Life Cycle Impact Assessment - Exercise

Exercise 4.1 Energy and CO2 Balance of a Gold Ring

Assume that your friend living in California has just ordered a gold wedding ring weighing 6 g. Since it is the week before the wedding(!), the ring must be flown 10,000 km by plane from the Netherlands (where it was made) to California. The manufacturing of the ring requires an electricity consumption of 2 kWh per kilogram of gold and it will eventually be buried (equivalent to being landfilled for this

example). Assuming an FU of one ring over the course of one marriage, calculate the reference flows, nonrenewable energy use, and CO2 emissions over the whole life cycle. Fill in all missing values in Table 4.14.

Table 4.14

Life Cycle Stage	Process	Unit	Energy (MJ/unit)	CO2 (kg/unit)	Reference Flow (unit/FU)	Energy (MJ/FU)	CO2 (kg/FU)
Raw materials extraction	Gold	kg	269000	16500	0.006	1614	99
Fabrication	Electricity	kWh	10.71	0.66	0.012	0.12852	0.00792
Transport	By airplane	ton-km	16.23	1.06	0.06	0.9738	0.0636
Elimination	Landfill	kg	0.2	0.01	0.006	0.0012	0.00006
Total						1615.10352	99.07158

Exercise 4.3 - Hand-Dryer: Energy and CO2 Balance

Consider the hand-drying scenarios discussed in Chapter 3. Use the reference flows and flowchart from Exercise 3.2 and the emission factors from Table 4.15. Assume that the manufacturing energy for both devices accounts for less than 1% of total life cycle energy consumption and emissions.

1. Using Table 4.15, estimate the nonrenewable primary energy used and the CO2 emissions due to each hand-dryer scenario (fill in Table 4.16).
2. For each process and for the sum of all processes, calculate the ratio of CO2 emissions to nonrenewable primary energy. Check if the value obtained for each ratio are consistent with typical values shown in Figure 4.2.

Hot-Air Dryer

Life Cycle Stage	Process (unit)	Quantity per FU (unit per FU)	Energy per Unit (MJ/unit)	Energy per FU (MJ/FU)	Emissions per Unit (kgCO2/unit)	Emissions per FU (kgCO2/FU)	Check (gCO2/MJ)
Materials
Iron	kg	8	64.3	514.4	3.9	31.2	60.65318818
Steel	kg	4	24.6	98.4	1.51	6.04	61.38211382
Fabrication
Cast Iron	-	-
Transport	ton-km	1.2	3.7	4.44	0.215	0.258	58.10810811
Use	kWh	5475	12.4	67890	0.703	3848.925	56.69354839
Elimination
Steel	kg	4	0.204	0.816	0.007	0.028	34.31372549
Avoided energy
Total				68508.056		3886.451

Paper Towel

Life Cycle Stage	Process (unit)	Quantity per FU (unit per FU)	Energy per Unit (MJ/unit)	Energy per FU (MJ/FU)	Emissions per Unit (kgCO2/unit)	Emissions per FU (kgCO2/FU)	Check (gCO2/MJ)
Materials
PP (plastic)	kg	6	97.5	585	3.11	18.66	31.8974359
Fabrication	-
Transport	ton-km	0.6	3.7	2.22	0.215	0.129	58.10810811
Use
Paper	kg	1960.05	17.2	33712.86	0.86	1685.643	50
Elimination
Paper landfilled	kg	1960.05	0.447	876.14235	0.015	29.40075	33.55704698
PP landfilled	kg	6	0.33	1.98	0.03	0.18	90.90909091
Avoided energy	-
Total				35176.22235		1733.83275

Perbandingan dengan figure 4.2 untuk emisi per energi

Untuk penggunaan hot air dryer

•  penggunaan transportasi untuk hot air dryer  58.108 gCO₂/MJ yang termasuk dalam rentang rasio yang pada figure 4.2 yakni 55-70 gCO₂/MJ.

