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Researchers Reveal Carbon Footprint of Plastics is Constantly Growing

ETH scientists investigated the global plastics value chain and revealed that the effect of plastics on health and climate is bigger than formerly believed because of the increased use of coal for electricity, process heat and as a raw material in production.

Researchers Reveal Carbon Footprint of Plastics is Constantly Growing.
Plastic not only causes problems in form of waste – greenhouse gases and air pollutants also occur during production. (Image Credit: Blende-8/Adobe Stock).

Plastics are practical, inexpensive and very popular. Worldwide demand for them has quadrupled in the last four decades and is projected to continue to grow, with negative implications for human health and the environment.

The public is conscious of the environmental hazard caused by plastics, mainly at the end of their life cycle, such as when they emit air pollutants and greenhouse gases when burned, or contaminate soil and water in the form of microplastics.

Research into the worldwide environmental effect of plastics has also concentrated largely on the disposal phase. Only a few studies cover the manufacture of plastics, which also affects air quality and climate. However, such a comprehensive analysis requires complete information about supply chains and processes so as to trace the relevant material and energy flows.

Assessing the Global Footprint of Plastics

So far, the simplistic assumption has been that the production of plastics requires roughly the same amount of fossil resources as the amount of raw materials contained in plastics – particularly petroleum.

Livia Cabernard, Doctoral Student, Institute of Science, Technology, and Policy (ISTP), ETH Zurich

The issue here is that the relative importance of production versus disposal has been considerably miscalculated.

Cabernard is part of a team of scientists headed by Dr. Stephan Pfister, senior scientist at the ISTP, and Stefanie Hellweg, ETH Professor of Ecological Systems Design at the Institute of Environmental Engineering. Through meticulous detective efforts, the team examined the climate and health impact of the global plastics supply chain spanning a 20-​year period.

The scientists reveal, in a study published in Nature Sustainability, that the worldwide carbon footprint of plastics has increased twice as much since 1995, touching 2 billion tons of CO2 equivalent (CO2e) in 2015. This signifies 4.5% of worldwide greenhouse gas emissions and is more than formerly thought.

During the same period, the worldwide health footprint of plastics from fine particulate air pollution had risen by 70%, causing about 2.2 million disability-adjusted life years (DALYs) in 2015.

Coal for Process Heat, Electricity and as a Raw Material

For their research, the team established that the greenhouse gas emissions produced across the life cycle of plastics – from extraction of fossil resource to processing into product classes and use, finally to end of life, including incineration, recycling and landfill.

The scientists ascertained growing plastics production in coal-based, recently industrialized nations, such as India, China, Indonesia and South Africa, as the key cause of the increasing carbon footprint of plastics.

The energy and process heat required for the manufacture of plastics in these nations comes mainly from the burning of coal. Coal in small quantities is also used as a raw material for plastics.

The plastics-​related carbon footprint of China’s transport sector, Indonesia’s electronics industry, and India’s construction industry has increased more than 50-​fold since 1995.

Livia Cabernard, Doctoral Student, Institute of Science, Technology, and Policy (ISTP), ETH Zurich

Worldwide, coal-​based discharges from plastics production have quadrupled since 1995 and presently make up for approximately half of the universal carbon footprint of plastics.

When combustion of coal takes place, it generates very fine particles that amass in the air. Such particulate matter is extremely harmful to health and can cause bronchitis, asthma and cardiovascular disease. As increasing amounts of coal are used to process heat and electricity, and as a raw material in plastics manufacture, the negative health implications are also growing.

Underestimated Plastics Production

Contrary to previous estimates, which believed that equal amounts of fuel and raw materials were used in the production of plastics, the ETH scientists have, at present, established that twice as much fossil energy is burned for the manufacture of plastics as is contained as a raw material in plastics.

This impacts the evaluation of the environmental consequences.

Even in a worst-​case scenario in which all plastics are incinerated, their production accounts for the lion’s share of total greenhouse gas and particulate matter emissions.

Livia Cabernard, Doctoral Student, Institute of Science, Technology, and Policy (ISTP), ETH Zurich

The total production phase of plastics is accountable for the huge majority (96%) of the carbon footprint of plastics.

Insights Thanks to New Methodology

There had earlier only been a single publication that inspected the international carbon footprint of plastics production.

This study underestimated greenhouse gas emissions, however, because it did not take into account the increasing dependence on coal due to the outsourcing of production processes to coal-​based countries.

Livia Cabernard, Doctoral Student, Institute of Science, Technology, and Policy (ISTP), ETH Zurich

The scientists used a new technique for their study that Cabernard had earlier formulated in her doctoral thesis under the guidance of Hellweg and Pfister. This method involves a multi-​regional, input-​output examination that accurately maps international value chains from production to consumption across countries, industries, and regions. 

Journal Reference:

Cabernard, L., et al. (2021) Growing environmental footprint of plastics driven by coal combustion. Nature Sustainability.​021-00807-2.


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