Life Cycle Impacts of Harvested Coal Ash Used as Cement Replacement in Concrete.pdf

Sabrina Bradshaw, University of Wisconsin-Madison
Craig Benson, University of Wisconsin-Madison
Tuncer Edil, University of Wisconsin-Madison

Description

Life Cycle Impacts of Using Harvested Coal Ash as a Cement Replacement in Concrete Authors Ms. Sabrina Bradshaw - United States - University of Wisconsin-Madison Dr. Craig Benson - United States - University of Wisconsin-Madison Dr. Tuncer Edil - United States - University of Wisconsin-Madison Abstract Environmental benefits of using harvested coal ash as supplementary cementitious material (SCM) in concrete were evaluated using life cycle assessment. Global warming potential (GWP), energy consumed, and water used to harvest and process ashes from landfills and impoundments to meet ASTM C618 SCM criteria were quantified and compared with fresh ash. The life cycle inventory for excavating, drying, grinding, and carbon treatment (thermal, electrostatic, and chemical) was obtained from industry interviews. Using harvested ash as a SCM in concrete is beneficial for each of the impacts considered, with benefits increasing as the cement replacement percentage increases. However, using harvested ash has greater GWP, non-renewable energy, and water use than using minimally processed fresh ash, as processing harvested ash requires effort in excavation and drying that is not needed with fresh ash. Similarly, carbon treatments had less benefit than untreated ash from added processing energy and emissions. Harvesting ash from landfills has slightly smaller impacts than harvesting from impoundments, primarily because the ash in impoundments is wetter, affecting the energy consumed and emissions generated when excavating and transporting ash. However, when avoided landfilling is considered, GWP and energy consumption of harvesting ash from impoundments is lower than harvesting ashes from landfills.

 
May 15th, 2:30 PM May 15th, 3:00 PM

Life Cycle Impacts of Harvested Coal Ash Used as Cement Replacement in Concrete.pdf

Grand Rapids, Michigan

Life Cycle Impacts of Using Harvested Coal Ash as a Cement Replacement in Concrete Authors Ms. Sabrina Bradshaw - United States - University of Wisconsin-Madison Dr. Craig Benson - United States - University of Wisconsin-Madison Dr. Tuncer Edil - United States - University of Wisconsin-Madison Abstract Environmental benefits of using harvested coal ash as supplementary cementitious material (SCM) in concrete were evaluated using life cycle assessment. Global warming potential (GWP), energy consumed, and water used to harvest and process ashes from landfills and impoundments to meet ASTM C618 SCM criteria were quantified and compared with fresh ash. The life cycle inventory for excavating, drying, grinding, and carbon treatment (thermal, electrostatic, and chemical) was obtained from industry interviews. Using harvested ash as a SCM in concrete is beneficial for each of the impacts considered, with benefits increasing as the cement replacement percentage increases. However, using harvested ash has greater GWP, non-renewable energy, and water use than using minimally processed fresh ash, as processing harvested ash requires effort in excavation and drying that is not needed with fresh ash. Similarly, carbon treatments had less benefit than untreated ash from added processing energy and emissions. Harvesting ash from landfills has slightly smaller impacts than harvesting from impoundments, primarily because the ash in impoundments is wetter, affecting the energy consumed and emissions generated when excavating and transporting ash. However, when avoided landfilling is considered, GWP and energy consumption of harvesting ash from impoundments is lower than harvesting ashes from landfills.