Implementation of Life-Cycle Assessment in the optimization of road pavement choice: comparative analysis based on a real case study.

Transcription

1 Pavement Life-Cycle Assessment Symposium 2017 Champaign IL April Implementation of Life-Cycle Assessment in the optimization of road pavement choice: comparative analysis based on a real case study Marco Pasetto Emiliano Pasquini Giovanni Giacomello and Andrea Baliello Andrea Baliello University of Padua, Padua, Italy Department of Civil Environmental and Architectural Engineering

2 Contents Introduction LCA in road engineering Research objectives LCA methodology Case Study a b c Life Cycle Inventory Scenario hypothesis Results and discussions 6 Conclusions

3 Introduction 1 Life Cycle Assessment Evaluation of the potential product/service impacts, considering all the life cycle stages (design, construction, utilization, maintenance and final disposal). Valid support to the decision-making processes conditioning the public policies and the industrial competitiveness. Its main objectives are addressed to the: reduction of energy and resource consumptions; health improvements; environment saving. Although without specific prescriptions (about methodology and procedures), LCA is defined in ISO and ISO (ISO 2006a, b) standards. 1

4 Introduction 1 Life Cycle Assessment ISO standards describe in detail principles, framework, requirements and guidelines for the LCA, mainly including: 1 Goal - Goal and scope definition 2 - Life Life Cycle Cycle Inventory analysis (LCI) 3 Life - Life Cycle Impact Assessment (LCIA) Life 4 - Life cycle Cycle interpretation Interpretation a) the goal and scope definition; b) the Life Cycle Inventory (LCI) analysis phase; c) the Life Cycle Impact Assessment (LCIA) phase; d) the life cycle interpretation phase; e) reporting and critical review of the LCA; f ) limitations of the LCA; relationship between the LCA phases; g) relationship between the LCA phases 2

5 LCA in road engineering 2 Road construction LCA in road engineering tries to evaluate the environmental impacts connected to transport infrastructures, facing the most important problems related to the material type and its transport, that strongly represent onerous items in road construction and maintenance. LCA is utilized in decision procedures to control final impacts (costs and environmental emissions) of road construction, management, maintenance and rehabilitation, as example considering: alternative design hypothesis; construction equipment and techniques; energy consumption levels; request of virgin materials; marginal materials reutilization; effect of transportations; importance of maintenance activities; etc. 3

6 2 LCA in road engineering The overall road life cycle could be divided in 5 main phases: 1. material production ; 2. construction ; 3. road use; 4. maintenance and rehabilitation (disposal of old material, production of new material, transportation and laying processes); 5. end-of-life (pavement demolition and material disposal). Recycled material Energy Fuel Wastes Virgin/recycled material Transport End-of-life phase Demolition works Material production phase Wastes Energy Fuel Emissions Transport Processing plant (asphalt/concrete) Emissions Energy Fuel Wastes Transport Rehabilitation works Energy Fuel Construction phase Emissions Workers Machinery Road construction Emissions Managment / maintenance phase Processing plant (asphalt/concrete) Transport Workers Machinery Traffic Utilization phase Road utilization Survey Virgin/recycled material Emissions 4

7 LCA in road engineering 2 Road construction Santero, Masanet & Horvath, Life-cycle assessment of pavements. Part I: Critical review. Resources, Conservation and Recycling. 55: Amini, Mashayekhi, Ziari & Nobakht, Life cycle cost comparison of highways with perpetual and conventional pavements. Int. J. Pav. Engineering. 13(6): Bryce, Katicha, Flintsch, Sivaneswaran & Santos, Probabilistic Life-Cycle Assessment as Network-Level Evaluation Tool for Use and Maintenance Phases of Pavements. TRR Butt, Mirzadeh, Toller & Birgisson, LCA for asphalt pavements: methods to calculate and allocate energy of binder and additives. Int. J. of Pav. Engineering. 15(4): Santos, Ferreira & Flintsch, A life cycle assessment for pavement management: road pavement construction and management in Portugal. Int. J. Pav. Engineering. 16(4): AzariJafari, Yahia & Amor, Life cycle assessment of pavements: reviewing research challenges and opportunities. J. Cleaner Production. 112:

