openLCA is a free LCA modeling environment (available at http://www.openlca.org/) available for Windows, Mac, and Linux operating systems. While installation and configuration can be quite complicated (and is not detailed here), various datasets are available. The tutorial assumes you have access to a working openLCA installation with the US LCI database, and discusses how to find the same US NREL-based LCI data as in Section 1.
After launching openLCA and connecting to your data source you should see a list of all of your databases, as shown in Figure 5-31. If you do not see the search and navigation tabs, you may add them under the "Window menu -> Show views option" to add them. If you have installed the US LCI database, it should be one of the options available.
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com Figure 5-31: List of Data Connections in openLCA
Browsing for process data in openLCA
Clicking on the triangle to the left of the folder allows you to open it and see the standard hierarchy of information for all data sources in openLCA, like in Figure 5-32. This is where you could see the process data, types of flows, and units.
Figure 5-32: Hierarchical Organization of Information for openLCA Databases
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com
If you double click on the "Processes" folder it will display the same sub-hierarchy of processes (not shown here) that we saw in the NREL/Digital Commons website in Section 1. All of the data for unit processes are contained under that folder. If you click on the
"Utilities" subcategory folder, then the "Fossil Fuel Electric Power Generation" folder, you will see the Electricity, bituminous coal, at power plant seen above, as shown in Figure 5-33.
Several of the other processes burning coal to make electricity and mentioned in the chapter would also be visible.
Figure 5-33: Expanded View of Electricity Processes in Fossil Fuel Generation Category
Searching for a process in openLCA
Instead of using the Navigation tab, a search for process data can be done using the Search tab. Clicking on the search tab brings up the search interface, as shown in Figure 5-34.
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com Figure 5-34: Default Search Interface in openLCA
In the first search option, you may search in all databases or narrow the scope of your search to only a single database (e.g., to the US-LCI database). In the second option, you may search all object types, or narrow the scope of your search to just "Processes", etc. Finally, you can enter a search term, such as "electricity". If you choose to search for "electricity"
only in your US LCI database (note you may have named it something different), and only in processes, and click search you will be presented with the results as in Figure 5-35. Note that these results have been manually scrolled down to show the same Electricity, bituminous coal, at power plant process previously identified.
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com Figure 5-35: Search Results for Electricity in US-LCI Database in OpenLCA
Unlike the other tools, there is no quick and easy way to skim metadata to ensure which process you want to use.
Viewing process data in openLCA
To view process data, choose a process by double-clicking on it from either the browse or search interface. This opens a new pane of the openLCA environment and returns the process data and metadata overview, as shown in Figure 5-36. Similar to the Digital
Commons website, the default screen shows high-level summary information for the process (not all of the information is shown in the Figure). Additional information is available in the Inputs/Outputs, Administrative information, other tabs at the bottom of this pane.
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com Figure 5-36: Process Data and Metadata Overview in SimaPro
Clicking on the Inputs/Outputs tab displays the flow data in Figure 5-37, which for this process is now quite familiar.
Figure 5-37: View of Process Flow Data (Inputs and Outputs) in openLCA
If you need to download this data, you can do so by choosing "Export" in the File menu, but you cannot export it as a Microsoft Excel file.
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com
Section 4 – Spreadsheet-based Process Flow Diagram Models Now that process data has been identified, quantitative process flow diagram-based LCI models can be built. Amongst the many tools to build such models, Microsoft Excel is one of the most popular. Excel has many built-in features that are useful for organizing LCI data and calculating results, and is already familiar to most computer users.
To make these examples easy to follow, we repeat the core example from Chapter 5 (and shown in Figure 5-5) involving the production of coal-fired electricity via three unit processes in the US LCI database. The US LCI database is used since it is freely available and indicative of many other databases (e.g., ELCD). To replicate the structure of the core model from Chapter 5, we need to manage our process data in support of our process flow diagram. The following steps illustrate the quantitative structure behind a process-flow diagram based LCI model.
