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on pulp supply and mix purchased by the facilities cannot be dis- closed due to legal agreements on data con fi dentiality. The particulate matter health effects indicator results were different between facilities, as shown in Fig. 5D. Particulate emis- sions < 2.5 m m for the newer facility are associated with the pro- duction line and other activities, while the older facility had sulfur dioxide and particulate emissions < 2.5 m m related to pulp pro- duction and electricity purchased for the manufacturing. A portion of both facilities' electricity came from coal and biomass, which contributes most to respiratory effects. The pulp purchased by Albany is responsible for more potential respiratory effect than that purchased by Box Elder. Other indicators that have no normalization factors, but are relevant for product systems like paper towels, are analyzed. Those indicators include Cumulative Energy Demand and Water Con- sumption. Cumulative Energy Demand (Fig. 5E) re fl ects a nearly identical contribution analysis pro fi le as the Fossil Fuel Depletion chart (Fig. 5A), in that the largest contributing phases are pulp followed by electricity and facility fuel. For water consumption (Fig. 5F) the dominant contributor varies by facility. The newer Box Elder facility is more water ef fi cient during production; however, electricity purchases by the facility dominate water consumption for Box Elder by 64%. Box Elder purchases electricity with a high contribution of hydropower in the grid, resulting in large evaporative water loss in reservoirs used to generate hydropower, which dominated the facility's life cycle water consumption. This water consumption is three times greater than direct water consumption at the production stage, which contributed 19% of total water consumption, just 3% greater than the contribution of pulp for this facility. For the older Albany fa- cility, the production line requires more water compared to all other life cycle stages (47% of total), followed by pulp (29%) and electricity (24%). Pulp production is the next most contributing component. The pulp mix used at Box Elder is slightly more water intensive than the pulp mix used at Albany.
signi fi cant amounts of water. Box Elder has lesser impacts for fossil fuel depletion, climate change, and land occupation, whereas Albany has a lesser impact on particulate matter formation and water consumption. The differences range from 7% for fossil fuel depletion to 54% for water consumption. These differences are explained in the contribution analysis. A contribution analysis enables a better understanding of the most signi fi cant life cycle stages and drivers for each impact cate- gory, and provides a “ hotspot analysis ” to focus future research and development. Based on early analysis, life cycle groupings that showed distribution of impacts by upstream contributors and downstream stages were identi fi ed. Upstream impacts were largely distributed across the electricity, fuel, and pulp supply chains for Bounty production. Direct impacts of the Bounty production facility were important to distinguish, as well as impacts related to the downstream stages of distribution and end-of-life. Fig. 5A shows the contribution analysis for fossil fuel depletion, the indicator most signi fi cant from the normalized comparison, for the paper towels made at each facility. Pulp purchased to make the paper towels is the largest contributor (49%). Some of the energy for making pulp is derived from non-fossil resources (~5%). The pulp combinations used at Albany contribute slightly more than the pulp materials at Box Elder (0.19 kg oil eq vs. 0.16, respectively). The residual wood from debarking and chipping are used as fuel for the pulp production. However, the wood milling process (making of logs, debarking, and chipping) uses residual fuel oil boilers (Wagner et al., 2009), which drives the fossil fuel depletion indicator in this case. Facility electricity and fuels are the next leading contributors to fossil fuel depletion following pulp production. A larger share of electricity purchased by the older Albany comes from fossil fuel sources because of the local electricity grid. The newer Box Elder has an overall smaller fuel energy requirement, for which it uses natural gas. Although Albany uses biomass from milling wastes (a non-fossil fuel source) for a percentage of its energy needs, the residues from debarking and chipping required fossil fuels for their harvesting and processing. Distribution of the product to wholesale and retailers requires long-distance trucking, which contributes approximately 6% to fossil fuel depletion. Global climate change was modeled to include both emissions of GHGs as well as sequestration of atmospheric CO 2 by trees used for pulp and fuel production. Signi fi cant contributors to emissions include pulp production, facility electricity, facility production lines, and end-of-life consumer disposal (Fig. 5B). Pulp production contributed the greatest share to GHG emissions. Pulp production, however, results in signi fi cant reductions due to carbon seques- tration during tree production. The net global warming potential from pulp is slightly negative ( 0.15 to 0.25 kg CO 2 -eq), as the sequestration slightly outweigh the emissions from the supply chains. The mix of tree species was different at each facility. Tree species production for pulp purchased by Box Elder provided more carbon sequestration, but Albany showed more carbon sequestra- tion overall when the biomass fuels at the facility were included. Facility electricity is the next most contributing life cycle stage, dominated by electricity from coal. Production Line and disposal emissions are relatively small as the third contributor, and Box Elder has reduced its lines' emissions more than Albany (0.16 kg CO 2 -eq vs. 0.22 kg CO 2 -eq). Disposed Bounty is assumed to degrade anaerobically in land fi lls, contributing to some land fi ll methane emissions. Agricultural land occupation is dominated by the Pulp life cycle stage (Fig. 5C). The Pulp combination used at the older Albany has slightly greater land occupation than Pulp used at Box Elder (2.3 m 2 yr vs. 2.2 m 2 yr, respectively). This life cycle indicator is in fl uenced by the differences in pulp suppliers; which include differing tree species, climate, time to yield, and operations. Details
4. Sensitivity analysis
4.1. IPSA vs traditional facility level allocations
Results of the scenario to understand if/which differences are brought about by using the new IPSA approach vs. a more tradi- tional facility-level mass allocation approach are shown in Table 3. Results show that the IPSA method produces line-speci fi c inputand emissions estimates that differ from facility averages. For Albany, the IPSA-based quantities are less than the traditional mass allo- cation approach by 14% for most inputs, and vary from 6 to 61% less for the emissions. This can be interpreted that the Albany produc- tion system for producing the paper towel during the time period of interest was less input-intensive and emitted less than the average line in the facility. On the other hand, the IPSA-based quantities for Box Elder are about the same as the average for the facility (0 e 2% þ ). There is less variation in Box Elder from the facility average because there was a single papermaking production line online during the sampling period, so the variation is only explained by the differences in the paper conversion line.
4.2. Pulp and regional electricity scenarios
Using national average pulp data on energy use and emissions resulted in the largest differences of any scenario. The input data for national average pulp is more energy and criteria pollutant emission-intensive than the pulps used by the facilities, but emits less GHGs. Due to this apparent inconsistency in these results, a consistency check was performed to compare the GHG emissions
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