Impact of building material recycle or reuse on selected emergy ratios

While the emergy evaluation method has been used successfully in recycling processes, this area of application still requires further development. One of such is developing emergy ratios or indices that reflect changes depending on the number of times a material is recycled. Some of these materials may either have been recycled or reused continuously as inputs to a building, for example, and thus could have various impacts on the emergy evaluation of the building. The paper focuses on reuse building materials in the context of environmental protection and sustainable development. It presents the results of an emergy evaluation of a low-energy building (LEB) in which a percentage of input materials are from recycled sources. The corresponding impacts on the emergy yield ratio (EYRB) and the environmental loading ratio (ELRB) are studied. The EYR which is the total emergy used up per unit of emergy invested, is a measure of how much an investment enables a process to exploit local resources in order to further contribute to the economy. The ELR however, is the total nonrenewable and imported emergy used up per unit of local renewable resource and indicates the stress a process exhibits on the environment. The evaluation provides values for the selected ratios based on different recycle times. Results show that values of the emergy indices vary, even more, when greater amounts of material is recycled with higher amount of additional emergy required for recycling. This provides relevant information prioritizing the selection of materials for recycling or reuse in a building, and the optimum number of reuse or recycle times of a specific material. (C) 2012 Elsevier B.V. All rights reserved.