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seeing himself as even slightly outdated or incapable?”- J. Mooallem.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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