L5. Environmental Assessment through LCA

Introduction

Thus far we have learned that human consumption of non-renewable resources is significant and growing. We also learned that we are likely not going to run-out of these resources any time soon. However, we also determined that the consumption of any natural resources will have a negative impact on the environment.

In this lesson we will discuss a method called Life Cycle Assessment (LCA) that can be used to quantify this environmental impact. Understanding LCA will allow you to make informed consumer decisions and evaluate how “green” or eco-friendly a product truly is. Or maybe we want to compare the environmental impact of steel vs wood construction, or a copper mine in northern Minnesota to a copper mine in Arizona.

This lesson starts with a video explaining the LCA process. There are some quiz questions from the video.

A Summary of the LCA Video

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A Life Cycle Assessment uses a systematic approach that quantifies all impacts from the beginning of the product all the way to the end of the products useful life. This is referred to as a “Cradle to Grave” assessment. “Cradle” is that first step of extracting the raw material from the environment and “Grave” is the final disposal of the product – often in a landfill. In between, there are stages in materials processing, manufacturing, distribution, and use of the product, system, or service. For some purposes, as we will discuss, people might do a partial LCA. This might be a “Cradle to Gate” analysis which might eliminate the distribution, use, and disposal of the product. Another LCA analysis might just look at one stage of the process or one environmental impact. These are referred to as partial LCA’s and are typically easier and quicker to evaluate.

The method for doing LCA has been standardized through the International Standards Organization (ISO) and is standard number ISO 14040 with the official title “Compilation and evaluation of the inputs, outputs, and the potential environmental impacts of a product system throughout its life cycle”.

To be clear, what follows is a very brief summary and overview of the LCA process. It is meant to provide enough background to help you understand the references to LCA throughout the course.

Why Do a Life Cycle Assessment?

We do an LCA because we are interested in protecting resources, comparing products or processes, or reducing the impact of a product by focusing on the individual aspects of a product, process, or system. Conducting the actual LCA is a complex process and requires significant expertise, a lot of data, and expensive tools. Yet, there are many users of the results from an LCA. Individual companies conduct an LCA done on a product or process to help with marketing (e.g 30% less emissions than other brands) or to reduce the product's environmental impact. Others who might be interested in the results of an LCA are policy makers as they try to evaluate policy options, consumers trying to make purchasing decisions or academics trying to understand the impacts of certain products or processes.

LCA Phases

Here is a common way to look at the phases of an LCA.

Goal: Why are we doing an LCA? What do we want to learn? Are we comparing products? Are we trying to market a product (green label)? Are we trying to reduce the impact of a new product design? Are we concerned only about one impact or all impacts? Are we policy makers needing to make some decisions?
In this goal and scoping process we set the boundaries for the study. For instance, are we looking at one phase of the product or all phases of the product? Are we concerned about one impact or several environmental impacts?
We also need to determine what is called a “Functional Unit.” To understand “Functional Unit” it is helpful to look at an example. Let’s say I want to compare the impacts of different ways of drying my hands. I want to compare things like paper towels, hot air dryers, or cloth towels to find out which is “better” for the environment. The functional unit could be defined as the “drying of two hands". However, in looking at all the processes involved and finding relevant data it would be better/easier to look at the drying of 100,000 pairs of hands. The larger scale fits with the manufacturing processes and numbers that companies are used to dealing with. If I were comparing two different chairs, the functional unit might be 10,000 chairs used in an office setting for 20 years.

Inventory Analysis: This next step involves documenting all of the products and processes used to get to the functional unit and their environmental impacts. For instance, the process of making a paper towel involves growing wood, harvesting wood, shipping the wood, processing the wood into paper towel, use of the paper towel, and disposal. It would also include things like the paper towel roll and the plastic packaging and shipping of the paper towel to the store and then to the consumer’s house. All of these processes require inputs of energy, water, and other materials. Each step of the process must be quantified in detail. This would include, not only how much water was used in the process, but where the water came from. There are many databases that have been assembled and can be used in this step (Figure 1).

Figure 1. One way of thinking about the categories of impacts in and LCA. (Source Links to an external site.)

Impact Assessment: The quantification of the environmental impacts involves a couple of steps.

Classification or Impact Categories: Categories include climate change, human toxicity, water acidification, land clearing, eutrophication, acidification, ozone, groundwater, smog, etc. Almost any environmental impact could be included as a category. There are some standard categories, but the most popular is climate change.
Characterization: Converting of the impacts of the different emissions into some common unit. Example: Carbon Dioxide, Methane and Nitrous Oxide are all greenhouse gas emissions we are concerned about, but each of these molecules contribute differently to climate change. Characterization of the impacts will standardize this. With Carbon Emissions we use Carbon Dioxide Equivalents or CO₂e. One kilogram of carbon dioxide has a value of 1, whereas 1 kg of methane has a value of 23 because of the larger impact it has on the climate.
Normalization: So now if you are comparing two products and product A has a CO₂e of 20 lbs and product B a CO₂eof 15 lbs what does that really mean? Product B would have less emission, but is 15 or 20 a big impact or not so big? Normalization is a way of standardizing these values based on a typical human's impacts on an annual basis. It is a way of comparing impacts across products and relative to the big picture. For instance, if a human CO₂e is 9,950 lb/year and annual drying of hands is 20 lb, this suggests that hand drying is a very small fraction of the total and likely not worth spending much time worrying about.
Weighting: This reflects the importance of each impact category. Assigning these values requires some analysis on which environmental impact is most important – e.g. water pollution, water quantity, deforestation, climate change, human toxicity, etc. Adding all the weighting scores for each environmental impact will result in one number that can be used to compare products.

