Choice 2: Scope
The second major consideration in assessing the sustainability of a product is the scope of analysis. For products, the scope is usually described by how much of its lifecycle is included in its impact assessment.
As with impact categories, there is not a single standard set of lifecycle stages, although there are certainly some that are most commonly used. In general, the full lifecycle of a product can be measured in five to seven stages:
Raw Material Extraction
This includes the energy and other resources used to acquire the basic materials used in the product, whether through mining ore, harvesting timber, extracting oil, etc. This stage can include harvesting materials from recycled sources if they are in the form of raw materials.
“My cup is plastic, so it starts with oil extraction,” said Priscilla.
“A lot of my toy does, too,” replied Tom. “But it also has some metal components, so that would include mining the ore.”
Raw materials are converted into forms used for manufacturing during this stage. It covers the processes required to make steel, copper, plastic feedstock, paper, gasoline, and the like.
“OK, so the oil for our plastics is then refined into the various hydrocarbon fractions to make the different plastic resins,” said Priscilla, idly sketching a distillation column.
“And the ores are refined into metals by melting or burning off impurities,” added Tom, wondering why Priscilla was sketching a missile silo.
This stage covers single, or at least simple, part manufacturing. Common processes include injection molding, metal stamping and machining, weaving, and milling.
“My cup is made from PET plastic—polyethylene terephthalate. This is where the PET is injection-molded into a cup shape.”
“The plastic that makes up most of my toy is molded, too, but from ABS plastic. The siren sound comes from a little speaker component that I purchase; I’m not sure what’s in it, but I’m sure there’s a lot of copper, so I’ll just model it as a copper part. The spring is made of a steel alloy—probably regular carbon steel.”
In many cases, products need to be assembled using processes that go beyond the creation of individual components. Because this is usually the first stage that brings together a disparate assortment of materials (e.g., a plastic handle and a metal container), environmental impact assessments significantly increase in complexity.
“I don’t really have any assembly steps,” said Priscilla, “since my cup is molded in a single pass from a single material.”
“I do have some assembly steps, but most of the parts just snap together. And of course, the battery is wired up to the siren and the lights.”
Any energy used, emissions generated, other resources affected directly by the product during its actual use are counted during this phase. This includes waste that occurs in the context of a product’s use, such as discarded packaging.
“My product is powered by a person picking it up and drinking from it!” laughed Priscilla. “No product impacts there.”
“Mine isn’t,” Tom sighed. “I guess I’ll take a hit for it using energy from the battery. But aren’t most interactive toys like this one battery-powered?”
End of Life
Once a product is no longer used, it has reached its end of life. This usually means that the product is no longer usable, although there are many examples of end of life coming before end of usability (e.g., paper cups). This stage is usually broken down into three resulting streams: the fraction of a product being sent to landfill, to incineration, and to reuse or recycling.
Priscilla knew that recycling was a big issue for her PET plastic cup. “I guess the recycling rate depends on where the product’s being used,” she said. “I’ll bet it’s higher in Europe than in the US.”
“I’m not so sure about that,” Tom said. “We recycle a lot of our steels and aluminums in the US, if not as much of our plastics. We also landfill more of the rest of the materials, rather than incinerate them, which they favor a bit more in Europe.”
Transportation is not typically given as a lifecycle stage, since transportation legs actually occur between each of the lifecycle stages, but it’s an important consideration to account for in the product’s lifecycle impacts. Transportation can be included among the stages according to where it takes place (e.g., the shipping of raw materials to processing centers could be considered a piece of the processing stage). In some cases, transportation may appear as a separate lifecycle component, especially between Assembly and Product Use for consumer products, since there are typically several stops along the way (e.g., wholesaler, retailer, delivery). No matter how it’s handled, it is important to make sure that transportation doesn’t fall through the cracks.
“Most of my components are made in Asia,” Tom jumped in, “but a couple of them aren’t. The speaker comes from Japan, and the acrylic light fixtures come from a little shop in Europe. After the product is assembled in Asia, it’s sent by ship to my main market in the US.”
“Simple for me,” said Priscilla. “The cups are packaged and sent from our factory in Asia and are also sent to the US. I wish we could make them locally,” she added, “I’m sure that would be better for the environment.”
Doing environmental assessments can sometimes be like chasing fractals. Product lifecycles intersect a great many processes, some more directly linked to the product than others. Since an assessment can’t always cover everything, system boundaries clarify what it will include. It’s often helpful to draw a process diagram, and then trace a boundary around what will be measured.
For example, the following figure shows a possible system boundary chart for an assessment of a polystyrene cup, with a functional unit of one cup.
Some of the standard product lifecycle system boundary scopes include
“Cradle to grave” – Usually denotes all phases from raw materials through disposal.
“Cradle to cradle” – Like cradle to grave except that it tracks where the product’s elements go after end of use, with special attention to recycling and reuse.
“Cradle to gate” – Includes part of the product lifecycle, typically either:
all upstream phases, not including the assessing company’s own processes; this is used to assess the “environmental burden” of raw materials coming through the door; or
all phases through the assessing company’s manufacturing and assembly (the factory gate), bound for the customer, since this is the end of most manufacturer’s ability to directly influence impact.
“Gate to gate” – A narrowly-scoped lifecycle assessment, focused on only one particular stage or set of stages of the product lifecycle.
Priscilla grabbed a dry-erase marker and sketched out her cup’s process diagram:
“What about packaging?” asked Tom. “You mentioned that the cups are packed into bags of 100 cups, your functional unit.”
“Oh yeah,” said Priscilla. She added the packaging step to the diagram. “I think the bag is pretty minimal compared to the cups, though,” she said. “So until I get a chance to talk to our packaging group about materials and sizes of the packing materials, I’ll exclude that from my system boundary.” Finally, she grabbed a thick orange marker and drew a box for her system boundary.
Her final sketch was as follows:
“Mine’s more complex,” said Tom. He stepped to the whiteboard and began to fill his own process steps into Priscilla’s boxes, and add a few of his own:
“I’ll have to make some more assumptions,” Tom said, stepping back from the diagram. “I include a rechargeable battery with my toy, and I’ll assume the parent recharges the battery ten times before the kid gets bored with the toy, or outgrows it. But since I want to compare this toy to other interactive ones, I’m going to assume the comparisons are also powered by batteries, so I won’t include that in my system boundary.”
With their lifecycle scopes determined—both were versions of a cradle-to-grave assessment, they realized—and their boundaries drawn, Tom and Priscilla were ready to move to the third and final choice.
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