collier alles 2010 materials ecology

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DOI: 10.1126/science.1197478, 919 (2010);330Science

Paul Collier and Carina Maria AllesMaterials Ecology: An Industrial Perspective

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It is possible that cerebral A amyloidosis alsorequires brain-specific endogenous amyloid-

enhancing factors. Plaque-associated proteins

and lipids, such as apolipoprotein E, proteo-

glycan, and ganglioside, might serve as cofac-

tors and facilitate A aggregation (10). Thechemical and physical features of the amy-

loid-inducing factor remain to be determined.

The cell-to-cell passage of misfolded

proteins opens up the possibility of new

treatment strategies for their associated

disorder, such as antibodies or small mole-

cules that block transmission of the protein.

However, such transmission imposes a cau-

tionary caveat for stem cellbased therapy.

Conveyance of misfolded protein into the

transplanted stem cells might limit thera-

peutic benefits.

References

1. B. Frost, M. I. Diamond, Nat. Rev. Neurosci.11, 155(2010).

2. Y. S. Eisele et al.,Science330, 980 (2010).

3. J. Hardy, D. J. Selkoe,Science297, 353 (2002).4. J. D. Harper, P. T. Lansbury Jr.,Annu. Rev. Biochem.66,

385 (1997).5. M. D. Kane et al.,J. Neurosci.20, 3606 (2000).6. M. Meyer-Luehmann et al.,Science313, 1781 (2006).7. Y. S. Eisele et al., Proc. Natl. Acad. Sci. U.S.A.106,

12926 (2009).8. G. Legname et al.,Science305, 673 (2004).9. F. Wang, X. Wang, C. G. Yuan, J. Ma,Science327, 1132

(2010).10. J. Kim, J. M. Basak, D. M. Holtzman, Neuron63, 287

(2009).

10.1126/science.1198314

Materials Ecology:An Industrial Perspective

MATERIALS SCIENCE

Paul Collier1 and Carina Maria Alles2

Careful process design that considers material

use and reuse over the entire product life cycle

is important for a sustainable industry.

CREDIT:ADAPTEDFROMWWW.EMERALDINSIGHT.CO

M/CONTENT_IMAGES/FIG10240170604001.PNG

There are many reasons for the cur-rent drive for more sustainable indus-

trial processes, including a desire

for enhanced societal value, lower-energy

demand, less waste, and more effective prod-

ucts. Much of this drive comes from a new

generation of industry CEOs who are com-

mitted to sustainability (1). Sustainability

naturally includes a view on what to do with

products at the end of their lives, and the best

modern products are designed to make recy-

cling easier. However, there is much that is

not deemed to be worth recycling and goes

into landfill (2

). Population increase andchanges in consumption patterns combined

with the inefficient use of materials push us

toward a crisis point. To achieve stable long-

term growth, something will

have to changeand perhaps

a new approach based on the

materials themselves can help.

Industrial ecology is now

a thriving sector of engineer-

ing design and practice and

has become a welcome part of

modern industrial life (3, 4). It

derives from a high-level sys-

tems study of the energy andmaterial flows through industrial

processes. The aim is to improve

sustainability by closing loops

and recycling materials. Mate-

rials ecology, a less well known concept, wasexamined at a recent Frontiers of Engineer-

ing event (5). Several of the ideas presented

below crystallized during the series of talks

and ensuing panel discussion. This term has

been used before, principally to describe met-

als and minerals (6); however, before our

modern age such philosophies were surpris-

ingly widespread (7).

Materials ecology is a subset of industrial

ecology and offers a materials-centered view

of manufacturing processes rather than a sys-

tems view. Materials ecology is about the

interconnectivity of materials and the rela-tive cost of loop closure with respect to other

materials and the environment. Loop closure

refers to a process for converting a product at

the end of its life into a new material and irelated to the term cradle to cradle (8). B

necessity, it operates at smaller scales but i

intimately meshed with industrial ecology a

larger scales (see the figure).

