Coelho Brito

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Influence of construction and demolition waste management on the environmentalimpact of buildings

Andr Coelho, Jorge de Brito

Department of Civil Engineering and Architecture, Instituto Superior Tcnico, Universidade Tcnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal

a r t i c l e i n f o

Article history:

Received 1 February 2011Accepted 24 November 2011

Available online 17 December 2011

Keywords:

Construction and demolition waste

Life Cycle AnalysisWaste management options

a b s t r a c t

The purpose of this study is to quantify comparable environmental impacts within a Life Cycle Analysis(LCA) perspective, for buildings in which the first (Materials) and last (End of Life) life cycle stages are

adjusted to several waste/material management options. Unlike most LCAs, the approach is top-downrather than bottom-up, which usually involves large amounts of data and the use of specific software

applications. This approach is considered appropriate for a limited but expedient LCA designed tocompare the environmental impacts of different life cycle options.

Present results, based on real buildings measurements and demolition contractor activities, show that

shallow, superficial, selective demolition may not result in reduced environmental impacts. Calculations

actually show an increase (generally less than 5%) in most impact categories for the Materials and End ofLife stages because of extra transportation needs. However, core material separation in demolition oper-ations and its recycling and/or reuse does bring environmental benefits. A reduction of around 77% has

been estimated in the climate change impact category, 57% in acidification potential and 81% in thesummer smog impact (for the life cycle stages referred).

2011 Elsevier Ltd. All rights reserved.

1. Introduction

The work described here stems from a wider study which anal-yses selective and traditional demolition practices in technical andeconomic terms. It is also linked with construction and demolitionwaste (CDW) generation (Coelho and de Brito, 2010a) and distribu-tion quantification in Portugal (Coelho and de Brito, 2010b).

The work as a whole is an analysis of the technical, economicand environmental viability of a large-scale fully-developed CDWrecycling plant in Portugal. It is a tentative comparative analysisof the environmental impacts of different options in CDW manage-

ment at the end-of-life stage of a buildings life cycle. The purposeis to quickly quantify the environmental effects of applying decon-

struction techniques and recycling options by incorporating theseprocesses into the environmental impact of producing materials

and transporting them to site (closing the cycle).The environmental impact of a buildings life cycle has been

researched widely in recent years by various authors (Junnila,2004b; Pinto, 2008; Balazs et al., 2001; Pascualino et al., 2008;

Blengini, 2006, 2008; Xiaodong et al., 2010; Krogmann et al.,2009; Schuer et al., 2003). Building projects not intended for re-search purposes but which include LCA approaches in the designphase are very few, however (Hes, 1998, 2001a,b). One of the major

barriers to this is the reluctance to move design time lines toaccommodate the extra time needed for an LCA, even though thismight offer clear financial and environmental benefits (Hes,

2001a).Most of these studies have adopted a bottom-up approach

using databases with embodied energy and emissions of severalconstruction materials (Gonzlez and Navarro, 2005; Peuportier,

2001; Junnila, 2004b). These environmental impact analyses ofbuildings rely heavily on drawings, specifications and/or data fromthe actual buildings.

This approach is generally adequate when information on

building quantities (bill of quantities), final drawings and appropri-ate construction products environmental impact databases is

available, bearing in mind the location of the buildings in relationto building materials suppliers and waste management operators.

When these conditions are met, with high levels of transparency(clear definition of system boundaries, clear allocation methods,no mixing of data from different sources, etc.), along with coherentend-of-life and recycling considerations, present-day LCA software

tools will provide reasonably accurate environmental impactresults, reproducible to about 10% (Peuportier & Putzeys, 2005).Neglecting some or all of these requirements will naturally makeLCA unreliable, or at least questionable.

This is calledthe process-based LCAand it enables very specificanalysis, although it requires detailed information, which makes ittime consuming and costly. In fact, the longer the supply chain

0956-053X/$ - see front matter 2011 Elsevier Ltd. All rights reserved.doi:10.1016/j.wasman.2011.11.011

Corresponding author. Tel.: +351 218443659; fax: +351 218443071.

E-mail address:[email protected](J. de Brito).

