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Solid Waste Analysis and the Building Industry

May 18, 2009

Life Cycle Assessment of Reducing Waste from Residential Building Construction and Demolition in the State of Oregon

I.      introduction

Over the past decade, the volume of solid waste entering Oregon landfills has grown at an alarming rate. A recent study by the Department of Environmental Quality (DEQ) indicates that between 1993 and 2005, solid waste increased 70%. DEQ research also indicates that building related waste (i.e., construction, renovation, and demolition debris) is a major source of the expanding solid waste volume, particularly building waste composition from renovation and demolition activities that have been purchased and installed years or decades ago.[1] As a result, landfills are filling up faster than anticipated and posing long-term management concerns related to capacity and human and environmental health.

Such concern has prompted the DEQ to reexamine the solid waste stream and its contributing factors in an attempt to identify reduction options and benefits that may result in waste stream reduction policies. One effort is the investigation of the residential building industry's waste stream from a life cycle assessment (LCA) perspective. An LCA approach identifies and quantifies the entire waste stream of a building material, component, or practice, and lends insight into how each element contributes to the waste stream.

This article briefly describes the DEQ's LCA of building materials and practices project. The project is being conducted by Earth Advantage Institute as part of a team with the Oregon Home Builders Association and Ecointesys - Life Cycle Systems. Though the project is only 30% complete and lacks results, its structure and approach are unique. This venture has the potential to help policymakers understand the building industry's solid waste stream and to help them make decisions that reduce future waste volumes.

II.      assumptions

Oregon DEQ recognizes that a successful waste prevention policy must take an approach based on life cycle analysis (LCA). Upstream (resource extraction and production of goods) and downstream (end-of-life/waste management) impacts need to be addressed, as do impacts that occur from the use of a product or system. This perspective is necessary for the DEQ to achieve its three objectives from its Waste Prevention Strategy:[1]

• Environment - Strategically reduce GHG emissions, waste generation, and environmental impacts.
• Sustainability - Demonstrate that preventing waste can have a positive economic, social, and environmental impact, and that prevention is a relevant component of a sustainable society by addressing the broader impacts of materials, product use, and design.
• Waste Generation - Take strategic actions that prevent waste generation and contribute to achieving Oregon's waste prevention (generation) goals established in state law.

The project is guided by three main tenants. First, given the wide range of possible actions, resource limitations necessitate that well-informed policy decisions are made, that the most effective measures are chosen, and that those of negligible or negative impacts are avoided. Second, decisions that promote solid waste reduction have impacts that range far beyond the generation of waste to include climate change, energy use, resource use, human health, and ecological health. Therefore, ensuring that all actions achieve a net environmental improvement requires a decision framework that accounts for impacts of the building sector within all these areas.

Third, there will be tradeoffs between actions selected. Reducing building materials (dematerializing) could impact another phase of a building's life cycle, such as heating and cooling efficiency. Effective ways of reducing direct waste production may have a detrimental overall impact on the environment when all effects of such actions are properly considered. Therefore, it is necessary to have a decision framework in place that properly accounts for the full impacts of residential buildings over their entire life cycles. This framework must accurately and quantitatively assign criteria used to evaluate building practices/materials, allowing the most important practices to be weighed and ranked.

III.      project structure

The project has two phases. Phase I screens a large number of building practices and the associated typical materials to identify the waste reduction actions that will most likely have the greatest overall environmental benefits. In Phase II, a detailed and thorough LCA-based analysis is conducted for those Phase I options that show the most promise. While Phase I involves a simplified LCA-based approach as a partial decision criterion, the second phase is based on creating a robust LCA study of residential buildings in Oregon. This study will be used as the primary criteria for making a definitive identification of which waste reduction actions provide the greatest environmental benefits.

For the LCA performed in both phases, the functional unit will be the provision of housing to one family for a period of 70 years (the assumed lifetime of a single-family home). The study will include data about the production and manufacture of all materials comprising the structure of the home, the transportation of these materials to and from the site of the home, the construction of the home, maintenance of the structure, the use of the home, its demolition, and the management of all waste materials. Consideration of the use of the home will be limited to heating and cooling, with attempts to also account for any other aspects of occupancy that can reasonably be linked to the home's design or construction as determined by the practices under consideration.

The following practices will be considered in this study:

IV.      PROJECT STEPS

Phase I - Screening

Phase I has the following five steps:

1.      Develop a grading system, such as a report card, that allows for the organization of information needed to evaluate each building practice according to a set of waste prevention measures.

2.      Characterize the waste prevention impact of each practice. Information will be drawn from a literature review, team expertise, vendor product data, and interviews with experts, among other sources.

3.      Assess the waste prevention and feasibility aspects of each option. Waste prevention will be measured in weight of material that does not enter the waste stream. Further, waste will be differentiated as either upfront savings (at the time the measure is implemented), reductions over the use phase of the home, or end-of-life reductions.

4.      Conduct preliminary screening-level LCA for each waste reduction measure, which provides the environmental criteria for making the report card evaluations.

5.      Complete the report card for each waste prevention measure being considered. The results will be based on net and ranked impacts/benefits per home, per dollar cost, and per ton of waste avoided.

Phase I will end with a ranked list of building practices based on their LCA waste prevention impacts.  This will allow for the identification of a short list of building practices to conduct more detailed LCA in Phase II.

Phase II - Detailed LCA

The actual work details for Phase II will be based on the outcome of Phase I. A refined work scope will be prepared as the first phase is completed and an understanding of steps that need to be taken in the final phase is reached. It is anticipated that work will be conducted in the following three areas:

Model Creation

A full building LCA model will be developed for residential building types. This will be designed to represent as completely as possible all aspects of the building's construction, maintenance, use, and demolition.

Impact Assessment

An impact assessment will be conducted on each of the building practices that have been selected for detailed LCA modeling. It will be based on several existing tools: the TRACI (Tool for the Reduction and Assessment of Chemical Impacts) methodology, the global warming potential factors published by the International Panel on Climate Change (IPCC), and a check on the robustness of the conclusions reached with TRACI using the IMPACT 2002+.

Scenario Definition and Evaluation

Each waste reduction measure will be characterized by a broad set of variables. Alternate scenarios may be conducted depending on result outcome and uncertainty level. For example, a waste reduction option that influences house heating and cooling efficiency may be compared to an alternate scenario representing Oregon's different temperature zones or geographic distribution. In cases of high uncertainty, minimum-maximum scenarios might be run. It may be possible to assess alternative behavior patterns of occupants to determine how that might impact waste reduction.

The assessment of each scenario will consider the implementation of the identified waste reduction practices for the residences in the study (i.e., constructed, maintained, or demolished) in year 0 of the study. The temporal boundaries of the study will extend to the point at which each practice ceases to have an influence, the limit of which will be the end-of-life of a newly constructed home at year 70.

V.      Results

At the end of the study, the DEQ will have detailed information not only on the entire waste stream of each building practice but also the life cycle costs, energy use, resource use, human and ecological health, and waste reduction potential.

This will directly inform the DEQ on further steps that it can take to achieve its goal of reducing overall residential building waste in the most environmentally beneficial way. This study will "support decisions by the Oregon Department of Environmental Quality and others in their efforts to form programs, policies and actions to reduce waste generation from the residential building sector in a way that maximizes overall environmental benefits."

[1] Oregon Department of Environmental, Quality Waste Prevention Strategy Background Paper #1: Solid Waste Generation in Oregon, (February 2007), p. 2.

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