Life Cycle Assessment (LCA) Flashcards
What is life cycle assessment
- involves quantification of environmental BURDENS of a product, process or activity (For example, energy and materials used and wastes released to the environment)
- quantification of environmental IMPACTS (translates burdens into potential impacts)
- identification of opportunities for IMPROVEMENTS along the whole life cycle of a product, process or activity
LCA methodology
1) Goal and scope definition
- purpose of study
- system boundaries
- functional unit
2) Inventory analysis
- system definitions
- data collection
- estimation of environmental burdens
3) Impact assessment
- selection of environmental impact categories
- estimation of impacts
4) Interpretation
- identification of significant issues
- evaluation of results
- conclusion
Purpose of the study
- to identify ‘hot spots’ in the system
- to identify main impacts
- to identify opportunities for improvement
- to design a product or process
- to compare alternatives
System boundaries
From ‘cradle to grave’
- extraction and processing
- product manufacture
- use
- re-use and/or recycle
- (end of life) disposal
There is use of transport throughout
* from ‘cradle to gate’
Functional unit
- defines function of the system
- enables comparison of different system on equivalent basis
Inventory analysis
Bj = SUM(bj,i * xi)
Bj= total burden j per functional unit bj,i = burden j from activity i xi= mass flow in activity i
Environmental impacts
transform burdens into potential impacts
- global warming (carbon footprint)
- ozone layer depletion
- photochemical smog
- eutrophication
- human toxicity
- eco toxicity
- acidification
- resource depletion
Estimation of environmental impacts
Characterisation: quantification of potenial environmental limits
Ek = SUM( ekj* Bj)
Ek= total environmental impact k ekj= environmental impact coefficient Bj= environmental burden contributing to impact k
Global warming potential
- A measure of how much heat a greenhouse gas traps in the atmosphere up to specific time horizon, relative to carbon dioxide. It is expressed as CO2- equivalent.
Global temperature change potential
- The change in global mean surface temperature at a certain point in time in response to an emission pulse, relative to that of CO2.
Normalisation
- Normalisation of impacts on the total emissions or extraction of a certain area over a given period of time.
E.g a system that has a carbon footprint of 4.7million tonnes CO2 eq/fu
UK ghg emissions in 2012 were 577 million tonnes.
normalised ( 4.7/577)= 0.85%
Valuation
- Valuation: contributions of impact catergories are weighted and compared to social values and preferences
EI= SUM( wk *Ek)
EI = total environmental impact. wk= weights of importance of different impacts Ek= environmental impacts
Acidification potential
- caused by emission of acid gases (mainly those containg S, N)
- deposited on soil or water
- measure in SO2 equivalent
Eutrophication potential
- caused by fertilising/nutrient compounds (containing N, P) flowing into waterways
- either by emissions or run-offs
- If the nutrient is a growth limiting factor for algae , algae blooms occurs
- measured in PO4 3- equivalent
Human toxicity potential
- Caused by emissions of substances toxic to humans.
- Can occur to air, water or land.
- Measured as 1,4- dichlorobenzene equivalent.
