Plastics in the environment – can a plastic emissions budget help?
In order to create a political decision-making basis for dealing with plastic emissions, researchers from Fraunhofer UMSICHT and Ruhr University Bochum have proposed a plastic emissions budget. The associated project has now been completed. During the project, they answered the following questions: What quantities of plastic are currently being released into the environment and what quantities have already accumulated? What amount of plastic is barely acceptable in the environment? How long does it take for plastics to degrade in real environmental compartments and are the risks posed by different plastics adequately represented? The answers will be used to calculate a per capita emissions budget.
In the area of greenhouse gas emissions, a budget approach was already presented in 2009 by the Scientific Advisory Council on Global Environmental Issues. The annual emissions budget was calculated as 1 ton of carbon dioxide per capita per year based on the 2° guideline. While actual emissions were 9,2 tons of carbon dioxide per capita per year in 2018, they dropped to 7,7 tons per capita per year in Corona Year 2020 (EU 27: 5.9 tons per capita and year). The comparison of emissions budget and actual emissions makes the dimension of the challenge transparent and manageable. In the project Plastikbudget, which was funded by the German Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung - BMBF), the participating researchers from Fraunhofer UMSICHT and Ruhr-Universität Bochum recently proposed to follow a similar approach for plastic emissions.
Six percent of global petroleum consumption goes into the plastics industry - and the trend is rising. While the plastics industry is an important economic factor in many countries, more and more plastic waste is ending up in soils and oceans in the form of plastic litter, microplastics or soluble polymers. The problem of plastic emissions has similarities with that of greenhouse gas emissions:
- plastic emissions come from a variety of very different sources,
- once released into the environment, they are hardly retrievable,
- they are distributed via rivers and ocean currents and have global relevance.
When plastics enter the environment, negative consequences to organisms range from asphyxiation to transfer within the food chain to physical impacts on an ecosystem. In addition, there are chemical hazards due to the release of additives, monomers and critical intermediates of metabolic processes, the metabolites. The actual long-term impact of plastic emissions has not been determined at this time. Nevertheless, there is a consensus in society that the current situation must not be allowed to continue and that the precautionary principle must be applied.
Due to the global and intergenerational dimension of the problem, it is important that science, industry and consumers work together to find a solution. One goal of the collaborative project was therefore to quantify current plastic emissions and derive a plastic emissions budget. On this basis, the researchers were able to formulate initial quantitative emission targets that can serve to legitimize environmental policy decisions. In particular, the combination of scientific calculation approaches and normative values to a concrete emission budget forms the main objective of the project.
To measure plastic pollution, researchers developed the persistence-weighted plastic emission equivalent (PPE) metric. It indicates how many years it takes for plastic emissions to degrade, for example, in soil, freshwater or seawater. Relevant properties for this are the region, the material type, the type of plastic emission, as well as the characteristic size of the emitted plastic object and the environmental compartment into which the plastic is initially emitted. The plastic emission equivalent is expressed in kilograms. Plastics that are difficult to degrade are given a mass in kilogram plastic emission equivalents that is multiples of their real mass.
Based on the hypothesis that the total amount of plastics already accumulated in the environment has just reached a critical level, the researchers were able to estimate the globally available plastic emissions budget (PPE) at 250 million tons of plastic emission equivalents. If this amount were emitted permanently, the situation would remain as it is today. Assuming equal emission rights, this results in a per capita plastic emission budget of about 32 kilograms of PPE. At the same time, the researchers determined the plastic emission equivalents of various emission sources. For example, driving a car 15,000 kilometers a year generates 16.5 kilograms of PPE, throwing away 10 coffee-to-go cups a year generates 13.5 kilograms of PPE, and the consumption of one spool of nylon thread for a lawn trimmer results in 5.1 kilograms of PPE. Overall, the researchers estimate that the average German emits about 216 kilograms of PPE per year. The budget is thus currently exceeded by a factor of 6 to 7.
To ensure that the plastic emissions budget can be met in the future, the researchers examined various scenarios. They propose a solution where a 50% reduction in emissions is achieved through more durable products and policies against littering, combined with a much greater use of more degradable plastics in all areas where emissions cannot be completely eliminated. This combination would allow the plastic emissions budget to be met and the amount of plastic in the environment to stagnate. If the amount in the environment is to be significantly reduced, more far-reaching measures are required. However, we are currently on a path where the amount in the environment will increase significantly in the coming years and decades. The use of the plastic emission equivalent in product labeling and as part of life cycle assessment and the plastic emission budget in environmental communication, could make this development transparent and show which parameters should be changed.
The project is part of the research focus "Plastik in der Umwelt" (PidU) of the German Federal Ministry of Education and Research (BMBF), in which 18 collaborative projects with around 100 partners from science, industry, associations and municipalities aim to clarify fundamental questions about the production, use and disposal of plastics. The research focus "Plastik in der Umwelt - Quellen, Senken, Lösungsansätze" is part of the Green Economy flagship initiative of the BMBF framework program "Forschung für Nachhaltige Entwicklung" (FONA3).
 https://edgar.jrc.ec.europa.eu/country_profile/DEU; Last access: 13.05.2022
 https://link.springer.com/content/pdf/10.1007/s11367-022-02040-1.pdf ; Last access: 13.05.2022