PET's Link to the Environmental Crisis: Impact Assessment and Mitigation Strategies

Recently, a research team from the Chinese Academy of Sciences conducted a cradle-to-cradle life cycle assessment (LCA) of PET bottles to evaluate their environmental sustainability. From carbon emissions to the release of toxic substances, this assessment offers insights into PET's multifaceted impacts on the Earth's atmosphere, water bodies, and ecosystems.

Assessing PET Production's Contribution to Global Carbon Emissions

The emission of greenhouse gases (GHGs) amplifies the greenhouse effect in Earth's atmosphere, contributing to global warming by trapping heat in the Earth's atmosphere. Within the PET industry chain, GHGs mainly result from reliance on fossil fuels and the use of high-carbon-intensity electricity during production processes.

Based on the Life Cycle Impact Assessment (LCIA) conducted by the research team, the emission factor for PET bottles is 1.6 × 10−1 kg CO2 equivalent, with an impact factor of 4.6 × 10³ kg CO2 equivalent per kilogram. This indicates that the production of one kilogram of PET bottles results in emissions of approximately 4.6 metric tons of CO2 equivalent.

So, is PET production truly a major contributor to global carbon emissions?

Indeed, global carbon emissions primarily originate from the combustion of fossil fuels (such as coal, oil, and natural gas), industrial activities (including steel, cement, and chemical production), transportation (cars, airplanes, ships), construction (heating, cooling, and electricity use), agriculture, and land use changes.

According to data from the EPA and other sources, plastic production, including PET production, indeed contributes a considerable amount of carbon dioxide emissions. However, compared to other major emission sources, the total amount from plastic production is relatively small.

Even under higher estimates, plastic production emits approximately 500 million metric tons of carbon dioxide annually, accounting for only about 1.3% of the global total emissions (based on the 2019 global emissions of approximately 37 billion metric tons of carbon dioxide).

Impacts on Environmental Toxicity and Aquatic Ecosystems

The production of PET resin or PET bottles(preforms) emits hazardous compounds like carcinogenic ethylene oxide and formaldehyde, presenting substantial health hazards including respiratory ailments and allergic responses. Studies reveal that manufacturing one kilogram of PET bottles releases around 14 metric tons of toxic substances equivalent to 1,4-dichlorobenzene, underscoring considerable potential health risks.

Moreover, life cycle impact assessments of PET bottles indicate profound toxicity effects on aquatic ecosystems. Chemicals released during PET production can enter rivers and lakes via wastewater discharge, eventually reaching the oceans, contributing to both terrestrial and marine aquatic ecotoxicity. Improper disposal of PET bottles exacerbates these impacts, generating microplastics that endanger aquatic organisms and disrupt ecological equilibrium. Ultimately, these harmful substances can enter the human body through the food chain.

Freshwater eutrophication is another significant impact of PET on aquatic ecosystems. This primarily refers to an excessive presence of nutrients such as phosphorus and nitrogen in water bodies, leading to overgrowth of algae and aquatic plants, deterioration of water quality, fish mortality, and reduced biodiversity, thereby severely impacting aquatic ecosystems. 

Photochemical Air Pollution and Soil Acidification Concerns

Photochemical air pollution primarily consists of photochemical smog formed under sunlight by nitrogen oxides (NOx) and volatile organic compounds (VOCs) from vehicle exhausts, including PET production processes.

Soil acidification refers to increased soil acidity due to deposition of acidic substances such as sulfur dioxide (SO₂) and nitrogen oxides, adversely affecting plants and soil microbial communities.

During PET production, combustion of fossil fuels and industrial emissions contribute acidic substances, leading to soil acidification and disrupting ecosystem balance. Nitrogen oxides not only trigger various respiratory diseases but also constitute major sources of photochemical smog and acid rain. Additionally, ethylene glycol, a primary raw material in PET production, evaporates during the preparation of PET resin at temperatures up to 90 degrees Celsius, potentially posing environmental and human health risks.

Assessment indicates that PET bottles have a photochemical oxidation impact factor of 1.2 kg C₂H₄ equivalent/kg and a soil acidification impact factor of 5 × 10⁻¹ kg SO₂ equivalent/kg. Reducing dependence on fossil fuels and implementing effective measures to manage photochemical air pollution are crucial for protecting the ecological environment.

