The Environmental Impact of Recycling Polymers

First published 2023

The environmental challenges facing our planet today are daunting, with climate change, pollution, and resource depletion at the forefront. In this context, recycling can be viewed as a key strategy for mitigating the negative impacts of consumerism and industrialisation. Among the various materials that can be recycled, polymers, commonly known as plastics, hold a prominent place due to their ubiquity in modern society. Recycling polymers not only conserves valuable resources but also helps reduce the environmental burden associated with their production and disposal.

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One of the main environmental benefits of recycling polymers is resource conservation. Recycling polymers reduces the demand for virgin raw materials, such as petroleum, which is the primary source of plastics. By reusing existing polymers, we can conserve finite fossil fuel resources, ultimately decreasing greenhouse gas emissions and mitigating climate change. Moreover, recycling also saves water and energy, as the production of plastic resin is a resource-intensive process.

One of the most significant environmental impacts of plastics is their persistence in the environment. Plastics can take hundreds of years to degrade in landfills, contributing to the problem of limited landfill space. Recycling diverts plastics from landfills, reducing the need for new disposal sites. Furthermore, recycling helps prevent plastics from entering oceans and waterways, where they harm marine life and ecosystems.

Plastic waste has the potential to be reclaimed and undergo mechanical processing to be used in the production of plastic goods. Recycling single-polymer plastic streams is the easiest since it doesn’t involve worrying about immiscibility problems, which are similar to the separation seen in oil and water mixtures. However, the primary obstacles in mechanical recycling are the variations in plastic composition and the presence of impurities. Effective separation, thorough cleaning, and proper preparation of plastic solid waste are all crucial steps to yield superior, transparent, pure, and uniform final products.

Producing plastic from recycled materials typically requires less energy than producing it from raw materials. This energy savings translates into reduced carbon emissions and a smaller environmental footprint. The energy saved through polymer recycling can be redirected toward cleaner and more sustainable energy sources, further aiding in the fight against climate change.

Moreover, the production of polymers from virgin materials often involves the release of harmful pollutants into the air, contributing to air quality issues and health problems in nearby communities. Recycling polymers reduces the need for these polluting manufacturing processes, resulting in improved air quality and better overall public health. While recycling polymers offers numerous environmental benefits however, there are also challenges and considerations that need to be addressed. Contamination of recycled polymer materials with non-recyclable items can reduce the quality and effectiveness of recycling efforts. Education and better sorting systems are essential to minimise contamination and improve recycling rates.

Furthermore, not all communities have access to comprehensive recycling programs, which can hinder recycling efforts. Expanding recycling infrastructure and accessibility is crucial to increasing recycling rates. There are also certain technological limitations that need to be considered. Certain types of plastics are more challenging to recycle due to their composition and properties. Developing advanced recycling technologies that can process a wider range of polymer types is therefore essential to maximise recycling potential. A further factor is that recycling polymers is more effective when there is a robust market demand for recycled plastic products. Encouraging businesses to use recycled plastics in their products and consumers to choose recycled products can help drive demand.

Life Cycle Assessment research has determined that when it comes to disposing of waste plastics, mechanical recycling is a more environmentally friendly choice compared to other methods. This is mainly because it helps reduce the environmental impact by avoiding the production of new plastic materials. These findings align with the waste hierarchy guidelines, which recommend prioritising mechanical recycling as the preferred waste management approach, following source reduction and reuse, to safeguard the environment and conserve natural resources. Considering the continued demand for recycled plastics, the relatively low rates of plastic recycling, and ongoing technological advancements, there appears to be significant potential for the expansion of mechanical recycling in the future.

Overall, therefore, it is clear that recycling polymers is a vital component of our efforts to address environmental challenges. It conserves valuable resources, reduces pollution, and mitigates climate change. However, for recycling to reach its full potential, it requires a concerted effort from individuals, businesses, and governments to improve infrastructure, promote recycling awareness, and develop innovative technologies. By recognizing the environmental impact of recycling polymers and actively participating in recycling initiatives, we can contribute to a more sustainable and environmentally friendly future.

Links

https://publications.jrc.ec.europa.eu/repository/handle/JRC122455

https://www.hprc.org/environmental-impacts-of-recycling-2/

https://lavergne.ca/news/the-positive-impacts-of-recycling-plastic/

The Impact of Agriculture on Biodiversity

First published 2023

Agriculture is the world’s second largest emitter of greenhouse gasses and is responsible for 13% of total global emissions. It is one of the biggest contributors to biodiversity loss and is due to increased demand for food from an exponentially expanding population. By converting natural habitats and ecosystems into intensely managed farmland to create monocultures of crops, the index of species diversity is mostly reduced. Businesses amplify this negative impact through energy use, transport and waste which further reduces global biodiversity and heavily contributes to greenhouse gas emissions.

