Division of Environment and Natural Resources

DGRADE - Constraints to degradation of biodegradable plastics in terrestrial systems

Active Last updated: 23.11.2020
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 organic 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 is likely to struggle 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.

 

During the project, we first want to determine if biodegradable mulch films used in agriculture are truly and fully degraded in cold climatic regions like Norway, as opposed to accumulation of macro- or microplastics remaining in soil, causing environmental damage and public concern. Secondly, we want to describe the fate of biodegradable and compostable plastics in waste streams, to determine to what extent intended end-of-life treatments (composting and biogas production) leak biodegradable 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 providing farmers with advice on which type of biodegradable plastic products to use for specific purposes and conditions.

Outcomes and impacts

  • Determining if biodegradable plastics are truly and fully degraded when encountering realistic end-of-life conditions in cold climatic regions like Norway, as opposed to accumulation of macro- or microplastics remaining in soil/compost, causing environmental damage and public concern.
  • Determining to what extent intended end-of-life treatments leak biodegradable/compostable plastics to the environment.
  • Describing the environmental costs/benefits of biodegradable plastics and assess whether they represent materials which align with circular economy.
  • Provide the recycling and composting sector with the information needed to make sound decisions on questions regarding biodegradable materials.
  • Provide farmers with advice on which type of biodegradable plastic products to use for specific purposes and conditions and which costs/benefits are associated with the available options, including environmental impact at end-of-life.

Work packages and tasks

WP1. Project management 

WP2. Biodegradation in soil
This WP focuses on the degradation of biodegradable mulch films in soil under Nordic conditions. Task 2.1 Analysis and selection of currently used materials, Task 2.2 Mineralization kinetics in soil free incubations, Task 2.3 Mineralization kinetics in soil slurry incubations, Task 2.4 Limiting factors during incubation in intact soil, Task 2.5 Field incubations in mesh bags, Task 2.6 Macro scale degradation/multiyear accumulation and dispersal in the field.

WP3. Biodegradation in waste streams
This WP focuses on the fate of a range of selected materials and products during waste treatment: composting of compostable plastics, and degradation of biodegradable plastics during biogas production. Task 3.1 Biodegradation in lab-scale composting conditions, Task 3.2 Degradation in full-scale composting facility, Task 3.3 Degradation in lab-scale biogas reactors

WP4. Life cycle assessment
This WP focuses on LCA and environmental footprint analysis of biodegradable plastic materials relevant to the agricultural and waste handling sectors. Task 4.1 Define the value chains to be analysed and the need for data, Task 4.2 Model and analyze of the systems, Task 4.3 Follow ongoing research on development of LCA methodology to include plastic litter

WP5. Dissemination

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.