There has been much discussion regarding the carbon footprint of different pavement types, namely concrete vs. asphalt. Judging by the various opinions expressed, it appears that there are strongly opposing views.
As such, it was refreshing to hear Dr Helen Murphy, director, Environmental Services for VicRoads, present her paper – “The Carbon Footprint of Road Construction,” at the 2008 Roading New Zealand Conference held in Wellington recently.
Dr Murphy stressed that the main reason for the dissimilar carbon footprint estimates cited by the concrete and asphalt industries, stems from the different methods of calculation each adopts to present its case.
The asphalt industry has traditionally restricted its method of carbon footprint calculation to the embodied energy approach, while the concrete industry has taken a more comprehensive life cycle assessment approach.
In discussing potential future actions for greenhouse gas abatement, Dr Murphy examined vehicle and fuel technologies, travel behaviour and urban planning, as well as road design and construction. She emphasised that to gain an understanding of a roading project’s true carbon footprint, it is essential to perform a life cycle assessment.
Nicholas Stern, in his groundbreaking report – “The Economics of Climate Change: The Stern Review,” also chose to follow the life cycle assessment path, and it has become standard for many government departments here in New Zealand.
The term ‘life cycle’ refers to the notion that a fair, holistic assessment requires the consideration of raw material production, manufacture, distribution, use and disposal (or reuse/recycling), including all intervening transportation steps necessary or caused by the product’s existence. The sum of all those steps – or phases – is the life cycle of the product. The procedures of life cycle assessment are part of the ISO 14000 environmental management standards: in ISO 14040:2006 and 14044:2006.
As the appropriate means to investigate and value the environmental impacts of a product, caused or necessitated by its existence, a life cycle assessment fully accounts for the durability, low maintenance, and reduced fuel consumption benefits of concrete roads. This approach has recently been adopted by the Athena Institute, a non-profit organisation specialising in the science of life cycle assessment, who were commissioned by the Cement Association of Canada to produce a comprehensive report comparing the carbon footprint of concrete and asphalt roads.
The report – “A Life Cycle Perspective on Concrete and Asphalt Roadways: Embodied Primary Energy and Global Warming Potential,” is available at www.cement.ca/index.php/en/Life_Cycle_Perspective_.html
The report presents estimates of embodied primary energy usage and global warming potential over a 50-year life cycle for the construction and maintenance of a range of comparable rigid concrete and flexible asphalt pavements for highly trafficked roads.
In all cases, the embodied primary energy use is lower for the rigid concrete pavement. The report also demonstrates that if concrete shoulders and concrete restoration with no overlay are implemented as part of the maintenance and rehabilitation schedule, the primary embodied energy requirements will be 5.6 times higher for the asphalt option.
In order to measure direct global warming potential, the report also converts all greenhouse gas emission estimates (CO2, CH4 and N2O), using the well-accepted CO2 equivalence method developed by the International Panel on Climate Change. The results vary depending on pavement structure, but in some instances are up to 11 per cent higher for the asphalt design compared to the concrete alternative.
As illustrated by the Canadian report, if the true carbon footprint of a pavement type is to be calculated, then the inclusive methodology of life cycle assessment must be adopted. This requires that a service life of at least 50-years (not a mere 30-years) be the norm, and that all resources consumed in relation to maintenance and fuel consumption during the service life, be considered.
The ability to accurately gauge the superior long-term maintenance and user benefits of concrete roads through life cycle assessment methodology, must inevitably lead to their uptake for highly trafficked roads in New Zealand. This requirement is more pressing if the New Zealand Transport Agency is to contribute to an affordable, integrated, safe, responsive and sustainable transport system, and even more so if the Prime Minister’s vision for New Zealand becoming the world’s first carbon neutral country is to be realised.
By Patrick McGuire, Cement & Concrete Association of New Zealand (CCANZ)
As such, it was refreshing to hear Dr Helen Murphy, director, Environmental Services for VicRoads, present her paper – “The Carbon Footprint of Road Construction,” at the 2008 Roading New Zealand Conference held in Wellington recently.
Dr Murphy stressed that the main reason for the dissimilar carbon footprint estimates cited by the concrete and asphalt industries, stems from the different methods of calculation each adopts to present its case.
The asphalt industry has traditionally restricted its method of carbon footprint calculation to the embodied energy approach, while the concrete industry has taken a more comprehensive life cycle assessment approach.
In discussing potential future actions for greenhouse gas abatement, Dr Murphy examined vehicle and fuel technologies, travel behaviour and urban planning, as well as road design and construction. She emphasised that to gain an understanding of a roading project’s true carbon footprint, it is essential to perform a life cycle assessment.
Nicholas Stern, in his groundbreaking report – “The Economics of Climate Change: The Stern Review,” also chose to follow the life cycle assessment path, and it has become standard for many government departments here in New Zealand.
The term ‘life cycle’ refers to the notion that a fair, holistic assessment requires the consideration of raw material production, manufacture, distribution, use and disposal (or reuse/recycling), including all intervening transportation steps necessary or caused by the product’s existence. The sum of all those steps – or phases – is the life cycle of the product. The procedures of life cycle assessment are part of the ISO 14000 environmental management standards: in ISO 14040:2006 and 14044:2006.
As the appropriate means to investigate and value the environmental impacts of a product, caused or necessitated by its existence, a life cycle assessment fully accounts for the durability, low maintenance, and reduced fuel consumption benefits of concrete roads. This approach has recently been adopted by the Athena Institute, a non-profit organisation specialising in the science of life cycle assessment, who were commissioned by the Cement Association of Canada to produce a comprehensive report comparing the carbon footprint of concrete and asphalt roads.
The report – “A Life Cycle Perspective on Concrete and Asphalt Roadways: Embodied Primary Energy and Global Warming Potential,” is available at www.cement.ca/index.php/en/Life_Cycle_Perspective_.html
The report presents estimates of embodied primary energy usage and global warming potential over a 50-year life cycle for the construction and maintenance of a range of comparable rigid concrete and flexible asphalt pavements for highly trafficked roads.
In all cases, the embodied primary energy use is lower for the rigid concrete pavement. The report also demonstrates that if concrete shoulders and concrete restoration with no overlay are implemented as part of the maintenance and rehabilitation schedule, the primary embodied energy requirements will be 5.6 times higher for the asphalt option.
In order to measure direct global warming potential, the report also converts all greenhouse gas emission estimates (CO2, CH4 and N2O), using the well-accepted CO2 equivalence method developed by the International Panel on Climate Change. The results vary depending on pavement structure, but in some instances are up to 11 per cent higher for the asphalt design compared to the concrete alternative.
As illustrated by the Canadian report, if the true carbon footprint of a pavement type is to be calculated, then the inclusive methodology of life cycle assessment must be adopted. This requires that a service life of at least 50-years (not a mere 30-years) be the norm, and that all resources consumed in relation to maintenance and fuel consumption during the service life, be considered.
The ability to accurately gauge the superior long-term maintenance and user benefits of concrete roads through life cycle assessment methodology, must inevitably lead to their uptake for highly trafficked roads in New Zealand. This requirement is more pressing if the New Zealand Transport Agency is to contribute to an affordable, integrated, safe, responsive and sustainable transport system, and even more so if the Prime Minister’s vision for New Zealand becoming the world’s first carbon neutral country is to be realised.
By Patrick McGuire, Cement & Concrete Association of New Zealand (CCANZ)
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