Sustainability: What Does It Mean for Mechanical Engineers?

The Sustainability Concept Triple Bottom Line People: Good for Society Fair practices for all people and does not exploit interest of separate parties based on money, status or growth. Planet: Good for the Environment Management 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 Timber Surface Water Solar Wind Non-renewable Resources Fossil Fuels Coal Natural Gas Petroleum Metal Ores Aluminum Copper Iron

Waste Management/Resource Conservation Hierarchy Why is reuse preferred above recycling? Why is recycling preferred above energy recovery? Source:

Example: Resource Conservation A 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, 2 nd edition. McGraw-Hill, Boston.

Example: Resource Conservation Considerations (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 UseDemolition Design Material Selection Site Selection Manufacturing

Life Cycle Stages Use Demolition Distribution Operation Maintenance

Life Cycle Stages Use Disposal Grave Destruction Disposal

Example: Biodiesel for Cleaner Energy Life Cycle Stages Stage 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 for Cleaner Energy Sustainability Impacts People : Provide a more sustainable alternative fuel for existing combustion-based vehicles (stage 3). Planet : Reuse vegetable oil waste (stage 1). Emit less CO 2 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 for Cleaner 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 Sustainability Other Material use Energy use Waste generation Water use Emissions generation Toxic releases Other Sustainable Design Checklist

Example Checklist for Mechanical Design (Partial) Sustainability Metric Yes/No QuestionsAlt. AAlt. 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