8 Research objective 3 Study aims Evaluating the validity of LCA in order to mitigate environmental impacts, decrease costs and control energy consumption (fuel, electrical energy, etc.). Determining the importance of maintenance policies and future investments (definitely affecting costs and environmental impacts). Contribute to enlarge the worldwide database about the implementation of LCA for pavements. Based on a real designed motorway in Italy, LCA analysis was applied in order to compare alternative asphalt pavements (with marginal materials) with respect to traditional (high-quality, expensive) ones. 6

9 LCA methodology 7 PaLATE Pavement Life cycle Assessment Tool for Environmental and Economic Effects LCA applicator (Excel tool) useful to assess the pavement and road life cycle considering extraction, production, construction, maintenance and end-of-life. Input structure Divided into different sheets, each one able to collect input data/information (engineering, environmental and economic-based) and return a wide range of output: Design Initial construction Maintenance Equipment Unitary costs Output structure Costs [material production, transportations, processes, equipment]. Impacts [energy (E), water consumption (WC), carbon dioxide (CO2), nitric oxide (NOx), particulate matter (PM10), sulfur dioxide (SO2), carbon mono-oxide (CO), heavy metals (Hg and Pb), hazardous waste generated (HWG), human toxicity potential cancer (HTPC) and human toxicity potential non-cancer (HTPNC)]. 4

10 A3 motorway Case study 5 Case study is based on a real Italian road construction project, the A3 motorway from Salerno to Reggio Calabria. Life Cycle Assessment was applied to a unitary motorway stretch (1000 m long) for a total period of 20 years (from construction to end-of-life). 50 mm: porous wearing course M 70 mm: asphalt binder course T 150 mm: asphalt base course T 200 mm: cement sub-base course 200 mm: Unbound sub-basecourse T With traditional binder M With polymer-modified binder * Subgrades, drainages, tack coat, road markings and other particular street furniture were not considered. A semi-rigid pavement was designed calculating the Equivalent Single Axle Load (ESAL) number during the infrastructure life-time according with AASHTO method. All data were collected from: Italian motorways company Autostrade per l Italia ; asphalt concrete producers and transport companies; typical Italian price lists and specifications. 8

11 Case study * Embankments were not included in LCA analysis. ** The left shoulder was considered not paved. 0 New-Jersey device 1 2 Retaining device Cross section Stretch length: 1000 m Two lanes per each direction Paved emergency lane Single lane width: 3.75 m Emergency lane width: 3.00 m Left shoulder 1.30 m 0.70 m Lane 3.75 m Lane 3.75 m m Emergency lane 3.00 m Semi-width: m Total width: m Double New-Jersey separation Border guard-rails 9

12 Materials Life cycle inventory a Typical Italian road materials with verified properties were considered to match the local specifications. Data derived from quarries and plants close to the construction site, asphalt concrete producers and typical Italian price lists were obtained for: virgin aggregates; bitumen (traditional or polymer-modified); recycled materials (RAP); industrial by-products (steel slags). Impacts Input of data concerning transportations (by road only), consumptions and emissions, regarding: machinery performance fuel, water and energy consumptions truck capacities material densities emissions to air leachate 10 * Feedstock energy was not examined. ** Negligible emissions from paver machine were not accounted.

13 11 Life cycle inventory a Costs Typical Italian price lists gave single prices of raw materials (for production, construction and maintenance) and processes. As examples: pavement laying cost; full depth reclamation cost; asphalt plant cost; machinery use cost. Discount rate: actualization index of the overall costs of road infrastructure (2 tested scene): BASE SCENE: 1.0 % ALTERNATIVE SCENE: 4.0 % Company profit: On the total cost of infrastructure: 23%

14 Maintenance Scenario hypothesis b Scheduled maintenance during pavement life-time (20 years from construction). During the binder layer maintenance phase (milling and reconstruction), 30 % of RAP coming from the milling of the same layer is expected to be used. RAP re-use can be carried out with a hot recycling procedure: RAP is sent to plant and mixed with virgin aggregates and bitumen * ESAL Years Milling and re-construction of the layer * Calculation of approximate ESAL number (AASHTO method) 12

