In the previous post on quantifying the functional unit, I described the studies, assumptions, and calculations used to develop the reference amount used to compare two product alternatives. Since LCA is based on the function of the product, and since both products, the facial tissue and the handkerchief are used differently, great care needed to be taken in developing analogous amounts. 785 paper facial tissues or 30 cloth handkerchiefs washed 14.97 times were calculated to be the functional units, covering use by an average American’s yearly during respiratory illnesses and well times.
However, life cycle assessment covers all aspects of a product’s manufacture, transport, use, and disposal. We cannot only quantify the amount of product needed – we also need to determine the amount of packaging used, the amount of soap and water used during washing, and the energy needed for washing and drying. These are the reference flows. According to ISO standard 14044, reference flows are a “measure of the outputs from processes in a given product system required to fulfill the function expressed by the functional unit.” For either the facial tissue or handkerchief scenarios, these reference flows will need to be quantified, as specified by the system boundaries:
Paper Facial Tissue
- paper facial tissue
- packaging (cardboard box and LDPE packaging film)
- transport to retail
- disposal of facial tissue and packaging
Cloth Handkerchief
- cotton handkerchief
- handkerchief packaging (cardboard box, kraft paper, packaging film)
- transportation to retail
- machine washing and drying (water, detergent, detergent packaging, electricity & natural gas for heating/drying, sewage treatment of water, disposal of detergent packaging)
- disposal of handkerchief packaging
To calculate the quantity of each reference flow, we need to determine the mass of the products used. For this LCA, disposable facial tissue use is based on a 200 count, 2-ply cardboard printed box of white facial tissues with a polyethylene (PE) plastic insert. The facial tissues are manufactured in Ontario, Canada. Reusable handkerchief use is based on a 6 pack of 100% cotton handkerchiefs in a printed cardboard box with a polyethylene sleeve, packed with kraft paper. The handkerchiefs are manufactured in China. Details of the mass and volume of the products can be found in Table 1 in the full LCA.
To facilitate calculating the reference flows, the mass of a single facial tissue or handkerchief and the proportional amount of packaging are determined:
- Single Facial Tissue: 1.29 g facial tissue, 0.295 g cardboard box, 0.010 g PE insert
- Single Handkerchief: 15.0 g handkerchief, 7 g cardboard box, 2.3 g PE sleeve, 1 g paper insert
To calculate the reference flow, the quantities for a single item need to be multiplied by the number used as dictated by the functional unit.
For example, for the facial tissue:
- 1.29 g facial tissue x 785 = 1013 g
- 0.295 g cardboard box x 785 = 232 g
- 0.010 g PE insert x 785 = 7.85 g
Calculating the reference flows for the facial tissue or handkerchief and packaging is quite simple. In the next post, we will explore some of the assumptions that need to be made when calculating reference flows for transportation, use, and disposal.
[…] Last post, we introduced the concept of reference flows, which are a measure of the outputs from processes required to fulfill the function expressed by the functional unit of the LCA. We also illustrated how the reference flows are calculated for facial tissues and the facial tissue packaging. Those reference flows were very simple to calculate: they are just the weight of one facial tissue (or the proportion of the packaging for one facial tissue) times the total number of facial tissues used. But to calculate many of the reference flows needed to fully describe the product system as defined by the system boundaries, information from other studies and carefully considered assumptions need to be applied. We at, Ecosystem Analytics, believe that how reference flows are calculated should be fully transparent – all reference sources behind the calculations need to be cited and the assumptions made documented. In the full LCA on facial tissue versus handkerchief use, all reference flows are listed in the Appendix in Tables A1 and A2, and the references and assumptions behind each is listed in the tables or in the footnotes at the end of the tables. We will illustrate an example of how research and informed assumptions helped us calculate reference flows for the end-of-life for facial tissues. […]