Interview: The fourth version of the marine litter model

Interview: The fourth version of the marine litter model

29.05.2020

Seven years ago, the market research company Conversio Market & Strategy GmbH developed a new calculation model on behalf of the BKV to estimate the quantities of plastic litter ending up in the seas. It was entitled: "From Land to Sea – Model for the documentation of land-sourced plastic litter". The model has, since then, been frequently further developed and revised to include fresh data. The fourth version, which has now been released, also contains a number of new features. We asked Managing Director Christoph Lindner about the content and importance of this and also asked him to tell us how the model would progress in the future.

Mr. Lindner, the fourth version of the "From Land to Sea" model is now available. How does it differ from the previous version?

The focus when compiling the fourth version of the report was to completely update the data and to also integrate the latest results from the three special reports on the discharge of plastics from compost and digestate, the discharge into the seas of tyre abrasion from Germany, and the verification of the factor 'improperly disposed-of waste'. Apart from that, the report shows for the first time in detail the discharged quantity of plastics into the individual discharge pathways. Another important new aspect of the updated report is the chapter on "Sensitivity analysis". Because, with some key model factors, only rudimentary data have so far been available, increasing use has been made of estimates from market experts. With the help of a sensitivity analysis, the sensitivity of the quantity discharged into the seas is demonstrated when individual factors are varied.

For the first time, the plastic waste quantities that get into the discharge pathways or discharge sources are also shown in the model. What importance do these data have for the model?

Until now, the focus was on the quantity of plastic waste entering the seas. Describing the quantities entering the discharge pathways helps to make the model more transparent and contributes to a better understanding of the calculation principle. Basically it can be said that the more variables in a calculation are known, the easier it is to understand the calculation. Furthermore, the more detailed quantity figures give us a better idea of the quantities that get into the environment or end up in a discharge pathway. As a result, we have better information for devising action needed to reduce or even avoid land-sourced marine litter.

Until now, the focus of the "From Land to Sea" model was on plastics in the sense of polymer materials. Now, it also includes details on tyre abrasion. Why was the discharge of tyre abrasion included in the model and how has it been integrated?

In most studies dealing with the topic of plastics in the environment, tyre abrasion is counted as microplastic and identified as an important source of plastic waste entering the environment. In order to also take into account the discharge into the seas of tyre abrasion from Germany, we devoted ourselves to this topic in the form of a special report entitled "Discharge of tyre abrasion from Germany into the seas". In the "From Land to Sea" report, tyre abrasion is counted neither as microplastics nor as macroplastics, but is shown separately.

How will you proceed in future with the model?

Current discussions and developments are tending to concentrate less on the discharge of plastics into the seas and more on the topic of plastics in the environment. This will be taken into account in the further development of the Marine Litter model. In an ongoing study, we therefore deal specifically with the topic of plastics in the environment, covering only litter that gets into the environment outside the regulated, systematically documented waste. In addition to an overall evaluation, the study will look at individual plastic products and sources especially from the microplastic segment, such as emissions during waste disposal, pellet losses or releases on building sites.

(May 2020)

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