Waste Management 32 (2012) 532541

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This option has naturally meant that only a scenario compari-son has been possible, and not an absolute environmental impact

value ranking. Calculations have therefore been made in the origi-nal environmental impact parameter units (kg CO2eq/m

2, kgSO2eq/m

2 and so on) but the resulting values are not used strictlyto obtain environmental impact figures, in those same units, for

buildings in other contexts.

However, considering all data retrieved from real buildings anddemolition operations, the purpose is to give a representative im-age of Portugal as a whole, as far as End-of-Life and Materials life

cycle stages of existing buildings over 30 years old, chosen usingthe criteria established in (Coelho and de Brito, 2010a) areconcerned.

InJunnila (2004a)a detailed environmental LCA was performed

for all life cycle stages in the buildings under analysis, althoughscenarios involving deconstruction were not included. Among theresulting conclusions were:

Similar results are to be expected in housing and services build-ings, from a life cycle environmental impact point of view.

Different services buildings, designed by different teams, built

by different contractors and occupied by different organiza-tions, show a similar pattern for each life cycle stage proportionwithin the buildings global environmental impact.

The end-of-life stage impact is generally below 3%, which is

small compared with the global impact in all the analysed cat-egories. But the differences found in the inclusion of recycledmaterials can lead to significant changes in the summer smogand heavy metals categories (38% and 20% respectively).

Furthermore, Junnilas work used case studies chosen in a ratio-nale of replication to obtain similar results for buildings with sig-nificantly different characteristics. This means that average

values (here taken from Junnilas case studies) can be used to esti-mate the environmental impact distribution over the life cycle of ageneralized housing or office building to compare scenarios which

may influence the environmental impacts of one or more life cyclestages.

For this comparison, some LCAs use weighting methodologies toreach single score indexes (Blengini et al., 2010; Mithraratne andVale, 2004), which may help decision-makers to read and easily

interpret LCA results. However, the comparison presented in thisstudy does not attribute different relative importance factors tothe impact categories, which were chosen according to Junnila(2004a).

The impact categories are: climate change (kg CO2eq/m2), acid-

ification (kg SO2eq/m2); summer smog (kg C2H4eq/m

2); nitrifica-tion (kg PO4eq/m

2); and heavy metals (kg Pbeq/m2). They result

from the emission of a wide array of substances, all of which areknown to be important pollutants. Natural resources extraction

and waste generation have not been considered explicitly, but itnaturally follows that waste management practices involving the

recycling and/or reuse of materials/components lead to less extrac-tion of raw materials and less waste generation, since these prac-tices limit new raw materials use.

Importance factors were not used in relation to impact catego-

ries because of the subjectivity and controversy implied (Craighill& Powell, 1999).This aspect is aggravated by the many variablesat stake which may give rise to the higher or lower relative impor-tance of certain factors over others: the ecological sensitivity of

certain regions, human concerns about that region, stakeholdersinterests/opinions, time constraints, economic reasons, amongothers.

By not applying these factors this study attributes equal impor-

tance to all impact categories under consideration.

A snapshot of the global impacts calculated in (Junnila, 2004a)for each building is presented inTable 1. Averaging the life cycle

impact proportions for the buildings referred to inTable 1(also ta-ken directly from Junnilas work) will provide the above general-ized/reference buildings life cycle stage average impacts, as usedhere, as both percentage proportions and environmental impact

units (Table 2).

As an example, the climate change impact factor of 271 kgCO2eq/m2 for the generalized building Materials stage was ob-

tained as the result of a 7.3% share of the 3700 kg CO2eq/m2 global

average climate change impact presented in Table 1. All otherTable 2figures were obtained in the same way.

The average life-cycle shares are calculated from (Junnila,2004a), from the buildings A, B and C individual shares. Only the

Materials and End-of-Life cycle stages were considered in the anal-ysis, mainly to eliminate differences in impacts that may occur inthe operational phase of buildings located in Finland and Portugal.

These differences in impacts may appear for several reasons,such as climatic differences, building features and living habits.However, results including the complete life cycle (even thoughwith basic data sourced from Finnish LCA case study) are also

shown so as to give an idea of the possible impact of the proposedMaterials and End-of-Life scenarios when all life cycle stages areaccounted for (Table 12).

