The chemical sector is the largest industrial energy consumer and the third largest industry subsector in terms of direct CO
2 emissions
[50]. This is largely because around half of the chemical subsector’s energy input is consumed as feedstock—fuel used as a raw material input rather than a source of energy. In 2021, direct CO
2 emissions from primary chemical production reached a total of 925 Mt
[51]. In the Net-Zero Emissions by 2050 Scenario, CO
2 emissions will be reduced by 17% until 2030—both the private and public sectors will need to achieve technological innovation, efficiency gains and higher recycling rates. Ammonia production is responsible for the highest fraction of emissions, followed by high-value chemicals (i.e., ethylene, propylene, benzene, toluene, and mixed xylenes) and methanol.
2.4.1. Chemical Industry
Direct CO
2 emissions from primary chemical production reached 925 Mt in 2021
[51]. This represents a 5% increase from the previous year, due to higher production levels than in 2019
[52]. However, the CO
2 intensity of primary chemicals has remained relatively stable at around 1.3, indicating the mass ratio of emitted CO
2 to primary chemicals produced. On a global level, the chemical industry is responsible for about 4% of global greenhouse gas emissions.
On a more positive note, the chemical industry in the EU has made remarkable progress in reducing its environmental impact. Despite an increase in the production of more than 43% since 1990, greenhouse gas emissions from chemical production in the EU-27 have decreased by 55% compared to 1990
[53].
Industrial chemicals, such as ammonia, methanol, and ethylene, are crucial feedstocks for over a dozen different sectors—from healthcare, agriculture, and construction, to packaging, cars, and textiles
[54]. However, the chemical industry is also deeply involved in many issues related to Planetary Boundaries, such as greenhouse gas emissions, the discharge of waste plastics into the oceans, deviations from the natural cycle of nitrogen and phosphorus, and the loss of biodiversity
[1].
The chemical industry plays a significant role in global emissions due to its energy-intensive processes and reliance on fossil fuels. However, several promising and state-of-the-art technological innovations are emerging to shift the industry towards net-zero emissions.
Carbon Capture, Utilization, and Storage (CCUS) [55][56]. CCUSs capture CO
2 emissions from industrial processes and either store CO
2 underground by injecting it into suitable geological formations or utilize it for other purposes
[57]. Technologies such as electrochemical conversion
[58][59], catalytic hydrogenation
[60], and photocatalytic conversion of CO
2 [61] have the potential to reintegrate captured CO
2 into the value chain by converting it into fuels and chemicals.
Electrification and renewable energy integration. Shifting from fossil fuel-based energy sources to renewable energy is crucial for decarbonizing the chemical industry. The electrification of processes
[62][63], by switching from fossil-powered processes to electricity-powered processes (e.g., electrical furnaces and boilers, heat pumps) and the integration of renewable energy sources
[64][65][66][67], such as solar, wind and biomass, can reduce or eliminate the need for fossil fuel combustion.
Hydrogen as a feedstock and energy carrier. Hydrogen produced from renewable sources (green hydrogen) can serve as a clean feedstock and energy carrier in chemical manufacturing processes. It can be produced by biological processes
[68][69], e.g., direct, and indirect photolysis, photo-fermentation, or dark fermentation), by thermochemical processes
[70], e.g., biomass pyrolysis and gasification, or electrolysis of water
[71], by electrolysis, e.g., proton exchange membrane electrolysis, anion exchange membrane electrolysis
[72], or solid oxide electrolysis
[73].
Bio-based feedstocks. The utilization of bio-based feedstocks derived from biomass can help reduce the industry’s reliance on fossil fuels. Biomass, such as agricultural residues
[74], and food wastes
[75], can be converted into bio-based chemicals through various processes such as fermentation
[76], enzymatic conversion
[77], or thermochemical conversion
[78].
Process optimization and advanced catalysts. Improving the efficiency of chemical processes and developing advanced catalysts
[79][80], can reduce energy consumption and emissions through increased conversion and selectivity and milder operating conditions with respect to temperature and pressure.
Circular economy and recycling. Embracing a circular economy approach within the chemical industry involves designing products for reusability, recycling, or biodegradability
[81]. Developing innovative recycling technologies, such as chemical recycling, enables the recovery of valuable materials and reduces the need for virgin feedstocks
[82].
Artificial intelligence (AI) and data analytics. AI and data analytics can be employed to optimize processes
[83], predict and detect anomalies
[84], etc. AI and data analytics will play a major role in boosting new product development, increasing the safety and reliability of chemical production processes, and enhancing the sustainability of chemical supply networks.
