Musings From the Front Lines October 2021

PK's Sustainability Commissioner is engaged in supporting Contra Costa County in adopting an embodied carbon ordinance that puts limitations on the carbon footprint of concrete used in construction within the county.  This has been emboldened by successful ordinances promulgated throughout the country and recently in Marin County in the SF Bay Area.  The meetings summary is included below with PK's thoughts in italics.

Musings from Meeting on 10/1/21

The goal of the Embodied Carbon Policy Study Group is to develop regionally consistent policy recommendations. This is a good concept as long as it doesn't impede progress within individual counties.

While natural pozzolans (Pozzolans are a class of materials that can be added to cement to control setting, increase durability, reduce cost and reduce pollution without significantly reducing the final compressive strength or other performance characteristics) like volcanic ash or calcined clay can be substituted for fly ash, they don’t necessarily mitigate the health hazards. Ground to the consistency needed for a concrete additive, these alternates can also become airborne and adversely affect workers and nearby communities.  What's more, if fly ash is not recovered and recycled, thus containing the heavy metals it contains, it will be deposited into landfill, where the pollutants can leach into soil and groundwater.
Fly ash contains heavy metals which are toxic carcinogens.  However, if handled properly and in compliance with state and federal regulations, the emissions would be controlled and have negligible impact.  We agree at PK that low-carbon concrete as it is a worthwhile recycling application and waste minimization measure.  It is a proven add-in to concrete and its use should continue.

The argument that the Sierra Club has made--that creating a market for a byproduct of fossil fuel plants extends their life--makes no sense. No company would burn oil just to sell the fly ash. Wholeheartedly agree with this statement.

Glass pozzolan is increasingly becoming available in the Bay Area. (Question: Does glass pose the kind of health risks that the Sierra Club found with lly ash and slag?)
With all these materials the concern is PM2.5 emissions as these are the fine particulate that is most bio-available.  If managed correctly, with the appropriate plans and controls in place, these materials can be used safely along with fly ash.

Another question: A slide was shown attributing 10-15% of concrete’s GHG emissions to the aggregate. Substitution of a synthetic aggregate (like Blue Planet’s) might not only bring that number to zero but have a net negative effect on total EC because it sequesters CO2 (captured at power plant stacks) and avoids the emissions from quarrying and long-haul transport of the gravel. Is that a correct conclusion?
Agree but we would need an Environmental Product Declaration (EPD) to verify the alternate products carbon footprint.