Having characterized the generalized reference building in

terms of environmental impacts, scenarios can now be defined.Five cases were considered, depending on end-of-life managementactivities: traditional demolition with landfill or recycling anddeconstruction, the material quantities landfilled, and different op-

tions for incorporating recycled or reused materials in new con-struction. These scenarios are summarized inTable 3.

Demolition/end-of-life environmental consequences are mainlyconditioned by transportation, even though the impacts of direct

demolition activities and materials transportation have both beenconsidered in the specified scenarios. In fact, according toBlengini(2006), demolition environmental consequences only account for

7% of total demolition/end-of-life stage activities, the rest arisesfrom transportation.

Even though Blenginis figure applies only to energy consump-tion, it is here assumed valid for other impact categories since ithas been demonstrated that around 80% of all emissions into the

atmosphere derive from energy production (International EnergyAgency, 2005).

Different demolition procedures, from traditional demolition tototal piece-by-piece deconstruction, will naturally lead to different

energy consumption and waste generation patterns from the activ-ities themselves, but given the relatively small importance of thissub-stage in life cycle environmental impacts, the differences were

ignored.The demolition activity impacts for scenario 1 were therefore

considered constant for all scenarios. Transportation impacts, withmuch higher relative importance, were specifically considered for

each scenario, depending on recycling and reuse percentages.Fifteen demolition cases were analysed to establish a relation-

ship between the percentage of materials sent for recycling andtransportation distance, with information supplied by a specialized

contractor. This data is given by a sample of this contractors nor-mal activity, which involves selective demolition, demolition, on-site separation and transport.

Demolished buildings comprise houses, schools, office buildings

and commercial sites. Manual labour is generally used for theselective demolition of accessible covering elements such as woodfloors, doors, windows, cabinets and ceilings. The core dense struc-tural materials, i.e. bricks, stone and concrete, plus various at-

tached materials such as structural wood frames, fixed sanitary

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Table 1

Global environmental impacts obtained by (Junnila, 2004a), by impact category and by building analyzed.

Impact category Unit Building A Building B Building C Average

Climate change kg CO2eq/m2 4700 3100 3300 3700

Acidification kg SO2eq/m2 15.1 8.5 9.8 11.1

Summer smog kg C2H4eq/m2 2.1 1.6 2.3 2.00

Nitrification kg PO4eq/m2 1.6 1 1.3 1.30

Heavy metals kg Pbeq/m2 0.0021 0.001 0.001 0.0014

Notes:(1) All life cycle impact phases are included, from Materials (extraction, production and transport) to End-of-Life (demolition and waste management operations); (2)

Life span considered: 50 years; (3) Main climate conditions: Finland.

Table 2

Environmental impacts, by category and life cycle stage, for the average reference building.

Impact category Unit Life cycle stages reference case generalized building

Materials Demolition/end-of-life Total

Quantity % Quantity % Quantity %

Climate change kg CO2eq/m2 271 7.3 37.0 1.0 308 8.3

Acidification kg SO2eq/m2 1.26 11.3 0.37 3.3 1.63 14.7

Summer smog kg C2H4eq/m2 0.51 25.3 0.05 2.7 0.56 28.0

Nitrification kg PO4eq/m2

0.13 10.0 0.06 4.7 0.19 14.7Heavy metals kg Pbeq/m2 0.00057 42.0 0.00003 2.3 0.0006 44.3

Note:Percentages of total life-cycle environmental impact, for each impact category.

Table 3

End-of-life and materials life cycle stages scenario.

Scenario Short description Notes/observations/assumptions

1 Complete demolition of building and transport of materials to

landfill

1. Environmental impacts are considered equal to those of the generalized reference

building.a However, no extra transportation distance was added (due to recycling), since

this scenario does not involve recycling

2 Selective demolition of non-structural elements (soft

stripping), followed by complete demolition of all other

materials

1. Elements removed during soft stripping: mechanically fixed coverings, water supply

and waste water drainage pipes, electrical cables, doors, windows. Destination:

recycling2. Elements destroyed during traditional demolition: masonry walls, structural support

elements (concrete, steel and wood). Destination: landfill.