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By filling in ponds and draining marshlands, more farmland space is created to grow crops. By eradicating wetlands in this way, inland aquatic ecosystems severely decline, leading to major habitat loss for fish, reptiles and amphibians. Habitats provide food and shelter for organisms meaning this loss increases competition among species with similar ecological niches; therefore not all of them survive so species diversity decreases. Farmers can reduce this impact by leaving wet corners of fields rather than draining them and maintaining existing ponds. In 2013, a study of 94 ponds across farmlands in Spain was carried out which concluded that natural ponds within farms increase species richness and diversity compared to artificial ponds but still more so than no ponds.

Additionally, the increasing use of inorganic chemical fertilisers and pesticides indirectly causes a decrease in the species diversity within farmlands. Whilst the use of fertilisers aims to improve the supply of nutrients and promote plant growth, fertiliser runoff can trigger a process called eutrophication. This starts when the nutrient rich fertilisers (containing nitrates and phosphates) are washed into rivers or lakes. These nutrients are taken in by phytoplankton (algae) which grow and reproduce quickly, forming a thick bloom layer on the water’s surface. This prevents sunlight reaching photosynthesising plants underwater which therefore die. The algae will die when it runs out of nutrients from the water. Then bacteria decompose the dead algae, releasing nutrients back into the water. As the bacteria divide and grow, they consume oxygen causing the water to become anoxic. This causes organisms such as fish to die, which disrupts the aquatic food chain, causing lower biodiversity levels. However interestingly, trees can act as natural water filters. As their roots absorb rainwater to minimize the amount of runoff entering rivers and lakes, minimising the effect of eutrophication.

Although they increase the yield of crops, the use of pesticides and herbicides kill insects and weeds respectively which may threaten the survival of the farmers’ plants. To manage this, farmers could use biological control such as the release of parasitic wasps to control aphids (a plant pest which removes nutrients from the plant) or the farmer could use organic rather than inorganic fertilizers.

Furthermore, a lack of crop rotation causes less nutrients in the soil, an increase in soil erosion, and an increase in plant diseases and pests. Crop rotation is the systematic planting of different crops in a particular order over several years in the same growing space. By rotating crops, different nutrients favoured by different plants are absorbed from the soil, preventing any severe lack of one type of nutrient in a certain area of soil. To prevent the negative effects, farmers could use crop rotation that includes a nitrogen-fixing crop, rather than fertilisers, which would improve soil fertility. This would therefore increase the variety of nutrient species and microorganisms underground, leading to an overall increase in biodiversity.

Alternatively, a positive impact of increased agriculture on biodiversity is that soil biodiversity can be increased by intensive farming, Soils form complex ecosystems that make farming possible because there are millions of both microorganisms (such as bacteria and fungi) and macroorganisms (such as worms, mites, ants and spiders) that live in soil. Nutrients provided by fertilisers and growing plants feed organisms. When they eat and dig underground burrowing organisms, like earthworms and termites mix the upper layers, redistribute nutrients and increase the amount of water absorbed by the soil and therefore by the plant. This demonstrates interdependence between plants and organisms within agriculture. Furthermore, some macroorganisms are critical to local farming techniques. For example, Farmers in Burkina Faso and in other areas of West Africa encourage termites to live and burrow in their farm plots because they improve the soil.

To conclude, the trade-off between sustaining a large population agriculturally and maintaining global biodiversity remains a critical challenge. However farmers collectively can reduce the impact of agriculture on biodiversity through less intensive farming techniques and conservation of naturally occurring species.

Links

https://www.researchgate.net/publication/258331948_Diversity_in_Mediterranean_farm_ponds_Trade-offs_and_synergies_between_irrigation_modernisation_and_biodiversity_conservation

https://www.wri.org/insights/everything-you-need-know-about-agricultural-emissions

https://www.nature.com/scitable/knowledge/library/eutrophication-causes-consequences-and-controls-in-aquatic-102364466/

The Process of Eutrophication

First published 2021; revised 2022

The increasing use of fertilisers within the agricultural industry has undoubtedly contributed to the widespread occurrence of poor water quality and depleting fish species within natural ecosystems across the globe. This is due to a process known as Eutrophication which occurs mostly due to too much leaching of artificial nutrients (usually nitrate ions) into water sources. Other causes of Eutrophication include human sewage, animal slurry, ploughing old grassland and the use of organic manures.

