Assessing the carbon footprint of road projects and related sustainability initiatives in Abu Dhabi - technical report II: carbon footprint from road life cycle and development of a framework for carbon footprint calculation of road in the city of Abu Dhabi

Assessing the carbon footprint of road projects and related sustainability initiatives in Abu Dhabi - technical report II: carbon footprint from road life cycle and development of a framework for carbon footprint calculation of road in the city of Abu Dhabi

In January 2015, the Infrastructure and Municipal Asset Sector of the Abu Dhabi City Municipality (ADM) invited the Roadway, Transportation and Traffic Safety Research Centre (RTTSRC) at the United Arab Emirates University (UAEU) to submit a proposal for consultancy services regarding carbon footprint calculation and sustainability issues in road projects in the Emirate of Abu Dhabi. The RTTSRC, UAEU responded to ADM invitation and signed a contractual agreement on November 24, 2015 with the ADM (contract number 283/2015) to execute a two year long consultancy project entitled “Assessing the Carbon Footprint of Road Projects and Related Sustainability Initiatives in Abu Dhabi”.

The goal of the project is to make road projects in the city of Abu Dhabi more sustainable towards the environment. The project aims to estimate the carbon footprint of road construction and improvement projects in the city with a comprehensive approach considering the life cycle of roads. The objectives of the project are to:
• Conduct an extensive literature review of road construction; carbon footprint; sustainability issues; national and international environmental treaties and rules; strategic, environmental and social impact assessment of road projects;
• Calculate carbon footprint of road construction, operation and maintenance phases, including development of a framework for carbon footprint calculation of road projects in the city of Abu Dhabi; and
• Delineate sustainability issues in road projects and scenario modelling to evaluate potential mitigation measures of reducing the carbon footprint.

This report is the revised second technical report that covers the second objective of the project. It delineates development of conceptual frameworks for road carbon footprint estimation, development of a model to estimate greenhouse gas (GHG) emissions over road life cycles, and the application of the model to estimate GHG emissions from three road construction/improvement projects in the Emirate of Abu Dhabi. The second technical report was submitted in May 2017 and the ADM experts provided their review comments on the report in August 2017. This revised report is amended according to the comments, and a separate document addressing the comments is included in Appendix B at the end of this report.

Prior to this report, the first technical report covered a comprehensive literature review that was conducted in this study. Since the project aimed at building a model to estimate emissions, a proper guideline from the International Panel for Climate Change (IPCC) was studied in this regard. The software CHANGER was among the different tools that could be used to estimate carbon footprint from road construction. However, CHANGER cannot be used to estimate carbon footprint emissions for the entire life cycle of a road project. After completion of the study, the third and final report will cover scenario modelling for evaluation of potential mitigation measures to reduce carbon emissions from road projects.

In this report, a model named “RoadCO2” was developed using Microsoft Excel. It consists of four phases of the road life cycle, namely pre-construction, construction, operation, and maintenance-rehabilitation phases. The model for the construction phase has been designed user-friendly by matching it with ADM standard bill of quantities (BOQ). The operation phase consists of two worksheets: the summary and the input data worksheets. Emissions in the pre-construction and maintenance phase are calculated using worksheets used for the construction phase. A user manual of the Microsoft Excel-based RoadCO2 model is included in Appendix A. The model is included in a CD, attached to this report.

The GHG emissions from three road construction/improvement projects in the Abu Dhabi were estimated using the developed RoadCO2 model. The three projects are (1) internal roads and services in Al Rahba City (2) upgrading Al Salam Street (official name is Sheikh Zayed Bin Sultan Street), and (3) widening of the Eastern Abu Dhabi Corniche road. The results were compared to a UAE case study by Huang et al. (2013), which used commercially available software CHANGER. The total emissions from the construction of three case studies were 541, 11568, and 2090 tons CO2 eq/lane/km, respectively.

Al Rahba City internal roads and services project is the construction of a 30-km road project consisting of 2 lanes. Among the construction materials used, concrete class k140 contributed the most to GHG emissions (24% of total emissions), followed by aggregate (17%), concrete class k550 (15%) and glass reinforced plastic (15%). Among the equipment used in Al Rahba case study, the highest emission was estimated to be from compactors (4627 tons CO2 eq), followed by loaders (4606 tons CO2 eq), excavators (2770 tons CO2 eq) and tippers (2400 tons CO2 eq). Upgrading Al Salam Street to a project includes the construction of a tunnel of length 3.6 km. The highest emission, in terms of materials, was that of the concrete class k550 (71% of total emissions), followed by steel (13%) and concrete class k140 (5%). In the case of equipment used in Al Salam Street project, the highest emission of 21312 tons CO2 eq. resulted from the trucks used to transport concrete and other materials, followed by soil compactors (3413 tons CO2 eq) and excavators (3204 tons CO2 eq). For the Eastern Abu Dhabi Corniche road widening project, the highest emission was estimated to be from the asphalt materials (41% of total emissions), followed by concrete k140 works (34%), and high density polyethylene (6%). Emissions associated with equipment in this project were the highest from the front shovel (423 tons CO2 eq), followed by the excavators (289 tons CO2 eq).

In the operation phase, the traffic operating in the 2.18-km section of Al Salam Street project produces over 37.7 million kg CO2 eq/year. This street has a high traffic volume and a multilane road carrying a large number of heavy vehicles such as trucks and buses. On the other hand, the traffic operating in Al Rahba City road network produces about 2 million kg CO2 eq/year. This city road network is mostly accessed by residents’ passenger cars, which translates into much lighter traffic volumes. Emissions from passenger cars dominate in Al Rahba City internal roads, whereas light and heavy vehicles dominate in the case of Al Salam Street.

The IPCC 2006 emission factors are incorporated in the RoadCO2 model. In fact, the UAE is a member of the IPCC. Hence, the Abu Dhabi Road Standards were used in the model development. The input data in the model include materials used in construction, transport mode of materials whether delivered or imported to the site along with the distance travelled, type of equipment operated on the site and type of vehicles and project travelled distances. The data were extracted from their bill of quantities (BOQ). It is highly recommended to collect and use actual data to estimate more accurate results. UAE specific emission factors (i.e., values of the rate of emissions) are not available yet, therefore the IPCC Tier 1 was followed and the default IPCC emission factors were considered in this study. However, it is suggested by (EAD, 2012, 2016) to use local emission factors for more accurate emissions estimation. The model is designed in such a way that it can be updated with local emission factors once available.

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