3. Demolition (not transport) environmental impacts are considered equal to those

incurred by the generalized reference building

4. Environmental impacts due to transportation of materials for recycling are calculated

from scenario 1 basis (using the transportation distance enlargement factor)

5. Extra environmental impacts due to recycling operations are accounted for as a per-

centage of the original (scenario 1) impacts with the materials supply (as shown in

Table 9)

6. Input data from housing buildings measured in (Coelho and de Brito 2010a)3 Deconstruction of non-structural elements, followed by

complete demolition of all other materials

1. Demolished structural elements are sent to recycling, whenever possible (depends on

each real case situation)

2. Demolition (not transport) environmental impacts are considered equal to those

incurred for the generalized reference building

3. Total recycled aggregate quantity included in new construction is limited to 10% (only

general fills) of the total CDW generated from deconstruction and demolition of the

building parts

4. Input data from services buildings measured in (Coelho and de Brito 2010a), along with12 other real cases of demolition operations performed by a contractor

4 Full deconstruction, sending all materials to recycling 1. Hazardous materials are landfilled (in a controlled way)

2. Recovered masonry and concrete are recycled and used to produce new masonry bricks

and concrete

3. All other materials are recycled and used in new construction materials4. The same input data as in scenario 2 is used

5 Full deconstruction, sending all materials which cannot be

reused to recycling

1. Hazardous materials are landfilled (in a controlled way)

2. Recovery for reuse purposes do not cause significant environmental impacts (extra

impacts due to recovering activities are ignored), when compared to recycling impacts

3. Extra transportation needed for material reuse refers exclusively to these materials (not

mixed with those being recycled), assuming an average distance equal to where the

landfill is located

4. Of all recovered materials aimed for reuse, only 50% is actually reusable (the rest is

recycled)

5. The same input data as in scenario 2 is used

a

In the generalized reference building no allocation of emissions was assumed for the future products that are made from recycled building materials. This means that noreduction in the environmental impacts of the materials life cycle stage was considered. This derives directly from (Junnila, 2004a).

A. Coelho, J. de Brito / Waste Management 32 (2012) 532541 535


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elements, water and drainage pipes and roof shingles are demol-ished in a more traditional fashion, using mechanical equipment

(Coelho and de Brito, 2011).Transportation distances were calculated for each case and

material managed, given its destination. These destinations arenaturally selected by the contractor to be as close as possible to

the worksite, for optimization and cost savings; for our contractor

and for jobs in the Lisbon area, the distance will generally be lessthan 50 km).However, and especially when sending materials to be recycled,

local operators are not always available (e.g.: recycling operatorsfor wood, glass and some oil contaminated materials), which canimply transportation distances over 5 times more than the rest ofthe materials average transportation distance.

A sample table is shown (Table 4) with the quantities, destina-tions and transported distance related to a certain demolition job.A total transportation distance was derived from this, to be com-

pared with a reference (hypothetical) situation where all materialswould be sent to landfill. In the calculations, transported volumesare calculated from loose material densities, listed in Table 6.

Transportation distance in the latter case depends heavily on

the selected waste operator, and so its choice has been based onthese criteria:

1. The waste operator must be located within 100 km of the site,

or be the nearest waste operator otherwise.2. The waste operator must be a generalist (i.e. accepting several

types of CDW).3. After points 1 and 2 are considered, the waste operator chosen

will be the one to which, in reality, a greater distance was cov-ered (measured by the sum of all distances listed to each oper-ator which check criteria 1 and 2).

Criterion item 1 is used to give preference to close range generaloperator locations, which are generally (but not always) within100 km. Criterion item 2 excludes specialized operators (e.g.: glass

or wood only recyclers), which cannot receive loads of co-mingledCDW materials. The final criterion item selects the operator whichin practice, for each job and after the selection implied by items 1and 2, has been preferred by the contractor as far as total transportdistance is concerned.

Table 5was built up by applying these criteria and the methodused to compileTable 4to all remaining real demolition cases. Anaverage transportation magnification factor (Mt) could then be de-rived, along with an averaged percentage of recycled material that

could be used in new construction. Mtis calculated by dividing thetotal transportation distance for each real example (with its recy-cling options) by the distance calculated for all materials being

sent to landfill.Plotting the relationship Recycling % vs. Mtresults inFig. 1, from

which a quadratic function is fitted, with a good approximationfactor (R2 = 0.86). From this function it is now possible to estimate

Mt, for each scenario (using each recycling ratio as indicated inTa-ble 7), which will affect their environmental impacts considerably.