2.4.2. Pharmaceutical Industry
The pharmaceutical industry plays a vital role in advancing human health, but its environmental impact cannot be overlooked. The manufacturing processes involved in pharmaceutical production generate significant GHG emissions
[85], contributing to climate change. The pharmaceutical industry is responsible for an estimated annual direct emission of approximately 52 Mt of CO
2 equivalent worldwide
[86]. It is important to note that this estimation solely accounts for emissions directly generated by pharmaceutical activities, without taking into consideration the indirect emissions associated with energy use throughout the entire supply chain. Indirect emissions may arise from various sources such as the transportation of medicines, lighting and refrigeration in distribution facilities, and other energy-related processes.
The pharmaceutical industry is exploring various state-of-the-art technological innovations that hold promise for shifting towards net-zero emissions. Several key advancements have emerged in recent years:
Green Chemistry and Sustainable Synthesis. The adoption of green chemistry principles and sustainable synthesis methods is gaining traction in pharmaceutical manufacturing. This approach focuses on minimizing the use of hazardous materials
[87], optimizing chemical processes, and designing more environmentally friendly reactions to reduce waste generation and energy consumption
[88][89].
Process Intensification and Continuous Manufacturing. Process intensification involves optimizing manufacturing processes to improve efficiency, reduce resource consumption, and decrease emissions. Continuous manufacturing, as opposed to batch processing, allows for streamlined operations, reduced waste, and improved energy and material efficiency, thereby lowering the overall carbon footprint
[90][91][92][93].
Decentralized Energy Generation and Advanced Energy Management Systems. Utilizing waste-to-energy systems
[94], solar photovoltaic systems, wind turbines, and biomass energy facilities on-site can significantly reduce reliance on fossil fuels. Advanced energy management systems integrate energy storage, demand response, and smart grid technologies. This enables the optimization of energy use, real-time monitoring of energy consumption, and identification of opportunities to improve energy efficiency.
Circular Economy and Waste Reduction. Implementing circular economy practices within the pharmaceutical industry can minimize waste generation and resource depletion
[95][96]. Recycling and repurposing of materials
[97], implementing closed-loop systems
[98], and developing innovative recycling technologies
[99] enable the recovery of valuable resources, reducing the reliance on virgin materials and reducing emissions associated with raw material extraction and production.
Digitalization and Data Analytics. Leveraging digital technologies, such as artificial intelligence (AI), machine learning, and data analytics
[100][101], can identify novel and sustainable reaction pathways and thus directly or indirectly optimize processes, improve energy efficiency, and identify opportunities for emission reduction. Advanced modeling and simulation tools
[102] can also aid in designing more sustainable and environmentally friendly pharmaceutical manufacturing processes
[103][104].
2.4.3. Cement Industry
Around 40% of CO
2 emissions from fuel combustion worldwide and 25% of global GHG emissions are attributed to the built environment
[105]. Among these figures, cement production stands out as one of the most significant contributors, responsible for 6–10% of global CO
2 emissions
[106].
The cement and concrete industry can utilize the following strategies to accomplish their decarbonization objectives.
Reducing the fraction of clinker in cement. The emission from cement production is predominantly caused by clinker, accounting for roughly 90% of the total
[107]. This makes it imperative for industry stakeholders to prioritize finding solutions for clinker-related emissions. To decarbonize the industry, cement manufacturers can explore the possibility of replacing clinker with alternative materials such as fly ash
[108][109], granulated blast furnace slag
[110], calcined clays
[111] and even red mud, to some extent
[112][113].
Reducing energy-related CO2 emissions. To decrease emissions associated with energy usage, industry participants are actively investigating alternative fuels (biomass and municipal and industrial wastes and their mixtures)
[114][115], developing innovative technologies such as kiln electrification
[116][117], oxy-combustion
[118], and heat generation via plasma technology
[119].
Carbon capture, storage, and utilization. The CO
2 emissions captured from production processes
[120][121] can be reintegrated into the value chain through various means
[122]. For instance, they can be utilized in the production of recycled clinker (mineralization,
[123]) or incorporated into fresh concrete (carbon curing,
[124]). Moreover, concrete structures can absorb a substantial amount of CO
2 during their lifespan through a process called recarbonation.
4.4.4. Glass Industry
The UK glass industry has increased energy efficiency by 50% in the last 40 years by using waste heat, Organic Rankine Cycle, or steam turbine to preheat raw materials, fuel, or oxidants
[125]. Oxyfuel combustion is using oxygen instead of combustion air, yielding energy savings of 10–15% and reduced emissions. Fossil fuels can be replaced by biofuels with reduced emissions of NOx. All electric furnaces are an established technology in the glass sector and are more efficient than gas-fired furnaces. The latest development is using up to 80% electricity with 20% gas energy (hybrid furnaces) with the future opportunity to consider hydrogen combustion using 100% hydrogen as well as different proportions of hydrogen blended with natural gas for glass melting.
