This section discusses the calculation rules, data collection, and allocation rules for the Ultralight Door LCA study in accordance with ISO 14040 series and the CSA Group guidance document. The same life cycle inventory (LCI) methodology is applied for the Baseline and Ultralight door systems.
Calculation rules
The specific rules to calculate the total net change in production, use, and EOL stage and cradle-to-grave environmental profile of the Ultralight auto door parts are summarized in this Section 5.1.
The total net change in the cradle-to-grave environmental profile of the Ultralight auto doors, \( \Delta\;{E}_{\mathrm{Total}\kern0.5em ,d{,}_{wa}} \) (no P/T adaptation) and \( \Delta\;{E}_{\mathrm{Total}\kern0.5em ,d{,}_a} \) (with P/T adaptation), is calculated by Eqs. 1 and 2 (CSA Group 2014),
$$ \Delta\;{E}_{\mathrm{Total},d{,}_{wa}}=\Delta\;{E}_{P,d}+\Delta\;{E}_{\mathrm{Use},d{,}_{wa}}+\Delta\;{E}_{\mathrm{EOL},d} $$
(1)
$$ \Delta {E}_{\mathrm{Total},d{,}_a}=\Delta {E}_{P,d}+\Delta {E}_{\mathrm{Use},d{,}_a}+\Delta {E}_{\mathrm{EOL},d} $$
(2)
where,
- Δ EP,d:
-
total net change in the production stage environmental profile of the Ultralight auto doors,
-
\( \Delta\;{E}_{\mathrm{Use},d{,}_{wa}} \)
:
-
total net change in the use stage environmental profile of the Ultralight auto doors (no P/T adaptation),
-
\( \Delta\;{E}_{\mathrm{Use},d{,}_a} \)
:
-
total net change in the use stage environmental profile of the Ultralight auto doors (with P/T adaptation), and
- Δ EEOL,d:
-
total net change in the EOL stage environmental profile of the Ultralight auto doors.
The total net change in the production stage environmental profile of the Ultralight auto doors Δ EP, d is calculated by Eq. 3 (CSA Group 2014),
$$ \Delta\;{E}_{P,d}=\sum \limits_{k=1}^n\left({E}_{P,{m}_k}-{E}_{P,{b}_k}\right) $$
(3)
where,
-
E
P,
m
:
-
environmental profile of the production stage of the Ultralight auto doors exhibiting the mass change (MC),
-
E
P,
b
:
-
environmental profile of the production stage of the Baseline auto doors, and
-
n
:
-
total number of auto doors exhibiting the MCs (four), each auto door consists of 14 auto parts (Table 1).
The environmental impact associated with the process scrap operations (collection of the scrap, sorting, recycling process, and waste disposal) is reported as part of the production stage environmental profile (CSA Group 2014). Total amount of process scrap to secondary production is assumed to be generated during the auto door part fabrication processes. It is assumed that no process scrap is generated during the auto door assembly in vehicle process (Section 5.3).
Total net change in the use stage environmental profile of the Ultralight auto doors, \( \Delta\;{E}_{\mathrm{Use},d{,}_{wa}} \) (no P/T adaptation) and \( \Delta\;{E}_{\mathrm{Use},d{,}_a} \) (with P/T adaptation), is calculated according to Eqs. 4 and 5 (CSA Group 2014),
$$ \Delta\;{E}_{\mathrm{Use},d{,}_{wa}}={C}_{WA,d}\times \kern0.5em \left({E}_{FP}+{E}_{FC}\right) $$
(4)
$$ \Delta\;{E}_{\mathrm{Use},d{,}_a}={C}_{A,d}\times \kern0.5em \left({E}_{FP}+{E}_{FC}\right) $$
(5)
where,
-
C
WA,
d
:
-
the total life cycle mass-induced fuel savings (decrease) of the Ultralight auto doors exhibiting the MCs (no P/T adaptation), in liters (L),
-
C
A,
d
:
-
the total life cycle mass-induced fuel savings (decrease) of the Ultralight auto doors exhibiting the MCs (with P/T adaptation), in L,
-
E
FP
:
-
environmental profile of producing 1 L of gasoline, well-to-pump (WTP), and
-
E
FC
:
-
environmental profile of combusting 1 L of gasoline (vehicle operation), pump-to-wheel (PTW).
