Life Cycle Impact Assessment at Seventh Generation
Special Guest Blogger: Martin Wolf, Director Product Sustainability & Authenticity at Seventh Generation
There’s More to Life than Meets the Eye
And more to life cycle, too.
Seventh Generation designs, manufactures, and sells household and personal care products that emphasize four aspects of sustainability: human health, environmental health, performance, and cost. When selecting materials for a product or package, Seventh Generation typically uses environmental life cycle analysis (LCA) as a significant input (but not the only input) into its decisions. LCA is a powerful tool for estimating the environmental inputs (materials and energy) and environmental outputs (emissions to air and water and solid waste) associated with the production, use, and disposal of a product. In turn, these inputs and outputs can be used to estimate environmental impacts such as resource depletion, global warming, aquatic toxicity, and acidification of lakes and streams. This is called environmental life cycle impact assessment (LCIA). LCA tracks hundreds of inputs and hundreds of outputs over the course of a product’s life cycle. LCIA reduces this to roughly a dozen factors, making interpretation of results much more manageable!
Seventh Generation aspires to make all its products from biologically renewed materials (plants), or technically renewable (recycled) materials. One product line that leaves much room for improvement toward this aspiration is our baby wipes. A baby wipe consists of three major components, a substrate (typically a non-woven fabric), a cleansing solution, and a package. In consideration of improving the environmental profile of our baby wipes and moving toward our company aspiration of using more biologically renewed materials, we conducted LCIAs of three different substrates. The three substrates were:
- A blend of 65% viscose (rayon) and 35% polyethylene terephthalate (PET)
- A blend of 70% tissue (wood pulp) and 30% polyolefin (PO)
- 100% viscose
Tissue and viscose (rayon) are derived from trees, and are thus renewed materials. Using 100% viscose for the substrate would move us toward our aspiration of using 100% renewed materials. Unfortunately, making viscose is a chemically intensive process, so LCIA was needed to determine if the environmental burdens of making viscose would offset the environmental advantages of its renewability.
Unhappily, recycled PET and PO were not available for our substrate. The materials used in our baby wipes would have to be derived from petroleum or natural gas.
In addition to evaluating the substrates, we evaluated three different packaging systems:
- A traditional polypropylene (PP) tub
- A multilayer plastic film
- A multilayer plastic film with a PP dispenser
The advantage of a PP tub is that the material is recyclable, although facilities for recycling PP are limited. Multilayer plastic films are not recyclable. We turned to LCIA to determine if the benefit of using a greater mass of recyclable material (PP) outweighed the benefit of using a lower mass, but non-recyclable multilayer, flexible film pouch.
Key to any LCA or LCIA is defining a functional unit that accounts for differences among alternatives such as package size and product performance. For this project we settled on a functional unit of a fixed number of wipes. More information on defining functional units can be found here.
Also key is defining system boundaries that minimize the need for allocation of burdens between different alternatives. To accomplish this, the system boundaries were expanded to include displacement of virgin PP as more PP tubs were recycled. Thus, as more PP tubs were recycled, less virgin PP was required to make new products. More information about setting system boundaries can be found here.
Having defined the functional unit and system boundaries, we then set off to collect data and analyze them using SimaPro Life Cycle software. The results were not quite what we expected.
The first surprise result was finding that the mass of the PP tub had a much greater effect on the life cycle impacts of our baby wipes than the choice of substrate! Despite all our hand-wringing over the impacts of chemically-intensive viscose versus wood fiber, the real issue was the PP tub! As a result, we eliminated the PP tub from our product offering. For those consumers who wanted a “positive” closure we added a multilayer pouch with a PP dispensing closure.
The second major surprise came when we performed a sensitivity analysis on the data. The diagram to the left compares a Viscose/PET substrate to a wood pulp (tissue)/PO substrate. The “Baseline” chart uses site-specific data for the viscose/PET substrate, and EcoInvent data for the pulp/PO substrate. When the site-specific data for the viscose/PET are replaced with ecoInvent data, the viscose/PET substrate displays significantly higher environmental impacts. This latter finding is more in keeping with our expectations that the chemical intensity of viscose production should result in greater environmental impacts than pulp production. Our conclusion is that being consistent in data collection is very important, and comparing a product system with one source of data to a product system with a different source of data could lead to suspect results.
Seventh Generation continues to evaluate higher renewable content substrates for its baby wipes, and to develop packaging that is made from recycled materials and is recyclable. LCA and LCIA will be used to assess each proposed improvement. After all, everyone loves a surprise, and LCA is a great way to find them!