Sustainability: What Does It Mean for Mechanical Engineers?

The Sustainability ConceptTriple Bottom Line

People: Good for SocietyFair practices for all people and does not exploit

interest of separate parties based on money, status or growth.

Planet: Good for the EnvironmentManagement of renewable and non renewable

resources while reducing waste.Profit: Good for the Economy

Financial benefit enjoyed by the majority of society.

Renewable/Non-renewable Renewable Resources

TimberSurface WaterSolarWind

Non-renewable ResourcesFossil Fuels

CoalNatural GasPetroleum

Metal OresAluminumCopperIron

Waste Management/Resource Conservation Hierarchy

Why is reuse

preferred above

recycling?

Why is recycling preferred

above energy

recovery?Source: www.acmplc.com/Images/hierarchy.jpg

Example: Resource ConservationA bicycle manufacturer is considering changing from steel wheel rims to rims made from either aluminum or titanium alloy. From a resource conservation point of view, which alternative would you recommend?

Source: Davis, M. L. and Masten, S. J. (2009). Principles of Environmental Engineering and Science, 2nd edition. McGraw-Hill, Boston.

Example: Resource ConservationConsiderations (Partial Listing) Metals are non-renewable resource. Titanium alloy is created by adding other

elements to titanium to improve its properties.Aluminum is more abundant than titanium Aluminum is more easily recycled than

titanium. Titanium is more durable than aluminum.

Questions: Should decisions be made solely based upon this resource conservation hierarchy? Why or why not?

The Product Life-Cycle

Cradle-to-grave:Products are assessed at every

aspect throughout its entire life cycle (design to disposal)

Cradle-to-cradle:Products are evaluated for

sustainability and efficiency in manufacturing processes, material properties, and toxicity as well as

potential to reuse materials

Life Cycle Stages

Creation“Cradle” Use Demolitio

n

• Design• Material Selection• Site Selection• Manufacturing

Life Cycle Stages

Use Use Demolition

• Distribution• Operation• Maintenance

Life Cycle Stages

Use UseDispos

al“Grave”

• Destruction• Disposal

Example: Biodiesel forCleaner Energy

Life Cycle StagesStage 1:

Acquire resources, specifically diesel, vegetable oil (such as from crops or waste oil), and other chemicals for processing

biodiesel.

Stage 2: Manufacture biodiesel. This includes the production of

various grades of biodiesel fuels using different processes.

Stage 3: Burn biodiesel fuel to generate power, in particular, for

vehicles.

Biodiesel forCleaner Energy

Sustainability ImpactsPeople:

Provide a more sustainable alternative fuel for existing combustion-based vehicles (stage 3).

Planet: Reuse vegetable oil waste (stage 1).

Emit less CO2 compared to other fuels (stage 3).Chemical byproducts for other industries (stage 2).

Land usage (stage 2)Profit:

Create alternatives to typical fossil fuel resources (stage 1).

Biodiesel forCleaner Energy

What are the impacts?The performance of biodiesel vs. conventional fuels can be compared by collecting data on fuel efficiency, cost,

emissions, etc.The properties of the biodiesel can be improved by

collecting data on biodiesel manufacturing via different processes.

Where are better decisions possible?Optimize the performance of biodiesel fuels.

Minimize the cost of the biodiesel powered vehicle.

Analysis for Sustainability Safety Cost Manufacturability

Sustainability Other

Material useEnergy useWaste generationWater useEmissions generation

Toxic releasesOther

Sustainable Design Checklist

Example Checklist for Mechanical Design (Partial)Sustainability Metric

Yes/No Questions Alt. A Alt. B

Material Use Are the product materials recyclable or re-usable?Are materials durable ensuring a long usable life for the product? Will deposal of product produce recyclable materials or landfill waste?

Energy Use Is the manufacturing of the product energy intensive?

Waste generation

Will manufacturing or use of the product generate hazardous substances that could pollute?

Other Specify:TOTAL Points