Low-cost solar PV can turn CO2 into profitable materials enabling negative emissions

Reaching net zero emissions by 2050 is achievable, whereby any amount of residual and unavoidable CO₂ emissions must be compensated by carbon sinks, either natural or artificial. Unlike carbon capture, and sequestration (CCS) where CO₂ is captured from fossil exhaust gas streams with subsequent sequestration, carbon capture, and utilization (CCU) is often identified as an effective approach to capture CO₂ from the atmosphere and convert it into valuable products to generate an economical gain of the carbonaceous product rather than CO₂ disposal. However, not all CCU pathways contribute to net-negative emissions.

With this in mind, researchers at LUT University explored a broader perspective integrating CCU with carbon dioxide removal (CDR), forming carbon capture, utilization, and sequestration (CCUS). In this approach, captured CO₂ is treated as a precious raw material, enabling the production of profitable materials in which CO₂, or rather carbon, is sequestered with high permanence. This not only converts CO₂ into value-added products with many applications but also opens new pathways for materials innovation, leading to broader industrial defossilization.

Solar PV-powered CCUS pathways

Low-cost solar PV electricity plays an important role in ensuring that all processes related to CCUS are sustainable, while enabling the production of profitable materials and substantial negative emissions. Recent studies have investigated this potential as an effective CDR option across three specific materials, namely carbon fiber, silicon carbide, and graphene, which are highly energy intensive and highly CO₂-emissive in their conventional production value chains. These materials also exhibit strong market growth, wide-ranging applications, and high resistance to degradation, fulfilling essential criteria for CCUS.

Accordingly, defossilizing their conventional production processes through low-cost renewable electricity, combined with a carbon source derived from atmospheric CO₂ captured via direct air capture (DAC) systems, reveals the potential for substantial negative emissions alongside favorable economic outcomes by the mid-century. In this context, electricity-based carbon fiber (e-CF) production using atmospheric CO₂ shows the emergence of a viable business case, with a projected production cost of €10.3 ($12.1)/kgCF by 2050. Although the cost of carbon sequestration remains relatively high at €2949 /tCO₂, the projected profit reached is €1461 /tCO₂ by 2050. The electricity requirement for carbon sequestration is estimated at 53.7 MWh_el/tCO₂, while production requires 186.8 MWh_el/tProduct by 2050.

Similarly, electricity-based silicon carbide (e-SiC) production using atmospheric CO₂ as the carbon source and low-cost solar PV electricity shows strong application potential. The cost of carbon sequestration is estimated at €303 /tCO₂ in 2050, while a monetizable carbon removal loop is enabled through a projected production cost of €0.7 /kgSiC with a profit of €259 /tCO₂ by 2050. The electricity requirement for carbon sequestration is 9.9 MWh_el/tCO₂, by 2050 while production requires 24.2 MWh_el/tProduct by 2050.

Electricity-based graphene (e-GR), often referred to as the wonder material of the 21^st century, is evaluated for its suitability as an effective CDR option and for defossilization in processing and synthesis stages. Two specific bottom-up production approaches are considered, as they enable the formation of highly stabilised product, which directly influence sequestration permanence and overall CDR effectiveness. The production of e-GR using low-cost solar PV electricity and atmospheric CO₂ captured via DAC is assessed in terms of cost, energy demand, and sequestration potential for two specific production pathways namely the chemical vapour deposition (CVD) and electron beam plasma methane (EBPM) pyrolysis.

The results indicate that not all carbon utilization pathways perform equally. The CVD pathway produces high-quality e-GR but is economically and energetically unattractive as a CDR option, with a carbon sequestration cost of €24,402 /tCO₂, and a production cost of €89.5 /kgGraphene. In contrast, the EBPM pyrolysis pathway exhibits significantly lower energy demand, with electricity requirements of 13.1 MWh_el/tCO₂ for sequestration and 47.9 MWh_el/tProduct for production, showing a more viable pathway for CO₂ sequestration. The projected profit for the CVD method is €2643 /tCO₂ (€9693 /tProduct) by 2050, while EBPM pyrolysis yields €2351 /tCO₂ (€8621 /tProduct) by 2050.

