Carbon footprint of polyethylene produced from CO2 and renewable H2 via MTO route
Bhusal, Shree Ram (2021)
Diplomityö
Bhusal, Shree Ram
2021
School of Energy Systems, Ympäristötekniikka
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe202201041138
https://urn.fi/URN:NBN:fi-fe202201041138
Tiivistelmä
Plastics are important materials for various applications. The rate of global plastic production is increasing rapidly to satisfy the demand of the growing population. Since the plastics industry is dominated by fossil fuels and feedstocks, it is essential to discover innovative solutions to minimize greenhouse gas (GHG) emissions and other environmental impacts. Plastic production utilizing CO2 as a feedstock through power-to-X (PtX) technology could be a new opportunity to diminish GHG emissions as well as to minimize the pressure on limited fossil resources.
The goal of this thesis study is to calculate the carbon footprint of CO2-based polyethylene and to find out the GHG emissions hotspots in the production route. Furthermore, the thesis aims to compare CO2-based polyethylene with fossil-based and bio-based counterparts in terms of GHG emissions. As a methodology of the study, life cycle assessment is conducted in accordance with the ISO standards (ISO 14040, ISO 14044, and ISO 14067), and GaBi software is used to calculate the carbon footprint of polyethylene. The functional unit is chosen to be 1 kg of high-density polyethylene (HDPE).
According to the result of the study, the carbon footprint of HDPE is 3.11 kg CO2 equivalents (CO2eq) per functional unit. Considering the biogenic carbon content, the net global warming potential (GWP) of HDPE is -0.03 kg CO2eq, which means CO2-based HDPE embeds more carbon than it emits during its production. Electrolysis is found to be the major hotspot for GHG emissions as it is the most energy-intensive process. Replacing a kg of fossil-based HDPE with CO2-based HDPE could avoid emissions equivalent to 1.83 kg CO2eq. Bio-based HDPE seems to be a better net carbon sink than CO2-based HDPE; however, sustainability issues related to biomass cultivation should not be overlooked. Production of carbon-negative polyethylene looks conceivable with the European energy mix, but the electrolysis process needs to be powered with renewables such as wind. Similarly, the use of renewable heat or waste heat could significantly reduce overall GWP.
The goal of this thesis study is to calculate the carbon footprint of CO2-based polyethylene and to find out the GHG emissions hotspots in the production route. Furthermore, the thesis aims to compare CO2-based polyethylene with fossil-based and bio-based counterparts in terms of GHG emissions. As a methodology of the study, life cycle assessment is conducted in accordance with the ISO standards (ISO 14040, ISO 14044, and ISO 14067), and GaBi software is used to calculate the carbon footprint of polyethylene. The functional unit is chosen to be 1 kg of high-density polyethylene (HDPE).
According to the result of the study, the carbon footprint of HDPE is 3.11 kg CO2 equivalents (CO2eq) per functional unit. Considering the biogenic carbon content, the net global warming potential (GWP) of HDPE is -0.03 kg CO2eq, which means CO2-based HDPE embeds more carbon than it emits during its production. Electrolysis is found to be the major hotspot for GHG emissions as it is the most energy-intensive process. Replacing a kg of fossil-based HDPE with CO2-based HDPE could avoid emissions equivalent to 1.83 kg CO2eq. Bio-based HDPE seems to be a better net carbon sink than CO2-based HDPE; however, sustainability issues related to biomass cultivation should not be overlooked. Production of carbon-negative polyethylene looks conceivable with the European energy mix, but the electrolysis process needs to be powered with renewables such as wind. Similarly, the use of renewable heat or waste heat could significantly reduce overall GWP.