Life Cycle Assessment: Green Grows Up
Remember when you first noticed that “green” products were filtering into Main Street stores in significant numbers? Looking back just a few years ago, we can now see that these early arrivals were the harbingers of what has become an avalanche of environmentally sustainable products, available in virtually every market.
During those early stages, green was simple - a product was or it wasn’t. If it used less energy or water than everything else sitting on the shelf, it was green. As these products grew in number and performance claims, so did skepticism among consumers. Embarrassing revelations about products billed as “green” that lived on for millennia in landfills or were produced using highly toxic chemicals led to the coining of a new term: “greenwashing.” It soon became very clear to manufacturers and consumers alike, that the question was no longer whether a product is green, but “How green is that product?”
These days, environmental considerations enter into every aspect of a product’s sustainability: design, manufacturing, distribution, use and even disposal. Therefore, the only fair and balanced way to consider “greenness” is holistically over the product’s entire life. The challenge then becomes listing and accounting for all the environmental impacts of a product.
To better explain this challenge, let’s look at a green product virtually everyone has used. One of the darlings of the current environmental movement in the United States has been the compact fluorescent light bulb (CFL). These remarkable devices use 75% less energy than an incandescent bulb and last 10 times longer. Yet even these products, considered “green” by so many, have a dark side. Unlike the lowly incandescent bulb, each CFL contains small amounts of mercury. If large numbers of them end up in pieces, dumped in landfills, they could lead to mercury contamination of these sites.
In spite of that ugly possibility, CFLs are being promoted by most environmental organizations. Why? After comparing the potential mercury-contamination risks with the energy-saving rewards, the near unanimous opinion was that CFLs were the greener option.
My point here? Looking at individual products and systems holistically is not enough in the end. We also need a framework to compare the pros and cons: to weigh the savings in energy consumption and fossil-fuel use - to use our CFL example - against the negatives of groundwater contamination.
A Cradle-to-Grave ProcessThe solution that has finally emerged is a decision-making tool known as Life Cycle Assessment. LCA is not new, but it has been developed significantly in recent years. LCA was born out of early research into the cumulative energy requirements and sources for production in the chemical industry. Later refinements added material use and waste considerations to create a modeling technique that went beyond energy alone. In the early to mid-1970s, standard methodologies began to arise, as companies began to use this tool to make decisions. In the early 1990s, increased environmental interest led to the further development of LCA, culminating in the release of the first of the series of ISO 14000 Environmental Management standards in 1997.1
According to the National Renewable Energy Laboratory Web site, “LCA is a systematic, cradle-to-grave process that evaluates the environmental impacts of products, processes, and services.”2 It is a powerful tool that provides a framework for evaluating the inputs and outputs of a product or system as it moves through its various stages of life.
As shown in Figure 1 for a generic product, LCA organizes the life cycle by segmenting it into discrete elements, known as unit processes. In this “black box” approach, the inputs are aggregated into total materials and energy. Outputs are considered in the same way and may be waste, finished products or intermediate products. Product and material outputs can then serve as the inputs to a subsequent unit process.
LCAs are very flexible. They can be conducted for all or part of a product life cycle and can consider many or only specific impact categories. In Figure 1, for example, LCA could be used to focus on a unit process like product manufacturing or examine only airborne emissions. A practitioner must also decide on the appropriate depth for an analysis. It may be sufficient to consider the inputs and outputs from the manufacturing process itself without including other input-output information, such as for the creation and maintenance of the manufacturing equipment.
So, if our product manufacturing example involves a metal lathe, we must consider the electricity, raw metal rod stock and machining lubricant that this process consumes. Outputs include finished or intermediary products, waste metal shavings and waste lubricant. Most analyses would choose not to consider the energy, raw materials and waste involved in manufacturing the lathe itself. But without carefully established boundaries, an analysis can extend deep into the product cycle. The structure of an LCA is therefore dependent on the intended use, and must take into consideration the desired results and the necessary time and expense.