Untuk penggunaan paper towel:

• penggunaan plastik untuk paper towel sebesar 31,897 gCO₂/MJ lebih besar dari penelitian sebelumnya yakni 30 gCO₂/MJ. Hal ini bisa saja terjadi karena penggunaan material plastic pada figure 4.2 lebih sedikit. Dapat disimpulkan bahwa emisi yang dihasilkan lebih buruk dari standar yang ditentukan oleh penelitian sebelumnya (figure 4.2)
• penggunaan transportasi untuk paper towel sebesar 58,108 gCO₂/MJ yang masuk dalam rentang yang sudah distandarkan.
• untuk proses pembuangan plastic emisi yang dihasilkan 90,909 gCO₂/MJ lebih besar dari standar pada penelitian (figure 4.2) yakni 60 gCO₂/MJ. Dapat disimpulkan bahwa emisi yang ditimbukan dari plastic yang di landfill pada produk hot air dryer lebih buruk.

3. Now assume that the wastepaper towels, when incinerated, produce 18 MJ of energy per kilogram burned, 20% of which is recovered as usable electricity. Calculate how much nonrenewable primary energy you avoid per kilogram of paper burned, and use this to calculate the avoided energy per FU in the table.

4. Which scenario is better for energy and CO2? Which stages of the life cycle and which components are most important? What is the importance of the paper towel dispenser or of the electric dryer compared with the other life cycle stages?

Life Cycle Stage	Process (unit)	Quantity per FU (unit per FU)	Energy per Unit (MJ/unit)	Energy per FU (MJ/FU)	Emissions per Unit (kgCO2/unit)	Emissions per FU (kgCO2/FU)	Check (gCO2/MJ)
Materials
PP (plastic)	kg	6	97.5	585	3.11	18.66	31.8974359
Fabrication	-
Transport	ton-km	0.6	3.7	2.22	0.215	0.129	58.1081081
Use
Paper	kg	1960.05	17.2	33712.86	0.86	1685.643	50
Elimination
Incinerated Paper	kg	1960.05	0.292	572.3346	0.018	35.2809	61.6438356
PP landfilled	kg	6	0.33	1.98	0.03	0.18	90.9090909
Avoided energy
Incinerated Paper	kg	1960.05	-3.6	-7056.18
Total				27818.2146		1739.8929

Skenario yang lebih baik adalah scenario ketiga, hal ini dikarenakan energi dan emisi yang dihasilkan lebih kecil. Life cycle stage yang dipilih adalah “use”, karena dari ketiga scenario yang telah dibuat emisi yang dihasilkan pada penggunaan produk lebih besar.

Exercise 4.4 - Hand-Dryer: Input–Output Approach

Consider the hand-drying scenarios again, but this time using the LCA I/O approach

instead of the process-based approach. Assume that the consumer prices for handdrying

are:

Paper towels: $0.01/paper towel; $25/plastic dispenser

Electric hand-dryer: $0.01/kWh; $350/dryer

Use the data in Table 4.17 to estimate energy use and CO2 emissions (Table 4.18)

for each scenario. Note that the transportation to final user is not considered here,

but transportation from raw material is included in sector expenses and impacts of

each sector.

Life Cycle Stage	Process (unit)	Cost per FU (US$/FU)	Energy per $ (MJ/$)	Energy per FU (MJ/FU)	Emissions per $ (kgCO2/$)	Emissions per FU (kgCO2/FU)	Check (gCO2/MJ)
Materials	kg	350	44	15400	3	1050	68.1818182
Fabrication	unit
Use	kWh	54.75	93	5091.75	9.9	542.025	106.451613
Elimination	kg
Total				20491.75		1592.025

Life Cycle Stage	Process (unit)	Cost per FU (US$/FU)	Energy per $ (MJ/$)	Energy per FU (MJ/FU)	Emissions per $ (kgCO2/$)	Emissions per FU (kgCO2/FU)	Check (gCO2/MJ)
Materials	kg	50	23	1150	1	50	43.4782609
Fabrication	unit
Use	unit	5475	15	82125	0.95	5201.25	63.3333333
Elimination	unit	5475	11	60225	0.38	2080.5
Total				143500		7331.75