and completely that the products disappear in nature, and the label may encourage people think otherwise, enhancing littering. The aim of our study was to describe the fate of biodegradable materials and products during waste treatment, and more specifically during composting. How long does it take these materials to degrade? What are the conditions for degradation, and ultimately, for obtaining plastic-free compost products? To answer these questions, we selected relevant materials, including compostable serviceware, biodegradable plastic bags used for organic waste collection, and biodegradable agricultural mulch films. Composting experiments were performed both at lab-scale (1.5 L containers with externally applied heating) and larger scale (in 140 L insulated compost tumblers, with natural heating from the composting processes, continuously monitored). The endpoints studied were recovery, mass loss, changes in morphology and composition, and microbial analysis of the various composts. In addition, we assessed the applicability of chemical digestion methods used for sample pretreatment of environmental samples containing conventional plastics to biodegradable plastics. Biodegradable plastics is an umbrella term covering materials with diverse polymeric compositions and thus material properties. This was well demonstrated by our selected materials, which displayed distinct degradation behaviors under similar controlled conditions. The time-course of degradation during composting will be presented for all selected materials, together with the main parameters influencing their degradation rates. In addition, some methodological challenges in this research field will be discussed. Finally, experience from a municipal composting facility receiving biodegradable plastic waste will also be presented to put our laboratory-based results into perspective.

To document

Abstract

Plastics in terrestrial ecosystems negatively affect their functioning by altering physical properties and disturbing soil microorganisms. The same could be true for biodegradable plastics entering nature through incomplete degradation in composting plants, and their subsequent application to soil in fertilizer substrate. So far, no standard analysis protocol for biodegradable plastic degradation exist. This Master's thesis has focused on developing methods for the analysis of biodegradable plastic degradation in a compost matrix and lays a foundation which later research can be built upon. Fenton's reagent and hydrogen peroxide were tested as a sample up-concentrating pre-treatment of an organic matter matrix containing biodegradable microplastics. The degradation of four different biodegradable plastics in nylon bags in a compost tumbler and a compost oven incubation were assessed. Samples for pH and phospholipid fatty acids (PLFA) of different treatments were collected to compare their development and interchangeability. Fenton's reagent was the better suited up-concentrating pre-treatment for samples with some uncertainty remaining. Assessing the biodegradable plastic degradation indicated an incomplete process in home composts and (Norwegian) composting plants. pH values coarsely reflected the composting conditions and suggested interchangeability of most treatments. Analysis of pH together with PLFA results would have been optimal, but could not be accomplished as the COVID-19 epidemic hindered the PLFA analysis. While some uncertainties in the developed methods remain, it can be concluded that a basis for establishing biodegradable plastic degradation analysis was created. Subsequent research should continue their development to assess whether biodegradable plastic remains from composting plants contribute to the accumulation of plastics in terrestrial ecosystems.

Abstract

Stadig flere bønder bytter ut tradisjonell landbruksplast med bionedbrytbar plastfilm som kan freses rett ned i jorda etter bruk. Nå er forskere i gang med å undersøke hvor nedbrytbar den faktisk er under norske forhold.

Abstract

Resirkulering av organisk avfall er et prioritert tema innen sektorene landbruk, klima og avfall, og skal bidra til at organisk materiale og næringsstoffer føres tilbake til jord. Dette kan motvirke en langsiktig trend der moldinnholdet i matjorda gradvis blir lavere, noe som ser ut til å bli et økende problem i forbindelse med klimaendringer og økende behov for mat. Tilbakeføring av næringsstoffene i organisk avfall skal på sin side bidra til å redusere behovet for mineralgjødsel, og dermed minske behovet for energikrevende gjødselproduksjon og uttømming av begrensete ressurser av mineralsk fosfat.