The permanence of stored carbon is the big question.

UN Supervisory Body for the new 6.4 carbon market being set up has asked for feedback on what makes a carbon removal credit.

See doc here – questions listed as A-G (Paragraph numbering went a bit weird. Sorry. Refer to source doc):

Paste for convenience

Questions on specific elements
A. Definitions:
Discuss the role and potential elements of definitions for this guidance, including “Removals”.
B. Monitoring and Reporting:

1. What timeframes and related procedures should be specified for these elements referred
   to in A6.4-SB003-A03?
   a. For initial monitoring and submission of monitoring reports (paragraph 3.2.14);
   (a) For subsequent monitoring and submission of monitoring reports (paragraph
   3.2.14);
   (b) For monitoring and submission of monitoring reports following an observed event
   that could potentially lead to a reversal (paragraph 3.2.14);
   (c) For monitoring and reporting, including any simplified reporting, conducted after
   the end of the last crediting period of activities involving removals (paragraphs
   3.1.10 and 3.2.13).
2. Discuss any further considerations to be given to the core elements for monitoring and
   reporting in A6.4-SB003-A03; where possible, identifying the applicable scope, i.e.,
   relevance to all 6.4 mechanism activities, to removals activities, or to specific removal
   activity categories or types.
   
   
   C. Accounting for removals:
3. Discuss any further considerations to be given to the core elements for accounting for
   removals in A6.4-SB003-A03; where possible, identifying their applicable scope, i.e.,
   relevance to all 6.4 mechanism activities, to removals activities, or to specific removal
   activity categories or types.
4. For activities involving removals that also result in emissions reductions, what are the
   relevant considerations, elements, and interactions between this guidance and the
   requirements for the development and assessment of mechanism methodologies,
   including.
   
   
   D. Crediting period:
   Discuss any further considerations to be given to the core elements for crediting periods in A6.4-
   SB003-A03; where possible, identifying the applicable scope, i.e., relevance to all 6.4
   mechanism activities, to removals activities, or to specific removal activity categories or types.
   
   
   E. Addressing Reversals:
   In order to minimize the risk of non-permanence of removals over multiple NDC implementation
   periods, and, where reversals occur, ensure that these are addressed in full.
   A6.4-SB005-A02
   Information note: Guidance and questions for further work on removals
   Version 02.0
   5 of 7
5. Discuss the applicability and implementation aspects of these approaches, including as
   stand-alone measures or in combination, and any interactions with other elements of this
   guidance:
   a. Non-permanence risk buffer (pooled or activity-specific);
   b. Insurance / guarantees for replacement of ERs where reversals occur
   (commercial, sovereign, other);
   c. Other measures for addressing reversals in full.
6. Discuss the appropriate timeframe(s) for applying the approaches, including any
   interactions with other elements of this guidance and the applicable scope, i.e., relevance
   to all 6.4 mechanism activities, to removals activities, or to specific removal activity
   categories or types.
7. What risks of non-permanence need to be minimized, and how can these risks identified,
   assessed, and minimized?
8. In respect of risk assessment, how should the following elements be considered in the
   implementation of the approaches in (a) and any other relevant elements in this guidance?
   a. Level of non-permanence risk assessment, e.g., activity- or mechanism-level
   b. Timing for risk assessment(s)
   c. Entity(ies) responsible for risk assessment(s), e.g., activity proponent, 6.4SB,
   actuary
9. How should the following elements be considered in the implementation of the approaches
   in (1) above and any other relevant elements in this guidance?
   a. Methods for determining the level of buffer pool contributions
   b. Composition of buffer pool, including in relation to ER vintages and contributing
   activity types or categories
   c. Intentional and unintentional reversals
   d. Treatment of uncancelled buffer ERs, including after the end of the last crediting
   period of the contributing activity
   e. Specifications for ERs that cancelled for compensate for reversals, including in
   relation to ER vintages and contributing activity types or categories
   f. Replenishment in case buffer cancellations exceed contributions; slide language
   on re-raising baseline level of storge before new crediting
10. In the event of a reversal, what interactions and implementation aspects should be
    considered in respect of other elements of the activity cycle?
    
    
    F. Avoidance of Leakage:
    Discuss any further considerations to be given to the core elements for leakage avoidance in
    A6.4-SB003-A03; where possible, identifying the applicable scope, i.e., relevance to all 6.4
    mechanism activities, to removals activities, or to specific removal activity categories or types.
    A6.4-SB005-A02
    Information note: Guidance and questions for further work on removals
    Version 02.0
    6 of 7
    
    
    G. Avoidance of other negative environmental, social impacts
    Discuss considerations to be given to core elements for avoidance of other negative
    environmental, social impacts; where possible, identifying the applicable scope, i.e., relevance to
    all 6.4 mechanism activities, to removals activities, or to specific removal activity categories or
    types.