In industrial ecology, a general approac

might be to examine a particular industria

systemfor example, for producing a refrig

eratorand to test inputs and outputs (cover

ing all raw materials, waste products, desire

products, pollutants, energy required, an

heat generated) against sustainability crite

ria. For each new product, this is repeated

recalculating inputs and outputs each time. Amaterials ecology viewpoint would comple

ment this approach by allowing us to mak

connections between the same material use

in different processes

For example, polyeth

ylene terephthalate i

used in many prod

ucts, such as fiber

and bottles. The mate

rials ecology approac

would focus on thi

individual materia

and consider it as th

center of a networanalysis diagram wit

connections to all th

products that can b

made from it. At eac

link, all material an

energy inputs and out

puts are evaluated i

terms of the closed

loop use of the mate

rial (i.e., includin

recycles) and classi

1Johnson Matthey Technology Centre,Blounts Court Road, Sonning Common,Reading, RG4 9NH, UK. 2DuPont Engi-neering Research and Technology, DuPontBuilding D5085, 1007 Market Street,Wilmington, DE 19898, USA. E-mail: [email protected], [email protected] In the loop. Schematic representation of manufacturing networks.

Published by AAAS


3/312 NOVEMBER 2010 VOL 330 SCIENCE www.sciencemag.org920

PERSPECTIVES

fied as an environmental payment or credit.

It may be possible to extend this and include

other environmental impact parameters,

such as water demand, environmental toxic-

ity, and pollutants.

Categories of material rather than individ-

ual ones could also be the focus. For example,

if we are interested in polymer fibers for cloth-

ing, then all of the materials capable of form-

ing fibers could be compared in terms of their

potential for closed-loop processing, to allow

us either to select between them or to look for

improvements on the current material.

A further interpretation of materials ecol-

ogy puts emphasis on avoiding end-of-life

situations where a material cannot be reused

or recycled, or the energy required to do so is

prohibitively high. Are there ways to validate

this concept? Perhaps one way is to view the

amount of energy required to place a mate-

rial in a closed loop and consume it as a start-

ing material for another industrial process.

This could be in terms of the energy requiredfor a conversion. For example, carbon diox-

ides Gibbs free energy of formation is very

high. This means that a lot of energy input is

required to convert CO2

into a useful prod-

uct in a closed-loop system. In a materials

ecology network analysis diagram, CO2

will

appear as an island with a relative high cost of

closed-loop processing.

In the worst cases, products are treated as

dead-ends, because complex products, par-

ticularly with many constituent materials, are

not really designed for reuse. Materials ecol-

ogy is about the evolution of a new genera-

tion of products that can easily be reused else-

where at the end of their lives. For example, a

modern automobile is a very complex product

requiring many thousands of parts. At the end

of its life, the car is dismantled and much of it

is recycled, especially the metals. Some com-

ponents are less effectively recycled and go

to landfill. However, there is a growing trend

in some industries to reuse polymer waste

rather than landfill it, and materials ecol-

ogy embraces this potentially lower-energy

option. The modern term upcycling is actu-

ally an old tradition: In rural communities,

objects are endlessly reused and adapted for

new uses as they age. This was actually prac-

ticed by the father of mass production, Henry

Ford. Almost 100 years ago, Ford shipped

model A trucks in wooden crates from the

Ford factory; the crates were then used as the

floorboards for the vehicle when sold.The current obsession with elemental-

ism, that is, striving to return all objects

as close to the pure element state as possi-

ble, regardless of the environmental cost, is

going to look rather odd in the future. New

industrial processes will be required to take

in objects and reshape them for new uses

rather than crush and melt them down into

pure elemental streams

The key success parameters of the new

industrial landscape are no longer ba

solely on profit margin, but now include en

ronmental, social, and ethical measures. T

will only increase in the future, and the m

successful materials will be the ones t

thrive in this more complex framework

materials ecology.

References and Notes

1. T. Ellis, The New Pioneers: Sustainable Business SuccThrough Social Innovation and Social Entrepreneurs

(Wiley, Hoboken, NJ, 2010).