15 13 Scenario hypothesis b A 100 km Virgin C 10 km Virgin Scenario A The use of virgin aggregates only was supposed. Transportation distance for supply was assumed up to 100 km. Scenario C The use of virgin aggregates only was supposed. Transportation distance was assumed up to 10 km (available in situ). Tested scenarios Scenario B Steel slag and RAP was used in partial substitution of virgin aggregates. Transportation distance for supply was assumed up to 100 km. Scenario D Steel slag and RAP was used in partial substitution of virgin aggregates. Transportation distance was assumed up to 10 km (available in situ). B 100 km Recycled D 10 km Recycled

16 14 Results and discussions c Scenario A Virgin 100 km Production Transportation Process Total E [MJ] WC [kg] CO 2 [Mg] NO x [kg] PM 10 [kg] SO 2 [kg] CO [kg] Hg [g] Pb [g] HWG [kg] HTPC HTPNC Scenario B Recycled 100 km Production Transportation Process Total Environmental impact results

17 14 Results and discussions c Scenario A Virgin 100 km Production Transportation Process Total E [MJ] WC [kg] CO 2 [Mg] NO x [kg] PM 10 [kg] SO 2 [kg] CO [kg] Hg [g] Pb [g] HWG [kg] HTPC HTPNC Scenario B Recycled 100 km Production Transportation Process Total Environmental impact results As expected, impacts generally decreased with the substitution of virgin aggregates with recycled materials. Since innovative production techniques of asphalt concrete were not used, slightly lower impact reductions in comparison to those found in other bibliography demonstrated the cruciality of process in final impact results.

18 14 Results and discussions c Scenario A Virgin 100 km Production Transportation Process Total E [MJ] WC [kg] CO 2 [Mg] NO x [kg] PM 10 [kg] SO 2 [kg] CO [kg] Hg [g] Pb [g] HWG [kg] HTPC HTPNC Scenario B Recycled 100 km Production Transportation Process Total Environmental impact results As expected, impacts generally decreased with the substitution of virgin aggregates with recycled materials. Since innovative production techniques of asphalt concrete were not used, slightly lower impact reductions in comparison to those found in other bibliography demonstrated the cruciality of process in final impact results. As example, RAP use during maintenance and by-products (steel slags) reutilization reduced total requested energy and water consumptions (less material disposals to landfill were needed).

19 Environmental impact results Similar findings for Scenario C and Scenario D (transportation distance up to 10 km material available in situ): Scenario C Virgin 10 km Production Transportation Process Total E [MJ] WC [kg] CO 2 [Mg] NO x [kg] PM 10 [kg] SO 2 [kg] CO [kg] Hg [g] Pb [g] HWG [kg] HTPC HTPNC Scenario D Recycled 10 km Production Transportation Process Total Results and discussions c

20 Environmental impact results Similar findings for Scenario C and Scenario D (transportation distance up to 10 km material available in situ): about general impacts; Scenario C Virgin 10 km Production Transportation Process Total E [MJ] WC [kg] CO 2 [Mg] NO x [kg] PM 10 [kg] SO 2 [kg] CO [kg] Hg [g] Pb [g] HWG [kg] HTPC HTPNC Scenario D Recycled 10 km Production Transportation Process Total Results and discussions c

21 Environmental impact results Similar findings for Scenario C and Scenario D (transportation distance up to 10 km material available in situ): about general impacts; about energy and water consumptions. Scenario C Virgin 10 km Production Transportation Process Total E [MJ] WC [kg] CO 2 [Mg] NO x [kg] PM 10 [kg] SO 2 [kg] CO [kg] Hg [g] Pb [g] HWG [kg] HTPC HTPNC Scenario D Recycled 10 km Production Transportation Process Total Results and discussions c

22 16 * According with other study: Initial construction impact Maintenance impact End-of-life dismission impact 5 % Phases of pavement life Processes and equipment involved in construction and maintenance phases constituted the smallest contributions. 25 % 75% Results and discussions Environmental impact results With regard to the use of materials, initial construction, maintenance and end-of-life dismissions phases presented significant differences in terms of environmental impacts. c