Environmental Implications of Ozone Layer Depletion

The ozone layer protects Earth's surface from harmful ultraviolet radiation from the sun. During the production of PET bottles, substances such as chlorofluorocarbons (CFCs) may be released, with an impact factor of 1 kg CFC-11 equivalent per kilogram of PET. Although the use of CFCs has significantly decreased, their long-term effects still warrant attention. Ozone layer depletion increases ultraviolet radiation, which negatively impacts human health (e.g., skin cancer and cataracts) and ecosystems.

How can we ease the environmental crisis

To address the aforementioned environmental impacts, manufacturers in the PET industry can adopt various strategies to improve their production processes.

From a production standpoint, implementing closed-loop systems can minimize emissions and waste. Enhancing production equipment and promoting technological innovation, such as designing waste reuse solutions like wastewater and gas treatment, can further reduce negative environmental impacts.

Strict environmental management and monitoring measures are essential. These include real-time monitoring, compliance with relevant environmental regulations and standards, and preventive measures to avoid accidents and pollution incidents.

Additionally, the use of clean and renewable energy sources, such as solar and biomass energy, can significantly reduce carbon emissions.

Finally, developing bio-based PET and recycled PET can reduce reliance on fossil resources. Optimizing their production processes ensures that their performance and sustainability meet market demands.

From a consumer standpoint, it is essential to dispose of used PET bottles in accordance with regulations rather than casually discarding them. This necessitates fostering environmental consciousness among individuals.

Wankai's Sustainable Practices in PET Production

Wankai New Materials Co., Ltd., a global PET resin manufacturer, has implemented comprehensive measures to enhance energy efficiency, toxic compound release and reduce carbon emissions while actively researching green PET to promote sustainable development.

The company utilizes advanced continuous poly-condensation (CP) and solid polymerization (SSP) equipment designed by the China Kunlun Contracting Engineering Co.,Ltd. (CKCEC) and Switzerland BUHLER (Polymetrix), respectively. These highly sealed processes reduce pollutant emissions from the source and enforce various air pollution control measures.

At Wankai's Haining factory, renewable energy initiatives such as esterification waste heat power, marsh gas power, and rooftop photovoltaic power generation have substantially reduced reliance on fossil fuels and carbon emissions. In 2022, the factory produced approximately 14,386.878 MWH of renewable energy, resulting in a reduction of approximately 8,204.837 tons of CO2 emissions. Furthermore, enhancements in energy efficiency across cooling towers, heaters, and thermal medium stations saved 2,942.4 MWH of electricity and 6,227.12 tons of standard coal, further cutting CO2 emissions by about 18,942.74 tons.

Wankai has also taken innovative measures to reduce wastewater and air emissions. The development of low-nitrogen combustion technology for water-coal slurry boilers cut nitrogen oxide (NOx) emissions by about 30%. An exhaust gas collection system was designed to capture and recycle glycol from emissions, preventing resource waste and air pollution.

For wastewater treatment, the company implemented rain and sewage separation and established multiple wastewater collection systems, including production wastewater, domestic sewage, initial rainwater, and emergency wastewater. Their integrated wastewater treatment plant employs advanced processes such as "hydrolysis acidification + anaerobic + anoxic + aerobic + secondary sedimentation + three-phase reaction" to ensure treated water meets discharge standards. Continuous online monitoring of wastewater ensures compliance with environmental standards.

Wankai and its key subsidiaries strictly adhere to China's environmental protection laws and regulations, covering air, water, solid waste, noise, soil pollution prevention, and environmental impact assessments. They also comply with national and industry standards for surface water, groundwater, ambient air, sound environment, and soil quality.

To develop more sustainable polyester, Wankai has pursued multiple strategies. In collaboration with the Chinese Academy of Sciences, they developed Polyethylene 2,5-furandicarboxylate (PEF), a new bio-based polyester. Recently, Zhink Group, Wankai’s parent company, has partnered with France's Carbios, planing to build a 50,000-ton-per-year recycled PET (RPET) production line using advanced enzyme degradation technology to achieve circular economy. This company has also successfully developed and marketed high-temperature-resistant PET containing 12% bio-based content.

Conclusion

The life cycle impact assessment of PET bottles highlights substantial carbon emissions, toxic releases, and ecological impacts. Nevertheless, companies like Wankai are actively addressing these challenges through closed-loop production systems, integrating clean energy sources, optimizing wastewater treatment, and advancing sustainable PET solutions. These initiatives underscore their strong execution and responsibility in environmental stewardship and sustainable development within the plastics industry.