Sabbie Miller @ UC Davis
Abstract:
Construction is the largest driver of materials demand worldwide, and as a function of this high level of consumption, these materials are a significant contributor to global environmental burdens. Among construction materials, cement and cement-based materials have received substantial attention for environmental impacts associated with their production and have sparked great interest from local, national, and international political groups. Considerable focus has to date been given to the greenhouse gas (GHG) emissions from cement production - cement and cement-based materials are responsible for ~8% of global anthropogenic GHG emissions. However, demands for these materials also drive other environmental impacts as well, including cement-based materials leading to ~3% of global energy demand and ~2% of global water withdrawal. Understanding the drivers of these environmental impacts and how we can re-engineer the world’s most popular infrastructure material is essential to mitigate these burdens. This talk will present technical approaches to determining such environmental burdens including examination of drivers of environmental impacts and exploration of why reducing GHG emissions from cement-based materials has been difficult.
Bios:
Sabbie Miller is an Assistant Professor in the Department of Civil and Environmental Engineering at the University of California Davis. Professor Miller’s research focuses on lowering the environmental impacts of the built environment, specifically on methods to quantify, assess, and mitigate the climate, health, and resource burdens from materials demand. She is developing methods for improving materials design procedures to concurrently assess environmental impact and material performance by linking concepts from structural engineering, materials engineering, and life-cycle assessment. She is also developing methods to quantitatively and systematically determine the ability to sequester greenhouse gases in building materials. Professor Miller serves on several national and international committees pertaining to infrastructure material sustainability, she is a recipient of the National Science Foundation’s CAREER award, and she is an editorial board member for the Institute of Physics Environmental Research and Infrastructure Sustainability journal. She received her PhD from Stanford University in Civil and Environmental Engineering with a concentration in Structural Engineering and Geomechanics. Prior to joining the faculty at the University of California Davis, she was a postdoctoral scholar at the University of California Berkeley with a concentration in Industrial Ecology.
Summary:
This walk is a case study on how cement is used in construction; Usage of other materials can be analyzed likewise.
Materials consumption
Since 1900, half our materials consumption went to building construction
Large fraction of our greenhouse gas emissions are due to construction
Of those, a large fraction is due to concrete production
Concrete production industry doesn’t have good strategies for eliminating emissions (~7% of global emissions)
Consumption: mostly streets/highways and residential buildings
Many uses are long-lived
Good opportunities for sequestering carbon
New materials must be very robust and long-lived
Consumption increases as world population grows richer
Construction workflow
Very complex and incorporates many different processes and materials
Alternative materials must meet the functional requirements of the job
Concrete: final product
Composed of aggregate and paste (by volume)
Paste:
7-15% Cement: binder for cement and other materials
8%: Air
14-21%: Water
Aggregate: 60-75%: Rocks & gravel of various sizes
(most US mineral production is for this)
Life cycle analysis
Stages
Raw Materials Acquisition
Material Processing
Manufacture Y& Assembly
Use
Disposal
Each stage has inputs/outputs and emissions
Inventory assessment
Total energy use
Greenhouse gas emissions/uptake
Ozone depleting emissions
Air pollution
…
Impacts
Global warming
Human health
Resource depletion
Land overuse
Ecosystem damage
…
Cement analysis
Raw Materials & Preparation: quarrying, crushing, raw meal grinding
Clinker production: preheating, precalcining, rotary kiln, cooling & storing
Cement grinding: addition of gypsum, blending, storage in silos
Final cement
Concrete analysis
Batch Materials: cement, aggregates, water, admixtures, fibers
Mixing: electricity, diesel for mixing trucks, site equipment
Concrete construction (at construction site): pumping, vibrating, finishing
Final concrete
Emissions vary by region
Many materials are locally sourced
Use electricity from the regional grid
Contents of coal varies regionally, which affects emissions
Regional regulations (incentives, pollution laws)
Pollution/Impacts
Cement production is rising as are its carbon emissions
Emissions due to cement are largest portion of overall emissions due to concrete
Water use from concrete production is split among cement and as a direct ingredient
When looking at geographics
Can examine the relative contribution of cement production to each nation’s emissions
Water use of cement production within a given watershed
Mitigation:
Alternative materials
Lock-in (if we used concrete for a road, we have to repair it with concrete)
Using wood as material changes the calculation significantly. There are issues of deforestation and carbon emissions after disposal. Needs complete reanalysis.
Alternative sources of power
Use cement and concrete differently (stronger material, so can use less)
End-of-life (concrete can capture carbon dioxide)
Carbon capture technologies have a lot of promise since much carbon emission is caused by chemical reactions, e.g. CO2 stream can be used to cure cement