Cheap solar energy can convert CO2 into profitable materials that enable negative emissions – SPE

Achieving net zero emissions by 2050 is achievable, with any amount of residual and unavoidable CO₂ the emissions must be offset by carbon sinks, natural or artificial. Unlike carbon capture and sequestration (CCS) where CO₂ is collected from fossil exhaust gas flows with subsequent storage, carbon capture and use (CCU) is often seen as an effective approach to capturing CO₂ from the atmosphere and converts it into valuable products to generate an economic profit from the carbon-containing product instead of CO₂ availability. However, not all CCU routes contribute to net negative emissions.

With this in mind, researchers from LUT University explored a broader perspective that incorporated CCU carbon dioxide removal (CDR)forming carbon capture, use and sequestration (CCUS). In this approach, captured CO₂ is treated as a precious commodityallowing the production of profitable materials containing CO₂or rather carbon, is captured with high sustainability. This not only converts CO₂ in value-added products with many applications, but also opens new avenues for material innovation, leading to broader industrial defossilization.

Solar powered CCUS trails

Cheap solar PV electricity plays an important role in ensuring that all processes associated with CCUS are sustainable, while enabling the production of profitable materials and significant negative emissions. Recent studies have explored this potential as an effective CDR option for three specific materials viz carbon fiber, silicon carbideAnd graphenewhich are very energy intensive and emit a lot of CO2₂-emissive in their conventional production value chains. These materials also demonstrate strong market growth, broad applications and high resistance to degradation, meeting essential criteria for CCUS.

Accordingly, defossilizing their conventional production processes through cheap renewable electricity, combined with a carbon source derived from it atmospheric CO₂ captured via Direct Air Capture (DAC) systemsreveals the potential for substantial negative emissions alongside favorable economic outcomes by mid-century. In this context, electricity-based carbon fiber (e-CF) production using atmospheric CO₂ shows the emergence of a viable business case, with an expected production cost of €10.3 ($12.1)/kgCF in 2050. Although the cost of carbon sequestration remains relatively high at €2949/tCO₂the expected profit is €1461/tCO₂ by 2050. The electricity requirement for carbon sequestration is estimated at 53.7 MWh_el/tCO₂while 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 cheap solar PV electricity show strong application potential. The cost of carbon sequestration is estimated at €303/tCO₂ in 2050, while enabling a monetized carbon removal cycle through an expected 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/tCO₂by 2050, while production requires 24.2 MWh_el/tProduct by 2050.

Electricity-based graphene (e-GR), often called the wonder material of the 21^st century, is being 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 allow the formation of highly stabilized products, which have a direct impact on the sustainability of storage and the overall effectiveness of CDR. The production of e-GR using cheap solar PV electricity and atmospheric CO2₂ captured via DAC is assessed in terms of cost, energy demand and sequestration potential for two specific production routes, namely chemical vapor deposition (CVD) and electron beam plasma methane pyrolysis (EBPM).

The results indicate that not all carbon use pathways perform equally well. The CVD route produces high quality e-GR, but is economically and energetically unattractive as a CDR option, with carbon sequestration costs of €24,402 /tCO₂and production costs of €89.5/kg Graphene. In contrast, the EBPM pyrolysis route shows a significantly lower energy demand, with an electricity requirement of 13.1 MWh_el/tCO₂ for sequestration and 47.9 MWh_el/tProduct for production, which shows a more feasible route for CO2₂ storage. The expected profit for the CVD method is €2643/tCO₂ (€9693/tProduct) in 2050, while EBPM pyrolysis yields €2351/tCO₂ (€8621/tProduct) by 2050.

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

Defossilization of materials on nano, micro and macro scales

A key insight from this research stream is that substantial negative emissions are achievable through CCUS pathways powered by low-cost renewable electricity enabled by solar energy, with atmospheric CO₂ It serves as a carbon feedstock and transforms conventional production processes of valuable products into fully sustainable systems. The successful deployment of a monetized and fully de-carbonized e-CF production value chain highlights the possibility of further exploring the CDR potential of other materials whose fundamental structural units lie at the microscale.

The negative emission potential of e-CF, together with its exceptional properties such as high tensile strength and modulus, positions e-CF reinforced concrete as a potential replacement for structural steel. Each ton of e-CF produced can store approximately 3.5 tCO₂due to the high carbon content of the final product, allowing a total negative emission potential of at least 0.7 GtCO₂/a by 2050.

In the same way, e-SiC presents a promising pathway for the industrial defossilization of materials whose fundamental structural units span the micro to macro scales. High combustion points and chemical inertia of e-SiC make it particularly attractive as an effective CCUS option. Given the compatibility of the grain size of e-SiC with construction sand, e-SiC can serve as a solution replacement for construction sand. If 50% of the global demand for construction sand were replaced by e-SiC, the total volume of CO captured would₂ could reach 13.6 GtCO₂/a by 2050. When applied to meet 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 reaction is… nanomaterials to CO₂ sequestration and negative emissions are equally important. Graphene is one carbon nanomaterial, known for its exceptional physical properties. With a very high carbon content of almost 99% in the final product, the total volume of captured CO₂ in graphene can amount to 2.57 GtCO₂/a by 2050. The cumulative CDR implementation of e-CF, e-SiC and e-GR is estimated at 843.5 GtCO₂ towards the end of the century, due to the gradual defossilization of energy-intensive and highly carbon-emissive industrial materials at nano, micro and macro scales.

The role of e-GR as a CDR option is further enhanced by its emerging potential as an electrode material in lithium-ion batteries. Using graphene as electrode additive in lithium-ion batteries increases the storage capacity of lithium ions, increasing battery performance and extending battery life compared to conventional batteries. This helps reduce the pressure associated with the mining, processing and refining of critical raw materials, easing the pressure challenges in the supply chain for raw materials such as lithium. e-GR can play an important role as an electrode material sodium-ion batteries.

The broader defossilization of materials also includes the steel production and perhaps the restructuring of the respective steel value chains. In the same way the chemical industry can be defossilized, which is also possible chemical value chain restructuring, more convergence of the chemical industry with the energy systemand it will include e-ammonia And e-methanol as important raw materials for the chemical industry with main products such as e-plastics. The whole defossilization of energy-intensive industry will use the same amount direct electrical solutions possible, but also hydrogen-based solutions where necessary.

While the defossilization of the global chemical industry is still in its early stages, promising defossilization pathways can be encouraged for nano-, micro-, and macro-scale materials through the use of cheap 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. Materials scientists and industry stakeholders can be encouraged to further explore CCUS pathways powered by renewable electricity and DAC systems. Solar dominated CDR systems for the energy industry could contribute to mitigating climate change by defossilizing materials and economically viable carbon dioxide removal.

Authors: Maheshika HK Premarathna, Dominik Keiner and Christian Breyer

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

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