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How much carbon emissions can be reduced by producing ethylene through biological methods compared to the petroleum route? What are the current technical bottlenecks?
The amount of carbon emissions that can be reduced by bioproduction of gaseous ethylene compared to the petroleum route varies depending on the specific process and raw materials. According to relevant studies, bioproduced ethylene can reduce 3.2% - 15.1% of carbon emissions compared to traditional fossil ethylene. For example, the greenhouse gas emissions of bioproduced ethylene from using corn straw as the raw material can be as low as approximately - 1.0 kg CO₂-equiv/kg ethylene, while the petroleum route ethylene production using shale gas as the raw material has greenhouse gas emissions of about 1.4 kg CO₂-equiv/kg ethylene. Additionally, using bioproduced bituminous oil as the raw material and utilizing existing steam cracking units to produce bioproduced ethylene can reduce carbon emissions by 50% - 80% compared to petroleum-based raw materials.
The current technical bottlenecks in bioproduction of gaseous ethylene mainly include the following aspects:
Low-cost fermentation ethanol technology: Currently, most ethanol is produced from starch-based grains, which is costly, with the raw material cost accounting for approximately 60%. Utilizing lignocellulosic materials such as corn straw for ethanol production is an internationally recognized technical challenge, involving challenges such as raw material pretreatment, biodegradation, and the utilization of fermentable sugars.
Catalytic technology for ethanol dehydration to ethylene: Alumina-based catalysts are currently the most mature catalysts in industrial application, but they have strict reaction conditions, high reaction temperatures, and require a volume fraction of ethanol of 90% or more, resulting in high overall energy consumption. Heteropoly acid catalysts have high activity, but their lifespan and thermal stability have not been resolved. Among zeolite molecular sieve catalysts, the ZSM-5 type is the most promising for successful industrial application, but its hydrothermal stability and lifespan still need to be further improved, and the tolerance to fermentation ethanol impurities also requires in-depth research.
Process coupling integrated technology: The existing ethanol dehydration to ethylene process routes are relatively outdated and consume significantly. It is necessary to integrate the two processes of biomass fermentation to produce ethanol and ethanol dehydration to produce ethylene organically, develop new process coupling integrated technologies to enhance the market competitiveness of bioproduced ethylene.
The current technical bottlenecks in bioproduction of gaseous ethylene mainly include the following aspects:
Low-cost fermentation ethanol technology: Currently, most ethanol is produced from starch-based grains, which is costly, with the raw material cost accounting for approximately 60%. Utilizing lignocellulosic materials such as corn straw for ethanol production is an internationally recognized technical challenge, involving challenges such as raw material pretreatment, biodegradation, and the utilization of fermentable sugars.
Catalytic technology for ethanol dehydration to ethylene: Alumina-based catalysts are currently the most mature catalysts in industrial application, but they have strict reaction conditions, high reaction temperatures, and require a volume fraction of ethanol of 90% or more, resulting in high overall energy consumption. Heteropoly acid catalysts have high activity, but their lifespan and thermal stability have not been resolved. Among zeolite molecular sieve catalysts, the ZSM-5 type is the most promising for successful industrial application, but its hydrothermal stability and lifespan still need to be further improved, and the tolerance to fermentation ethanol impurities also requires in-depth research.
Process coupling integrated technology: The existing ethanol dehydration to ethylene process routes are relatively outdated and consume significantly. It is necessary to integrate the two processes of biomass fermentation to produce ethanol and ethanol dehydration to produce ethylene organically, develop new process coupling integrated technologies to enhance the market competitiveness of bioproduced ethylene.
