Sustainability is a difficult term to get a hold of because at times it seems to mean just about anything folks want it to mean. But, what does “sustainable” really mean? And how does it apply to hot mix asphalt pavements? Let’s try and describe it in a way that can provide some sort of direction for the HMA industry.
Sustainability is a system characteristic that reflects the system’s capacity to support natural laws and human values. So what does that all mean? By natural laws we are talking about nature and the ecosystems that make it up (like desserts, forests, praries, coral reefs, etc.) and by “human values” we are talking about meeting human needs (i.e., food and water, safety, participation, freedom, etc.) and economic needs (i.e., using our resources – money being a key one – wisely). From this definition, we can extract 5 fundamental rules for sustainability:
- Do not take things out of the earth faster than nature puts them back in. For instance, as of 2008 there were 1,258 billion barrels of proven oil reserves and our world consumption rate was about 31 billion barrels/year, meaning we have about 42 years left. While we may argue these numbers, we can at least agree that the current consumption rate is not sustainable.
- Do not produce things faster than nature can break them down and reintegrate them into nature. For instance, global production of CO2 is about 9.1 billion metric tons per year, of which only about 5 billion metric tons are processed or absorbed by nature. Clearly, we are producing more CO2 than can be reintegrated into nature, which is not sustainable.
- Do not degrade ecosystems because our health and prosperity as humans depends upon their proper functioning. For instance, humans have converted over 2/3 of the world’s temperate forest land into other uses.
- Seek quality of life for all humans. Whether it is for mobility, access, better health or job creation, quality of life is the fundamental reason we undertake most any job.
- Use resources wisely. This includes money, but also includes our time, manufactured items and natural resources. Clearly we are in an era where each one of these resources is severely limited.
Sustainability for the HMA Industry
So if these are the rules, what do we do in the HMA industry? There are two answers here. First, continue to work on some of the current hot topics. For example: use more recycled material (helps us comply with rules 1, 3 and 5), use less energy with warm mix asphalt (rules 1, 2, 4 and 5) and provide stormwater solutions with porous pavements (rules 2, 3, 4 and 5). These are the items that get attention these days and rightfully so. Second, and perhaps more importantly, we should continue to focus on quality construction, long-lasting pavements and proper preservation and maintenance of existing infrastructure. These “big 3” help us comply with all 5 rules; and in a big way. So, these three traditional areas of emphasis within the industry may not be as popular as other green solutions, but they have the biggest impact on sustainability and we should continue to promote them and, most importantly, get better at them.