Thanks to their flexibility and structured approach, LCA analyses can have a myriad of uses. Done comparatively, they can help choose among several potential products, processes or systems. During the design phase, they can help designers select among different materials and technologies. For existing products, they can reveal areas where the greatest environmental improvement in a product, process or system can be achieved. The strength of LCA is that, if done properly, it can prevent or highlight the kind of “problem shifting” that has been the basis of many greenwashing charges. That is, problem shifting…
- …from one stage of life to another;
…from one sort of problem to another;
…from one media to another (e.g., uses less water, but consumes more energy);
…from one location to another.4
LCA analyses permit products to be viewed holistically, which avoids glossing over problem areas. Perhaps just as importantly, they prevent misperceptions that can lead us to assume that a product has a relatively poor environmental performance. The results can sometimes be surprising. (See “LCA Case Study on Food Waste Disposers” below.)
It is equally important to understand what an LCA is not. It is not a fully inclusive, decision-making tool. It will tell the user nothing of the performance of a product or system. Nor will it necessarily provide information on cost effectiveness, even though product life factors into analyses. Therefore, results derived from it must be prioritized and weighed against other, outside information.
Above all, it is not a simplistic, one-size-fits-all method. Its very flexibility, which makes it so versatile, also makes its results murky at times. LCAs cannot be compared side by side, unless they were specifically constructed for that purpose. Results from different LCAs will look differently, as some will focus on parts of systems or only on certain environmental impacts.
For this reason, the results of analyses can be easily misunderstood or abused. This, in turn, has led to reluctance on the part of some to cite LCA results widely. Because of these characteristics, it is extremely important for those who encounter LCA results to have a sense for its constructs, elements and, most importantly, limitations.
The Four PhasesAs shown in Figure 2, there are four phases to an LCA process, as set forth by the ISO 14000 standards. Before delving into them, we should note that all flow lines in the illustration go both directions, forward and backward. This is because LCA is a highly iterative process. Acquiring information on products and processes can lead to revisions in goals, changes to scopes, and the addition or deletion of environmental impacts. The four phases of an LCA are as follows:
1. Goal Definition and Scoping. This stage involves the establishment of project scope and system boundaries. This should be the result of a very careful description of the objective and the results needed. The researcher defines the unit processes, context, environmental-impact categories, and the depth to which the study is to be conducted.
While the process is iterative, the importance of this stage cannot be overstated. LCAs are, by their very nature, complex and potentially highly time-consuming. Careful forethought can avoid significant wasted effort or needlessly detailed studies.
2. Life Cycle Inventory (LCI) Analysis. This involves the identification and quantification of the inputs and outputs associated with the unit processes in a system. As shown in Figure 1, these are the materials and energy that flow into a system, and the waste and product that emerge. All flows are normalized for a specific quantity of product and for a reference indicator, to allow them to be compared and eventually aggregated.
A good example of this stage is an LCA conducted by the Pacific Institute in 2006 to examine the environmental impact - energy, water and emissions - of bottled water versus drinking water supplied from municipal sources.5 The analysis first found that the energy required to make a typical polyethylene terephthalate (PET) bottle, cap and packaging was approximately 3.4 megajoules (MJ) of energy. This was then normalized, based on the annual quantity of plastic consumed worldwide and the amount of energy in one gallon of oil. This calculation resulted in the often-quoted figure of the equivalent of 17 million barrels of oil needed to produce the plastic bottles.
Does this mean that a literal 17 million barrels were actually consumed? No. A variety of energy sources were used - electricity (gas, coal, wind, hydropower), natural gas and petroleum. But for the purposes of normalization, their energy values were converted to a petroleum equivalent. To further illustrate the point, the Pacific Institute factored in the energy used for filling, refrigerating, transporting and recycling or disposal. PI concluded that “the total amount of energy required for every bottle is equivalent, on average, to filling a plastic bottle 1/4 full with oil.”5
In this case, the objective of the researchers was to demonstrate that bottled water is environmentally undesirable compared with tap-water sources and drinking fountains - something the final value does very effectively.
3. Life Cycle Impact Assessment. During this stage, the LCA assesses the impact of resource and energy consumption, as well as waste releases on humans, the environment, and the ecology. For example, ecological disruption can come from resource consumption, airborne emissions and water contamination, to name a few.
