Eco Audit White Paper. - Granta Design

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Figure 12. The energy and carbon bar-charts generated by the Eco Audit Tool for the jug kettle.Family car—comparing material embodiedenergy with use energyIn this example, we use the Eco Audit Tool tocompare material embodied energy with useenergy. Table 5 lists one automaker’ssummary of the material content of a midsizedfamily car (Figure 13). There is enoughinformation here to allow a rough comparisonof embodied energy with use energy using theEco Audit Tool. We ignore manufacture andtransport, focusing only on material and use.Material proxies for the vague materialdescriptions are given in brackets.A plausible use-phase scenario is that of aproduct life of 10 years, driving 25,000 km(15,000 miles) per year, using gasoline power.Table 5. Material content of an 1800 kg family car.Material contentSteel (Low alloy steel) 850Aluminum (Cast aluminum alloy) 438Thermoplastic polymers (PU, PVC) 148Thermosetting polymers (Polyester) 93Elastomers (Butyl rubber) 40Glass (Borosilicate glass) 40Other metals (Copper) 61Textiles (Polyester) 47Mass (kg)The bar chart of Figure 14 shows thecomparison, plotting the data in the tablebelow the figure (energies converted to GJ).The input data are of the most approximatenature, but it would take very largediscrepancies to change the conclusion: theenergy consumed in the use phase (here84%) greatly exceeds that embodied in thematerials of the vehicle.Figure 13. A mid size family car weighting 1800kgFigure 14. Eco Audit Tool output for the car detailed inTable 5, comparing embodied energy and use energybased on a life-distance of 250,000 km.Phase Energy (GJ) Energy (%)Material 162 16Use 884 84Total 1046 100The CES EduPack Eco Audit Tool 12 © 2012, Granta Design
Figure 15. The comparison of the energy audits of a steel and an aluminum fender for a family car.Auto bumpers—exploring substitutionThe bumpers of a car are heavy; making themlighter can save fuel. Here we explore thereplacement of a steel bumper with one ofequal performance made from aluminum(Figure 16). The steel bumper weighs 14 kg;the aluminum substitute weighs 10, areduction in weight of 28%. But the embodiedenergy of aluminum is much higher than thatof steel. Is there a net saving?The bar charts on the left of Figure 15(overleaf) compare the material and useenergy, assuming the use of virgin materialand that the bumper is mounted on agasoline-powered family car with a life“mileage” of 250,000 km (150,000 miles). Thesubstitution results in a large increase inmaterial energy and a drop in use energy. Thetwo left-hand columns of table 6 below list thetotals: the aluminum substitute wins (it has alower total) but not by much—the break-evencomes at about 200,000 km. And it costsmore.But this is not quite fair. A product like thiswould, if possible, incorporate recycled as wellas virgin material. Clicking the box for “Includerecycle fraction” in the tool recalculates thematerial energies using the recycle content incurrent supply with the recycle energy for thisfraction 4 . The columns of the table list the newvalues. The aluminum bumper loses abouthalf of its embodied energy. The steel bumperloses a little too, but not as much. The energysaving at a life of 250,000 km is considerablylarger, and the break-even (found by runningthe tool for progressively shorter mileage untilthe total energy for aluminum and steelbecome equal) is below 100,000 km.Table 6. Material energies and use energies for steeland aluminum bumpers.SteelVirgin materialEnergy(MJ)Fraction(%)With recyclecontentEnergy(MJ)Fraction(%)Material: steel 446 6 314 4(14 kg)Use:7210 94 7210 96250,000 kmTotal 7691 100 7567 100AluminumMaterial: 2088 29 1063 17aluminum(10 kg)Use:5150 71 5150 83250,000 kmTotal 7275 100 6250 1004 Caution is needed here: the recycle fraction ofaluminum in current supply is 55%, but not all alloygrades can accept as much recycled material as this.Figure 16. An automobile bumper.The CES EduPack Eco Audit Tool 13 © 2012, Granta Design
Page 2 and 3: Contents1. Introduction ...........
Page 4 and 5: Figure 2.Despite the formalism that
Page 6 and 7: 60% or more of the energy—often m
Page 8 and 9: combustion, not an option for steel
Page 10 and 11: Figure 8. The 1 st -life energy and
Page 12 and 13: ecycle energy and recycle fraction
Page 16 and 17: A portable space heaterThe space he
Page 18 and 19: 6. Summary and conclusionsEco aware
Page 20 and 21: Eco Audit ReportProduct NameBottled
Page 22 and 23: Use:Energy and CO2 SummaryStatic mo
Page 24: Dead weight (100 litres of water) 1

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