Eco-audits and Tools

Eco-audits and Tools

Eco-audit

Fast initial assessment

Look for “hot spots” with greatest impact

material, manufacture, transport, use, disposal

Often one phase contains 80% of impact

Eco-audit

Main purpose is COMPARISON

This allows alternate designs to be investigated

Inputs to an Eco-Audit

Bill of materials

Process Choice

Transport Requirements

Duty Cycle

Disposal Route

Additional inputs

Data for embodied energies, process energies, recycle energies, carbon intensities

Use this data to match with first set of user inputs

Outputs

energy and/or carbon footprint of each phase of life

bar chart or table, as desired.

USER INTERFACE•Bill of materials•Shaping processes•Transport Needs•Duty Cycle•Disposal Route

LOOKUP TABLES•Embodied energy/CO2

•Process energy /CO2

•Transport energy /CO2

•Conversion efficiencies

TABULAR DATA•Life-phase energy•Data used•Calculation steps•Component breakdown•...

ECO-AUDIT TOOL

Bottled Water - example1 liter PET bottle with PP cap

bottle weighs 40 grams

cap weighs 1 gram

Both are molded and filled with water in France.

Filled bottles transported to London (550 km in 14 ton truck)

Bottles refrigerated for 2 days (average) before being served at restaurant

“Green” restaurant - 100% recycling.

Let’s use 100 bottles for our basis of study. This uses 1 cubic meter of refrigeration.

Bottled water BOM & Mfg.

ComponentMateria

lProcess

Mass (kg)

Matl Energy (MJ/kg)

Matl CO2 (kg/kg)

Proc Energy (MJ/kg)

Proc CO2 (kg/kg)

Bottle (100) PET Molded 4 84 2.35 6.8 0.79

Cap (100) PP Molded 0.1 95 2.7 8.6 0.27

Dead weight (water)

Water -- 100 -- -- -- --

TOTALS 104.1 345.5 9.67 28.06 3.19

Bottled water - transport

Traveling 550 km; and 100 bottles weight 104.1 kg

14 ton truck uses 0.9 MJ/ton-km

0.9 * 550* 104.1/1000 = 51.5 MJ

Bottled water - use

Bottles are refrigerated for an average of 2 days.

We can find that energy efficient refrigerators use 10.5 MJ/m3/day (and 13.5 MJ/m3/day for freezing)

100 bottles use up 1 cubic meter of space, so

21 MJ for 2 days of refrigeration

Electrical refrigerator, so must divide by efficiency (36%) -> 21/0.36 = 58.33 MJ

Bottled water - disposalIn general, we have 5 options:

Landfill

Incineration

Recycling

Re-engineer

Re-use

Bottled water - disposalOur restaurant has excellent recycling. Recycling actually contributes negative energy/carbon to the calculations.

We get 35 MJ/kg back from PET recycling, and save 0.98 kg/kg CO2.

We get 40 MJ/kg from PP and 1.15 kg/kg CO2.

4 kg of PET and 0.1 kg of PP -> 4*35+0.1*40

-144 MJ from recycling.

Summary

Step Energy (MJ) CO2 (kg)

Materials 345.5 9.67

Manufacturing 28.06 3.19

Transportation 51.5 6.66

Usage 58.33 3.8

Disposal -144 -4.03

Totals 339.39 17.59

Bottle - Energy

Bottle - Carbon

Energy breakdown

Carbon Breakdown

Case Study:Electric tea kettle

2 kW kettle

Made in SE Asia,

transport to Europe (12,000 km)

boils 1 liter in 2 minutes,

used 2x per day, 300 days/year

lasts for 3 years

sent to landfill at end

Bill of MaterialsComponent Material Process

Mass (kg)

Material Energy (MJ/kg)

Total Material

Energy (MJ)

Process Energy (MJ/kg)

Total Process

Energy (MJ)

Kettle body PP Molding 0.86 94 80.84 8.6 7.396

Heating element

Ni-CrDeformatio

n0.026 130 3.38 2.6 0.0676

Casing/heater StainlessDeformatio

n0.09 81 7.29 3.4 0.306

Thermostat Ni alloyDeformatio

n0.02 72 1.44 2.1 0.042

Internal insulation Alumina Powder 0.03 52 1.56 27 0.81

Cable sheath (1m) Nat. Rubber Molding 0.06 66 3.96 7.6 0.456

Cable core (1m)

CuDeformatio

n0.015 71 1.065 2 0.03

Plug body Phenolic Molding 0.037 90 3.33 13 0.481

Plug pins BrassDeformatio

n0.03 72 2.16 2.3 0.069

Packaging, padding Foam Molding 0.015 110 1.65 11 0.165

Packaging (box)

CardboardConstructio

n0.13 28 3.64 0.5 0.065

Other small Proxy: PCProxy:

molding0.04 110 4.4 11 0.44

Other phasesTransport: Air freight (8.3 MJ/ton-km)

8.3 * 12,000 * 1.35/1000 = 134.5 MJ

Usage: 3 years, 300 days/year, 3 minutes per day, twice per day

90 hours * 2kW = 180 kWhr = 648 MJ

Electric, so divide by efficiency to get actual usage (UK has 40% efficiency)

648/0.40 = 1,620 MJ

Land fill - 0.2 MJ

Overall

Tea Kettle

What is best choice of action?

