Integrated Circuits Towards Reducing E-Waste:

Future Design Directions

Torsten Lehmann and Tara J. Hamilton School of Electrical Engineering and Telecommunication

The University of New South Wales

Sydney, Australia

Email: tlehmann.t.hamilton@unsw.edu.au

Abstract-Electronic devices and systems are not usually envi­ronmentally friendly. Large amounts of energy and hazardous substances are required for their production, and discarded products end up in landfills; trends that are exacerbated by fast moving advances in consumer electronics. In this paper, we argue that the most promising way to reduce the environmental load of consumer electronics is to move towards reusable electronic components; components that are reliable, self-testing, and, most importantly, flexible in a manner that allow electronic systems to be build for a wide range of applications using only a few highly reconfigurable integrated circuits.

Index Terms-Electronics Waste Reduction, Green Circuits and Systems, Reusable Electronics, Reconfigurable Integrated Circuits

I. INTRODUCTION

It is estimated that between 20 to 50 million tonnes of

electronics waste (e-waste) is being produced world-wide

every year [1]. Last year approximately 234 million electronic

items were dumped in Australia representing an increase of

21 % from 2008 [2]. The dramatic increase in e-waste can be

attributed to fast-paced technological advancements and the

desire (and sometimes need) to upgrade computers, mobile

phones, TV s and so on.

W hile some changes in e-waste handling and regulations

are emerging, a substantial amount still ends up in landfills:

in the United States, for instance, about 80% of e-waste was

dumped in the early-to-mid 2000s [3]. This is concerning

particularly because e-waste contains many toxic substances

(such as lead, cadmium, mercury, and arsenic) and can lead to

serious pollution. Recycling the larger parts of e-waste (such

as cables, enclosures, and evacuated tubes) is relatively simple.

Printed circuit boards (PCBs) with their mounted components

are harder to recycle. Usually they must be ground up, burned

or acid washed in order to salvage raw materials (such as gold,

copper and aluminium) [4], [5]. There have been few attempts to salvage electronic com­

ponents (or PCBs) such as sophisticated integrated circuits

(ICs or chips) for reuse; components may be obsolete or

worn out, but also they are simply difficult to remove from

modern PCBs once mounted, without being damaged (e.g.

[6], [7], [8]). This is unsatisfactory from an environmental

point of view: firstly, waste products from PCB recycling

contains the toxic substances not salvaged by the process.

Secondly, the embodied energy in integrated circuits is very

high - for instance, a 2002 study estimated the embodied

energy of a typical small integrated circuit (a 1.2 cm2, 32MB

memory chip) to be 26 MJ, requiring 2.3 kg of fossil fuel for

its production [9].

Thus, in this age of global climate change and increasing

demand for electronics goods, we see an emerging need for

moving towards electronic systems that can, at least in part,

be reused in order to lower their environmental burden. To

enable efficient electronics reuse, the technical issues above

need to be addressed.

Power converters for windmills or photovoltaic panels make

extensive use of power electronics. Such electronics, by its

very nature, has a low environmental burden because of their

aid in generating renewable energy. However most electronic

systems, e.g. consumer electronics, does not fall in this cate­

gory; most electronic systems are users rather than providers of

energy. For the purpose of this work, by "electronic systems"

we understand "energy using" electronics.

In this paper, we discuss the challenges that lie ahead for

electronics circuits and systems designers if the electronics

industry is to move away from having an ever increasing

environmental load. In section II, we argue the case for the

future design of reusable electronics; in section ill, we discuss

the challenges of reusable electronics; in section IV, we argue

that further research into reconfigurable electronics is required;

in section V we summarise the future design directions for

reusable electronics; finally, in section VI, conclusions are

drawn.

II. REUSABLE ELECTRONICS

Lowering circuit power dissipation is often brought forward

as a primary approach to reducing the environmental burden

of electronic systems. For systems that use large amounts

of energy this is a valid avenue. However, lowing power

dissipation can arguably lead to an increase in environmental

burden: lowering power dissipation in a system may enable

it to be operated from a small battery and be portable, hence

increasing the system's market penetration and environmental

burden (e.g. the mobile phone); lowering the power dissipation

further enables increased functionality of the system, hence

creating consumer desire to upgrade their system at an envi-

978-1-4244-6878-2/10/$26.00 ©2010 IEEE 469

ronmental cost (e.g. the mobile phone ).1 Further, with the typical short life of todays complex

electronic devices, their embodied energy is typical much

higher than the energy they use - e.g. Williams et al. [9] found that only 27 % of the energy used over the life of a

32 MB RAM chip was during its operational life; the rest

was associated with manufacturing. In addition to the pure

energy considerations, the manufacturing of integrated circuits

require a large number of hazardous chemicals; their use being

a potential risk to workers and the environment.