Demolition/end-of-life environmental impacts are then quanti-fied based on the generalized building impacts, shown in Table 2.

Table 8 presents these values, for each impact category and foreach scenario, using each Mt value as a proportion factor, derivedfrom the equation presented inFig. 1.

As these scenario impacts all derive from the generalized build-

ing impacts described above, which implies a 27% recycling rate(and a complementary 73% landfill rate), then obtaining transpor-tation impacts for scenario 1 involves dividing the generalizedbuilding transportation only impacts by Mt (scenario 1 implies

0% of materials sent to recycling), while for the other scenarios itwill mean multiplying by Mt.

Besides the direct impact of demolition activities and materialtransportation at the end-of-life stage, other environmental effects

must be considered which result from the recycling processesthemselves; these will depend on the amount sent for recycling,in each scenario. As for reuse, certainly some impacts are intrinsicto the activity (apart from transportation), e.g.: cutting wood,

cleaning masonry bricks, storing material.

This aspect has been ignored in this analysis since the effectsare generally weaker than those inherent to recycling activities(Craighill & Powell, 1999; Gao et al., 2001). These references deal

with energy consumption and the broad environmental impact ofreusing scenarios. However, the results reported in Craighill &Powell (1999) consider transportation and comprise an averageof several case studies, mostly related to mineral extraction and

road maintenance.In spite of this, the reuse scenario in that study leads to an aver-

age reduction of almost 70% in environmental impacts compared

with the scenario involving 50% landfill and 50% recycling. In(International Energy Agency, 2005) reusing activities have beenassumed to add no energy consumption, in a direct comparisonwith recycling activities.

Data fromBlengini (2008)was used to quantify the extra im-pacts caused by recycling. According to this study, certain net envi-ronmental benefit reductions may be expected from recyclingoperations despite some additional impacts resulting from the pro-

cesses used to recycle aggregate and steel products.An average of three environmental impact indicators was calcu-

lated for the extra impacts from recycling, resulting in 17% foraggregates and 39% for steel products. These extra impact percent-

ages mean that, whatever the environmental impact reductionbrought about by recycling, the final impact of the considered lifecycle stages including recycling will be 17% and 39% higher foraggregate and steel mass respectively.

Knowing the quantities of materials used for the measuredbuildings/demolition examples in the listed scenarios (Table 3),particularly the aggregate and metals generated, these percentages

are applied to give the overall extra environmental impact percent-ages presented inTable 9.

The direct reduction of environmental impacts in the materialslife cycle stage equals the percentage of recycled (plus reuse, ifany) material in a certain scenario, as summarized in Table 7. In

other words, a simple subtraction takes the first into account bydeducting the equivalent environmental impacts of the new mate-rials initially planned for each scenario, but considering that somematerial sent for recycling may not be used again in building

construction (factor u as described in the equations below).The resulting figure is then affected by the extra recycling oper-

ations impact percentages described above. For scenario 3, how-

ever, even though most of the materials are sent to landfill, itwas assumed that when aggregates can be recycled only 10% are

used in new construction. This was to account for some generalbulk fills, which are relatively common practice today.

As for reuse (only in scenario 5), only part can actually be re-used and the rest is sent for recycling. This part is considered tobe 50%, based on published data (Guy, 2000, 2005; Southworth,2009).

Environmental impact values for the materials life cycle stagewere therefore finally calculated using the following expressions:

Scenario 2 : IC2i IC1i 1

PC2r uC2=100

100

! 1

AC2

100

! 1

In which:IC2i environmental impact value, for category i, in sce-nario 2; IC1i environmental impact value, for category i, in scenario

1;PC2

r material percentage sent for recycling, in scenario 2;uC2

weighted average, over waste weight, of possible recycled material



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Table 4

Total transportation distance, with and without recycling options (one of 15 real examples).

