In this paper, three of the leading options for large scale CO₂ capture are reviewed from a technical perspective. We consider solvent-based chemisorption techniques, carbonate looping technology, and the so-called oxyfuel process. For each technology option, we give an overview of the technology, listing advantages and disadvantages. Subsequently, a discussion of the level of technological maturity is presented, and we conclude by identifying current gaps in knowledge and suggest areas with significant scope for future work. We then discuss the suitability of using ionic liquids as novel, environmentally benign solvents with which to capture CO₂. In addition, we consider alternatives to simply sequestering CO₂—we present a discussion on the possibility of recycling captured CO₂ and exploiting it as a C₁ building block for the sustainable manufacture of polymers, fine chemicals, and liquid fuels. Finally, we present a discussion of relevant systems engineering methodologies in carbon capture system design.

Calcium looping is a high-temperature CO₂ capture technology applicable to the postcombustion capture of CO₂ from power station flue gas, or integrated with fuel conversion in precombustion CO₂ capture schemes. The capture technology uses solid CaO sorbent derived from natural limestone and takes advantage of the reversible reaction between CaO and CO₂ to form CaCO₃; that is, to achieve the separation of CO₂ from flue or fuel gas, and produce a pure stream of CO₂ suitable for geological storage. An important characteristic of the sorbent, affecting the cost-efficiency of this technology, is the decay in reactivity of the sorbent over multiple CO₂ capture-and-release cycles. This work reports on the influence of high-temperature steam, which will be present in flue (about 5–10%) and fuel (∼20%) gases, on the reactivity of CaO sorbent derived from four natural limestones. A significant increase in the reactivity of these sorbents was found for 30 cycles in the presence of steam (from 1–20%). Steam influences the sorbent reactivity in two ways. Steam present during calcination promotes sintering that produces a sorbent morphology with most of the pore volume associated with larger pores of ∼50 nm in diameter, and which appears to be relatively more stable than the pore structure that evolves when no steam is present. The presence of steam during carbonation reduces the diffusion resistance during carbonation. We observed a synergistic effect, i.e., the highest reactivity was observed when steam was present for both calcination and carbonation.

Several different carbon-capture technologies have been proposed for use in the cement industry. This paper reviews their attributes, the progress that has been made toward their commercialization, and the major challenges facing their retrofitting to existing cement plants. A technology readiness level (TRL) scale for carbon capture in the cement industry is developed. For application at cement plants, partial oxy-fuel combustion, amine scrubbing, and calcium looping are the most developed (TRL 6 being the pilot system demonstrated in relevant environment), followed by direct capture (TRL 4–5 being the component and system validation at lab-scale in a relevant environment) and full oxy-fuel combustion (TRL 4 being the component and system validation at lab-scale in a lab environment). Our review suggests that advancing to TRL 7 (demonstration in plant environment) seems to be a challenge for the industry, representing a major step up from TRL 6. The important attributes that a cement plant must have to be “carbon-capture ready” for each capture technology selection is evaluated. Common requirements are space around the preheater and precalciner section, access to CO₂ transport infrastructure, and a retrofittable preheater tower. Evidence from the electricity generation sector suggests that carbon capture readiness is not always cost-effective. The similar durations of cement-plant renovation and capture-plant construction suggests that synchronizing these two actions may save considerable time and money.