1) Find all required process data
In the first few sections of the advanced material for this chapter, we showed how to find the required process data from the US LCI database via several different tools. Using similar browse and search methods, you can find the LCI data for the other two processes so that you have found US LCI data for these three core processes:
• Electricity, bituminous coal, at power plant
• Bituminous coal, at mine
• Transport, train, diesel powered
Depending on which tool you used to find the US LCI process data, it may be easy to export the input and output flows for the functional unit of each process into Excel. If not, you may need to either copy/paste, or manually enter, the data. Recall that accessing the US LCI data directly from the LCA Digital Commons can yield Microsoft Excel spreadsheet files.
2) Organize the data into separate worksheets
A single Microsoft Excel spreadsheet file can contain many underlying worksheets, as shown in the tabs at the bottom of the spreadsheet window. For each of the downloaded or
exported data modules, copy / paste the input/output flows into a separate Microsoft Excel worksheet. If you downloaded the US LCI process data directly from the lcacommons.gov website, the input/output flow information is on the "X-Exchange" worksheet of the downloaded file (the US LCI data in other sources would be formatted in a similar way).
The Transport, train, diesel powered process has 1 input and 9 outputs (including the product output), as shown in Figure 5-38.
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com
Figure 5-38: Display of Extracted flows for Transport, train, diesel powered process from US LCI
3) Create a separate "Model" worksheet in the Microsoft Excel file
This Model worksheet will serve as the primary workspace to keep track of the relevant flows for the process flow diagram. This sheet uses cell formulas to reference the flows on the other worksheets that you created from the process LCI datasets.
Beyond just referencing the flows in the other worksheets, the Model worksheet must scale the functional unit-based results as needed based on the process flow diagram. For example, in Equation 5-1, results were combined for 1 kWh of electricity from bituminous coal, 0.46 ton-km of train transportation, and from 0.44 kg of coal mining. Since the process LCI data modules are generally normalized on a basis of a functional unit of 1, we need to multiply these LCI results by 1, 0.46, or 0.44.
Basic LCI Spreadsheet Example
In this example, a basic cell formula is created on the Model worksheet to add the output flows of CO2 from the three separate process worksheets. We first make a summary output result cell for each of the three processes where we multiply the CO2 emissions value from each worksheet (e.g., the rounded value 0.019 in cell G8 of Figure 5-38) by the functional unit scale factor listed above. Then we find the sum of CO2 emissions across the three processes by typing = into an empty cell and then successively clicking on the three scaled process emissions values.
The Chapter 5 folder has a "Simple and Complex LCI Models from US LCI"
spreadsheet file following the example as shown in the Chapter (which only tracked emissions of fossil CO2). Figure 5-39 shows an excerpt of the "Simple Model" worksheet in the file. The same result as shown in the chapter (not rounded off) is visible in cell E8, with the cell formula =B8+C8+D8.
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com Figure 5-39: Simple Spreadsheet-Based Process LCI Model
This simple LCI model shows a minimal effort result, such that using a spreadsheet is perhaps overkill. Tracking only CO2 emissions means that we only have to add three scaled values, which could be accomplished by hand or on a calculator. However this spreadsheet motivates the possibility that a slightly more complex spreadsheet could be created that tracks all flows, not just emissions of CO2.
Complex LCI Spreadsheet Example
Beyond the assumptions made in the simple model above, in LCA we often are concerned with many (or all) potential flows through our product system. Using the same underlying worksheets from the simple spreadsheet example, we can track flows of all of the outputs listed in the various process LCI data modules (or across all potential environmental flows).
This not only allows us a more complete representation of flows, but better prepares us for next steps such as impact assessment.
In this complex example, we use the same three underlying input/output flow worksheets, but our Model worksheet more comprehensively organizes and calculates all tracked flows from within a dataset. Instead of creating cell formulas to sums flows for each output (e.g., CO2) by clicking on individual cells in other worksheets, we can use some of Excel's other built-in functions to pull data from all listed flows of the unit processes into the summary Model worksheet. An example file is provided, but the remaining text in this section describes in a bit more detail how to use Excel's SUMPRODUCT function for this task.