EWL Code Name Weight

kg

Destination % of

total, in

weight

Waste

operator

Site distance,

km

Volume

m3

Number

of

journeys

Transportation

distance, km

Usa

con

prorecy

With recycling options

170107 Mixture of concrete 23020 Landfill 10.74 Citri 48 16 1 48

170201 Wood 97220 Recycling 45.38 Ecociclo 210 324 17 3570 Yes

170202 Glass 3680 Recycling 1.72 Vidrologic 234 11 1 234 Yes

170405 Iron and steel 10380 Recycling 4.84 Palmela

recycling

centre

46 12 1 46 Yes

170407 Mixed metals 14440 Recycling 6.74 16 1 46 Yes

170603 other insulation materials

containing dangerous

substances

7940 Landfill 3.71 Quimitcnica 37 611 32 1184

170604 Glass wool 8520 Landfill 3.98 Citri 48 655 34 1632170903 CDW with dangerous

substances

23440 Landfill 10.94 Quimitcnica 37 156 9 333

200101 Paper and cardboard 3200 Recycling 1.49 A.S Simes 27 32 2 54 Yes200301 Mixed municipal waste 17520 Landfill 8.18 Citri 48 117 7 336

200121 Fluorescent tubes and other

mercury-containing waste

130 Recycling 0.06 Ambicare 48 0 1 48 Yes

200136 Discarded electrical and

electronic equipment

920 Recycling 0.43 Ambitrena 48 6 1 48 No

200138 Wood 3840 Recycling 1.79 Ecociclo 210 13 1 210 Yes

EWL Code Name Weight

kg

Destination Waste

operator

Site distance,

km

Average

loose waste

density, kg/m3

Volume

m3Number

of

journeys

Transportation

distance, km

Without recycling options

170903 Construction anddemolition wastes

containing dangerous

substances

214.250 Landfill Citri 48 404 531 28 1344

Total transportationdistance, with

recycling options, km

7789

Total transportation

distance, without

recycling options, km

1344

Notes:The number of journeys is calculated using standard 19.3 m3 sized trucks; Volumes are calculated, from weights, using loose material density values shown inTable 6


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use in new construction; AC2 recycling operations averaged extra

environmental impact, in percentage.Eq. (1) applies to scenario 3, using a different percentage for

recycling materials and so a different value for Mt. As for scenario4, since all materials are considered to be incorporated into new

construction, the uC factor equals 100% and can be eliminated,and so Eq. (1) becomes:

IC4i IC1i 1

PC4r100

! 1

AC2

100

! 2

Finally, for scenario 5, which includes a certain amount of reusedmaterials, the equation is simply updated as follows:

IC5i IC1i 1

PC5r pC5r

100

! 1

AC2

100

! 3

In whichpC5r equals the reused material percentage, for scenario 5.

4. Results and conclusions

The results for each scenario are presented in Table 10. The

totals for each scenario make it possible to determine percentilevariations from scenario 1, representing a traditional approach of

landfilling all materials. Table 11 summarizes these variations,considering only the Materials and End of Life impact stages. Forgeneral perspective purposes only,Table 12shows the percentagevariations with regard to scenario 1, when all the life cycle stages

are accounted for.Table 10shows that the impacts share assigned to the Materials

phase is always over 75%, for any analysed impact category, in sce-narios 1 through 3. This is because, as replacement levels of input

materials is low in these scenarios


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sending more than 95% of the materials for recycling/reuse, signif-icant impact reductions are possible at the Materials stage. Impacts

resulting from this stage can even be lower than those comingfrom End-of-Life, assuming that these recycled materials are dulyreused in the construction of new buildings.

Table 10also shows that the highest total impact reductions oc-cur in the Heavy Metals (88%), Summer Smog (81%) and ClimateChange (77%) categories, when shifting from scenario 1 up to 5.These are the impact categories where the highest relative contri-butions of the Materials stage happen. So, when the latter under-

goes a sharp reduction due to inclusion of recycled/reusedmaterials in new construction, it affects mostly the highest con-tributors (in a proportional manner).

