Dr. J. Richard Willis National Center for Asphalt Technology/Auburn University NAPA Annual Meeting 1
Overview Carbon footprint models BEES Athena Institute Colas Model United Kingdom Highways Agency Reducing our carbon footprint Summary 2
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Carbon Footprints a measure of the amount of carbon dioxide released into the atmosphere by a single endeavor or by a company, household, or individual through day-to-day activities over a given period. Collins English Dictionary, 10 th Ed., 2009 Typically use CO 2 e because other greenhouse gas (GHG) contributions 4
Common Model Components Component material production Asphalt binder Aggregates Composite material production Material transport Construction 5
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BEES Basics U.S. National Institute of Standards and Technologies (NIST) Current Model: BEES 4.0 Program uses two methods to assess performance Environmental performance: ISO 14040 Economic performance: ASTM International Standard Overall performance based on synthesis of two 7
Environmental Performance Cradle to grave Raw material acquisition Product manufacture Transportation Installation Operation Maintenance 8
Brian Prowell, HMAT (2008) 9
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Athena Institute Not-for-profit consulting agency 2006 study sponsored by Cement Association of Canada Comparison of embodied energy The caloric potential of unburned asphalt cement Not process related energy Embodied energy is not released 11
Athena Institute 12
Athena Institute Results Most life-cycle carbon footprint analyses do not use embodied energy When embodied energy is removed, Athena study values are similar to other comparisons Asphalt pavements produce significantly less greenhouse gases 13
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Colas Group 2003 Publication (Chappat and Bilal) Asphalt Concrete High Modulus Asphalt Concrete Warm-mix Asphalt Asphalt Emulsion Mixtures Hot-Recycled Asphalt Mixtures RAP Mixtures Concrete Cement Pavements Energy consumption and greenhouse gas emissions 15
Colas Group Energy Consumption and Greenhouse Gas Emissions Binder Production Aggregate Processing Material Manufacturing Transportation Laydown 16
Colas Study 17
Colas Study Construction of cement pavements have higher carbon footprint than asphalt pavements Majority of asphalt pavement s carbon footprint is associated with binder and mixture production Asphalt pavement had a carbon footprint 25 to 30% that of concrete 18
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United Kingdom Highways Agency Developed asphalt Pavement Embodied Carbon Tool (aspect) in 2008 Calculates carbon emissions associated with Production of raw materials Asphalt mixture production Mixture transportation Laydown/compaction 20
aspect Beta Beta version released in October Maintenance and end of life included Re-surfacing Surface dressing work Patching Excavation and material management 21
aspect Inputs Electricity and fuel consumed on site for raw materials and material production Plant type Production rate Water used at the asphalt plant Distances traveled (raw materials and mixture, laborers travel) Fuel consumption for construction equipment 22
RAP/RAS RAP easily used as an input in aspect Must know %RAP in mix by total weight of mixture Must know binder content of RAP 60% savings in embodied energy using RAP Embodied: Energy taken to bring materials to point of use RAS is not specifically included in program Use as a RAP material with high asphalt content 23
Warm-Mix Asphalt Considered a special plant process To get inputs for aspect, monitor complete continuous runs for both the special and standard processes for at least 100 tons Measure each type of fuel required for runs 24
Preliminary aspect Results Most of asphalt carbon footprint is associated with extraction and production of raw materials Results similar to Colas study 29.6 kg of CO 2 e per ton of mix 25
Other Models NAPA Greenhouse Gas Calculator Granite construction (2010 TRB) PaLATE (Pavement Life-cycle Assessment Tool for Environmental and Economic Effects) Consortium on Green Design and Manufacturing University of California, Berkley 26
Reducing our Carbon Footprint MA: 109 lbs of CO 2 eq per ton of mix WMA: 97.6 lbs of CO 2 eq per ton of mix 27
Recycled Asphalt Shingles 10,000 tons of ground shingles replaces: 468,000 gallons of asphalt 8,000 tons of aggregate Using 5% RAS in HMA reduces carbon emissions by approximately 7.0% 28
Courtesy of : Robert Lee
Courtesy of : Robert Lee
Combined Technologies WMA with 15% RAP and 5% RAS 83 lbs of carbon emissions per ton of mix as compared to 109 for typical HMA 23% reduction in emissions 31
Summary Tools are available Must know the models for direct comparisons Do not include embodied energy Asphalt pavements have favorable carbon footprints compared to other pavement structures for most models 25-30% PCC We can further reduce our carbon footprint by effectively using RAS, RAP, and WMA 32
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