Life Cycle Assessment 生命週期評估

1. Life Cycle Assessment生命週期評估 福島康裕　助理教授 國立成功大學環境工程學系

2. ~ ~ Production Recycling Use Recycling rates • There are a number of ways to express recycling rate • Recycling rate (reuse rate) • Collection rate: d/(c+d) • Recycling rate after losses: f/(c+d) • Return rate: g/(g+a) • Trip number g a f b Q: How can we convert trip number into recycling rates? e d c

3. Recycling rates • For simplicity, assume that loss in recycling is negligible, and closed loop recycling is considered. • Collection rate, recycling rate after losses, and return rate are equivalent under this assumption a Production 1 g a b = c + d Use 1 c = b / N ~ Recycling 1 ~  d = c (N-1) Production f Production 2 recycling rate r = d/(c+d) b Use 2 Recycling Recycling 2  r = 1 – 1/N Use e d  N = 1 / (1 - r) Production N c Use N c

4. What does it imply? • Because LCI results depend linearly to r, • If N is high, increasing trip number is not so important … • If N is low, it is important to increase trip number … r N

5. 100 × 100 × 100 × r 1-r r 1-r r 1-r More realistic question … • Of our plastic bags, x×100 % are reused once as a plastic bag, and the remaining goes to the waste. Calculate the overall recycling rate r×100 %. 100 100 Use 1 100x Use 100(1-x) Use 2 r 1-r 100x Inflow to the overall system : 100 Outflow to the overall system : 100 Inflow to “Use”: 100 + 100x = 100 + Outflow from “Use” : 100(1-x) + 100x + 100x = 100 + 100

6. r 1-r r is at most 0.5 in this system… • x =

7. Exercise • Express r as a function of x1 and x2 • Express trip number as a function of x1 and x2 • Express trip number N as a function of r • What is the maximum r ? • (x1, x2) = (0.4, 0.1) , (0.3, 0.25) Which has higher r? Use 1 x1 Use Use 2 r 1-r x2 Use 3

8. r 1-r r is at most 0.5 in this system… • x1(1+x2) =

9. Objectives of LCIA • Describe environmental consequences of environmental loads • It is not possible to track all the consequences  only major / known / relevant consequences are considered • Roles • make information more relevant, comprehensive, and easier to communicate • make results more comparable

10. Consequences… • 「風が吹けば桶屋が儲かる」If the wind brows, then tub producers will make more money. (Japanese traditional comic story telling, 落語(rakugo) ) • Spring wind brows • Sand dust blown up • Sand dust hurts people’s eyes • Cause eye disease • People play shamisen (string instrument that use cat skin on its body) and make a living • less cats • more mice • people use tub to catch mice, but mice would make a hole on tubs and run away • people need to ask tub producers to fix their tub • tub producers will make money

11. LCIA: Life Cycle Impact Assessment • Calculate how much impact of interest is associated with the LCI results (environmental loads) Characterization Classification Normalization Weighting CO2 Global warming HCFCs Ozone depletion Indicator SOx Acidification NOx Human health <category indicators> <env. loads> Indicators LCI results Impact categories

12. Exercise & Discussions • Global warming • What property of GHGs is useful for characterizing its potentials? • How is the GWP defined? • What are other substances than GHGs that could affect the warming mechanism? • Eutrophication • Raise three environmental loads that are classified to Eutrophication. • What is the property all those loads have in common, and thus used for characterization of eutrophication? • What are the two important nutrients? • Explain limiting nutrients in 1) terrestrial plants, 2) aquatic ecosystems in freshwater, and 3) aquatic ecosystems in sea water. • Why is it difficult to account for geographical variations in eutrophication? • What is the typical waste heat source? • What is the typical expression of eutrophication potential?

13. Small test • May 17 10:10- • Chapter 3. Goal and Scope Definition • 3.1 and 3.4 • The worksheet …