As society becomes increasingly aware of the devastating effects of global warming and the collective efforts needed to drive down harmful emissions, we are presented with an abundance of new terminologies to describe environmental issues.
A fast-expanding list of terms are filtering their way into everyday language and reporting - specifically carbon definitions for the built environment. While sustainability experts are throwing around “net zeros”, “whole life carbons” and “carbon neutrality”, non-experts have just about got their heads around GHGs!
The bottom line is that many of these terms are used incorrectly. Instead of enriching the description of a project, they end up distorting it. At Construction Carbon we feel the need for a universal understanding of the meanings and definitions of the most used industry terms.
Take ‘net-zero’, for example. It gets used in different contexts all the time especially after having been made the star of The Paris Agreement and other important initiatives such as the UN Race to Zero.
The official definition of a net zero asset according to the WLCN [Whole Life Carbon Network] is as follows: The sum of all asset related carbon emissions (both embodied and operational) is minimized in line with the Paris Agreement 1.5°C trajectory, meets local carbon, energy and water targets, and is brought to be equal to zero with the aid of offsets to neutralize any eventual residual emission.
When using this definition, we must remember the term ‘net zero’ is generally used to describe buildings which have succeeded in neutralizing their operational impact irrespective of the impact of their embodied carbon. By purely assessing buildings on how much operational carbon they release while in use, and not taking into consideration the embodied carbon (emissions linked to production of materials and construction phase of the building), this distorts the ratings. All existing high-level certification schemes only award operational performance and neutrality which makes buildings with a good operative-stage performance, seem impact free.
Five to ten years ago this type of misunderstanding could have been taken more lightly, as embodied carbon, compared to operational carbon, counted for a small percentage of the total emissions of a building (given that energy efficiency standards and state of the art technologies were nowhere as advanced as they are today).
Imagine embodied and operational carbon as two horses pulling two differently sized carts: the first one smaller and lighter and the second bigger and much more heavily loaded. If we started with two incomparable loads, we are now in front of two horses pulling almost undistinguishable carts. However, the approach to the two horses has not yet evolved accordingly: the operational horse keeps receiving help and praise for carrying a load that is now virtually the same as that of the second, actively ignored, nag.
This is what is happening in the construction industry. Studies, such as The Embodied Carbon Review by Bionova, show that if the trend doesn’t change, as the construction industry keeps expanding to meet the needs of a growing population, embodied carbon will end up accounting for around 80% of the industry’s emissions. For this reason, it is highly misleading, to exclude embodied carbon from evaluations. Embodied and operational carbon cannot be looked at differently when it comes to newly built houses where the embodied carbon may be responsible for more than half of a building’s whole-life emissions. That would leave out a more than significant slice of the industry’s total emissions.
The second issue is attributed to the unreliable nature of a good portion of the offset present on the market. An Oxford paper on good practice about carbon offsetting declares that, in order to be effective, offsets must be of a certain quality. Preferably, they should involve long term carbon capture and storage and the risk of reversibility (ie. the risk for the stored carbon to be freed again after unforeseen events, such as forest fires) must be kept at a minimum.
Another thing that is seen as potentially mining offsets is that they can be subject to double spending: the same offset emissions can be sold multiple times, or they can be sold again by the first purchaser after the project is completed. According to the Oxford study, the current state of the market does not offer enough long-term carbon storage for all companies looking at offsetting their residual emissions to be able to purchase them. This puts most of them in a delicate position: the choice of offsets must be well aimed and backed up by solid proof that the offsets are high quality and that there is no risk of double spending for an asset to become net zero.
Furthermore, WLCN guidance sets out clear rules for how offsets should be calculated and offset. In practice: embodied carbon (Modules A1-A5) residual emissions should be calculated and offset post practical completion, operational emissions (Modules B1-B7) should be calculated from actual activities and offset annually, lastly end of life processes-related emissions (Modules C1-C4) should be offset post deconstruction.
Overall offsetting can be a powerful tool to reach net zero while suitable solutions are developed to reduce emissions - but these need to be used with care.
In relation to offsetting, a clear distinction should be made between net zero and another widely used term: carbon neutrality. In order to achieve net zero one must minimize emissions as much as possible and only then offset the residual ones. Carbon neutrality simply describes the act of reaching overall zero emissions with the use of offsets, without any need to perform any specific in-project emission reduction.
For the above-mentioned reasons, keeping the need for offsets to a minimum is very important to ensure reliably greener performance. Net zero can be seen as more ambitious. As such it has been chosen by official environment action bodies as the ultimate goal to strive for.
The same semantic issues apply to the concept of climate positivity: if a building is energetically efficient and produces the necessary renewable energy to operate independently of the grid but is entirely built out of steel, glass and concrete with a lot of redundant structures, it cannot be described as climate positive (if the emissions connected to its construction have not been properly accounted for and mitigated).
A slightly similar term is carbon negative, with the only difference being the scope of the definitions: carbon negativity is a subgroup of climate positivity or net negativity (as it only considers carbon out of all GHG).
At this critical phase of development, it is important to have the means to aim with precision and push efforts in the right direction. In order to do so, stakeholders need a clear picture of performance trends and of the distribution of emissions throughout the supply chain and the built environmental body. True advances cannot be made if the perception of environmental performance indicators is not re-considered.