Understanding Carbon - Gap Analysis

A few gaps come to mind: 1.  Carbon Capture and Sequestration:  this list is all about reducing the source emissions, but every building has the potential to use CCS.  This includes onsite, offsite, purchasing offsets and RECs. 2.  Biodiversity loss:  paving asphalt over a greenfield represents a long-term loss of potential carbon sequestration.  We don't talk about the CO2 potential absorption (adsorption?) of the site. (and this one is dark, but still quantifiable)  3.  Exhaling:  more people on Earth mean more people exhaling CO2.  The CO2 levels in a gym are higher than in an office (working out causes more exhaling.)

One other gap: GWP of insulation blowing agents. Not typically captured under "embodied." For grid-related operational emissions based on time-of-use data: NREL is working on a tool called "Cambium" that will estimate emissions from future electric grid scenarios on an hourly basis through 2050. (This begs the question, should we include sensitivity analysis into our analyses of carbon impacts so we can capture the "likely range" of impacts rather than a single number that hides the many assumptions we make to get there?) For one of our projects I've been aiming to minimize 30-year carbon impact, including embodied + operational + blowing agents. Even with this limited scope it's been time-consuming and requires lots of iteration between LCA and the energy model. The 30-year timeframe is somewhat arbitrary but based on the idea that we need to get to zero CO2 by 2050. I've often wondered if we should apply a discount rate to carbon emissions, with the idea that carbon emitted now is more damaging than carbon emitted in the future. But perhaps sensitivity analysis of future grid scenarios could get to essentially the same place. Carl *Carl Sterner, *AIA, LEED AP, CPHC Director of Design & Sustainability cell 347 604 0257 | office 513 455 8228 x710 | fax 513 455 8227 www.soldesignconsulting.com

This is great.  I often try to make the point that our current zero energy buildings are not even half way to where we need to be. One other factor that I feel might be missing is transportation.  This has previously been considered separate only because of the fuel source.  As our vehicles rapidly electrify it becomes reasonable to consider emissions from charging as part of our projects.  For instance, the PV arrays on our zero energy schools would need to be roughly 20% larger to account for electric school buses.  However, residential projects will represent the bulk of this usage since most charging takes place at home.

Kjell, I've been trying to develop a methodology for looking at this for each project and doing what the GHG accounting people call a 'de minimis' exercise. I've developed the attached slide (based on a simple calculator) to illustate the point, noting that the relative impact of each area is project specific.  I think the phase we're reached is what the rest of the GHG community calls Scope 3 accounting. If someone like eBay did their GHG accounting, they could legitimately exclude the emissions from shipping, which likely accounts for ~99% of their total, since it's a Scope 3 source and that's not strictly required. That said, many organizations are now essentially saying that significant Scope 3 sources can't be ignored, and that action should be taken to address it.    That's more or less where the building industry is. It's saying, even though embodied materials emissions and refrigerant emissions are Scope 3, we should start accounting for them and doing what we can to address them. I'd include transportation emissions as well. If interested, I'll be presenting this at an upcoming USGBC webinar, linked here. Josh   

I'll agree with Brian and Joshua's comments about electrification of transportation.  transportation is the largest source of GHGs that AEC can impact with the design and contruction. how our parking spaces, lots, and structures support the needed exponential growth in electricified transportation may be the largest lever we have to reduce GHGs. fossil fuels for transportation is the least efficient use for fossil fuels. the electrical grid is getting cleaner with or without our help (although i suggest we keep helping!) EVs and EV charging stations need to be completely normalized and a default setting in our project proposals, renderings, and designs. gas cars in renderings should be about as palatable as smokers on your sidewalks and greenspaces. yes, they i really there...but i doubt you draw them in! :)