Urban development is a typical feature in cities today. Land conversion of resource related uses (farming) into urban-related uses (homes, buildings) is on the rise to cater to growing populations. Urban development is composed of urban infrastructure such as buildings, roads, water supply, energy supply, telecommunication networks, etc. Each urban element has its own life cycle. Through its raw material manufacturing to construction of each element until its demolition and recycling, tremendous amounts of energy and materials are consumed and part of the processes, produce harmful emissions and wastes. It is therefore important to trace all information on the urban elements and its processes on a life cycle basis. Life cycle analysis (LCA) can be a methodology to be able to address this issue. Life Cycle Analysis (LCA) is a procedure to assess the sustainability of a product through consideration of all environmental implications of development, from primary inputs to disposal of final output and by-products, their included wastes. In that respect, LCA can be used to assess an eco-balance of a product. However, LCA alone cannot address all the impacts of a project such as economic and social effects associated to the activity/strategy. The problem is how we should assess the sustainability of urban infrastructure. Indicators should be developed to be able to assess a sustainable urban development. Indicators such as emissions produced from the development, wastes generated, energy consumed and others should be considered. Economic and social impacts should also be taken into account in assessing sustainability.
I have analyzed environmental emissions mainly CO2 emissions from road construction using the LCA approach. My dissertation developed a carbon emission model based on the System of National Accounts Framework focusing on the emissions generated by the road construction industry. The hybrid rectangular input-output model (HRIO) was used to formulate the carbon emission model to be able to accurately account for the secondary production of industries. The I-O model simulates the flow of goods and services between the different sectors in an economy based on certain internal and external parameters. A twenty-year historical trace of carbon emissions generated by road construction commodities was also one of the highlights of the research. The lowest emission intensity for the 20-year period of analysis is in 1990. Results show that the bulk of the relevant contributions from the carbon producing industry are concentrated on a few sectors, such as steel and cement, thereby reduction of carbon emissions from the construction industry can be achieved by reduction of material usage from the major contributors of emission. The important sources of changes induced by road construction during the 20-year period of analysis were modeled using the structural decomposition analysis (SDA). The changes in emission structure, non-construction input structure, non-construction product-mix and road construction technology has been clearly defined in the model. The structural changes in the economy induced by road construction, which led to the decrease in emission levels, were due to major technological advances. A further decomposition of the technological changes is another feature of this dissertation. Technology is decomposed into fabrication or manufacturing technology changes and substitution or replacements in the existing material inputs. The bipoportional method is used as the decomposition method. It was shown that fabrication effects contribute more to the changes in technology in Japan as compared to the substitution effects. The last contribution of my research is the comparison of carbon emissions among Japan, China and the Philippines. The use of the carbon emission quotient (CEQ) identifies the embodied emissions due to trade as well as the core trade specialization of the region compared to the benchmark country. Emissions from trade between China and Japan are higher compared to that of the Philippines and Japan; for policies of tradable emission permits, emissions in the Philippines are still lower so Japan can use this information for consolidating a permit plan.
Aside from being able to calculate emissions, the I-O model can also be applied to know the social impact of a certain development. Social impacts such as effects of governmental decisions, like taxes, effects of changes in final demand of its output to the output of other sectors, effects of developments in neighboring areas / areas with significant economic interaction with the city, effects of technological change and effects of developments in neighboring cities.