Edinburgh Napier University

  The climate change burden associated with buildings and construction is increasingly globally recognised by the many stakeholders involved. For decades there has been an unnecessary divide between the operational and embodied impacts of buildings, with the former attributed to the energy sector and the latter attributed to (yet mostly ignored by) the construction industry. This has shadowed the real size of environmental impacts of buildings and construction but there finally is an increasing trend to look at buildings in their entirety, which has fully revealed the enormous challenge that lies ahead to decarbonise our built environments.

Given the above, and the technicalities of the construction sector (which is a top user of hard-to-decarbonise materials such as steel and cement), there is an emerging consensus that net zero targets can only be realistically achieved through the inclusion of carbon offsets, as for instance acknowledged by the World Green Building Council (WGBC) in its Net Zero Carbon Building Commitment. In short, these are carbon accounting mechanisms whereby the remaining emissions in a project or product that cannot be further lowered with optimization, efficiency, or technological gains are offset by financing projects aimed at carbon capture and storage (CCS); biogenic uptake and sequestration (e.g. planting trees or preserving forests); development of renewable energy generation (wind, solar, etc.) or any other intervention project for which a reduction in GHG impacts can be credited.

Carbon offset schemes (and their trading markets) are booming. As instruments to tackle the climate crisis they are not good or bad per se, but it all rather depends on how the associated credit is measured and hence certified. Outcomes can range from effectively drawing down greenhouse gas concentration in the atmosphere to the most common greenwashing and marketing mechanisms. In this chapter, we demonstrate, using causal reasoning and a simple thought experiment, that an offsetting project should be assigned a carbon credit only if a physical (empirically measurable) net reduction in atmospheric concentration occurs, and hence dismissing carbon offsetting schemes based upon counterfactual baseline scenarios of avoided emissions. Financing a carbon avoidance offset rather than a carbon removal offset, results in emission reductions that are non-existent (best case), or in an increase in atmospheric GHG concentrations (worst case). This while both types of offsets can be used for net zero reporting of buildings and construction projects. We demonstrate that if every single carbon emitting activity on this planet (including buildings and construction) is offset with a carbon avoidance scheme, we get the paradoxical result of a net zero global society with rising GHG concentration levels.