The full fuel cycle is the combination of the WTP and PTW, which is also commonly referred to as a well-to-wheels (WTW). The WTP cycle includes resource extraction, initial processing, transportation, fuel production, and distribution of the fuel to pump. PTW cycle covers the end use of fuel in vehicle operations. WTW LCI profiles account for all the energy and emissions necessary to produce the fuel used in the car (WTP) and the operation energy and emissions associated with the vehicle technology (tail pipe emissions, other emissions, and energy efficiency of the vehicle). The WTW LCI profile of the gasoline was generated with GREET-1 2016 Software, version 1.3.0.13130, July 2017 (Elgowainy et al. 2016).
The total life cycle mass-induced fuel savings of the Ultralight door design CA, d (with P/T adaptation) is calculated according to Eq. 6 (Koffler and Rohde-Brandenburger 2010; CSA Group 2014),
$$ {\displaystyle \begin{array}{l}{C}_{A,d}=\sum \limits_{k=1}^n\left({m}_{d_k}\hbox{-} \kern0.5em {m}_{b_k}\right)\times {F}_{\mathrm{CP}}\times {\mathrm{LTDD}}_V\\ {}=\left(78.1\hbox{-} 127.6\right)\ \mathrm{kg}\times \kern0.5em 0.38\ \mathrm{L}/\left(100\ \mathrm{km}\times 100\ \mathrm{kg}\right)\times 250,000\ \mathrm{km}\\ {}=-470\ \mathrm{L}\end{array}} $$
(6)
where,
-
m
d
:
-
mass in kg of the Ultralight auto doors exhibiting the MCs, total of 78.1 kg,
-
m
b
:
-
mass in kg of Baseline auto doors, total of 127.6 kg,
-
F
CP
:
-
mass-induced fuel change potential value, with P/T adaptation, 0.38 L/(100 km × 100 kg), based on U.S. EPA combined fuel economy of 55% city Federal Test Procedure 75, and 45% Highway Fuel Economy Test Cycle (Koffler and Zahller 2012; CSA Group 2014),
- LTDDV:
-
Baseline vehicle lifetime driving distance, 250,000 km (CSA Group 2014), and
- − 470 L:
-
Minus sign (−) represents a decrease in fuel consumption (fuel savings).
The total life cycle mass-induced fuel savings of the Ultralight door design CWA, d (no P/T adaptation) is calculated according to Eq. 7 (Koffler and Rohde-Brandenburger 2010; CSA Group 2014),
$$ {\displaystyle \begin{array}{l}{C}_{WA,d}=\sum \limits_{k=1}^n\left({m}_{d_k}\hbox{-} {m}_{b_k}\right)\times {F}_{\mathrm{CO}}\times {\mathrm{LTDD}}_V\\ {}=\left(78.1\hbox{-} 127.6\right)\ \mathrm{kg}\times 0.161\ \mathrm{L}/\left(100\ \mathrm{km}\times 100\ \mathrm{kg}\right)\times 250,000\ \mathrm{km}\\ {}=\hbox{-} 199\ \mathrm{L}\end{array}} $$
(7)
where,
-
F
CO
:
-
mass-induced fuel consumption value, no P/T adaptation, 0.161 L/(100 km × 100 kg), based on U.S. EPA combined fuel economy (Koffler and Zahller 2012; CSA Group 2014).
The total net change in the EOL stage environmental profile of the Ultralight auto doors Δ EEOL, d is calculated according to Eq. 8 (CSA Group 2014),
$$ \Delta\;{E}_{\mathrm{EOL},d}=\sum \limits_{k=1}^n\left({E}_{\mathrm{EOL},{m}_k}-{E}_{\mathrm{EOL},{b}_k}\right) $$
(8)
where,
-
E
EOL,
m
:
-
environmental profile of the EOL stage of the Ultralight auto doors exhibiting the MCs, and
-
E
EOL,
b
:
-
environmental profile of the EOL stage of the Baseline auto doors.