23 17 Distance: 100 km Transportation impacts Distance: 10 km Scenario A Scenario B Scenario C Scenario D E [MJ] WC [kg] CO2 [Mg] NOx [kg] PM10 [kg] SO2 [kg] CO [kg] Hg [g] Pb [g] HWG [kg] HTPC HTPNC Results and discussions Environmental impact results Material production owned a marginal weight in life cycle of road pavement with respect to the transportation processes. c

24 17 \ Transportation impacts Distance: 100 km Distance: 10 km Scenario A Scenario B Scenario C Scenario D E [MJ] WC [kg] CO2 [Mg] NOx [kg] PM10 [kg] SO2 [kg] CO [kg] Hg [g] Pb [g] HWG [kg] HTPC HTPNC Results and discussions Environmental impact results Material production owned a marginal weight in life cycle of road pavement with respect to the transportation processes. c Significant concern of transportation process: great impact reduction with available in situ materials. Transportation processes give a contribution close to the 20% of the total impact. Higher specific gravity of steel slags burdens on the transportation costs; for this reason, project implied only the use 30% of slags by the total aggregate weight (to prevent the increasing of total impact).

25 Scenario A costs During initial construction phase, material costs were greater with respect to the equipment and worker ones. Vice versa, during maintenance phase, equipment and worker costs prevailed. Since initial costs were the same, alternative scene, with a discount rate of 4.0 %, obviously gave a significant reduction in total costs due to lower maintenance expensiveness. 52% Initial construction cost Maintenance cost 41 mln. 41 mln Total cost Total cost 20 years 20 years BASE SCENE Discount rate: 1.0 % 48% Construction costs: Maintenance costs: Total costs: % Results and discussions 35 mln. 41 mln Total cost Total cost 20 years 20 years ALTERNATIVE SCENE Discount rate: 4.0 % 61% Construction costs: Maintenance costs: Total costs: Due to the exclusive use of natural aggregates, Scenario A costs were higher because of the onerous activities connected to waste materials disposal towards landfills. c 18

26 BASE SCENE Discount rate: 1.0 % Results and discussions c Construction costs Scenario B: Scenario C: Scenario D: Scenario B: Scenario C: Scenario D: Total costs Scenario B: Scenario C: Scenario D: 94% 90% 84% Maintenance costs 98% 95% 91% 97% 92% 87% B, C, D costs B and D scenarios request lightly reduced investments (with respect to the scenario A) due to slightly lower costs for marginal material rehabilitation operations in comparison with the use of virgin aggregates Difference are also related to the contribution of onerous material disposals during maintenance activity. Greater cost reductions were otherwise connected to the shorter distances for material availabilities (C and D scenarios). Percentages with respect to costs of scenario A. 19

27 c Results and discussions ALTERNATIVE SCENE Discount rate: 4.0 % B, C, D costs In analogy, effectiveness of marginal material rehabilitation (with lower disposal costs) and reduction of supply distance were also identified in ALTERNATIVE SCENE (with a discount rate of 4.0 %) Scenario B: Scenario C: Scenario D: Maintenance costs Scenario B: Scenario C: Scenario D: Construction costs 94% 90% 84% 97% 96% 93% Between BASE (1% discount rate) and ALTERNATIVE scenes (4 % discount rate), a light decrease in maintenance costs (thus in total investments) with the highest discount rate was evinced. Scenario B: Scenario C: Scenario D: Percentages with respect to costs of scenario A. Total costs 96% 92% 88% 20

28 21 Conclusions 6 Conclusions The LCA appeared to be a useful tool to check the suitability of projects, and, in general, a successful way to support decision-making processes considering environmental impact assessment and costs evaluation. An advanced LCA analysis, performed during design phases of infrastructures, is definitely able to objectively and univocally state the best design and construction alternative, evaluating the most (social and environmental) sustainable construction and maintenance technologies for the correct integration of the work.

29 Thank for you attention Questions? University of Padua Padua Italy Department of Civil Environmental and Architectural Engineering Andrea Baliello