Xavier Gabarrell Durany

Building waste management core indicators through Spatial Material Flow Analysis: Net recovery and transport intensity indexes

In this paper, the material and spatial characterization of the flows within a municipal solid waste (MSW) management system are combined through a Network-Based Spatial Material Flow Analysis. Using this information, two core indicators are developed for the bio-waste fraction, the Net Recovery Index (NRI) and the Transport Intensity Index (TII), which are aimed at assessing progress towards policy-related sustainable MSW management strategies and objectives. The NRI approaches the capacity of a MSW management system for converting waste into resources through a systematic metabolic approach, whereas the TII addresses efficiency in terms of the transport requirements to manage a specific waste flow throughout the entire MSW management life cycle. Therefore, both indicators could be useful in assessing key MSW management policy strategies, such as the consecution of higher recycling levels (sustainability principle) or the minimization of transport by locating treatment facilities closer to generation sources (proximity principle). To apply this methodological approach, the bio-waste management system of the region of Catalonia (Spain) has been chosen as a case study. Results show the adequacy of both indicators for identifying those points within the system with higher capacity to compromise its environmental, economic and social performance and therefore establishing clear targets for policy prioritization. Moreover, this methodological approach permits scenario building, which could be useful in assessing the outcomes of hypothetical scenarios, thus proving its adequacy for strategic planning.

Increasing Precision in Greenhouse Gas Accounting Using Real‐Time Emission Factors

For many companies, the greenhouse gas (GHG) emissions associated with their purchased and consumed electricity form one of the largest contributions to the GHG emissions that result from their activities. Currently, hourly variations in electricity grid emissions are not considered by standard GHG accounting protocols, which apply a national grid emission factor (EF), potentially resulting in erred estimates for the GHG emissions. In this study, a method is developed that calculates GHG emissions based on real‐time data, and it is shown that the use of hourly electricity grid EFs can significantly improve the accuracy of the GHG emissions that are attributed to the purchased and consumed electricity of a company. A model analysis for the electricity delivered to the Spanish grid in 2012 reveals that, for companies operating during the day, GHG emissions calculated by the real‐time method are estimated to be up to 5% higher (and in some special cases up to 9% higher) than the emissions calculated by the conventional method in which a national grid EF is applied, whereas for companies operating during nightly hours, GHG emissions are estimated to be as low as 3% below the GHG emissions determined by the conventional method. A significant error can therefore occur in the organizational carbon footprint (CF) of a company and, consequently, also in the product CF. It is recommended that hourly EFs be developed for other countries and power grids.

Energy Intensity of the Catalan Construction Sector

We used a thermodynamic framework to characterize the resource consumption of the construction sector in 2001 in Catalonia, the northeast region of Spain. The analysis was done with a cradle�?to�?product life cycle approach using material flow analysis (MFA) and exergy accounting methodologies to quantify the total material and energy inputs in the sector. The aim was to identify the limitations of resource metabolism in the sector and to pinpoint the opportunities for improved material selection criteria, processing, reuse, and recycling for sustainable resource use. The results obtained from MFA showed that nonrenewables such as minerals and natural rocks, cement and derivatives, ceramics, glass, metals, plastics, paints and other chemicals, electric and lighting products, and bituminous mix products accounted for more than 98% of the input materials in the construction sector. The exergy analysis quantified a total 113.1 petajoules (PJ) of exergy inputs in the sector; utilities accounted for 57% of this exergy. Besides exergy inputs, a total of 6.85 million metric tons of construction and demolition waste was generated in 2001. With a recycling rate of 6.5%, the sector recovered 1.3 PJ of exergy. If the sector were able to recycle 80% of construction and demolition waste, then exergy recovery would be 10.3 PJ. Hence the results of this analysis indicate that improvements are required in manufacturing processes and recycling activities, especially of energy�?intensive materials, in order to reduce the inputs of utilities and the extraction of primary materials from the environment.

Exergetic Life Cycle Assessment: An Improved Option to Analyze Resource Use Efficiency of the Construction Sector

This article presents an effort to pinpoint how efficiently resources are used in the construction sector applying exergetic life cycle assessment methodology in a cradle-to-grave life cycle approach. Polypropylene (PP) and polyvinyl chloride (PVC), two widely used thermoplastics in construction applications, are chosen as case study materials in this analysis involving raw material extraction, resin manufacturing, and post-consumer waste management life-cycle stages. Overall life cycle exergy efficiency of PP and PVC is quantified 27.1% and 9.3%, respectively, characterized by a low efficiency of manufacturing and recycling processes for both materials. Improving the efficiency of manufacturing and recycling processes will thus reduce exergy losses from the system. From resource conservation point of view, mechanical recycling can be the viable option for end-of-life plastic waste management, since it loops materials back directly into new life cycle, and thus reduces primary resource inputs in the production chain and associated environmental impacts.

Exergy analysis of construction material manufacturing processes and assessment of their improvement potentials

This study presents the application of exergy analysis in assessing how effectively resources are utilised in construction material manufacturing. The role of exergy is discussed from several key perspectives such as quality, energy conservation and process improvement potentials. Both primary and secondary processes (recycling) of nine major non–renewable construction materials (steel, aluminium, copper, cement, concrete, ceramic, glass, polypropylene and polyvinylchloride (PVC)) have been evaluated in this study. The outlined theoretical exergy efficiency approach assesses the improvement potentials of the present manufacturing processes. The large difference between theoretical and industrial exergy demand suggests that exergy resources are utilised very inefficiently in current technologies. The study reveals that more than 55% of exergy is being lost in current technologies even though a significant amount of waste heat is recovered in different segments of the case study processes. Thus, attention is required to reduce the specific exergy losses through improved process design and introduction of new technology.