Ipatv2.pdf

IPAT

Disaggregating the Problem Goods & Services Impact Impact = Population × × Person Goods & Services Impact of Population Growth. Paul R. Ehrlich; John P. Holdren. Science, New Series, Vol. 171, No. 3977. (Mar. 26, 1971), pp. 1212-1217.

I = P× A× T Análisis de Ciclo de Vida & Ecología Industrial Departamento de Ingeniería Química

The IPAT equation is a mathematical identity that shows that the underlying

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The IPAT Equation and Its Variants Changing Views of Technology and Environmental Impact Marian R. Chertow School of Forestry and Environmental Studies Yale University New Haven, CT USA

Keywords environmental technology Factor X IPAT equation master equation technological change technological optimism

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Summary In the early 1970s Ehrlich and Holdren devised a simple equation in dialogue with Commoner identifying three factors that created environmental impact. Thus, impact (I) was expressed as the product of (1) population, (P); (2) affluence, (A); and (3) technology, (T). This article tracks the various forms the IPAT equation has taken over 30 years as a means of examining an underlying shift among many environmentalists toward a more accepting view of the role technology can play in sustainable development. Although the IPAT equation was once used to determine which single variable was the most damaging to the environment, an industrial ecology view reverses this usage, recognizing that increases in population and affluence can, in many cases, be balanced by improvements to the environment offered by technological systems. ❙

Disaggregating the Problem Goods & Services Impact Impact = Population × × Person Goods & Services

I = P× A× T The IPAT equation is a mathematical identity that shows that the underlying environmental problems are related to ìscaleî. Growth in Population and

Summary

eco-efficiency efficiency R E S E A R C H A N D A N A LY S I S This work explores the historical effectiveness of efficiency improvements in reducing industrial ecology humankind’s consumption of energy resources. Ten activities are analyzed, including pig IPAT equation iron production, aluminum production, nitrogen fertilizer production, electricity generation rebound effect from coal, electricity generation from oil, electricity generation from natural gas, freight resource consumption

Can Efficiency Improvements Reduce rail travel, passenger air travel, motor vehicle travel, and residential refrigeration. The data Resource Consumption? and analyses presented here demonstrate the dynamic interplay between technological

Supporting information is available on the JIE Web site

innovation, market forces, and government policy. They also show that, historically, over

A Historical Analysis ofimprovements Ten Activities long time periods, incremental in efficiency have not succeeded in outpacing increases in the quantity of goods and services provided. Thus, the end result over these

Jeffrey B.periods Dahmushas been, not surprisingly, a sizeable increase in the consumption of energy time

Keywords: eco-efficiency efficiency industrial ecology IPAT equation rebound effect resource consumption

resources across all ten activities. However, there do exist a few examples of shorter, decade-long time periods in which improvements in efficiency were able to match or outpace increases in quantity. In these cases, efficiency mandates, price pressures, and industry upheaval led to periods of reduced resource consumption. These cases suggest that with appropriate incentives, including, for example, efficiency mandates and price mechanisms, future resource consumption, and its associated environmental impacts, could be stabilized and even reduced. Summary

This work explores the historical effectiveness of efficiency improvements in reducing humankind’s consumption of energy resources. Ten activities are analyzed, including pig iron production, aluminum production, nitrogen fertilizer production, electricity generation from coal, electricity generation from oil, electricity generation from natural gas, freight rail travel, passenger air travel,and motor vehicle travel,progress and residential environmental to occurrefrigeration. (DeSimoneThe anddata Popoff Introduction and analyses presented here demonstrate the dynamic interplay between technological 1997; OECD 1998; WBCSD 2000). Efficiency improvements are often touted as effective and unmarket policy. Theyengineers also showtothat, overimAlthough encouraging focushistorically, on efficiency obtrusive means of reducing resourceinnovation, consumption. For forces, many, and government Supporting information is available long time periods, incremental improvements in efficiency have not succeeded in outpacing andonperhaps, in site particular, for engineers, the idea that reduc- provements certainly has economic and social benefits, the nothe JIE Web increases in the quantity of goods and services provided. Thus, end result over these tion that such improvements leadthe to overall reductions in retions in resource consumption, and thus a reduction in the astime periods has been, not surprisingly, a sizeable increase in the consumption of energy have sociated environmental impacts of resource consumption, can source consumption is less certain. After all, engineers resources across all ten activities. However, thereefficiency do existimprovements a few examples of shorter,yet, successfully realized for centuries; be achieved through technology-based solutions is especially decade-long time periods which improvements efficiency were able to match or these product-inand process-level efficiency improveattractive. As such, improving efficiency is often mentioned as in despite outpace increases in quantity.ments, In these cases,system-level efficiency mandates, pressures, and absolute reductionsprice in resource consumpa critical component of green engineering or design for environupheaval led to reduced resource occurred. consumption. These casesby suggest tionofhave not generally Instead, driven growing ment (DfE) guidelines for engineers industry (Fiksel 1996; Graedel andperiods that with including, for example, efficiency mandates andbehavior, price increasing affluence, changing consumer Allenby 1998; Anastas and Zimmerman 2003;appropriate Allwood et incentives, al. population, future and itsresource associated environmental could and other factors, consumption has impacts, continued to in2013). More broadly, such efficiencymechanisms, improvements haveresource been consumption, crease. Clearly, in order for efficiency improvements to reduce stabilized andeconomic even reduced. embraced as “win-wins” in that theybeallow for both

