The global petrochemical industry’s greenhouse gas emissions could increase by around 50 per cent by 2050 under a business as usual scenario, rising from an estimated 2.0 ± 0.8 gigatonnes of carbon dioxide equivalent (GtCO2e) in 2023 to 3.0 ± 1.2 GtCO2e, according to a study published in Nature Sustainability.
The study led by Fanran Meng of the School of Chemical, Materials and Biological Engineering at the University of Sheffield, provides a facility level assessment of global petrochemical emissions. Researchers mapped emissions from 37,379 production facilities, covering 81 chemicals and 2,043 manufacturing processes.
The petrochemical industry is responsible for 13 per cent of global industrial greenhouse gas emissions and 3.5 per cent of total greenhouse gas emissions. Production has increased 500 per cent since 1980 to nearly one billion tonnes a year. The industry accounts for 30 per cent of industrial energy use, 14 per cent of global oil demand and 9 per cent of natural gas demand.
The International Energy Agency (IEA) projects production of primary chemicals to increase from 680 million tonnes in 2020 to 971 million tonnes in 2050, representing a compound annual growth rate of 1.3 per cent. Plastics alone account for 420 million tonnes of production, while other major petrochemical products include nitrogen fertilisers, fibres, rubbers, solvents, additives and explosives.
The research found that petrochemical emissions are highly concentrated. Just 10 per cent of facilities account for 53 per cent of emissions on a cradle to gate basis. The study said this concentration creates an opportunity to prioritise the highest emitting facilities for decarbonisation rather than applying measures uniformly across the industry.
At the country level, the concentration is similarly pronounced. The top nine emitting countries accounted for 63 per cent of emissions in 1990, 76 per cent in 2020 and are projected to account for 79 per cent by 2050. China, the United States and India together are expected to account for 63 per cent of global production emissions in 2050 under the base case scenario.
China was the largest emitter in 2020, accounting for 37 per cent of the global total, or 660 ± 260 million tonnes of carbon dioxide equivalent. The study found that 83 per cent of emissions attributed to downstream products are embodied emissions from upstream primary and intermediate chemical production, highlighting the importance of tackling emissions earlier in the production chain.
Ethylene and ammonia were the largest emitting primary chemicals in 2023, producing 290 ± 50 million tonnes and 250 ± 50 million tonnes of carbon dioxide equivalent, respectively. Both are widely used in products including plastics, food packaging, fertilisers and household cleaning products.
The study’s broader 2020 assessment estimated global petrochemical emissions at 1.8 ± 0.7 GtCO2e a year. Indirect energy use accounted for 45 per cent of emissions, at 820 ± 320 MtCO2e, while feedstock extraction and processing accounted for 34 per cent, at 620 ± 280 MtCO2e. Carbon dioxide accounted for 74 per cent of the emissions impact over a 100 year period, while methane and nitrous oxide accounted for 15 per cent and 11 per cent, respectively.
Under the business as usual scenario, global petrochemical production emissions are projected to reach 2.3 ± 1.0 GtCO2e in 2030 and 3.0 ± 1.2 GtCO2e a year in 2050. The study found that no single mitigation measure can bring the sector to net zero.
The researchers assessed a combination of electricity grid decarbonisation, carbon capture and storage (CCS), feedstock substitution and other mitigation measures. Even the most optimistic scenario, which assumes the IEA’s Sustainable Development Scenario for electricity generation, 100 per cent deployment of CCS at eligible facilities and sufficient bio based feedstocks to replace fossil feedstocks, does not achieve net zero emissions by 2050.
Electrification could reduce emissions in the longer term once electricity grids are substantially decarbonised. However, the study found that electrification in regions with carbon intensive electricity systems could increase emissions in the near term. It also found that reducing demand could deliver larger emissions reductions than any single supply side measure.
The researchers found that the benefits of targeting individual facilities could be significant. A prioritised rollout of decarbonisation measures could save 23 ± 3 GtCO2e by 2050 compared with an unprioritised approach. In the model, this could bring emissions below 2020 levels by 2025 instead of 2045, representing an upper bound scenario.
The study also highlights differences between chemical production processes. Ammonia and ethylene had comparable emissions in 2020 at 260 ± 50 MtCO2e, but their production structures differ significantly, meaning the same decarbonisation measures cannot be applied uniformly. Integrated petrochemical complexes can make feedstock substitution particularly difficult because changes to one process can affect interconnected operations.
For example, about 95 per cent of butadiene is produced as a by-product of naphtha steam cracking for ethylene. Changes in feedstocks and production routes have reduced butadiene yields even as global demand has continued to grow, highlighting the interdependence of petrochemical production networks.
The study found that supply side measures alone cannot address the indirect emissions that dominate the sector’s footprint. It therefore identifies demand reduction as an integral part of a pathway towards net zero petrochemical production.
The researchers also caution against relying entirely on bio based feedstocks. While renewable carbon could reduce emissions associated with fossil feedstocks, replacing all fossil feedstocks with biomass could create ecological and social consequences, including biodiversity loss, land use change, competition with food production, soil depletion and water pollution.
CCS also faces limitations. The study notes that suitable geological storage sites and substantial transport and pipeline infrastructure would be required. In its 100 per cent CCS scenario, the amount of CCS required plateaus at 20 MtCO2 a year by 2050, while proposed global CCS projects face considerable uncertainty.
“Emissions from the petrochemical industry are already enormous and yet our research has found that they are on course to rise by 50 per cent by 2050 under a business as usual scenario,” said Dr Fanran Meng, Senior Lecturer in Sustainable Chemical Engineering at the University of Sheffield.
“Unfortunately given the complexities of the petrochemical industry and the crucial role it plays in underpinning many of the everyday products that modern society is built on, there is no silver bullet,” he said.
Meng said that even an extremely optimistic combination of grid decarbonisation, CCS deployment and bio based feedstocks would not take the sector to net zero by 2050. Reducing demand for petrochemical products, alongside cleaner production, would therefore need to form part of the solution.
The researchers said facility level emissions data can help industry and policymakers identify priority plants, products and processes for intervention. The study used production and capacity data from the Independent Commodity Intelligence Services (ICIS), the International Fertilizer Association (IFA) and the Food and Agriculture Organization (FAO), along with electricity carbon intensity projections from the IEA.
The analysis covers cradle to gate emissions and does not quantify emissions during the use or end of life stages of petrochemical products. The researchers said future assessments should link facility level production with trade, consumption and end of life pathways to understand the full lifecycle emissions of petrochemical products.