Rediseño de los procesos

There is a variety of theoretical work conducted in the field of urban flows and stocks and studies relevant to urban metabolism at different scales, from the scale of small neighborhoods to larger scales, such as multiple countries. However, the gap between theoretical work and feasible applications is yet to be filled (Kennedy et al., 2011). By interpreting the results of theoretical studies in ways that are useful and understandable, effective changes can be implemented in cities.

In order to manage the material use, we need to measure what we have already consumed.Being aware of the construction materials embedded in cities will help municipalities better identify the resources at risk and develop more sustainable resource management plan.

In this research, using the available GIS data from the region, a more comprehensive data set is developed that consists of the building, road, and sidewalk stocks’ material compositions for the studied materials for each stock alongside other existing characteristics such as footprint, use, number of stories, and year of construction for buildings, in addition to length, width and type for roads. This dataset can be expanded as new stocks are built in the cities and can be used as a valuable source for applying urban mining strategies to construction materials. This can be done by comparing the required materials for building or maintaining future stocks with the current

74

available materials. By investing in the reusing and recycling potentials of the in-use material stocks, cities will be able to rely on these materials for developments and decrease the use of virgin materials. The available datasets will help locate the future material flows and bring insights regarding the quantity of these potential material flows (Tanikawa et al., 2015). Therefore, the future material waste flows can be treated as useful input material flows which will help municipalities take effective steps towards achieving circular economy, which is a more sustainable approach than linear economy (Korhonen, Honkasalo, and Seppälä, 2017). Material loops can be partially closed in construction activities by increasing the use of recycled materials and preventing the entrance of new virgin material flows in construction activities.

MSA results also help indicate the material hotspots in cities and shed light on the required intervention points in construction material consumption patterns in urban areas. Building awareness of the material use conditions by measuring the amount of in-use materials helps in waste and resource management in the construction sector. The next step is to seek consumption reduction strategies to decrease the use of virgin materials. Less virgin material use means less need for natural resources and landfill space. Construction and demolition waste normally end up in landfills and take up a lot of landfill space (Wu et al., 2014). Providing suitable landfill sites in urban areas has always been a challenge due to the toxicity that these landfills produce affecting the population living in the city (Vrijheid, 2000). Therefore, by reducing or even preventing construction materials from ending up in landfills, the pressure on landfill sites in urban areas will decrease.

75

Among the construction materials studied in this research, aggregates have a special position. The Ontario Stone, Sand, and Gravel Association (OSSGA) have estimated that each year around 164 Mt of aggregate is being consumed in Ontario (OSSGA, 2018). Supplying aggregates to meet the increasing demand of this material will be challenging in the coming years (Ministry of Natural Resources and Forestry, 2016). At the same time, this research shows that in 2018, 32 Mt of aggregates were embedded in KW. Although these materials are currently in-use, considering their recycling potential can help in planning for future aggregate demands.

Canadian cities spend over $10 Billion annually on pavement maintenance (Hajek, Hein, and Olidis, 2004). This translates into millions of tonnes of pavement materials getting used to rebuild pavement structures and simultaneously millions of tonnes of pavement waste production.

Municipalities do not permit the use of more than a certain percentage of RAP, which is a type of recycled asphalt, in pavement construction. Therefore, even if all the waste from pavement deconstruction is recycled there is no practical use for it in pavement sections. Improving RAP quality that has the essential strength to be used more widely should be assessed by pavement engineers. The technical details for enhancing RAP quality do not fit into the scope of this research.

Here, it is only mentioned as a policy recommendation derived from the results of this study.

Professionals in the field of road and pavement design can further investigate the production of recycled pavement layers that can substitute virgin materials in pavement construction.

The GHG emissions associated with the material use for both constructing new stocks or maintaining the current ones increases with the use of virgin materials. Decreasing virgin material use by implementing effective resources and waste management strategies will directly impact the

76

GHG emissions and help cities contribute to mitigating GHG emissions and achieve their GHG reduction targets. Buildings account for 40 percent of the global GHG emissions (UNEP, 2017).

Construction material use in buildings is responsible for a fraction of these emissions which can be better controlled with the help of MSA results by reducing virgin material use and bringing awareness regarding the recycling and reusing potential of existing materials.