3.1 Introduction

An integral aspect of an engineer’s role is converting energy and raw materials into technology, goods and services required by society. Look around you and pick an object. What materials were needed to make that object, and where did they come from? What processes did they go through to get to the final product? What will happen to the product once it's reached the end of its useful life?

 

Figure 3.1.1 Processes during the life of a magazine

(Source Carbon Model [see reference 1])
Figure 3.1.1 sourced from Carbon Model under a Creative Commons Attribution 3.0 United States License
http://carbonmodel.org/lca/

The pie chart below shows the percentage of global C0₂ emissions by source. The first chart shows that 64% is from energy usage and the second splits this up fairly evenly between industry, building and transport. The last chart is the industry section in more detail, showing that steel, cement, paper, plastic and aluminium are all the biggest contributors to C0₂ emissions worldwide.

Figure 3.1.2 Global sources of C0₂

(Source Sustainable Materials With Both Eyes Open [see reference 2])

Figure 3.1.2 sourced with permission from Sustainable Materials With Both Eyes Open. This book is available free to view online
http://withbotheyesopen.com/index.html

Having covered the sustainability issues surrounding energy, we will now cover material production. This will start by outlining the four main materials that are used by industry and other parts of society – steel, aluminium, plastic and cement. The main uses for each of these materials will be discussed and we will look into how they are produced.

The environmental concerns highlighted by their production will then be looked at, specifically the energy used in the materials' manufacture, known as “embodied energy” and the waste produced once they have finished their life. The chapter will conclude with steps an engineer can take to reduce the environmental impacts of the materials they use, and certain tools they can use to achieve this.

This chapter is limited in its scope by only covering the “big four” materials in depth, as the “other” section is a sizeable 45%. As well as the C0₂ effects of these other materials, there are huge environmental and social problems associated with the production and disposal of materials such as copper, textiles, chemicals, pharmaceuticals, gold, and other precious metals such as cobalt used in mobile phones. The mining of such precious metals specifically has devastated landscapes in Africa and South America, and the undistributed wealth patterns caused from distribution of these precious metals has brought on social unrest and in some case, civil war.

The resource depletion of common metals such as copper will eventually become a problem, as although they are highly recycled there is a finite amount of these metal ores left in the earth’s crust, which will eventually run out. The continued disposal of all materials into a linear waste stream which outputs vast amounts of toxic waste into landfill is beginning to take its toll on landscape and natural ecosystems. This chapter will cover two impacts of the specified materials in terms of the energy required to get them into use, and the waste created by their disposal after use.

It is essential for an engineer to be aware of these problems with material production and disposal when undertaking a project, and undertake measure to mitigate these effects.

 

Picture sourced from MIT Opencourseware under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License
http://dspace.mit.edu/bitstream/handle/1721.1/39134/1-964Fall-2004/OcwWeb/Civil-and-Environmental-Engineering/1-964Fall-2004/LectureNotes/index.htm