Environmental Life Cycle Assessment

8/27/2014 6:39:10 PM

Figure 1. LCA Framework

Photo By: Attaway, Denise

Figure 2. Simplified process flow diagram of biofuel/biochemical production.

Photo By: Attaway, Denise

Environmental Life Cycle Assessment (LCA) is a methodology that assesses environmental impacts and human risks from all of the steps in the production chain of a product or a service.

The LCA method is standardized up to a certain degree under the International Standard Organization (ISO) 14040, which allows a common understanding between scientists and interested individuals.

According to ISO 14040, the LCA methodology consists of four main phases.The phases of an LCA study are:

  • Definition of Goal and Scope,
  • Inventory Analysis,
  • Impact Assessment, and
  • Interpretation of Results (Figure 1).
This framework is not a one direction method, but a process in which each phase provides feedback to the previous one according to what the following phase determined or revealed.This means an LCA project may start with specific objectives, but when the data in the inventory analysis are evaluated, the practitioner found that additional evaluation is needed, which add value to the study, therefore the practitioner proceeds to expand the scope accordingly.

Simultaneously, with the LCA method, other methodologies are used to estimate some of the quantities needed such as greenhouse gases (GHG) from land use change, indirect land use change, emissions from solid waste that are sent to landfills, and use of petroleum based fuels.For example, one of these methods to estimate GHG from land management has been developed by the Intergovernmental Panel on Climate Change (IPCC) method which is used to calculate the emissions from direct land use change due to agriculture.

Goal and Scope
The definition of goal and scope is the first step in making a LCA, and it consists of defining several key parameters and objectives. Each LCA should state what will be the system boundary (Figure 1) and what is the intention of the study. The system boundary includes the process to be studied, materials and energy flows to and from each of the process. The intention of the study could include, for example, determining what is the production phase that has the biggest environmental impact or what could be the environmental and human risks of producing a specified product. In this section, the study must define what unit of measurement will be used to assess the product under evaluation according to the intended function of that product, this is known as the functional unit. In other words, an LCA of ethanol production may have a functional unit of mega joules or miles traveled under a specific car. Finally, the goal and scope must state what is the intended audience of the study.

Life Cycle Inventory Analysis
The inventory analysis includes the collection of relevant data and calculation that is required to estimate inputs and output quantities of the processes.

Life Cycle Impact Assessment
In accordance with the ISO 14040, the impact assessment will involve the calculation of specific environmental potential impact categories from the emissions estimated or collected in the inventory analysis. An impact category is a quantity in terms of a standardize unit which has the potential to cause and environmental damage or impact. An example of this are kilograms of CO2, which is a greenhouse gas that cause global warming. Additional impact categories and the standardized unit or characterization factors are illustrated below according to the geographical impact (global, local or regional).

Impact Category Scale Characterization Factor Description
Global Warming    Global Carbon Dioxide (CO2) equivalents at 100 years
Eutrophication Local Phosphate (PO4) equivalents
Stratospheric Ozone Depletion Global Trichlorofluoromethane (CFC-11) equivalents
Acidification Regional/Local Hydrogen (H+) equivalents
Photochemical Smog     Local Ethane (C2H6) equivalents
Terrestrial Toxicity Local LC50
Aquatic Toxicity Local LC50
Human Health Global/Regional/Local LC50
Resource Depletion (fossil
fuel used)    
Global/Regional/Local Amount of fossil fuel used
Land use     Global/Regional/Local Area of land used as compared with land used by petrochemical production of the equivalent product
Water use     Regional/Local Amount of water used as compared with land used by petrochemical production of the equivalent product

Interpretation
Findings from the impact analysis are evaluated together to have a more informed view of the environmental impact of the product or service under the study. In this way and in the case of comparing product or alternate processes, the analyst and the interested individuals can identify the trade off that result from the environmental impacts. From the analysis the practitioner develops conclusions and recommendation, which can be used by the audience to draw conclusion from the production of the product.

Application of LCA to Biofuels and Renewable Commodity Biochemicals
As LCA evaluates the environmental burden of each process step, including the energy and environmental burden of each material input, we can identify which of these steps have the most impact. Having made this analysis, we can make modification to reduce the environmental impact of the process step that has a high impact by modifying the technology or addressing material inputs. For example, agriculture is usually a production step with high GHG emission in the production of biofuels from sugar cane or corn, and a significant portion of this emission comes from the application of nitrogen fertilizers that is not used by the crop. Therefore, optimizing the application of nitrogen (using the minimum amount of nitrogen to have maximum crop yield) is a way to reduce the emission from biofuels production by addressing a process step that has significant environmental impact. Similarly, increasing crop yield can have an impact from fossil fuel used for transportation of the crop to the processing facility because the collection distance is reduced by the increase of crop production by area (crop yield).

Contact:

Dr. Robert Anex. University of Wisconsin-Madison.


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