This global environmental impact comparison (based on a top

down LCA methodology) of building demolition scenarios withdifferent waste management approaches and recycled/reusedmaterials incorporation considerations in the materials life cycle

stage enables the following conclusions to be drawn:Soft-stripping, or the removal of non structural elements for

recycling, followed by a traditional demolition of all other materi-als and their removal to a landfill, will generally not imply any

environmental impact reduction in the impact categories studied.It may even slightly aggravate the environmental impact (scenario2 and some impact categories in scenario 3, although generally be-low 5%) because of longer transportation distances and because of

some extra recycling activity impacts. This is largely to do with themeans of transportation mostly used in the construction/demoli-tion industry: by road, with diesel trucks. The use of (net energysaving) biofuels, running electric vehicles and/or greater use of rail

transport could thus tip this environmental balance to the side ofsavings.

Medium to low material reuse percentage will not translate intoappreciable environmental impact reductions compared with the

equivalent recycled quantities (scenario 5 compared to scenario4). This is mainly because what really brings down environmental

y = -0,00054x2

+ 0,09360x + 1,45338R = 0,86588

0

1

2

3

4

5

6

7

8

0 20 40 60 80 100Averagetransportationmagnificationfactor(Mt)

Recycling %

Fig. 1. Relationship between the recycling percentage and Mt.

Table 7

Recycling and reuse weight percentages for the scenarios under consideration.

Scenario Recycling (+ reuse), %

1 02 1.9

3 7.9

4 96.35 96.3

Note:Only scenario 5 includes reuse.

Table

8

Dem

olition/end-o

f-lifeenvironmentalimpactsforallcategoriesandscenarios.

Impact

category

Un

its

Genera

liz

edbuil

ding

Tota

l

Genera

liz

edbu

ilding

demo

litionon

ly

Transportation

on

ly

Tota

l

Lan

dfill73%;

Rec

yc

ling

27%

Genera

liz

ed

bu

ilding

Scenario

1

Scenario

2

Scenario

3

Scenario

4

Scenario

5

Scenario

1

Scenario

2

Scenario

3

Scenario

4

Scenario

5

C

limate

change

kg

CO

2eq

/m2

37

2.6

2

34

.4

9.5

15

.9

20

.9

51

.8

51

.8

12

.1

18

.5

23

.5

54

.4

54

.5

A

cidification

kg

SO

2eq

/m2

0.3

7

0.0

3

0.3

4

0.1

0

0.1

6

0.2

1

0.5

2

0.5

2

0.1

2

0.1

9

0.2

4

0.5

5

0.5

5

Summersmog

kg

C2

H4

eq

/

m2

0.0

53

0.0

04

0.0

50

0.0

14

0.0

23

0.0

30

0.0

75

0.0

75

0.0

17

0.0

27

0.0

34

0.0

78

0.0

78

N

itri

fication

kg

PO

4eq

/m2

0.0

61

0.0

04

0.0

56

0.0

16

0.0

26

0.0

34

0.0

85

0.0

85

0.0

20

0.0

30

0.0

39

0.0

89

0.0

89

H

eavy

meta

ls

kg

Pbeq

/m2

3.1

9E

-05

2.2

6E

-06

2.9

6E

-05

8.2

0E

-06

0.0

0001

1.8

0E

-05

4.4

7E

-05

4.4

72E

-

05

1.0

5E

-05

1.6

0E

-05

2.0

3E

-05

4.6

9E

-05

4.6

9E

-05



9/10

impact is replacing raw materials with recycled and/or reused ele-ments, with very little being due to recycling or reuse. This is trueeven when considering that recycling entails more embodied im-pacts than reuse. The average reuse percentage calculated in the

present study is 25%, which is considered low but technicallyattainable, considering the typical buildings analysed (in the Portu-guese context). Greater impact reductions through reuse will re-quire much higher percentages of materials to be reused, which

could, in extremely favourable conditions, reach an average of50% as a theoretical maximum reusable material weight. Otherstudies have considered reuse percentages of 17% (Gao et al.,

2001) and as much as 100% (Craighill & Powell, 1999), resultingin a 11% lower energy consumption in the first case and a 68% aver-age environmental impact reduction in the latter (compared to anall-landfill standard options, concerning End-of-Life and Materialslife cycle stages). To reach the 50% level, however, for typical Por-

tuguese buildings over 30 years old, special care must be takenwith deconstruction. The careful extraction of wooden elements,masonry bricks and metal elements, for instance, cannot be doneby standard construction or demolition crews; experienced decon-

struction workers are needed who know exactly how to take thevaluable pieces apart and handle them with reuse in mind. Given

this reality it is currently better to direct policy efforts to increase

recycling and reinsert materials into the construction industry cy-cle than to make the extra effort to encourage materials reuse, ex-cept obvious examples such as clean, straight wooden girders, orwell-maintained sanitary equipment.

