As an introduction to engineering, you may choose to watch the What is Engineering? video below.
Engineers consider the environmental impacts to our air, water and natural resources when creating a new product. To do this, engineers consider the entire life cycle of a product — from materials acquisition, materials processing, manufacturing, packaging, transportation, use and disposal of the product. These represent all the life phases of a product, similar to the life cycle of an animal found in nature.
For example, butterflies pass through four stages during their life cycle: egg, caterpillar, chrysalis and butterfly. You can use the example of a butterly and ask students the following questions to help them compare and contrast product life cycles with the life cycles of living things.
- What are some steps of the life cycle of a butterfly? (Answer: birth, caterpillar, chrysalis, butterfly, decompose.)
- What are some steps in the life cycle of a product? (Answer: materials acquisition, materials processing, manufacturing, packaging, transportation, use and disposal.)
- How is the life cycle of an organism similar to the life cycle of an engineered product? (Possible answers: Both life cycles follow the object from birth to death, or beginning to end. Both cycles involve the flow of energy through the lifetime of the object.)
- How do the two cycles differ? (Answer: Often the life cycle of a product ends with disposal, where the life cycle of a natural organism is recycled into nutrients in the Earth. Looking at the life cycle of a product helps us understand the Earth's natural resources and energy and, particularly, how we produce waste.
An engineer uses a life cycle assessment to measure how much energy and impact a product has on the environment, from its creation to its final disposal. There are several general steps to determining the overall environmental impact of a manufactured product. The first step is called aninventory analysis. In this step, the product's energy and materials that are used during the life cycle are calculated. A number value is assigned for energy and physical materials for all the phases of the life cycle (materials acquisition, materials processing, manufacturing, packaging, transportation, use, and disposal of the product). The next step is an impact analysis, where the number values from step one are added together. This final number represents the total impact on the environment. The lower the number, the less negative impact the product has on the environment. Lastly, an improvement analysis is performed to determine if there is any way to reduce the product's impact on the environment. For example, conserving energy or water during any of the phases of the life cycle or exchanging materials for less hazardous waste producing ones would help reduce the impact. Engineers sometimes design products with durable parts that will have a long lifespan, and other times they design products that are designed to last a relatively short amount of time, but have easy to reuse or recycle parts. Then, the changes are inserted back into the inventory analysis to determine if the total environmental impact can be reduced.
There are several types of life cycle assessments for engineered products. Some of them include:
- Cradle-to-Grave: The full life cycle of a product from raw materials (cradle) to the disposal phase (grave).
- Cradle-to-Gate: A partial product life cycle assessment that investigates a product from raw materials (cradle) to the gate of the manufacturing facility before transportation to the consumer.
- Cradle-to-Cradle: A product life cycle assessment, where the end phase includes recycling of the product into a new product. The recycled product can be identical or different to the original product.
A great example of a product manufactured for cradle-to-cradle is a Nike sneaker. This is a product students will be familiar with, and designers at Nike have been working to create a product that will not add harmful waste to the environment and can be engineered with sustainable inputs. For more information visit: http://www.mcdonough.com/writings/inspiration_innovation.htm
