Post on 18-Dec-2015
Growing cradle-to-cradle metal flow systemsApplication of agent-based modeling to the study of global
flows of metals in mobile phones
L. Andrew Bollinger
Contents
1. Problem background
2. Model implementation
3. Results
Problem background – metals and sustainability
Increasing metal scarcity
Low recovery ratios
Growing stocks of metal waste
High demand growth
Platinum, multilayer ceramic capacitors
Indium, LED displays
Neodymium, alternator magnets in wind turbines
Electronics waste
Cradle-to-cradle
Technical metabolism: “A closed-loop system of manufacture, recovery, and reuse that enables a material to maintain its highest value through many
product life cycles”
Open cycles and complex flows
Open cycles:• Multiple changes of ownership, with no connection between the
final owner and the manufacturer• Products of high mobility• No clear distinction between an end-of-life and a second-hand
product• Diversity of flow structures
Complex flows:• Many actors, each with their own interests• Evolving relationships amongst actors• Numerous linkages amongst materials
Hypothesis and research question
Hypothesis
In cases of open cycles and complex flows, agent-based modeling can help to illuminate the paths toward cradle-to-cradle metal flow systems.
Research question
What conditions foster the development of a cradle-to-cradle flow network for metals in mobile phones?
Netlogo model
Example 1: two species
Example 2: four species
Example 3
System description – global flows of metals in mobile phones
Material perspective
Technology perspectiveProcess perspective
Actor perspective
Regulatory perspective
Geographical perspective
Economic perspective
System description – material perspective
System description – process perspective
Umicore Precious Metals Refining (Hoboken, Belgium)
System description – actor perspective
“All that pressure to have the latest – something that people will be impressed by – is compounded by the fact that all of a sudden somebody is doing something with their mobile phone that you can't do. In other
words, it's because we've made phones such deep and indispensable extensions of ourselves that we dump them so quickly. Who can bear
seeing himself as even slightly outdated or incapable?”- J. Mooallem. The Afterlife of Cellphones. The New York Times. 13 Jan. 2008.
System description – geographical perspective
Mobile phones use as a percentage of population (2006)
System description – geographical perspective
• Developing countries account for 75% of a global total of 4 billion mobile phone subscriptions
• China is the world’s largest mobile phone market with over 700 million subscribers
• 200-300 million mobile phones are retired in China every year (2008)
• Africa has the fastest rate of mobile phone subscriber growth
Modeling approach
System decomposition
Agent
Input stock
Technology
Purchasing decision
Investment decision
Operational scale
Operational input(s)
Operational output(s)
Investment criteria
Expected profit
Purchasing criteria
Amount needed
Output stock
Physical flow contract
Operational cost Assets
Amount
Price
Good
Amount
Good
Amount
Good
Location
Developing countries
Industrialized countries
System decomposition
Parameters
• Technical lifetime of a mobile phone• Mobile phone use time • Metal content of a mobile phone • Price of gold• Price of copper• Price of silver• Price of palladium• Price of components• Price of batteries• Accessibility of collection pathways• Motivation of consumers• Incentive cost• Disposal tendency of consumers• Cost of mobile phone manufacture• Gold recovery rate of backyard metal recovery• Preferences of consumers
Metrics
How to transform the vague concept of cradle-to-cradle into usable indicators?
Cradle-to-cradle indicator:
Total mass of metal disposed:
phoneManufactureAphoneManufactureBphoneManufactureCphoneManufactureDphoneRetailNSPCollectionphoneRetailNSPCollectionPayusedPhoneRetailnewPhoneConsumptionnewHighEndPhoneConsumptioncheapPhoneConsumptioncheapHighEndPhoneConsumptionusedPhoneConsumptionphoneCollectionphoneTestingRefurbishingDisassemblyindustrialMetalRecoverybackyardMetalRecovery
Complete agent set
Decision-making rules• Purchasing• Processing• Investment
for…if... then...else...while...