Overall, all three e-material pathways demonstrate a competitive balance between cost, energy demand, and sequestration potential, with each material offering a wide range of applications.

Materials defossilization across nano, micro, and macro scales

An important insight from this research stream is that substantial negative emissions are achievable through CCUS pathways powered by low-cost renewable electricity enabled by solar PV, with atmospheric CO₂ serving as the carbon feedstock, transforming conventional production processes of valuable products into fully sustainable systems. The successful deployment of a monetizable and fully defossilized e-CF production value chain highlights the opportunity to further investigate the CDR potential of other materials whose fundamental structural units lie at the microscale.

The negative emission potential of e-CF along with its exceptional properties such as high tensile strength and modulus, positions e-CF-reinforced concrete as a potential substitute for construction steel. Each tonne of e-CF produced can store about 3.5 tCO₂, due to the high carbon content of the final product, enabling a total negative emission potential of at least 0.7 GtCO₂/a by 2050.

Similarly, e-SiC presents a promising pathway for the industrial defossilisation of materials whose fundamental structural units span the micro to macro scale. High combustion points and chemical inertness of e-SiC make it particularly attractive as an effective CCUS option. Given the compatibility of e-SiC grain size with construction sand, e-SiC may serve as a substitute for construction sand. If 50% of the global demand for construction sand were substituted with e-SiC, the total volume of sequestered CO₂ could reach 13.6 GtCO₂/a by 2050. When applied to meet the global demand for technical ceramics, the negative emission potential of e-SiC is estimated at 0.29 GtCO₂/a by 2050.

At the nanoscale, the response of nanomaterials to CO₂ sequestration and negative emissions is equally important. Graphene is a carbon nanomaterial, known for its exceptional physical properties. With a very high carbon content of nearly 99% in the final product, the total volume of sequestered CO₂ in graphene could reach up to 2.57 GtCO₂/a by 2050. The cumulative CDR deployment from e-CF, e-SiC, and e-GR is estimated at 843.5 GtCO₂ by the end of the century, reflecting progressive defossilization of energy-intensive and highly carbon-emissive industrial materials across nano, micro, and macro scales.

The role of e-GR as a CDR option is further reinforced by its emerging potential as an electrode material in lithium-ion batteries. Using graphene as an electrode additive in lithium-ion batteries increases the lithium-ion’s storage capacity, increasing the battery performance and extending battery lifetime compared to conventional batteries. This contributes to reducing pressures associated with mining, processing, and refining of critical raw materials, alleviating supply chain challenges for raw materials such as lithium. e-GR can play an important role as electrode material for sodium-ion batteries.

The broader defossilization of materials also includes the steelmaking and maybe restructuring of respective steel value chains. Similarly, the chemical industry can be defossilized, which may also go alongside chemicals value chain restructuring, more convergence of the chemical industry with the energy system, and it will include e-ammonia and e-methanol as major feedstocks for the chemical industry with main products such as e-plastics. The overall defossilization of energy-intensive industry will use as many direct electric solutions as possible, but also hydrogen-based solutions where required.

While the defossilization of the global chemical industry is still at an early stage, promising defossilization pathways could be encouraged for materials across nano, micro, and macro scales through the use of low-cost solar PV electricity and atmospheric CO₂ captured via DAC systems. These pathways enable substantial negative emissions by mid-century, highlighting a significant opportunity within the broader climate challenge. Material scientists and industry stakeholders may be encouraged to further explore CCUS pathways powered by renewable electricity and DAC systems. Solar PV-dominated energy-industry-CDR systems could contribute to climate change mitigation through material defossilization, and economically viable carbon dioxide removal.

Authors: Maheshika H.K. Premarathna, Dominik Keiner, and Christian Breyer

This article is part of a monthly column by LUT University.

Research at LUT University encompasses various analyses related to power, heat, transport, industry, desalination, and carbon dioxide removal options. Power-to-X research is a core topic at the university, integrated into the focus areas of Planetary Resources, Business and Society, Digital Revolution, and Energy Transition. Solar energy plays a key role in all research aspects.

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