[This is the second part of a two-part piece about permanence. Part 1 can be found here.]
Permanence is a concept that’s easily grasped but not well understood.
Arguably, that didn’t much matter when questions of permanence were confined to forestry and other LULUCF interventions. Specialists in these areas have long appreciated carbon reversibility risks: financial models, project management techniques and carbon crediting approaches have all been built around the potential transience (here today, gone tomorrow) of stored carbon.
But, as the number and diversity of climate interventions have grown, so, too, has the pervasiveness of permanence as a foundational concept.
But let’s start with a project where permanence is not a problem.
Consider the proposed CDM methodology NM0267, associated with the Shuixi Gou coalfield in China, which the CDM Methodology Panel reviewed in 2009. This methodology sought to extinguish and prevent the uncontrolled burning of underground coal mine fires. In rejecting the methodology, the Meth Panel noted that fires could resume after the project crediting period, thereby resuming greenhouse gas emissions – and, therefore, the permanence of emission reductions could not be assured.
This reasoning is flawed. If, in a fuel-switch project (for instance), the project developer resumed using the baseline fossil fuel instead of, say, renewable biomass, then credits would not be issued for the remainder of the crediting period. And what happened beyond the crediting period would be of no concern to the CDM. Precisely the same logic applies to NM0267. If coal fires resume within the crediting period, carbon credits would not be issued; and, if coal fires resume after the crediting period, still no carbon credits would be issued.
There is no logical difference between leaving fossil fuel in the ground because a project is using renewable biomass and leaving fossil fuel in the ground because a project is preventing fires; in both cases, avoided emissions are credited and in both cases emissions could resume after the end of the crediting period. Neither suffers from a permanence problem.
Instead, what distinguishes a project that has permanence issues from one that does not is storage – and, specifically, storage of the carbon asset that’s being credited.
Some interventions – such as renewable energy, energy efficiency, nitrous oxide decomposition and the diversion of organic waste from landfills (to name just a few) – are designed to avoid greenhouse gas emissions: no storage of greenhouse gases is involved and hence no permanence issues present themselves.
Carbon capture and storage (CCS), on the other hand, is a mitigation intervention that does involve storage, as does its ‘negative emissions’ counterpart, BECCS. In the case of CCS, it’s storage of CO2 from the combustion flue gas or from pre-combustion process streams; in the case of BECCS, it’s storage of CO2 from the post-biomass combustion flue gas which, if the biomass is sustainably harvested, can be considered to be CO2 extracted from the atmosphere.
Negative emissions with BECCS. Credit: IIASA
Hybrid mitigation/sequestration interventions complicate the picture. For instance, land degradation neutrality – maintaining a stable amount of land over time capable of supporting ecosystem functions – can be achieved through land restoration (i.e. increases in suitable land), through slowing down the rate of loss of suitable land or, more likely, through a combination of the two. From a carbon perspective, land restoration is a sequestration activity that involves carbon storage (in soils and vegetation), whereas reducing the rate of land degradation is a mitigation activity that doesn’t involve new storage.
REDD+ is also a hybrid. REDD, without the ‘+’, is a mitigation activity: credit is awarded for reducing the rate of deforestation below a baseline (the forest reference emission level or FREL), just as a renewable energy project is awarded credits for reducing energy-related emissions below a baseline. REDD is therefore concerned with avoiding emissions, not with the storage of project-captured or generated carbon.
Contrary to common belief, the ‘+’ in REDD+ does not refer to promoting the broader (non-carbon) sustainable development benefits of forest conservation but, rather, to carbon sink enhancement techniques such as restoring degraded forests and afforestation. Thus, REDD+ combines both emissions avoidance (plain ‘REDD’) and carbon sequestration (the additional ‘+’) – and, like LDN, REDD+ therefore mingles interventions with and without obvious permanence aspects.
But REDD goes further in complicating the concept of permanence. REDD avoids emissions (i.e. does not sequester new carbon) and, unlike CCS, does not store emitted greenhouse gases. But REDD activities do store existing carbon – the carbon embodied in the forest that is being preserved.
Storage is therefore involved, and it’s storage of the carbon asset that’s being credited, but the usual ‘equivalence’ considerations between carbon storage and avoided emissions do not apply. There is no need for tonne-year accounting or temporary credits, since 1 tCO2 emitted from (pre-existing) felled trees is exactly equal to 1 tCO2, not some temporarily-sequestered fraction of a tonne.
Indeed, one could argue that REDD is particularly vulnerable to permanence concerns. Interventions that avoid greenhouse gas emissions typically offer ‘functional equivalence’ – energy can be generated with renewables instead of fossil fuels, energy efficiency offers equivalent heating or lighting comfort with less energy, public transport offers mobility (even if it’s not a perfect substitute for a car).
But REDD is, at root, different: it doesn’t necessarily replace one service with another. Yes, forests provide all manner of watershed, biodiversity and other benefits, and these ‘services’ will clearly be preserved – and potentially enhanced – under REDD. But the drivers of deforestation revolve around other services – fuelwood, timber and land.
Sophisticated REDD interventions may provide alternatives – for instance, alternative construction materials for local residents or more intensive (and hence less expansionist) agricultural methods for farmers, in which case a degree of functional equivalence is preserved. But less sophisticated REDD interventions can simply involve fencing off a forest and posting guards. This isn’t desirable and nor, thankfully, is it particularly common. But it happens: it’s impossible to conceive of a project that claims carbon credits for depriving people of energy, but projects do exist that claim carbon credits for depriving people of forest access. And, in the absence of functionally-equivalent livelihood alternatives, standing forest can represent an attractive target for illegal logging and clearance.
REDD, in short, faces permanence risks, but the nature of the permanence is conceptually different than for sequestration projects or for other mitigation interventions.
Blurring the picture yet further is carbon capture and utilisation (CCU).
CO2 is already used in commercial processes. The obvious examples – and the ones usually trotted out in CCU discussions – are carbonation of drinks and atmospheric enhancement in greenhouses. But much more significant volumes of CO2 are currently used in urea production (for fertilizers), plastics, laminates, solvents and fuels. The compelling logic of CCU is to source this CO2 from emission streams – to treat CO2 emissions not as a waste to be vented or stored but, rather, as a raw material to be used.
Thermodynamics, the current state of catalyst science and industrial economics suggest that CO2 utilisation potential is somewhere in the region of 1-7% for the chemicals sector and 10% of the fuels sector. But new uses of ‘waste’ CO2 are appearing all the time – think of CO2-infused concrete and other building aggregates – and there is good reason to believe that the CCU market can and will grow rapidly.
The challenge from a carbon accounting perspective is that the various uses of CO2 have different degrees of permanence: the carbon is locked up for varying – and, in some cases, wildly varying – periods of time.
Transforming CO2 into inert carbonates – for example, for use in construction – is a truly long-term, potentially very long-term, solution, and plastics and laminates can lock up carbon for decades. But the carbon in urea fertilizer will likely escape back into the atmosphere after just a few months and the carbon in liquid fuels such as methanol could, in principle at least, be liberated after just a few hours.
Estimated carbon storage lifetimes. Credit: IPCC
We are, then, moving from a world where permanence used to be a rather obscure issue confronted by LULUCF specialists to one where a broad range of climate mitigation interventions, including some of the most promising ones, are affected.
Welcome, in short, to the wonderful world of carbon transience.