Car Bumpers

Bumpers provide energy absorption for passengers. Early bumpers were steel with chrome plating -- they have changed over the years, now typically plastic coatings.

Let’s compare a steel bumper to an aluminum one (underlying structure - not exterior skin).

Bumpers

Steel - 35 MJ/kg

Aluminum - 210 MJ/kg

BUT - we use less weight of aluminum for the same performance

Steel - 14 kg

Aluminum - 10 kg

Bumpers

The car has to move the bumper around when it moves. (F=ma). Gasoline powered cars use about 2.06 MJ/ton-km to move things.

If the car drives 25,000 km per year and lasts 10 years then we have 250,000 km. Multiply by the weight of the bumper and we get the energy of usage.

Bumpers

MaterialMass (kg)

Material Energy (MJ/kg)

Total Material Energy

(MJ)

Processing Energy (MJ/kg)

Total Processing Energy

(MJ)

Use Energy (MJ/ton-

km)

Total Use

Energy (MJ)

Low alloy steel

14 35 490 2.6 36.4 2.06 7,210

Aluminum

10 210 2100 2.6 26 2.06 5,150

Bumpers

Bumpers

The benefit to Al bumpers came primarily from the usage - the miles driven.

What if we assumed a different number of miles per year?

Or a different number of years that the car is kept?

The embodied energy is a combination of a fixed amount (material + manufacture) and a variable amount (usage - based on miles).

Family Car -use vs materials

Argonne National Labs has a model (GREET) to evaluate energy and emissions for automobiles.

They looked at many cars, but let’s look at a typical conventional ICE car compared to a lightweight ICE car.

The light weight car weighs 39% less than the traditional.

Material Conventional (kg)

Lightweight (kg)

Material Energy (MJ/kg)

Conventional

energy (MJ)

Lightweight Energy

(MJ)

Carbon steel 839 254 32 26,848 8,128

Stainless 0.0 5.8 81 - 470

Cast iron 151 31 17 2,567 527

Wrought Al (10% recycled)

30 53 200 6,000 10,600

Cast Al (35% recycled) 64 118 149 9,536 17,582

Cu/Brass 26 45 72 1,872 3,240

Mg 0.3 3.3 380 114 1,254

Glass 39 33 15 585 495

TP Plastics 94 65 80 7,520 5,200

TS plastics 55 41 88 4,840 3,608

Rubber 33 17 110 3,630 1,870

CFRP 0 134 273 - 36,582

GFRP 0 20 110 - 2,200

Pt (catalyst) 0.007 0.003 11,700 82 35

Electronics 0.27 0.167 3,000 810 501

Others 26 18 110 2,860 1,980

TOTALS 1,361 83667,26

494,27

2

Lightweight

So it is worse for the environment to make a lightweight car.

But, as we know transportation energy is significant. We should use less energy driving a lighter weight car.

Conventional gasoline cars use 2.06 MJ/ton/km

So the transportation energy will be:2.06 * mass * km driven

Usage

If we assume 15,000 mi/year and the car is kept for 5 years, then we can compare use energy:

It’s not even close for 5 years - these are reported in GJ (1,000 MJ)!

Conventional

Lightweight

336 GJ 207 GJ

Payback

Let’s consider a 2 kW wind turbine.

We can do the calculations of materials, manufacturing, transportation and usage based on a detailed description of the product.

Usage energy will be maintenance for one year.

Wind TurbinePhase Energy (MJ) CO2 (kg)

Material 18,000,000 1,300,000

Manufacture 1,200,000 97,000

Transport 280,000 20,000

Use (maint.) 190,000 14,000

TOTALS 19,670,000 1,431,000

Wind Turbine

The turbine is rated at 2MW.

That means at optimum performance it generates 2MW (wind blowing at speed). Let’s say it only gets 1/4 of that as a realistic estimate.

So we have 0.5 MW * 365.24 days * 24 hrs/day = 4,383 MW-hrs = 15,779,000 MJ in one year

ROIWe invested 19.7 TJ in making and installing and maintaining the turbine.

We get back 15.8 TJ each year.

19.7/15.8 = 1.25

So it takes 1.25 years (15 months) to get back the invested energy.

It is rated for 25 years, so we get back 20 times the invested energy.

But, it takes about 2,000 of these to replace a single coal plant

Exercise

1,700 W steam iron.

Weighs 1.3 kg

Heats up on full power for 4 minutes then used for 20 minutes on half power.

5 year life, after which it hits the landfill.

Component Mass Material Process

Body 0.15 PP Molded

Heater 0.03 Nichrome Drawn

Base 0.80 Stainless Cast

Cable sheath 0.18 PU Molded

Cable core 0.05 Copper Drawn

Plug body 0.037 Phenolic Molded

Plug pins 0.03 Brass Rolled

Bill of Materials