The SUMPRODUCT function in Microsoft Excel, named as such because it finds the sum of a series of multiplied values, is typically used as a built-in way of finding a weighted average. Each component of the function is multiplied together. For example, instead of the method shown in the Simple LCI spreadsheet above, we could have copied the CO2
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com
emissions values from the three underlying worksheets into the row of cells B8 through D8, and then used the function =SUMPRODUCT(B4:D4*B8:D8) to generate the same result.
The "Simple and Complex LCI Models" file has a worksheet "Simple Model (with SUMPRODUCT)" showing this example in cell E8, yielding the same result as above.
However the SUMPRODUCT function can be more generally useful, because of how Excel manages TRUE and FALSE values and the fact that the "terms" of SUMPRODUCT are multiplied together. In Excel, TRUE is represented as 1 and FALSE is represented as 0 (they are Booleans). So if we have "terms" in the SUMPRODUCT that become 1 or 0, we can use SUMPRODUCT to only yield results when all expressions are TRUE, else return 0.
This is like achieving the mathematical equivalent of if-then statements on a range of cells.
The magic of this SUMPRODUCT function for our LCI purposes is that if we have a master list of all possible flows, compartments, and sub-compartments, we can find whether flow values exist for any or all of them. On the US LCI Digital Commons website, a text file can be downloaded with all of the nearly 3,000 unique compartment flows present in the US LCI database. This master list of flows can be pasted into a Model worksheet and then used to "look up" whether numerical quantities exist for any of them.
A representative cell value in the complex Model worksheet, which has similar cell formulas in the 3,000 rows of unique flows, looks like this (where cells A9, B9, and C9 are the flow, compartment, and subcompartment values we are trying to match in the process data):
=E$4*SUMPRODUCT((Electricity_Bitum_Coal_Short!$A$14:$A$65=A 9)*(Electricity_Bitum_Coal_Short!$C$14:$C$65=B9)*(Electrici ty_Bitum_Coal_Short!$D$14:$D$65=C9)*Electricity_Bitum_Coal_
Short!$G$14:$G$65)
This cell formula multiplies the functional unit scale factor in cell E4 by the SUMPRODUCT value of:
• whether the flow name, compartment, and subcompartment in the unit flows for the coal-fired electricity process match every item in the master list of flows.
• and, if the flow/compartment/subcompartment values match, the inventory value for the matched flow.
Within the SUMPRODUCT, if the flow/compartment/subcompartment in the unit process data doesn't match the flow/compartment/subcompartment on the row of the Model worksheet, the Boolean values are all 0's and the result is 0. If they all match, the Boolean results are 1, and the final part of the SUMPRODUCT expression (the actual flow quantity) is returned.
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com Figure 5-40: Complex Spreadsheet-Based Process LCI Model
The Chapter 5 folder on the textbook website has spreadsheets with all of the flows and processes in the US LCI database, as downloaded from the LCA Digital Commons website.
The "Simple and Complex LCI Models" file has a worksheet "Complex Model" which shows how to use the SUMPRODUCT function to track all 3,000 flows present in the US LCI database (from the flow file above). Of course the results are generally zero for each flow due to data gaps, but this example model expresses how to broadly track all possible flows. You should be able to follow how this spreadsheet was made and, if needed, add additional processes to this spreadsheet model.
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com (the rest of these will be done, in order shown, but in no hurry to finish yet)
Section – Ecoinvent website
Section – Accessing LCI Data Modules in ILCD?
Reorder these Sections (e.g., ILCD after NREL since so similar)?
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com Photo Credit: © Chris Goldberg, 2009, via Creative Commons license (CC BY-NC 2.0)
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com
Chapter 6 : Analyzing Multifunctional Product Systems In Chapter 5, we showed the relatively simple steps of building a process flow diagram-based LCA model where there was only one product in the system. However, product systems in LCA studies may have multiple products, providing multiple functions. Analyzing these systems introduces new complexities, and this chapter demonstrates various methods (referenced in the Standard) for overcoming or addressing these challenges. The methods described herein modify either the systems studied or the input and output flow values so that the multifunction systems can be quantitatively assessed.