2. M. Hill,Understanding Environmental Pollution

(Cambridge Univ. Press, Cambridge, 2010).

3. T. E. Graedel, B. R. Allenby,Industrial Ecology(Prent

Hall, Upper Saddle River, NJ, ed. 2, 2002).

4. R. Ayres, L. Ayres, Eds.,A Handbook of Industrial Eco

(Elgar, Cheltenham, 2002).

5. U.S. National Academy of Engineering and Royal Ac

emy of Engineering, Frontiers in Engineering, EU-U

Symposium, Cambridge, UK, 31 August to 3 Septem

2010; www.raeng.org.uk/international/activities/fro

tiers_engineering_symposium.htm.

6. M. A. Reuteret al., The Metrics of Material and Meta

Ecology: Harmonizing the Resource, Technology and

Environmental Cycles (Developments in Mineral

Processing) (Elsevier Science, Amsterdam, 2005).7. P. Desrochers, K. Lam,Electronic J. Sustainable Dev.

(2007).

8. W. McDonough, M. Braungart,Cradle to Cradle:

Remaking the Way We Make Things (North Point Pres

New York, ed. 1, 2002).

9. We thank the speakers at the Materials Ecology sessio

(5): S. Suh, K. Hellgardt, J.-S. Thomas, and W.-P. Schm

as well as the event organizers: the U. S. National Aca

of Engineering and The Royal Academy of Engineerin

behalf of the umbrella organization of European engi

ing academies, Euro-CASE). P.C. also thanks S. Axon.

10.1126/science.119

Irremediable Complexity?

CELL BIOLOGY

Michael W. Gray,1 Julius Luke,2 John M. Archibald,1 Patrick J. Keeling,3 W. Ford Doolittle1

Complex cellular machines may have

evolved through a ratchet-like process

called constructive neutral evolution.

Many of the cells macromolecular

machines appear gratuitously com-

plex, comprising more components

than their basic functions seem to demand.

How can we make sense of this complexity

in the light of evolution? One possibility is

a neutral ratchet-like process described more

than a decade ago (1), subsequently calledconstructive neutral evolution (2). This model

provides an explanatory counterpoint to the

selectionist or adaptationist views that per-

vade molecular biology (3).

Seemingly gratuitous complexity is illus-

trated by RNA processing systems such as

splicing and editing. The most complicated

macromolecular machine in the cell may

be the eukaryotic spliceosome (4), which

removes noncoding regions (introns) from

precursor messenger RNA (mRNA) in a pro-

cess called splicing. The spliceosome usesfive small nuclear RNAs and hundreds of

proteins to do the same job that some cata-

lytic introns (called ribozymes) can do alone.

The mitochondrial RNA editing system of

trypanosomes, in which hundreds of guide

RNAs and several large protein complexes

insert and delete uridine residues to restore

mRNAs to their ancestral state, is similarly

complex (5). Even the multicomponent con-

temporary ribosome, which translates mRNA

into protein, boasts far more constituent parts

than most imagine its purely ribozym

ancestor would have required.

When faced with such complexity,

favored (adaptationist) explanation wo

surely be selection for improved basic fu

tion. For example, ribosomal complex

is not generally regarded as gratuitous,

rather the result of evolutionary accretof proteins that made this machine prog

sively faster, more stable, and more effic

at translation (6). For the addition of som

these proteins, selection probably did d

increased complexity, but there is no basi

assume that this explains all, or even most

the increased complexity of these machin

As an alternative to such adaptatio

thinking, Lynch invoked fixation of neu

or slightly deleterious features as a gen

and unavoidable source of complexity

1Department of Biochemistry and Molecular Biology, Dal-housie University, Halifax, Nova Scotia B3H 1X5, Canada.2Institute of Parasitology, Czech Academy of Sciences andFaculty of Sciences, University of South Bohemia, 37005esk Budjovice, Czech Republic. 3Department of Botany,University of British Columbia, Vancouver, British ColumbiaV6T 1Z4, Canada. E-mail: [email protected]

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collier alles 2010 materials ecology

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