Material flow analysis of the building sector in lleida

Resumen

One third of the total global consumption of natural resources are minerals intended for construction materials. Hence, the construction industry is great responsible for the high consumption of natural resources, the high energy consumption, and the significant generation of wastes that carries. The materials used in today's construction industry do not close the material cycles and, in many cases, they contain a high embodied energy. Furthermore, the building sector means two thirds of the volume of the construction industry in Spain. It has to be taken into consideration that the growth of the building sector is closely linked to the growth of material consumption, which in turn is linked to economic growth in a region. Nevertheless this growth does not consider the physical limits of the environment that are limiting the extraction of resources. It should be noted that in Spain the first decade of the XXI century has been characterized by a high growth of the building sector, mainly based on the construction of residential buildings. Due to these factors, residential building sector is an important area to analyze from a material and environmental point of view, thus contributing to the decrease in the consumption of natural resources, the energy consumption and the consequent environmental impacts. Likewise, the accounting of natural resource use and waste generation in the construction industry is essential to assess its current state and thus to contribute to develop future policies based on sustainability criteria. The general objective of this thesis is to analyze the flow of construction materials between the environment and the building sector at a regional scale. The particular objectives are (1) to implement the methodology "Material Flow Analysis" (MFA) on the building sector at a regional scale giving the key factors in the methodology for being applicable to different regions, (2) to analyze the movement (or flow) of building materials in the territory, between the environment and the anthroposphere, (3) to determine which is the required extraction of raw materials in the region for supplying the building sector, (4) to determine which materials are accumulated in the building sector, in which quantity and how the materials are varying along the period, (5) to determine the environmental impacts in the pedosphere, hydrosphere and atmosphere produced by the building sector by means of indicators derived from the methodology, and (6) to point out the strengths and weaknesses of today's use of materials in the building sector. The scope of the thesis is (1) the materials analyzed are those required to produce habitability by means of residential buildings, (2) the region of analysis is the demarcation of Lleida, and (3) the period of analysis is from 2000 to 2009. MFA consists in a systematic assessment of the flows and stock of materials within a system defined in space and time. The system is treated as a black box, where input and output flows are accounted. Because of the law of the conservation of matter, the results of an MFA can be controlled by a simple material balance, where total inputs are equal to total outputs plus net accumulation of materials in the system. The adaptation of the methodology to the case study leads to the design of a model that relates the flow of materials existing between the building sector and the environment. The extraction of natural resources, imports and exports of building materials in the region, outputs of wastes to nature, and the ecological rucksack of the used materials has been accounted. The methodology allows analyzing the impact of today's building sector in the environment by means of the derived indicators. These indicators are the domestic extraction of materials per capita, the ratios between the unused and used extraction of materials "by which the hidden flows, also known as the ecological rucksack of materials, are quantified" and the discharging of wastes to the soil, water and air that all together mean the domestic processed output to nature. Moreover, the flows of the main used building materials -concrete, ceramic, wood and metal- are analyzed individually for the year 2006. The resultant model shows that the metabolism of the building sector is characterized by a constant flow of materials between the environment and the anthroposphere. The materials are mainly extracted from the lithosphere (abiotic materials) and, in lower quantity, from the pedosphere (biotic materials). Raw materials come from both local environment and the rest of the environment, and they are processed for obtaining the construction materials. Finally, they are stored in the form of buildings in the anthroposphere. At the end of their useful life, these materials are returned to the environment (pedosphere, hydrosphere and atmosphere) in form of wastes with a lower quality. The thesis proves that the building sector can be analyzed not only from an economical point of view but also from an ecological point of view, and shows it as a system sustained by and closely linked to the environment. This thesis accounts and verifies that the building sector is consuming huge amounts of natural resources, and likewise it quantifies the discharges of wastes as output flows to the environment. Regarding to the analyzed territory, the province of Lleida, the thesis concludes that this region has not been able to supply the building material requirements of the building sector during the analyzed period, despite the availability of certain raw materials, such as quarrying and forestry products. The adequate management of these raw materials could let to a future material flow model based on local materials, allowing Lleida to become a self-sufficient region in material terms. In conclusion, the thesis contributes with objective data to the physic measure of the affectation of the building sector to the environment by means of the defined methodology. These data can be used in the decision of future policies regarding to sustainable construction that address the entire lifecycle of the material. Not only this but also industrial and economic policies about the production and use of building materials, policies on architectural design, use and maintenance during the life span of the building, and policies on management of construction and demolition wastes.