Address correspondence to: Jeffrey B. Dahmus, 1020 Union Street, San Francisco, CA 94133, USA. Email: [email protected] © 2014 by Yale University DOI: 10.1111/jiec.12110

Introduction

Volume 18, Number 6

Efficiency improvements are often touted as effective and unobtrusive means of reducing resource consumption. For many, www.wileyonlinelibrary.com/journal/jie and perhaps, in particular, for engineers, the idea that reduc-

Editor managing review: Reid Lifset

and environmental progress to occur (DeSimone and Popoff 1997; OECD 1998; WBCSD 2000). Although encouraging engineers focus onEcology efficiency 883 imJournal to of Industrial provements certainly has economic and social benefits, the no-

uantity – which represents the resource intensity of the goods and services provided – and

mpact over Many Resources – which represents the environmental intensity of resource consumption. variants on the IPAT identity exist, variants that often either combine terms for added

Resources Resources Quantity Resources Quantity x . Impact (4)(1) can be mPACT Identity, are in fact containedresource withinGDP (2) (Yamaji et al. and shown Ausubel improvements in reducing consumption, the 1991, basic Waggoner IPAT identity in Quantity , (1) Impact Population x x 002). Population GDP As definedfurther above, disaggregated the left side ofto, (4) represents the amount of resources consumed, while the first

can be easily shown that otherQuantity variants of IPAT for identity, including theInKaya Identitythe and the Resources x theterms . (4) simplicity, or further disaggregate added resolution. discussing role of efficiency

As the left represents amountofofgoods resources while the The first ermdefined on the above, right-hand sideside of of (4)(4) represents thethequantity and consumed, services provided. where affluence is represented as the Gross Domestic Product (GDP) per person and technology GDP Quantity Resources Impact term on the right-hand side of (4) represents the quantity of goods and services provided. The focusing on the role of technology-based solutions in reducing resource consumption, the (2) Population x econd term onImpact the right-hand side of x(4), representingx the amountxof resources consumed per , represented as the environmental impactPopulation per unit of GDP GDP (Graedel andQuantity Allenby 2003). While Resources second term on the sidecan of be (4), the amount of resources consumed per opulation affluence terms inprovided, (2) quantity ofand goods andright-hand services iscombined, arepresenting measureyielding of resource intensity, the inverse of which his disaggregation allows one to focus on individual aspects of sustainability, it is important to quantity ofwhere goods and services provided, a measure of resource the2005). inverse of which “Quantity” refers to and the is quantity or level of goods and services provided in a society and s resource productivity (Dahlström Ekins 2005, Huppes andintensity, Ishikawa Resource Impact1972). ote that these terms are not independentResources (Ehrlich and Holdren Impact Quantity x represents is resource“Resources” productivity (Dahlström andefficiency, Ekins 2005, Huppes Ishikawa 2005). .quantity (3) from (1) is to the xamount of resources consumed. In (2), affluence term productivity, also knownrefers as resource-use theand of the goods and Resource services Quantity Resources productivity, also known as resource-use efficiency, represents quantity ofa goods services represented the product of GDP overis Population –thewhich represents capita income – and provided per amount ofasresource consumed. This in fact an eco-efficiency, ratioper ofand economic Many variants on the IPAT identity exist, variants that often either combine terms for added provided per ofload resource consumed. This isthe fact aservices ratio economic focusing on amount resource consumption, as2005). compared toin environmental impact, can of beprovided further per unit of Quantity over GDP – which represents quantity of goods and(3) value to environmental (Ehrenfeld Thus, (4) canan beeco-efficiency, rewritten as Resources mplicity, or further disaggregate termsx for added resolution. In discussing the role of efficiency Resources Quantity . (4) value to environmental (Ehrenfeld 2005). can be rewritten mplified toincome. Theload technology term from Thus, (1) is(4) represented in (2) as the product of Resources over Quantity mprovements in reducing resource consumption, the 1 basic IPAT identity shown in (1) can be Quantity – whichQuantity represents – and (5) Resources x the resource intensity of ,the goods and services provided urther disaggregated to, 1 of resources Resource Productivi ty defined above, the left side of (4) represents the amount consumed, while the first , (5) Impact over Resources – which intensity of resource 3consumption. Resources Quantity x represents the environmental Resource Productivi ty m on the right-hand side of (4) represents the quantity of goods and services provided. The It can be easily shown that of the IPAT identity, including or GDPother variants Quantity Resources Impactthe Kaya Identity and the , per (2) Population x x amount of resources x condImpact term on the right-handx side of (4), representing the consumed or ImPACT Identity, are in fact contained within (2) (Yamaji et al. 1991, Waggoner and Ausubel Population GDP Quantity Resources 1 of resource intensity, the inverse of which antity of goodsResources and servicesQuantity provided,x is a measure 2002). . (6) 1 goods Eco efficiency where “Quantity” refers to the quantity or level of and services provided in a society and resource productivity (Dahlström and Ekins 2005, Huppes and Ishikawa 2005). Resource Resources Quantity x (6) Eco efficiency . Resources”also refers to theasamount of resources consumed. In the (2),quantity the affluence term (1) is oductivity, known resource-use efficiency, represents of goods andfrom services onin the rolefor of efficiency technology-based solutions in reducing resource consumption, the From (6) itInisfocusing clear that order improvements to successfully reduce resource epresented as the product of GDP over Population which represents per acapita – and ovided per amount of resource consumed. This is in–fact an eco-efficiency, ratio income of economic