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Firstly, atmospheric nitrogen is reduced to ammonia through a process known as Nitrogen Fixation. Next, Ammonification takes place which is where fungi and bacteria decay the ammonia to release Ammonium ions into the environment. These Ammonium ions are converted to nitrites and then into nitrates in the soil through nitrifying bacteria (namely Nitrosomonas and Nitrobacter bacteria respectively). As plants grow, their roots actively transport these nitrate ions from the soils into their roots within these ecosystems. Normally, these nitrate ions would be returned once the plant dies and decomposes. However, within agricultural systems like farmland, the plants are harvested instead so the nitrate ions do not naturally return to the soil and therefore have to be added manually through the use of fertilizer.

Eutrophication occurs when the nutrient concentration is too high within water sources such as freshwater lakes or the lower reaches of rivers. In most water sources, there is a very low concentration of these nutrients like nitrate ions. This means they are a limiting factor for the growth of plants such as algae in water. Leaching is a process whereby rainwater dissolves soluble nutrients from the soil and transports them to watercourses such as streams and rivers (far beyond the reach of the plant), which in turn, will drain into freshwater lakes. Leaching causes the nitrate ion concentration to increase within these freshwater lakes and is no longer a limiting factor for plant and algal growth.

As the algae population therefore increases (specifically at the surface of the lake), an algal bloom is formed. This is when the upper layers of the water become densely populated with algae. The algal bloom absorbs sunlight, therefore preventing any light reaching the plants at lower depths. This means light intensity now becomes the limiting factor for plants growing at lower depths, which proceed to die. Saprobiontic bacteria can now thrive due to the fact that the lack of dead plants is no longer a limiting factor for them because they can feed off of the dead organisms. This causes the populations of the saprobiontic microorganisms to increase.

However the saprobiontic bacteria create an increased demand for oxygen which they require for respiration. This results in a decreased concentration of oxygen within the water yet an increased concentration of nitrate ions released from the decaying plants. As the concentration of oxygen in the water decreases, oxygen then becomes the limiting factor for the population of larger aerobic organisms, such as fish. As the oxygen concentration within

the water reaches zero, the aerobic organisms die. In the absence of aerobic organisms, there is less competition for anaerobic organisms, whose populations now increase. The anaerobic organisms further decompose dead material, releasing more nitrates into the water in addition to some toxic wastes like hydrogen sulphide, which makes the water putrid.

Eutrophication not only contributes to the formation of putrid water and unattractive algal blooms, but it also decreases the biodiversity within the water habitat. The complete loss of anaerobic fish species limits interdependence from other species (except saprobiontic bacteria who now have a bigger food source). A real world example of the effects of Eutrophication on a river ecosystem can be seen within the Mono Lake, an alkaline lake in California, where a rare algal bloom (of the algae species known as Picocystis sp.) caused the oxygen concentration to sink below detectable limits. This led to a major increase in the prevalence of anaerobic microorganisms and presumably a decline in the larger aerobic species populations.

Interestingly, the effects of Eutrophication can be controlled, and even prevented, simply through controlling the amount and timing of fertilizer application. Furthermore, Eutrophication can be managed through planting vegetation such as grasses along the sides of water sources like freshwater lakes. These would absorb nutrients that have been leached from soils and dissolved in rainwater, ideally preventing them from reaching the water in the lake. Alternatively, the application of algacides and herbicides could be used in freshwater lakes to prevent the formation of the algal bloom to ensure the limiting factors for growth of organisms do not change. However, this is likely to be a more unfavourable option due to the potential side effects for larger organisms such as the fish species within the water source.

In conclusion, Eutrophication is a complex yet sadly common process which can easily affect thriving and biodiverse water sources (namely freshwater lakes) causing a reduction in biodiversity and lower water quality. It is caused by the leaching of nitrate ions which are ubiquitously used by plants (and indeed animals) for a myriad of applications including protein and amino acid synthesis.

Links

https://pubmed.ncbi.nlm.nih.gov/30120120/

https://www.researchgate.net/post/How_can_I_prevent_Eutrophication_in_a_lakeI_want_a_Practical_and_cost-effective_removal_of_phosphorus_from_a_lake_that_is_a_source_of_drinking_water

https://www.nature.com/scitable/knowledge/library/eutrophication-causes-consequences-and-controls-in-aquatic-102364466/