The needed ground infrastructure includes air fields (including runways and support infrastructure), the supply chain for sulfur (e.g. rail or ship) and facilities to convert sulfur to either H2S or SO2. Permitting for all of the above would also be required but this process itself is not included in the uncertainty here (as this database is currently intended to capture only scientific and engineering uncertainties and not (yet) societal ones. But the permitting will have implications for the technical considerations. For example, planes will likely be required to take off straight over the ocean, which would impact site choice and the build timeline. Additionally, this uncertainty will be impacted by what type of airports can be used based on the material selected (commercial, military, or purpose). We note the timeline for ground infrastructure can be longer without delaying deployment if restricting the deployment to for lower-latitude / high-altitude injection, for which the initial aircraft procurement is a longer step.
Metric
Time to develop ground infrastructure necessary to deliver ~1Mt/yr payload is over 5 years from first large-scale funding
Uncertainty
Largely unexplored (mostly because it hasn't been assumed to be a significant limiting factor). Satisfying stakeholders (govt/public) regarding safety and liability likely more challenging that the actual engineering involved, and may limit options
Decision relevance
Would delay deployment. Note the coupling with the question of high- vs low-altitude injection (i.e. new vs modified existing aircraft for the initial years of deployment); if the latter is an option for early deployment, then the ground infrastructure could be the limiting factor for when deployment could start, but if the latter is not an option (i.e. only high-altitude injection is acceptable), then ground infrastructure is less likely to be the limiting step.