The EOL stage environmental profile covers the environmental impact associated with EOL operations such as transport of the vehicle to a dismantler and shredder, dismantling, shredding, sorting, EOL recycling process, and waste disposal (CSA Group 2014).
Data collection
Adequate LCI data were used to model both auto door systems. LCI data is as representative, complete, consistent, reproducible, and transparent as possible with regard to the goal and scope of the study. The LCA model was created using PRé Consultants LCA software SimaPro version 8.3.0 2017. Primary data on the auto door part names, number of constituent parts per front and rear door assembly, mass per auto part and component in kg, material composition, fabrication process, and fasteners and adhesives were provided by Magna in 2017.
Secondary LCI datasets on material production, energy generation, transportation, auto part fabrication and assembly, fuel production and combustion, and EOL processes were provided by NA auto manufacturers and OEMs, NA and global metals, polymers, composites and other material industry associations, and NA and global LCI databases such as the U.S. National Renewable Energy Laboratory LCI database and ecoinvent 3.3, allocation, recycled content database, and GREET.net 2016 (Elgowainy et al. 2016).
Whenever available, for all upstream, core, and downstream material and processes, NA generic or industry-average LCI datasets were utilized. Ecoinvent 3.3 LCI datasets are adjusted for NA conditions by replacing electricity grid, heat, and transportation technosphere flows with the NA ones. Ecoinvent 3.3 LCI datasets were used for LCI modeling of U.S. electricity grid generation and life cycle processes of selected plastic, rubber, glass, GFRP, and other materials.
The transportation modes, distances, and Standard Classification of Transported Goods codes for all materials per type of activity are based on the most up-to-date U.S. Commodity Flow Survey (U.S. Census Bureau and the U.S. Bureau of Transportation Statistics 2015). Transportation activities are included consistently in the respective life cycle stages. In addition, Michigan, USA is the assumed location of the auto parts fabrication and assembly plants for the Ultralight and Baseline door systems. A default 50-miles (80 km) trucking distance is applied for the transportation of all fabricated parts to assembly sites. Trucking is the primary mode of transport for materials, auto door parts, scrap, and waste flows, followed by rail.
Baseline and Ultralight door systems are respectively identified as “mild steel” and “aluminum” intensive components. This way, “cradle-to-gate” LCI data of both NA aluminum and steel products, more specifically Al CRC and HDG steel, are of importance for the Ultralight Door LCA results. Table 4 presents the input scrap and CO2 emissions for the selected aluminum and steel products used for the manufacturing of Ultralight and Baseline doors in NA. Table 4 shows the critically reviewed NA cradle-to-gate LCI datasets for steel and aluminum products that were endorsed in December 2013 by the worldsteel in cooperation with the U.S. Steel Recycling Institute, based on the 2011 methodology LCI report (World Steel Association 2011) and the U.S. Aluminum Association (The Aluminum Association 2013), respectively.
Table 4 Input scrap and CO2 emissions for the selected NA aluminum and steel products Allocation and cut-off rules
The allocation and cut-off rules considered within the system boundary conform to ISO 14040 series and CSA Group LCA Guidance (ISO 2006a, b; CSA Group 2014).
This LCA applies the ISO 14044 and CSA Group LCA Guidance conformant “closed-loop” allocation procedure for recycling, also called “substitution”, “EOL recycling”, or “system expansion by substitution” approach (ISO 2006b, 2012; CSA Group 2014; Koffler and Finkbeiner 2018). ISO 14044, Clause 4.3.4.3.3 states: “A closed-loop allocation procedure applies to closed-loop product systems. It also applies to open-loop product systems where no changes occur in the inherent properties of the recycled material” (ISO 2006b). The “substitution” approach is deemed applicable for steel and aluminum recycling, based on the characteristics of steel and aluminum products, and recycling, which preserves the full physical properties of these metals without losses of quality no matter how many times they are recycled (The Aluminum Association 2013; World Steel Association 2011 < ISO 2012). The EOL recycling approach, a term typically used by the metals industry, is also recommended by the global metals industry for purposes of environmental modeling, decision-making, and policy discussions involving recycling of metals (Atherton et al. 2007).
