As we count down to the 4th International Conference on Carbon Dioxide Removal in Milano, we are hosting a series of discussions on the research that will be shaping our sessions this June! 
This research investigates the potential of naturally occurring sodium carbonate and bicarbonate minerals 
as highly scalable feedstocks for Ocean Alkalinity Enhancement, 
identifying substantial global trona and related mineral reserves capable of supporting massive, gigatonne-scale carbon removal for decades to come! 
The authors show that while raw evaporites have limited direct removal efficiency on their own, engineered conversion pathways to sodium carbonate and sodium hydroxide could enable net-negative and increasingly effective OAE deployment as global energy systems decarbonise 
and low-carbon processing technologies mature! 
Read the full paper here: Link 
Full Abstract: Harnessing Naturally Occurring Sodium Carbonate and Bicarbonate for Gigatonne-Scale Carbon Removal
Authors: James Campbell, Spyros Foteinis, Reinaldo Lee Pereira, Mijndert van der Spek, Phil Renforth
Ocean alkalinity enhancement (OAE) is a promising carbon dioxide removal (CDR) approach, but scaling to the much-needed gigatonne (Gt) per year level will require safe, sustainable, and abundant alkaline feedstocks. Here, we propose the use of a relatively unexplored resource for OAE: naturally occurring sodium (bi)carbonate evaporites whose resources and reserves remain poorly quantified. We identified and mapped 96 such deposits globally, but quantitative tonnage data were available for only 14 of these. Even so, these 14 deposits alone contain an estimated 169 Gt of trona (Na2​CO3​⋅NaHCO3​⋅2H2​O), concentrated mainly in the United States, with additional large occurrences in China, Turkey, and Africa. A further ~58 Gt of closely related Na-(bi)carbonate minerals, such as nahcolite and dawsonite, were also identified. Taken together, these inventories could in principle sustain CDR at >1 Gt CO2​ yr−1 for multiple decades.
However, trona and similar raw evaporites exhibit relatively low CDR capacities when used directly. We therefore evaluate engineering pathways that transform trona (gross CDR capacity 0.16 tCO2​ t−1) into sodium carbonate (Na2​CO3​, 0.31 tCO2​ t−1) or sodium hydroxide (NaOH, ~0.98 tCO2​ t−1 equivalent), while applying prospective life-cycle assessment (pLCA) to quantify future carbon penalties. Under an illustrative 2030 deployment scenario, all pathways are net-negative, with the simplest route, calcination to Na2​CO3​, yielding the highest net CDR capacity. As the energy system decarbonises and new kiln technologies, such as electric calciners, become widespread by 2050, a titanate looping process, producing aqueous NaOH, eventually surpasses the net CDR capacity of the Na2​CO3​ route. Overall, sodium (bi)carbonate evaporites emerge as a promising, soluble, safe, and scalable feedstock for OAE-based CDR.
As we try to scale up ocean carbon removal to a global level, how should we balance the environmental impacts of processing mineral deposits on land with the benefits they bring to the sea? 