Thus, we see is a very strong incentive to reuse electronics

components whenever possible. We see this as the approach

towards reducing the environmental burden of electronics with

the most potential; an approach which is radically different

than reducing power dissipation of devices. Today, there have

been only very few attempts at reversing the trend of "throw­

away" electronics (e.g. [12]). While there is seemingly an inexhaustible appetite amongst

consumers for the latest electronic gadget, there is much scope

for reusing electronic components. This can be understood

by noticing that there is a substantial difference between

the computational (and other) requirements and the electron­

ics in different applications. Personal computers have more

computational power than DVD players; DVD players have

more computational power than washing machines, and so

on. Also, as electronics become smaller and cheaper, even

more types of appliances are fitted with electronic control

systems ("intelligent" appliances), normally starting towards

the lower end of computational requirements. Oliver et al.

[13] use the term "technology food chain," and explain how

microprocessors could be reused, moving down the food chain

between technology generations. If designed so that they can

be reconfigured for different applications, this can apply to

most components such that components fitted in a DVD player

in one generation (say), move down the food chain and will

be fitted in a washing machine (say) in a following generation.

Thus, there is much scope for reconfigurable, reusable

electronic systems that can be reconfigured to perform dif­

ferent or varied functions for a particular application or

for different applications (e.g. the "technology food chain").

Such reconfigurable, reusable systems could significantly alter

future electronic design paradigms and significantly improve

the burden of the electronics industry on the environment.

III. CHALLENGES

There are many challenges that have to be overcome before

electronic devices can be reused in a sustainable and efficient

manner:

A. Obsoleteness

If an application requires the full capabilities of the very

latest electronic technology to operate, earlier generation com­

ponents can not be recycled for that application. Most appli­

cations do not require this, however, and their obsoleteness

1 Note that both the authors have extensive industrial and academic ex­perience in low-power circuit design, primarily in bio-inspired systems and implantable electronic systems (e.g. [ lOj, [11])

470

Fig. I. Typical signal flow in electronic system.

lie in their function rather than in the underlying technology;

for such applications, if components and sub-systems can be

reconfigured to perform a different function, the sub-systems

can be reused.

The generalised purpose of electronics systems is to sense

signals in a physical domain, manipulate these signals and

apply them to an (often different) physical domain as indi­

cated in Figure 1. Over the last two decades, reconfigurable

digital components, notably Field-Programmable Gate Arrays

(FPGAs), e.g. [14], [15], have matured to a stage where

they are used extensively for prototyping and increasingly

in products. Reconfigurable analogue components are more

sparsely reported; most of these address signal processing only,

e.g. [16], [17], [18], [19], though a few also include sensor

interfacing [20], [21]. Reconfigurable support functions, such

as power transfer and communications are the last functions in

typical electronic systems that must be made configurable in

order to enable the reuse of electronic sub-systems. From an

electronic circuit design point of view, the design of suitable

reconfigurable circuit components is the first challenge for

reusable electronics.

B. Wear-out

Electronic components wear out with use or stress; typical

consumer electronics have an expected life of about a decade.

Reusable electronics need to have an expected life that equals

the sum life of a number of products. Thus for successful

employment of reusable electronics, it is critical that such

components are designed for a long life, rather than for

optimising performance or power dissipation (such as reducing

voltage and temperature stress and having redundant circuit

functions, e.g. [22]). Note that such reliable systems are

commonly used in demanding applications such as military,

space or medical applications; the design practices just need

to be incorporated in consumer electronics.

When building a new product with a reused part, it may

become the responsibility of the product manufacturer (rather

than the part supplier) to ensure good parts are used. Hence,

we foresee reusable electronic components needing to include

automatic, thorough component testing (such as boundary scan

systems and built-in self-test, e.g. [23]). From an electronic

circuit design point of view, built-in self-test is the second

challenge for reusable electronics.

C. Unmounting

While sockets can be used to facilitate removal of compo­

nents from PCBs, they make equipment bulkier and, in some

applications, severely reduce performance or prevent opera­

tion. Processes to remove large surface mount components

Fig. 2. Conceptual block diagram of typical FPGA based electronic system.

Fig. 3. Conceptual block diagram of reusable electronic system.

from PCBs (e.g. [6]) should be in place for the adoption of

reusable electronics. Alternatively PCBs could be engineered

as modules with well defined interfaces and functions such

that entire PCBs could be reused.

D. Non-technical challenges

There are many non-technical issues that have to be ad­

dressed before widespread reuse of electronic components

can be realised; for instance standardisation issues, economic

issues, logistical issues and manufacturing issues, e.g. [24], [25]. However the technology first has to be in place with

circuit components designed specifically for reuse.

Thus, from a circuits and systems design point of view, we

see the primary challenge to achieve electronic components

that are well suited to reuse to be the design of flexible,

reprogrammable components for typical circuit functions that

are not currently so designed.