Where applicable, the “substitution” allocation approach is applied for all materials. According to this approach, EOL scrap output is balanced out with scrap input into manufacturing to avoid double-counting. The appropriate mass of the remaining net EOL scrap is then modeled as being sent to material recycling at EOL (World Steel Association 2011). If more scrap is generated by the product system than is used in the manufacturing stage (a positive net amount of EOL scrap, Fig. 2, left), the product system receives a “credit” equal to the “value of EOL scrap”. Similarly, if less scrap is generated by the product system than is used in the manufacturing stage (a negative net amount of EOL scrap, Fig. 2, right), the product system receives a “debit” equal to the “value of EOL scrap”.
In compliance with the CSA Group LCA Guidance for auto parts, the EOL recovery rate of old vehicles (also known as old vehicle collection rate) is assumed to be 95%. This LCA study assumes that none of the EOL auto door parts is recovered for reuse or remanufacturing. A recent study conducted by Center for Resource Recovery and Recycling, Worcester Polytechnic Institute, shows the weighted-average material collection rate for EOL vehicles that flow through a dismantling operation and a downstream separation system is 99.7% in the United States (Kelly and Apelian 2016). The yield of shredding and sorting (downstream separation) processes is assumed to be 100% for the Ultralight and Baseline door systems.
The concepts of “primary” and “secondary” material production, and the “value of scrap”, are indispensable to the application of the “substitution” approach (ISO 2012; World Steel Association 2011; The Aluminum Association 2013; CSA Group 2014). Figure 2 illustrates a simplified example of the “substitution” approach for stamped HDG and Al CRC auto door parts. CO2 is used as an illustrative flow in this example. The same approach applies to all inputs and outputs of the LCI. In the framework of this project, primary data was collected by Magna on stamping of both Baseline and Ultralight auto door parts. The fabrication yield (also called “material efficiency” or “material utilization”) of stamped steel and aluminum door parts are 49.9% and 57.5%, respectively. Based on NA automotive industry practices, the recovery rate of fabrication scrap (RRF) for both steel and aluminum parts is assumed to be 100%.
The cradle-to-gate LCI of a stamped HDG auto door part, including the fabrication scrap recycling, is calculated as follows:
$$ {\mathrm{LCI}}_{\mathrm{with}\ \mathrm{fabrication}\ \mathrm{scrap}}=4.116-1.004\times 1.409=2.702\ \mathrm{kg}\ {\mathrm{CO}}_2 $$
(9)
where 4.116 kg is the amount of CO2 emissions per 2.004 kg NA HDG steel (Table 4), 2.004 kg is the input amount of NA HDG steel used to fabricate 1 kg of stamped HDG auto door part, 1.004 kg is the amount of fabrication scrap recovered per kg stamped HDG auto door part (RRF = 100%), and 1.409 kg is the value of CO2 per kg of steel scrap (World Steel Association 2011).
The value of steel scrap is calculated as follows:
$$ {\mathrm{CO}}_{2\ \mathrm{Value}\ \mathrm{of}\ \mathrm{steel}\ \mathrm{scrap}}=0.916\times \left(1.92-0.386\right)=1.409\ \mathrm{kg}\ {\mathrm{CO}}_2 $$
(10)
where 0.916 is the process yield of the EAF route, 1.92 kg is the theoretical amount of CO2 emissions per 1 kg of 100% primary metal production from the BOF route, and 0.386 kg is the amount of CO2 emissions per 1 kg of secondary metal production from 100% scrap in the EAF (Table 4).
