The impact of plastic on the environment – now widely associated with pollution of water, land and air – also deserves to be considered from the point of view of greenhouse gas emissions into the atmosphere. At the current rate of growth in global demand for plastics, an emerging emergency is looming. In a recent scientific study, scenario analysis and strategies to implement.
Plastic and greenhouse gas emissions, 2020-2050 scenario
‘Strategies to reduce the global carbon footprint of plastics’. (1) The scientific study published in Nature Climate Change primarily considers greenhouse gas emissions in Life Cycle Assessment (LCA) of plastic materials. And their overall contribution to global emissions of Greenhouse Gases (GHG), thus contributing to climate change:
– resin production is the phase where most emissions occur (61%), especially when working with virgin polymers. Followed by conversion (30%) and end-of-life (9%) phases, meaning landfill disposal and incineration (calculation based on 2015 data).
– 15% of emissions of greenhouse gases (6.5 Gt of CO2e) will come from this production sector alone – by 2050 – if demand growth maintains the current pace (+4%, the average annual rate for 2010-2015). An emergency so far underestimated, given that plastic is currently attributed relatively modest GHG emissions contributions (3.5%, equal to 1.7 Gt of CO2e, 2015).
Plastics and greenhouse gases, strategies
The researchers of the Bren School of Environmental Science and Management (University of California, Santa Barbara, USA) have considered four strategies that could limit CO2 emissions related to the life cycle of plastics:
– reduction of the demand growth rate, from 4% to 2% per year,
– renewable energy. With the hypothesis of total decarbonization, with exclusive use (100%) of renewable energies by 2050,
– recycling. The most ambitious goal, paradoxically, is to reach 100% recycling by 2050 (completely excluding the still significant share of waste disposal),
– substitution of plastics from fossil fuels with those derived from biological material. (so-called bioplastics).
Prospects
The identified strategies project the following scenarios:
– the reduction of trend of plastic demand growth (from +4 to +2% per year) can substantially reduce emission levels. From -56% (with an energy mix unchanged from the present) to -81% (with only renewable energy), compared to the trajectory outlined for 2050,
– the conversion to renewable energy alone can reduce 62% of GHG related to plastics, at an unchanged consumption growth rate. Containing emissions within current levels, if combined with the reduction of trend demand growth. Reducing them further, if raw materials are then replaced with bio-based plastics,
– recycling of total plastic waste alone would allow for a reduction of one-quarter of emissions (-25%),
– substitution of petroleum-based plastics with plant-based materials – although useful to mitigate pollution of seas, including the Mediterranean, water and air from microplastics – does not have a significant impact on emission levels (2).
The synergy of the identified solutions – halved demand growth, 100% renewable energy, and recycling – can allow for a reduction of emissions related to the life cycle of materials. Minus 77%, 84%, 86%, respectively, on fossil fuel-based plastics and bioplastics from corn and sugarcane.
– if all plastic waste were incinerated, in 2050 greenhouse gas emissions would reach 8 Gt, 22% more than the baseline (6.5 Gt). Whereas if all plastic waste were recycled, emissions in 2050 would be 4.9 Gt, 25% less than expected,
Critical issues
The recycling rate (18%) is still decidedly low, compared to the volumes of global plastic production (4.07 million tonnes in 2015). And beyond the major commitments suggested globally – such as the ‘New Plastics Economy Global Commitment’ (NPEGC) – virgin polymers remain more advantageous for operators than those derived from recycling.
The low cost della materia prima da combustibili fossili rimane perciò la prima causa della resistenza alla transizione ecologica. Ed è perciò che gli operatori della filiera (di produzione, trasformazione e utilizzo dei materiali) devono venire chiamati a coprire gli immani costi della plastica sull’ambiente, a tutt’oggi esternalizzati sulle collettività. Servono politiche fiscali efficaci, incentivi agli impianti di riciclaggio e all’innovazione tecnologica.
The use of bioplastics does not by itself solve the waste problem, since their composting or incineration produces emissions similar or even higher than those produced by hydrocarbon plastics. In addition to requiring more selective separate collection and specific composting infrastructure. The production of biopolymers, like that of ‘biofuels,’ cannot be based on agricultural raw materials taken away from food production. (3)
‘Our results indicate that the absolute reduction in GHG emissions over the life cycle of plastics requires a combination of decarbonizing energy infrastructures, improving recycling capacity, adopting bio-based plastics, and demand management.’ (1)
Dario Dongo e Alessandra Mei
Notes
(1) JiaJia Zheng, Sangwon Sush (2019). Strategies to reduce the global footprint of plastics. Nature Climate Change, 9, 374-378. https://doi.org/10.1038/s41558-019-0459-z
(2) End-of-Life (EoL) management (End of Life) of bio-based plastics, especially biodegradable ones, requires systematic changes such as separate collection and recycling infrastructure. The inclusion of biodegradable plastics in the conventional plastic waste stream can actually affect the quality of recycled materials
(3) If the current demand for plastics were fully met by bioplastics, 250 million tons/year would be required. And if biopolymers were derived from commodities Agricultural – instead of by-products of their processing and mowing – it would be necessary to dedicate 5% of the cultivated land on the planet to their production. With worsening of the current crisis of food security.
Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT – Food Times) and Égalité.
Graduated in Law at the University of Bologna, she attended the Master in Food Law at the same University. She participates in the WIISE srl benefit team dedicating herself to European and international research and innovation projects.