Carros USA

FIGURE 9: Motor Vehicle Travel (Q) and the Efficiency of Motor Vehicle Travel (e) (US) g 5000

4000 6

Efficiency

5

3000

4

2000

3

Quantity 2 1000 1

0 1930

0 1940

1950

1960

1970

Year

1980

1990

2000

2010

(billion vehicle-kilometers of motor vehicle travel)

7

Q

e

(vehicle-kilometers of motor vehicle travel per liter of fuel consumed)

8

(bil

(bil

6

20

4

2

0

0

1950

1960

1970

1980

1990

2000

1950

2010

Year

FIGURE A9: Resources Consumed (R) in Motor Vehicle Travel (US data) g

700

500

600

(billion kWh of electricity consumed)

500

400

300

R

R

(billion liters of fuel consumed)

400

300

200

200

100 100

0 1930

0 1940

1950

1960

1970

Year

1980

1990

2000

2010

195

FIGURE 17: Historical Motor Fuel Prices and Corporate Average Fuel Economy (CAFE) Standards g

Q/Q

1960-1969 4%

1936-2005 1980-1989

Average Annual

1970-1979 3%

1990-1999 2%

2000-2006

1%

14

CAFE Standards

80

12

70 10 60

8

Fuel Prices

50

40

6

30 4 20 2 10

(kilometers per liter)

5%

(2007 cents per liter)

1940-1949 1950-1959

90

Average US Retail Price for Regular Motor Fuel

6%

US Corporate Average Fuel Economy Standards

FIGURE 16: Average Annual Q/Q versus Average Annual e/e for Motor Vehicle Travel (US data) g

0% -1.0%

-0.5%

0.0%

0.5%

Average Annual

1.0%

e/e

1.5%

2.0%

2.5%

0 1940

0 1950

1960

1970

1980

1990

2000

2010

Year

Over the almost seven decades shown in Table 5 and Figure 16, the average annual change in efficiency for motor vehicle travel has varied considerably. From the 1940s through the 1960s, efficiency declined, as motor vehicles became larger and more powerful.20 In the 1970s and early

Table 5 shows a decade-by-decade breakdown of average annual changes in efficiency and

average annual changes in quantity for motor vehicle travel. Like passenger air travel, motor

vehicle travel has made strong movements towards the line of constant resource consumption, yet has never realized a period in which (7) was satisfied.

Activity Motor Vehicle Travel

Time Period 1940-2006 1940-1949 1950-1959 1960-1969 1970-1979 1980-1989 1990-1999 2000-2006

Average Annual

Average Annual

0.3%

3.8%

-0.5% -0.5% -0.3% 0.4% 2.4% 0.5% 0.5%

5.3% 5.2% 4.3% 3.8% 3.2% 2.5% 1.6%

Table 5: Average annual e/e and average annual Q/Q for motor vehicle travel on a decade-by-decade basis. In this activity, there are no decades in which average annual e/e outpaced average annual Q/Q.

Figure 16 plots the decade-by-decade data from Table 5. Again, the dark diagonal line in Figure

2

Figure 1 Relationship of affluence (per capita income) to various environmental impacts. Sources: Hosier (1996) from Shafik and Bandyopadhyay, background paper; World Bank data.

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