Rev. Rul. 2021-13, page 152.

The revenue ruling explains that: (1) an acid gas removal unit at an industrial facility is a component of carbon capture equipment within the meaning of § 1.45Q-2(c); (2) an investor in certain components of carbon capture equipment at an industrial facility is not required to own every component of carbon capture equipment within a single process train at an industrial facility to be the person to whom the section 45Q credit is attributable under § 1.45Q-1(h), but must own at least one component of carbon capture equipment in the single process train of carbon capture equipment at the industrial facility; (3) solely for purposes of section 45Q(a), the original placed-in-service date of a single process train of carbon capture equipment at an industrial facility that includes the existing acid gas removal unit and new components of carbon capture equipment is the date that the single process train is placed in a condition or state of readiness and availability for the capture, processing, and preparation of carbon oxide for transport for disposal, injection, or utilization; and (4) the original placed-in-service date of the single process train for purposes of §§ 167 and 168.