It is particularly important to try and reintroduce recycled or re-used materials into new construction, thereby helping to close thematerials cycle. This will help to reduce the summer smogand heavy metals impact categories, since these account for

Table 9

Extra environmental impact percentages due to recycling, for the selected scenarios.

Scenario Aggregates sent to

recycling/total

waste mass, %

Metals sent to

recycling/total

waste mass, %

Extra environmental

impact weighted

average, %

2 0.66 0.10 0.15

3 4.8 2.05 1.624 93.7 0.64 16.3

5 53.9 0.63 9.48

Table 10

Environmental impacts, by category and life cycle stage, for all scenarios.

Impact category Unit Materials Demolition/end-of-life Total

Life cycle stages scenario 1

Climate change kg CO2eq/m2 271 12.1 283

Acidification kg SO2eq/m2 1.26 0.12 1.38

Summer smog kg C2H4eq/m2 0.51 0.017 0.52

Nitrification kg PO4eq/m 0.13 0.02 0.15

Heavy metals kg Pbeq/m2 5.74E-04 1.05E-05 5.84E-04


Climate change kg CO2eq/m2 267 18.5 285






Climate change kg CO2

eq/m2 252 24.3 277Acidification kg SO2eq/m

2 1.17 0.24 1.42





Climate change kg CO2eq/m2 11.6 54.4 66.0






Climate change kg CO2eq/m2 10.9 54.5 65.3





Note:The environmental benefits of recycling and reuse have been accounted for in the Materials phase, as prevented impacts.

Table 11

Global environmental impact percentage differences between scenarios 2 through 5

and scenario 1 (Materials and Demolition/end-of-life stages).

Impact category Scenario

2 3 4 5

Climate change 0.57 2.34 76.7 76.9

Acidification 3.02 2.49 56.7 56.9Summer smog 0.06 3.35 80.9 81.1

Nitrification 5.45 7.28 36.8 37.0

Heavy metals 0.78 5.01 87.8 88.0

Table 12

Global environmental impact percentage differences between scenarios 2 through 5

and scenario 1 (all life cycle stages).

Impact category Scenario

2 3 4 5

Climate change 0.045 0.19 6.08 6.10

Acidification 0.39 0.32 7.30 7.33Summer smog 0.016 0.91 22.0 22.0

Nitrification 0.65 0.86 4.36 4.38

Heavy metals 0.34 2.20 38.5 38.6



10/10

considerable parts of the life cycle impact from the materials stage(25.3% and 42% respectively, for scenario 1), even though all other

categories will also see their impacts reduced.Even though climatic differences, building features and living

habits may differ between Portugal and Finland, which is wherethe basic data for this study was collected, the potential environ-

mental impact reduction scenarios studied with global life cycle

impacts are much lower than those observed in Table 11. Table12shows around 6% and 7% reductions in climate change and acid-ification related impacts for scenarios 4 and 5, but a figure of

almost 40% is reached for the Heavy Metals category.From a complete life cycle perspective, and in order to get any

obvious environmental impact reduction, especially in the climatechange and acidification categories, recycling will have to be raised

to above 90%, and efforts must be made to incorporate the result-ing materials into new construction. Recycling percentages of thisorder of magnitude can be achieved and have actually been ex-

ceeded in recent real demolitions (Bjerregaard et al., 2007; Kohler,2007a,b; Kohler & Davies, 2007).

Acknowledgements

Thanks are due to the FCT (Foundation for Science and Technol-ogy) for the postdoctoral research grant awarded to the first authorand to the ICIST IST research centre. Special thanks are due to

Brito Cardoso and Vera Teixeira, from Ambisider, RecuperaesAmbientais, SA.

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