Transcript Intro LCA ppt

The Materials Life Cycle
Life Cycle Assessment
LCA traces the cycle of materials and processes
Documents resources consumed, emissions excreted
Life Cycle Assessment
Different levels are appropriate:
Full LCA scrutinizing every aspect (tedious, expensive)
A Sketch-like overview
Approximate
anything in between
Energy
Product
Manufacture
Feedstock
Transportation
Natural
Resources
Emissions:
CO2, NOx, SOx
Particulates
Toxic waste
Low grade heat
Material
Production
Product
Use
Product
Disposal
Emissions
There is a wide range of emissions:
Carbon dioxide, sulfur oxides, nitrous oxides, low grade heat, gas,
liquid and solid waste
In low concentrations, most of these are harmless. But in high
concentrations they can be damaging.
The sum of these unwanted by products often exceeds the capacity
of the environment to handle them.
Emissions damage
If the damage is local and the responsible agent deals with the cost
of containing and remediating, we say the environmental cost is
internalized.
If the damage is global and the agent is not held responsible, the
cost is spread over society and we say the environmental cost is
externalized.
Which is greener?
Life-cycle analysis is a method in which the energy and raw material
consumption, emissions and other factors are measured, analyzed
and evaluated over the product’s entire life.
Life-Cycle Analysis attempts to measure the “cradle to grave”
impact on the ecosystem.
LCAs started in the early 1970s, initially to investigate the energy
requirements for different processes.
Emissions and raw materials were added later.
LCAs are considered to be the most comprehensive approach to
assessing environmental impact.
cloth vs. disposable diapers
1990 –The American Paper Institute finds disposable diapers to be
preferable.
1991 – The National Association of Diaper Services concludes the
opposite.
1992 – Procter & Gamble reverses the conclusion once more.
Each time, additional considerations were brought in: -indirect of paper production
(increasing impacts of disposables) -production of detergents (increasing impacts of
washing cloth)
1992 – New study by Franklin Associates, concluding that the answer
depends on whether one looks at energy or water or solid waste.
Franklin and Associates
Total energy used by each diaper type in one year.
Feedstock and process energy includes energy used through
cotton growing, material processing and diaper manufacture.
It also includes energy used and embodied in bleach and
detergent.
Franklin and Associates
Volume of solid waste per year.
includes waste used to produce the diaper such as raw material
production and process, manufacture trimmings, and ash from
electricity generation.
Post consumer waste refers to substances thrown out: the diaper
itself, child waste, and packaging.
Franklin & Assoc.
Franklin & Assoc.
What is the conclusion?
Is energy or waste more important?
Other factors possibly involved as well
When conclusions are easily reversed, probably too close to call?
Methodologies
Initially, numerous variants of LCA “methods” were
developed/investigated, but today there is consensus that there is
only one basic method with a large number of variants
Currently IS0 14040-14043 is considered to be the LCA standard.
Four steps of LCA
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1. Goal definition (ISO 14040)
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2. Inventory Analysis (ISO 14041)
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Process tree for raw material to waste
Mass and energy balances are computed
All emissions and consumptions are accounted
3. Impact Assessment (ISO 14042)
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The basis and scope of the evaluation are defined.
Emissions and consumptions are translated into environmental effects.
The environmental effects are grouped and weighted.
4. Interpretation/Assessment (ISO 14043)
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Areas for improvement are identified.
1. Goal definition
establish beforehand what purpose the model is to serve, what one
wishes to study, what depth and degree of accuracy are required,
and what will ultimately become the decision criteria.
In addition, the system boundaries - for both time and place - should
be determined.
2. Inventory Analysis
inputs and outputs of all processes in terms of material and energy.
process tree showing events in a product’s life-cycle and their
interrelations.
the emissions from each process and the resources (raw materials)
used for each event
establish (correct) material and energy balance for each process
stage and event.
Processes:
Inputs:
Raw Materials Acquisition
Raw Materials
Energy
Outputs:
Atmospheric
Emissions
Manufacturing
Use / Re-use / Maintenance
Recycling / Waste Mgmt.
System Boundary
Waterborne Waste
Solid Waste
Co-Products
Other Releases
Coffee machine (simplified)
Coffee machine LCI
Problems with LCI
The inventory phase usually takes a great deal of time and effort
and mistakes are easily made.
There is data on impact of different materials
the data is often inconsistent and not directly applicable due to
different goals and scope.
hoped that the quantity and quality of data will improve in the
future.
Results are generalized improperly.
3. Impact Assessment
The impact assessment focuses on characterizing the type and
severity of environmental impact more specifically.
There are different ways to weight and assess impacts.
EPA 10 most wanted
Impact:
Measure:
Global Warming Potential (GWP)
kg CO2 Equivalent
Ozone Depletion Potential (ODP)
kg CFC Equivalent
Photochemical Oxidant Potential (PCOP)
kg NOX Equivalent
Acidification Potential
H+ Moles Equivalent
Eutrification
kg Nitrogen Equivalent
Health Toxicity (Cancer)
kg Benzene Equivalent
Health Toxicity (Non-Cancer)
kg Toluene Equivalent
Health Toxicity (Air Pollutants)
kg: DALYs Equivalent
Eco-Toxicity Potential
Fossil Fuel Use
kg 2,4-D Equivalent
MJ Surplus/Extracted Energy
Material/impact
Environmental effect
depletion of biotic resources
copper
CO2
CFC
SO2
NOx
Phosphorous
VOCs
heavy metals
PCB
pesticides
styrene
depletion of abiotic resources
greenhouse effect
ozone layer depletion
acidification
eutrophication
(summer) smog
human toxicity
eco-toxicity
odor
4. Interpretation
The final step in Life-Cycle Analysis is to identify areas for improvement.
Consult the original goal definition for the purpose of the analysis and the target group.
Life-cycle areas/processes/events with large impacts (i.e., high numerical values) are
clearly the most obvious candidates
However, what are the resources required and risk involved?
Good areas of improvement are those where large improvements can be made with minimal
(corporate) resource expenditure and low risk.
Paper or plastic?
Goal?
Inventory Analysis
Impact assessment
Analysis
Inventory
Materials: Paper and polyethylene + additives, colorants, etc.
Processes: film blow, paper forming, printing, etc.
1.5 plastic bags = 1.0 paper bags
Waste water, green house gasses
Recycling? Composting?
How to account for human variability?
Plastic Bags
Paper Bags
Paper or plastic?
Raw materials
Energy to make (MJ)
Solid waste (g)
Total emissions to air (kg)
CO2 equivalents (kg)
Paper
Wood
1.7
50
2.6
0.23
Plastic
Oil
1.5
14
1.1
0.53
Plastic bags generate 39% less greenhouse gas emissions than
uncomposted paper bags, and 68% less greenhouse gas
emissions than composted paper bags.
Plastic bags consume less than 6% of the water needed to make
paper bags
Plastic grocery bags consume 71% less energy during production
than paper bags.
total non-renewable energy consumed in plastic bag life is 36%
less than paper bags, and up to 64% less than that consumed by
biodegradable plastic bags.
Using paper sacks generates almost five times more solid waste
than using plastic bags.
After three uses, reusable plastic bags are superior to all other
types of disposable bags
Manufacturing
Paper consumes twice as much water and emits about 60% more
greenhouse gases than plastic.
biodegradable plastic bags generate higher levels of greenhouse
gas emissions, atmospheric acidification and eutrophification
Paper or plastic?