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Issue 06/2020

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Highlights: Films / Flexibles Bioplastics from waste-streams Basics: Eutrophication

Basics Eutrophication By

Basics Eutrophication By Michael Thielen When talking about bioplastics, every now and then the term eutrophication or eutrophication potential is heard. This article will try to explain the term. The Merriam Webster online dictionary defines eutrophication as “the process by which a body of water becomes enriched in dissolved nutrients (such as phosphates and nitrates) that stimulate the growth of aquatic plant life usually resulting in the depletion of dissolved oxygen” [1]. It is a term that is derived from the Greek eutrophos, meaning “well-nourished”. Be that as it may, eutrophication has today become a major environmental problem [1]. Causes of eutrophication Eutrophication arises through natural causes (natural eutrophication) and man-made causes (cultural eutrophication). Natural eutrophication can occur because of the natural process of aging of lakes, during which the nutrition status of the water system gradually increases. As a result, an oligotrophic (poor nutrient content) lake is converted into a eutrophic (high nutrient content) lake. The death of aquatic plants and animals also increases the nitrate and phosphate concentrations of the water environment, promoting the proliferation of phytoplankton, algal blooms and aquatic vegetation (water hyacinth, aquatic weeds, water fern and water lettuce) that provide ample food for herbivorous zooplankton and fish [2]. Cultural eutrophication, on the other hand, is a process that occurs when nutrients from human activities enter or flow into water bodies [2]. Cultural eutrophication can lead to 80 % more nitrogen and 75 % more phosphorus being added to lakes and streams. The most common sources of nutrient input into water bodies through human activity are phosphorus and nitrogen compounds from agricultural fertilization, combustion processes and wastewater [3]. Effects of eutrophication: Eutrophication leads to various physical, chemical and biological changes in water, deteriorating its quality. Effects are, for example, the decline of plants and microorganisms that depend on a low nutrient level. Excessive levels of nitrogen and phosphorus in water bodies facilitate the heavy growth of aquatic plants such as algae, causing algal bloom, which prevents the penetration of light into deeper layers [2, 3]. When these algal blooms die, they are decomposed by bacteria, a process that consumes oxygen, depletes dissolved oxygen levels and increases the level of carbon monoxide in the water. As a result of the low oxygen levels, aquatic organisms begin to die. Some of these blooms even produce toxins that can kill fish, mammals and birds [2, 4]. The loss of dissolved oxygen also results in anaerobic decomposition of organic matter that produces H 2 S, CH 4 , NH 3 causing a foul smell and taste of the water [2]. Bioplastics and eutrophication Bioplastics have a higher eutrophication potential than conventional plastics [6]. Biomass production during industrial farming practices causes nitrate and phosphate to filtrate into water bodies; this causes eutrophication [7]. Bioplastics also promote acidification [8]. Bioplastics may play a role in aggravating the processes of eutrophication and acidification due to the fact that chemical fertilizers are used in the cultivation of the renewable raw materials from which bioplastics are made [6]. The aim of this article is to explain the term eutrophication, as it is sometimes mentioned in the context of biobased plastics. A complete treatment of this issue is beyond the scope of this text. Eutrophication must always be considered in ecological assessments or Life Cycle Assessments (LCA), especially when comparing biobased and fossil-based plastics. As biobased plastics are commonly derived from cultivated biomass, eutrophication is a factor to be taken into account, whereas this is not the case for fossil-based resources. Equally, the grave environmental impacts of the crude oil production or coal mining industries in many countries of the world (cf e.g. [9] or [10]) that supply the feedstock for fossil-based plastics should also be taken into account in assessments of this kind. References [1] N.N.: Eutrophication, Merriam-Webster [2] Humagain, S.: Eutrophication: Causes, Effects and Controlling measures, November 24, 2018; eutrophication-causes-effects-and-controlling-measures [3] Endres, H.-J., Siebert-Raths,A.: Engineering Bioplymers; Carl Hanser Publishers, Munich, 2009 [4] N.N.: Contaminants and Eutrophication; http://www.aquaticlifelab. eu/4-7-contaminants-and-eutrophication [5] N.N.: Bioplastic; Wikipedia; [6]: Weiss, Martin, et al. “A Review of the Environmental Impacts of Biobased Materials.” Journal of Industrial Ecology, vol. 16, no. SUPPL.1, 2012, doi:10.1111/j.1530-9290.2012.00468.x. (in [5]) [7] Sinha, E., et al. “Eutrophication Will Increase during the 21st Century as a Result of Precipitation Changes.” Science, vol. 357, no. July, 2017, pp. 405–08. (in [5]) [8] Gironi, F., and Vincenzo Piemonte. “Bioplastics and Petroleum-Based Plastics: Strengths and Weaknesses.” Energy Sources, Part A: Recovery, Utilization and Environmental Effects, vol. 33, no. 21, 2011, pp. 1949–59, doi:10.1080/15567030903436830 (in [5]) [9] N.N.: What are the environmental impacts of economic development in Nigeria?; [10] N.N. Coal utilization in China: Environmental impacts and human health; utilization_in_China_Environmental_impacts_and_human_health 50 bioplastics MAGAZINE [06/20] Vol. 15

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