Sustainability

A sustainable product is a product that meets the current needs without compromising the ability of future generations to meet their needs while protecting human health and the needs of society. Chemical engineers are ideally suited to evaluate the sustainability of a wide range of products and technologies, and therefore, we present an overview of sustainability and green engineering as an example of one of the ways that chemical engineering can contribute to society today and into the future.

Current estimates indicate that the societies of the world are consuming 50% more resources (e.g., energy, water, minerals, the ability to produce food) than the world can sustain (what the population of the world consumes in one year requires 18 months to replenish). The United States consumes natural resources at a rate that is more than 13 times the rate for the rest of the world. With the rapid growth in the economies of China and India, who make up almost 40% of the world’s population, the world resource consumption rate is expected to accelerate.

In addition to preserving resources for the future, sustainable engineering involves protecting human health and the needs of society. That is, the effects of pollution and the impact on global warming are factors that also should be considered in any sustainable design project. As a result, a number of engineering professional groups are concerned that sustainability should be an integral part of future designs. That is, sustainability, or at least improved sustainability, should be an objective for engineering design work as opposed to basing design solely on minimum cost or maximum profit without regard to the impact on sustainability. The problem is that a sustainable design will, in general, cost more to implement than its nonsustainable counterpart. Therefore, the challenge for you as a future engineer is to develop new approaches that make sustainability as economically viable as possible.

As an example, consider a sustainable design for a building. The following features are aspects related to a sustainable design of a building:

• Nontoxic construction materials that can be produced from recycled materials using low-energy processing techniques
• Energy efficient design (e.g., low heat transfer rates to or from the building) using materials that require low amounts of energy to produce
• Renewable energy sources (solar panels, solar water heaters, etc.)
• High durability for the building, yielding a long service life; materials that develop character as they age
• Interior and exterior appearance as similar as possible to nature (i.e., producing a soothing environment for humans)
• Designing for a low total carbon footprint (i.e., the total carbon dioxide liberated during the production of the materials used in the building and the process of constructing the building)
• Using biomimicry (i.e., redesigning industrial processes along biological lines to produce building materials)
• Transferring ownership from an individual to a group of people, similar to car sharing
• Employing renewable materials that come from nearby sources

As you can see from this list, the design problem becomes more complicated when a more holistic approach to engineering is used, but on the other hand, this approach creates more opportunities for creative solutions.

1.4.1 Life-Cycle Analysis

A life-cycle analysis is a comprehensive method for developing a sustainable design (green engineering). A life-cycle analysis not only considers the effect of a product on the environment and on important resources but also considers all the steps used to produce a product and what happens to the product after its useful life has ended. Figure 1.2 shows a schematic example of a life-cycle analysis of a product.