For a given product, this stage would examine the total effect of all of these impacts on the ecology. Unlike the previous stage, this is fairly subjective, especially when the researcher attempts to lump all impacts on an entity into a single score. Value judgments inevitably come into play, and the use of an expert review panel is often desirable.2
4. Life Cycle Interpretation. This last stage involves the prioritization and assessment of the results of the preceding steps. The most significant impacts and unit processes are identified, and potential mitigating steps are discussed. In the case of product or process comparisons, this stage would be used to establish the environmentally preferable choices and their rationales. This step also usually involves a significant measure of subjectivity and is sometimes omitted from LCA analyses.
Final CautionsDevelopment of LCA continues at a rapid pace. As it is further standardized and packaged, engineers can expect to encounter LCA results and analyses in many different venues. While it is beyond the scope of this article to teach readers how to conduct an LCA, the above outline should enable you to be an informed and effective user of the results. In general, it is best to keep a few general tips in mind when dealing with an LCA:
Know the scope. Which parts of the life cycle were included? Which were omitted? What environmental impacts were included?
Be aware of the researcher in light of his or her objectives and any value judgments that may have been made.
Understand normalizations. As with the bottled water example, references to tons of CO2, barrels of oil or MJs of electricity may not be literal. Instead, they may be used as indicators. Watch for the word “equivalent” in connection with such results.
Consider your local conditions. LCA analyses are often done nationally or globally, and consider average inputs. If you intend to apply the results in a more localized region, you may need to adjust them to account for local waste-handling practices (mix of recycling, reuse, landfill, incineration, etc.) and energy sourcing (combinations of coal, petroleum, wind, hydro, etc).
Know your alternatives. When LCAs are done comparing products and processes, review the options studied. Be sure that there are no other options that you would like to consider.
Consider other data points.As noted, LCAs cannot provide information on the performance, cost effectiveness or risks associated with products, processes or systems. Gather all necessary information and prioritize with LCA information appropriately. Determine if others have done LCAs that you can use as well.
After so many cautions, you might be tempted to avoid LCA results. That would be a mistake. LCA has the ability to take us beyond simplistic, single-variable considerations of green, to a holistic and more honest view of sustainability. As with any other sophisticated and versatile tool, use it with care - but use it.
References1. “Life Cycle Assessment: Principles and Practice,” USEPA, May 2006.
2. National Renewable Energy Laboratory Website:www.nrel.gov/lci/assessments.html.
3. Life Cycle Assessment: The Environmental Performance Yardstick, Rita Schenck, 2002.
4. “Life Cycle Assessment – What it is and How to Do it,” United Nations Environment Programme.
5. “Bottled Water and Energy” – A Pacific Institute fact sheet.
6. “Life Cycle Inventory of the Production of Plastic Pipe and Fittings For Use in Three Piping Applications,” PPFA, 2008.
LCA Case Study on Food Waste Disposers: One of the most useful applications of Life Cycle Assessment within the
plumbing industry is helping municipalities understand their options for
managing food waste. Several studies from around the world have assessed the
disposal of food waste in landfills, composting and food-waste disposer units
that can convert food scraps into a liquid for processing and then into
renewable power at wastewater treatment plants.
Overlooked, Misunderstood and Surprisingly "Green"
At first glance, it might seem logical to dismiss food-waste disposers as environmentally challenged. After all, they are appliances that consume water and energy with each use. A closer look, however, reveals a surprising and far more complicated situation - and begins with the re-thinking of food scraps as a resource, not a waste product.
Disposal in landfills is often the default choice, which involves truck-based collection and transporting the food scraps to distant sites, using fossil fuels. This is especially inefficient, given that food is about 70% water, making it heavy. As it decomposes in a landfill, food releases significant quantities of methane - a greenhouse gas 21 times more potent than carbon dioxide. Some landfills capture this methane, but their effectiveness varies.
In contrast, food-waste disposers send pulverized food waste (that has been converted) into a slurry through existing underground sewers to a wastewater treatment plant. There, the waste can be converted into three renewable resources - water, fertilizer products (known as biosolids) and biogas - when anaerobic digestion is used for processing the solids. That biogas generates both heat and power for operation of the treatment plant itself. Water use related to a household disposer is typically less than 1% of household consumption, with electricity costing approximately $0.50 per year.
The conclusion? In nearly all circumstances, food-waste disposers can be an environmentally preferable solution. Which helps explain their ubiquitous presence in U.S. homes and growing international acceptance. Sometimes the results of an LCA can truly be enlightening.