The cradle-to-gate LCI of the stamped HDG auto door part, including EOL scrap recycling, is calculated as follows (World Steel Association 2011):
$$ {\mathrm{LCI}}_{\mathrm{with}\ \mathrm{EOL}\ \mathrm{recycling}}=2.702-\left(0.95-0.880\right)\times 1.409=2.604\ \mathrm{kg}\ {\mathrm{CO}}_2 $$
(11)
where 0.95 kg is the EOL recovered scrap rate per kg auto door part (RREOL = 95%) and 0.880 kg is the amount of input scrap in 2.004 kg NA HDG steel (Table 4).
Similarly, the cradle-to-gate LCI of a stamped Al CRC auto door part, including the fabrication scrap recycling, is calculated as follows:
$$ {\mathrm{LCI}}_{\mathrm{with}\ \mathrm{fabrication}\ \mathrm{scrap}}=8.343-0.741\times 6.930=3.208\ \mathrm{kg}\ {\mathrm{CO}}_2 $$
(12)
where 8.343 kg is the amount of CO2 emissions per 1.741 kg NA CRC aluminum (Table 4), 1.741 kg is the input amount of NA CRC aluminum used to fabricate 1 kg of stamped Al CRC auto door part, 0.741 kg is the amount of fabrication scrap recovered per kg of stamped Al CRC auto door part (RRF = 100%), and 6.930 kg is the CO2 value per kg of aluminum fabrication scrap (Eq. 13).
$$ {\mathrm{CO}}_{2\ \mathrm{Value}\ \mathrm{of}\ \mathrm{Al}\ \mathrm{fabrication}\ \mathrm{scrap}}=0.957\times \left(7.875-0.634\right)=6.930\ \mathrm{kg}\ {\mathrm{CO}}_2 $$
(13)
where 95.7% is the yield for the recycling of fabrication scrap (The Aluminum Association 2013), 7.875 kg is the amount of CO2 emissions per 1 kg of primary aluminum ingot, and 0.634 kg is the amount of CO2 emissions per 1 kg of aluminum recycling ingot from 100% scrap (Table 4).
The cradle-to-gate LCI of the stamped Al CRC auto door part, including EOL scrap recycling, is calculated as follows:
$$ {\mathrm{LCI}}_{\mathrm{with}\ \mathrm{EOL}\ \mathrm{recycling}}=3.208-\left(0.95-1.130\right)\times 6.471=4.373\ \mathrm{kg}\ {\mathrm{CO}}_2 $$
(14)
where 0.95 kg is the amount of EOL recovered scrap per kg auto door part (RREOL = 95%), 1.130 kg is the amount of input scrap in 1.741 kg NA Al CRC (Table 4), and 6.471 kg is the CO2 value per kg of Al EOL scrap (Eq. 15).
$$ {\mathrm{CO}}_{2\ \mathrm{Value}\ \mathrm{of}\ \mathrm{Al}\ \mathrm{EOL}\ \mathrm{scrap}}=0.96\times \left(7.875-1.134\right)=6.471\ \mathrm{kg}\ {\mathrm{CO}}_2 $$
(15)
where 96.0% is the yield for the recycling of Al EOL scrap (The Aluminum Association 2013) and 1.134 kg is the amount of CO2 emissions per 1 kg of secondary aluminum ingot (with primary metal and alloy added) (Table 4). The difference between the two LCI data formats (value of Al fabrication and EOL scrap) is in the involvement of primary aluminum metal and alloying elements. The aluminum recycling ingot (100% scrap) LCI dataset does not involve the addition of primary metal and alloying elements, while the secondary aluminum production LCI dataset does (The Aluminum Association 2013). Based on the “substitution” allocation procedure, the cradle-to-grave LCA results of the Ultralight design relative to the Baseline are not influenced by the amount of input scrap for both NA industry average cradle-to-gate LCI profiles of aluminum and steel products (Table 4). Instead, the NA EOL-recovered scrap rate per kg aluminum and steel door part (RREOL = 95%) is the defining allocation parameter (Fig. 2).