Goods• Mobile phones• Components (batteries, circuit boards, “other” components)• Metals (gold, copper, silver, palladium)
Model setup
phoneManufactureAphoneManufactureBphoneManufactureCphoneManufactureDphoneRetailNSPCollectionphoneRetailNSPCollectionPayusedPhoneRetailnewPhoneConsumptionnewHighEndPhoneConsumptioncheapPhoneConsumptioncheapHighEndPhoneConsumptionusedPhoneConsumptionphoneCollectionphoneTestingRefurbishingDisassemblyindustrialMetalRecoverybackyardMetalRecovery
Simulation
Video 1
Video 2
Experiments
• 33,516 simulation runs
• 15 parameters varied
• 100 timesteps (quarters) each
• 400 GB of data collected (~9,642,401 sheets of paper)
How do we produce cradle-to-cradle behavior?
Results
Results – Default case
What’s happening with the agents in the system?
Manufacturer agents
Refurbisher agent
Results – Default case
What’s happening with the phones in the system?
Size = value of phone ($)Color = location of phone (which agent?)
Results – Default case
What’s happening with the metals in the system?
Results
Which parameters have the most leverage to produce desired system behavior?
Results
How “cradle-to-cradle” can we be?
ResultsWhich combinations of parameter values are most effective?
Number of runs in which various combinations of parameter values gave rise to a cradle-to-cradle indicator > 0.97
Results
What about the financial performance of agents?
Results
What patterns can we see in the variability of the results?
Some metal losses are INEVITABLE.
SINGLE interventions are limited in their ability to improve system performance.
Large improvements in cradle-to-cradle performance are possible through COMBINATIONS of interventions.
The most effective combinations of interventions simultaneously:• Increase the COLLECTION RATE.• Increase the METAL RECOVERY RATE.
Especially in DEVELOPING COUNTRIES.
What did we learn about generating cradle-to-cradle performance?
Refurbishing technology
Refurbisheragent
Condition(new, used, refurbished, etc.)
Age
Metal content(mass Au, Cu, Ag, Pd)
Category(high-end, low-end)
Functionality (functional, nonfunctional)
Remaining lifetime
Condition : UsedFunctionality: NonfunctionalRemaining lifetime: 0 quarters
Condition: RefurbishedFunctionality: FunctionalRemaining lifetime = 12 quarters
Model setup
Representation of mobile phones
Results
What about the financial performance of agents?
Results – Sweep 2 (Combined variation of parameters)
Results – Sweep 2 (Combined variation of parameters)
Which parameters values tend to co-occur most frequently in the runs that produced the desired behavior?
Results – Sweep 3 (Variability test)
To what degree can we trust the results in sweeps 1 and 2?
Results – Sweep 1
Which parameters have the most leverage to produce desired system behavior?
Results – Sweep 2 (Combined variation of parameters)
Which parameters values are essential to achieving desired behavior?
Results – Sweep 2 (Combined variation of parameters)
Which parameters values are essential to achieving desired behavior?
… Consumers purchase mobile phones that have been made available to them by retailers. A consumer uses his phone for an average of six quarters, after which time he immediately purchases a new one. If a consumer’s phone dies (becomes nonfunctional) during the time he is using it, he immediately purchases a new one. When a consumer is finished using a mobile phone, he puts it up for sale to designated collectors. Consumers have an inherent level of motivation to give their mobile phones to proper collection pathways after use. A consumer with low motivation is more likely to simply throw away his phone or put it in a drawer and forget about it than a highly motivated consumer. Consumers are more highly motivated to give their used phones to collectors who offer to pay them…
Narrative
Model implementation
Software tools: •Protégé (for creating and editing ontologies)•Eclipse (IDE for Java programs)
Narrative development
Narrative
Manufacturers…
Retailers…
Consumers…
Collectors…
Refurbishers…
Metal recoverers…
Results
How “cradle-to-cradle” can we be?
cradle-to-cradle indicator
Cradle-to-cradle indicator vs. gold disposed
Distribution of cradle-to-cradleIndicator value over all runs
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