IV. RECONFIGURABLE CHIP S

While the purpose of electronic systems is to manipulate

and transfer signals between physical domains, a number of

support functions are required for system operation - for in­

stance energy sources, power supplies and power distribution,

voltage references, oscillators, bias control for sensors, drivers

for actuators, and communications hardware, see Figure 2 and

e.g. [26]. Complex generic components (such as field-programmable

gate arrays, field-programmable analogue arrays, micro­

controllers, and digital signal processors) are relatively easy

to reuse for different applications because the functions

they perform are determined by digital configuration data

(or firmware) that can be uploaded to the component. This

updating of configuration data, however, requires a suitable

interface though, despite this (see [13]), such components are

considered reconfigurable.

471

Application specific hardware for the physical interfaces -

typically power supplies, sensor biasing, drivers and commu­

nication systems - are harder to reuse because the functions

they perform are determined by their component types and

interconnecting wires. The reason that current reconfigurable

electronic circuits address the signal processing rather than the

required physical interfaces is that the physical requirements

to the latter are highly application specific (operating at vastly

different voltages, currents, and frequencies, for instance) and

require electronic components suited to each application - or

reconfigurable circuits of extraordinary flexibility.

Thus to facilitate practical reuse of electronic systems, the

physical interfaces must be designed in a less application

specific manner; reconfigurable circuits need to be devised for

these functions.

Assuming complete PCBs are designed for reuse, it would,

in principle, be possible to implement reconfigurable, reusable

electronics using largely existing electronic components. There

are, however, a number of compelling reasons why such

electronics should be implemented primarily on integrated

circuits (ICs or chips): Firstly, due to their micro-scale, com­

ponents on ICs are much smaller than their PCB equiva­

lents; this is critical as general-purpose, reconfigurable sub­

systems are more resource intensive than custom hardware

(Le. some hardware is dedicated to reconfiguration rather than

function, and some hardware will be unused; compare FPGAs

vs. Application-Specific Integrated Circuits). Secondly correct

function of components need to be verified before they can

be reused: specific hardware for self-test should be included,

further increasing the hardware overhead on the reconfigurable

system. Thirdly, on-chip integration of functions increases

system reliability, which is critical when the expected useful

lifetime of the system increases with reuse. Finally, when

PCBs are not reused as whole, the need to unmount fewer

components would increase the likelihood of function reuse

- note that some work on environmentally friendly PCBs

haven been reported, e.g. [27], thus PCB reuse may be less

critical than component reuse.

Therefore, we envisage reusable electronic systems to look

somewhat like Figure 3: having fewer, more configurable,

more highly integrated components than current systems.

Components such as energy storing elements and application

specific sensors and actuators will still need to be off-chip; the

challenge from a circuits and systems design point of view is

to integrate everything else on chip - and to determine which

functions to best to integrate on the same chip. These concepts

are embodied in our idea for a Field-Programmable Electronics

Support System (FPESS).

V. DESIGN DIRECT IONS

In summary, in order best to address the environmental

burden of electronic systems, design focus should be on

reusable components; such components need to:

• be very reliable - component failure rates should be long

enough such that they can be used over the lifetime of

several systems;

• be self-testing - components should be able to thor­

oughly test themselves without the aid of the component

manufacturer in order to qualify for reuse;

• be highly integrated - in order to avoid having to

unmount a large number of discrete components and to

include reconfigurability and self-test in a way that is

transparent to the system designer;

• be highly reconfigurable - in order to be useful in a

large variety of applications.

All of these requirements are feasible when design strategies

are targeted towards reuse and reconfigurability. For instance,

both reliability and self-testing are integral parts of chips

manufactured for implantable medical devices. Such devices

must maintain functionality for the lifetime of the recipient.

Thus, by employing design techniques used in the medical

device industry, for instance, reliability over an extended

lifetime is possible.

Chips with a large number of integrated components (e.g.

inductors, diodes, etc.) are possible especially when silicon

technologies such as silicon-on-sapphire (SOS) are utilised;

although this is not imperative. While reconfigurability will

come at the cost of greater area and digital programming com­

plexity (and possibly reduced performance), reusable chips

will have the potential for having a much reduced environ­

mental burden over their lifetime.

VI. CONCLUSION

In this paper, we discussed future design directions for

electronic systems with a reduced environmental burden than

what is currently practiced. We argued that it is not the power

dissipation of employed systems that should be the primary

technology driver for environmentally friendly electronic sys­

tems; rather it should be the total environmental load of the

systems ("from cradle to grave") - as integrated circuits have

large embodied energy and as they require large amounts

of resources to manufacture, prolonging the useful life of

the integrated circuits is a most promising avenue towards

reducing their total environmental load. We thence argue

a need towards the use of reusable electronic components.

From a circuits and systems design point of view, this means

designing reconfigurable integrated circuits, for functions not

currently designed thus, and designing system partitioning in

such a manner that systems can be implemented using few,

smart components each having a long life and extensive built­

in self-test. Only energy storing components and application

specific sensors and actuators should be left off chip.

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