Learning Objectives for the Chapter At the end of this chapter, you should be able to:
1. Discuss the challenges presented by processes and systems with multiple products and functions.
2. Perform allocation of flows to co-products from unallocated data.
3. Replicate results from database modules containing unallocated and allocated flows.
4. Estimate inventory flows from a product system that has avoided allocation via system expansion.
Multifunction Processes and Systems
Many processes and product systems are simple enough that they have only a single product output that provides a single function. However, even when tightly scoped, there are also many processes and systems that will have multiple products that each provide their own function. A good example is a petroleum refinery that has outputs of gasoline, diesel, and other products. LCA studies typically have function and functional unit definitions related to the life cycle effects of only one product. As such, a method is needed to connect input and output flow data with a desired functional unit, subject to the data associated with multiple products. The method chosen can have a significant effect on the results, and thus, the choice of method is controversial. How to deal with such systems is subject to much debate.
Building on the example figures and discussion in Chapters 4 and 5, Figure 6-1 shows a generic view of a unit process with multiple product outputs that each provides their own
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com
function. In this case, there are three Products, A, B, and C, associated with functions 1, 2, and 3, respectively.
Co-products exist when a process has more than one product output – which is a fairly common outcome, given the complexity of many industrial processes. If the goal of our study is to assess the effects associated with Product A, which provides Function 1, we need to find a way to deal with the provision of Products B and C, which provide Functions 2 and 3. In the context of a particular study, typically the product of primary interest (i.e., Product A above) is referred to as the product, and any other products (i.e., Products B and C above) as co-products, but this is not a standard terminology.
The Standard suggests two ways of approaching this problem: either by partitioning the process so that a set of quantitative connections are derived between the inputs and outputs and the various products (known as allocation), or by changing the way in which we have defined our system so that we can clearly show just the effects associated with Product A and its associated function (known as system expansion). While system expansion is the preferred method, we discuss allocation first because it is simpler to understand and also helps to frame the broader discussion.
Figure 6-1: Generic Illustration of a Unit Process with Multiple Products or Co-Products
Life Cycle Assessment: Quantitative Approaches for Decisions That Matter – lcatextbook.com
Allocation of Flows for Processes with Multiple Products
For a unit process, the goal of allocation is to assign a portion of each input and non-product (e.g., emission) output to each of the various non-products, such that the sum of all product shares equals the total input and output flows for the process. Allocation is also referred to as partitioning.
In Chapter 5, we accessed the US LCI database information and directly used all of the data without modification in our model for the bituminous coal-fired electricity process flow diagram. We even used some of the information in the process data to decide the multipliers needed in using our other process data sources. The reason we would directly use all of the data is because the Electricity, bituminous coal, at power plant process listed only one product: electricity (see Figure 5-6).
For other LCA models, we may have to manipulate the data in some way to make it fit the needs of our study. However, one could envision an alternative process where aside from generating electricity, the process also produced heat (e.g., a combined heat and power, or CHP system). Such a process has multiple products, heat and power, each of which has a different function. Furthermore, we might want to derive a mathematical means of associating a relevant portion of the quantified inputs and outputs to each of the products (i.e., to know how much pollution we associate to each product of the system). This energy, etc.) and quantifies all outputs (e.g., diesel, gasoline, etc.). Alternatively, process data
For other LCA models, we may have to manipulate the data in some way to make it fit the needs of our study. However, one could envision an alternative process where aside from generating electricity, the process also produced heat (e.g., a combined heat and power, or CHP system). Such a process has multiple products, heat and power, each of which has a different function. Furthermore, we might want to derive a mathematical means of associating a relevant portion of the quantified inputs and outputs to each of the products (i.e., to know how much pollution we associate to each product of the system). This energy, etc.) and quantifies all outputs (e.g., diesel, gasoline, etc.). Alternatively, process data