Carbon Footprint.

You heard the term "Carbon Footprint" in the video and probably other places. Carbon footprint refers to the total amount of greenhouse gas emissions associated with an activity or product. To determine a carbon footprint, an LCA must be conducted that has a focus on greenhouse gasses and is typically evaluated from cradle to grave. Below you will see reference to the carbon footprint of a can of coke. An LCA looked at the total amount of GHG emissions for every process involved in making the coke and the can that holds the coke. Everything from the mining of the aluminum for the can and the growing of the sugar for the coke to the consumers refrigeration of that can of coke.

Carbon footprints have been done for travel so we can compare biking, car travel, bus travel and plane travel. Carbon footprints have also been done on lifestyles such as eating a vegetarian diet vs a meat diet.

Carbon footprints are primarily related to the energy input in products or activities because that is where the carbon comes from. For instance, in the growing of sugar of the can of coke there is natural gas involved in making the fertilizer that is used to fertilize the sugar beets. There is petroleum used to till the field, plant the crop, and harvest and process the crop. There is electricity used in several phases of producing the coke and the coke can. The carbon emissions in this production phase is from the coal or natural gas that is used to produce the electricity.

The results of a carbon footprint are typically reported as CO₂e per "unit". For instance per 30 grams of CO₂e per lb of chicken meat or 10 grams of CO₂e per mile traveled. CO₂e is Carbon Dioxide Equivalents and is a way to combine all types of greenhouse gasses into one number that quantifies the impact on the climate.

Problems with LCA

Here are just a few of the problems with an LCA.

Too many classifications or impact categories.
Not enough data to assess all impacts.
'Functional unit' is hard to define. For example, is there some other value for hand drying – "speed of drying", for example, a preference that cannot be easily quantified.
Importance of categories (weighting). Weighting may be regional – climate change or water--depends on where you are at.

Here is an example of one problem with a partial LCA done by Coca-Cola and evaluating only CO₂e. Figure 2 shows the comparison of coke to a roast turkey, grapes or a airplane flight. It is clear that a can of coke has less CO₂e emissions than these items and there is nothing wrong with this type of assessment. However, some would argue that the comparison should have been made on the nutritional value of the food. How would these results look if we compared CO₂e on a "per pound of protein" basis? What about if it looked at some other environmental impact such as water consumption? What is reported is accurate, but could be misleading.

The figure below also compares a can of coke to an airline trip suggesting that drinking 588 cans of Coke has the same emissions as one trip to New York. Accurate and true, but is there some value in an airline trip that is not in drinking 588 cans of Coke? How do we "value" or weight these factors? The key to this comparison is not to complain about the carbon footprint of drinking a can of coke if you are flying all over the world on multiple vacations!

Figure 2. Carbon Footprint of Coke (Source Links to an external site.)

More LCA Examples

Milk

This milk study is a "partial" LCA and looked at CO₂e (Climate Change) impacts. They broke the LCA into 7 phases. (Figure 3). The “Milk Production” phase (emissions generated on the farm) is where most (about half) of the emissions were generated. Another large portion of the emissions comes from the growing of the feed for the cows. About 5% of the emissions comes at the end of the supply chain with the refrigeration of the milk by consumers and also from milk wasted by consumers. Wasted, you know, that milk at the bottom of the bowl of cold cereal that you dump down the drain : )

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Figure 3. Milk Carbon Footprint (From Thoma et al, 2013)

BioJet Fuel - Compare to Fossil Fuel

Here is one that is very applicable to our future discussions that will compare renewable and non renewable resources.

How will we use LCA in this class?

One of the concerns about the use of non-renewable resources is their environmental impact. As you will see, biorenewable resources are not a perfect solution either. Throughout the class we will be using LCAs to compare products made from renewable resources to those made from non-renewable sources. The big impact we will look at is greenhouse gas emissions, but we will also be thinking of water, land use, human health, and other impacts.

There are no easy answers even when using a complete LCA. Even with good information there are many variables to consider and value judgements that are hard to make. Despite these shortcomings, LCA provides a standard, quantitative way to evaluate the environmental impacts of products, allowing for meaningful comparisons. As consumers, we have choices about the types of products that we buy. It is important to make informed decisions, and not take a label’s “eco-friendly” claims at face value. Later in the semester we will dive deeper into how to be an informed consumer. For now, you have the basic knowledge needed to understand LCA references in this course.

Take home points:

Life Cycle Assessment is a standard method for evaluating the environmental impacts of a material, product, system or service.
Even with the best data, LCAs do not provide an easy answer. Classifying and weighting impacts can be tricky, and ultimately the results should be considered carefully to avoid misinterpretation.
We can use LCA to compare the “eco-friendliness” of two or more products. In this class, we will make references to LCA when comparing bio-based products to products made from non-renewable resources.