An environmental and material flow analysis of the UK steel construction sector

The stock of steel and the annual end-of-life arisings from the UK steel construction sector has been predicted using a dynamic material flow analysis (MFA) model of the sector. This model used data on the historical consumption of steel construction products, the typical life span and life span distributions, and derived re-use and recycling rates of steel construction products. Historical consumption data of steel construction products were estimated back to 1900 to incorporate life spans of up to 90 years in predicting current and future end-of-life arisings. Re-use and recycling rates of steel construction products were determined from surveying members of the National Federation of Demolition Contractors. Sensitivity analyses were carried out to determine the effect of changing input variables (life span, life span distribution and recycling rates) on the end-of-life arisings and the stock of construction steel. These sensitivity analyses revealed that the life span of the products had the greatest effect on the end-of-life arisings. Model validation was implemented to determine the accuracy of the dynamic modelling. One approach involved deriving the stock of construction steel by using statistics on the floor space of UK buildings, steel's market share in these buildings and the weight of steel in them building. A second approach involved undertaking an MFA for the whole of the UK steel sector; this MFA used data from the steel construction MFA and was validated against actual data on end-of-life arisings of steel products for recycling. Both validation approaches suggested that the end-of-life arisings predicted from the steel construction dynamic model were accurate. Finally, recently compiled life cycle inventory data on steel construction products was coupled with the MFA data to assess the total energy consumption, carbon dioxide, volatile organic compounds and waste emissions of the sector. The coupled data were validated against energy consumption and carbon dioxide emissions determined from steel producers as part of the UK climate change umbrella agreement and showed a good correlation. All these data and accounting methodology of the current work could be used as a starting point for collecting future data, to compare against, to assess if the UK steel construction sector was improving its sustainability performance.