Process emissions can be reduced by using a higher fraction of recycled glass which substitutes the carbonate raw material and reduces CO
2 emissions
[125]. Alternative raw materials, such as calcium oxide, mineral slags, waste incineration ashes, etc., can replace carbonate raw material or reduce the melting temperature of the glass and thereby energy requirements. CCUS may be needed as a final stage for decarbonization.
2.5. Biotechnology
Industrial biotechnology, based on renewable resources, can save energy and significantly reduce CO
2 emissions. Bio-based chemicals can replace their fossil-based counterparts with significant GHG emissions reductions
[126]. Bio-based plastics are potentially attractive in terms of specific emissions and energy savings. Governmental intervention can play a significant role in the effort to advance the industrial biotechnology sector toward lower GHG emissions, e.g., emissions trading systems (ETS) or tax for transportation emissions, pollution costs charged to petrol-based materials, labeling systems for bio-based materials and biofuels, public procurement supporting bio-based materials and sustainably produced biofuels
[127].
2.6. Metals Production
2.6.1. Iron and Steel
CO
2 emissions and energy use in European steel production have already been halved since 1960
[17]. Presently, the EU steel industry is mainly focusing on hydrogen-based steelmaking as a decarbonization strategy. Carbon capture and utilization technologies will be developed in partnership with the chemical industry. Recycled iron and steel waste, and the electrolytic reduction of iron ore will be used for iron and steel production. Renewable electricity and transmission networks, hydrogen-related infrastructure or CO
2 transport, and storage infrastructures will be built.
2.6.2. Aluminum
An aluminum net-zero transition strategy will require
[128]:
-
Power decarbonization is critical: all smelters will need to switch to low carbon power by 2035, equating to approx. 1000 TW h of low-carbon electricity demand.
-
Power decarbonization is necessary but not sufficient to decarbonize the sector; new technology for low carbon anodes and new refining technologies need to be commercialized by 2030.
-
Recycled aluminum plays a critical role, expanding from 33% of supply in 2020 to over 50% by 2050.
-
Mobilizing approximately 1 TUSD (1012 USD) of the investment over the next 30 years will be needed to deliver the transition for the primary aluminum sector, with over 70% of the sum required for supporting infrastructure, most of it for power supply.
2.7. Pulp and Paper
-
The pulp and paper industry is among the top five most energy-intensive industries globally and is the fourth largest industrial energy user. This industry accounts for approximately 6% of global industrial energy use and 2% of direct industrial CO
2 emissions
[129]. As the paper production will increase, greater efforts must be made to reduce the emissions intensity of production by 2030 by substituting fossil fuels with renewable energy sources, e.g., biofuels, accelerating the energy efficiency improvements, and reducing the energy needed for drying
[130].
-
Substituting more pulp by recycled wastepaper to over 60% by 2030.
-
Installation of high-temperature heat pumps using waste heat sources inside the production process.
-
On-site waste heat recovery and co-generation.
-
Emerging technologies, e.g., heat recovery from thermomechanical pulping, black liqueur gasification, microwave drying, supercritical CO2 or deep eutectic solvent.
EU believes that by 2050 the European pulp and paper industry can reduce its energy consumption by 14% and greenhouse gas (GHG) emissions by 62% compared to 2015 levels
[131]. Carbon capture and storage (CCS) could further reduce GHG emissions. Biorefinery products from the pulp and paper mills could replace fossil fuels for light duty vehicles, be used as raw materials in the chemical industry, or as fertilizers.
2.8. Key Technologies Related to Net-Zero Emission
Several technologies, directions, and approaches have been identified as important for the transition to a net-zero economy. Some of these are tailored to a specific industry, such as the reduction of the fraction of clinker in cement in the cement industry, while others are across industries, such as carbon capture, electrification, waste reduction, etc. To indirectly assess the activity of the development and interest in respective fields as they pertain to net-zero emissions, a Google search was performed relating some of these to net-zero emissions.
3. Conclusions
In conclusion, recognizing the complex interlinkages between sectors and understanding that emissions need to be addressed holistically across the value chain are crucial aspects to successfully achieving this ambitious goal. Furthermore, the roadmap toward net-zero emissions must encompass not only net-zero energy production, but also net-zero feedstock production.