Materials
Although the primary life cycle impact of HVAC systems is likely to be operational energy usage, consideration of the impacts of production of HVAC equipment may also be important. At the most basic or ideal level, natural ventilation would replace air conditioning equipment thereby negating the need to produce and maintain that equipment. However, since natural ventilation in the Boston area is likely to be part of a hybrid strategy, it is not likely that air conditioning equipment would be completely replaced. Nonetheless, the following analysis helps understand the impacts associated with the production of air conditioning equipment.
To begin with, consider the materials needed to produce a commercial air conditioner. Iron (steel), aluminum, copper, other metals, polymers, and hydrocarbons are but a few of the materials that go into the production of air conditioning equipment, as shown in the non-exhaustive list in Table 6. To reduce the impacts of producing this equipment, an understanding of which inputs have the largest environmental impacts is needed. To gain a high-level perspective on the impacts of the production phase, an Input-Output Life Cycle Analysis (IO LCA) assessment was performed using Open LCA software (www.sylvatica.com). Open LCA is an open-source tool for Life Cycle Assessment (LCA) modeling and for optional integration of life cycle cost (LCC) modeling, with additional options for strategic analysis of scenario-based, dynamic, hybrid, uncertain and/or non-linear LCA/LCC modeling.
IO LCA allows an analyst to study a product’s supply chain by assuming that a commodity sector is a good representation of an individual product and that expenditures in dollars of that sector are a valid proxy for consumption and emissions of the processes that contribute to production of that product. The software contains all 512 commodity groups in the US input/output accounts. For this analysis, the sector “Refrigeration and Heating Equipment” is assessed as a proxy for air-conditioning equipment (commodity group 52.0300).
The results from the IO LCA analysis, shown in Table 7, show the relative contribution to total NOx, SO2, and CO2, emissions to produce heating and refrigeration equipment. The results indicate that electricity is a major contributor to overall NOx, SO2, and CO2, emissions for this phase (63%, 39%, and 39% of total emissions respectively). For SO2 emissions, primary smelting and refining of copper is the largest contributor, accounting for 41% of total emissions. Blast furnaces and steel mills are also important for all three pollutants (NOx, SO2, and CO2: 10%, 6%, and 18% respectively). Other input sectors that contribute to NOx, SO2, and CO2 emissions in the production of heating and refrigeration equipment include industrial inorganic and organic chemicals, paper and paperboard mills, crude petroleum and natural gas, plastics materials and resins, petroleum refining, and iron and steel foundries. Transportation (by air) and wholesale trade make the list for CO2 emissions. In summary, although absolute amounts of emissions are not given, analysis of this representative sector indicates that energy and material inputs are likely to be the important contributors to pollution emissions in the production of air conditioning equipment.
To compare the relative impacts of the production and operational phases of air conditioning equipment, a more detailed “Process LCA” could be conducted. Inputs would include a detailed bill of materials (i.e. amounts of each material), production process specifications (ex. electricity consumption in the production line, etc.), and expected energy consumption during operation. Model outputs would provide emissions information for each of the two specified phases. However, because natural ventilation is likely to be part of a hybrid strategy which also requires the use of air conditioning equipment, a comparative assessment of the hybrid strategy to the traditional equipment strategy would not require full analysis of the production of air conditioning equipment as both strategies would require such equipment. |
