**2.4 Sustainable material allocation throughout the maintenance process**

Growing concerns about depletion or shortage of resources, in addition to increasing demands for more materials, explains the necessity of efficient resource allocation [24]. Depending on the type of infrastructure and the depth of the maintenance operations, the volume of required materials for the maintenance can vary from small amounts to enormous quantities. For example, tons of concrete can be required in the replacement of a bridge segment. The way these materials are selected, shipped, and used in the maintenance operations have impacts on the triple bottom lines of sustainability. According to the World Counts, on average everyone uses 16 kilos of resources extracted from the earth every day, and for people in the western world, this number is much higher—up to 57 kilos of newlymined minerals per day [25]. Based on the United States Geological Survey (USGC) the U.S. apparent consumption of raw materials at the beginning of the century has

**25**

**Figure 9.**

*Maintaining the Sustainability of Critical Infrastructure DOI: http://dx.doi.org/10.5772/intechopen.85915*

increased more than six times from 1940s (see **Figure 8**). The infrastructures are massive consumers of resources worldwide. For example, a total of approximately 1.5 billion tons of aggregates, 35 million tons of asphalt, 48 million tons of cement,

In addition to the depletion of resources, transportation and shipping of raw materials can affect the environment in multiple direct or indirect ways. The massive amount of construction materials that were mentioned in the example above must be transported to sites through thousands of trips by heavy equipment that contributes to air, water, and noise pollution as well as fuel consumption. The indirect effects of trips to supply the materials for the infrastructure can indirectly contribute to global warming, climate change, and threaten the health of human beings. Additionally, continuous traffic of heavy equipment to an infrastructure (such as plants and refineries) will have impacts of the property value of the surrounding neighborhoods and affect the economy bottom-line of sustainability.

These examples indicate that any improvement in the way the infrastructure materials are procured is expected to significantly contribute to sustainable development.

Purchase of materials is commonly done through bidding and choosing the least expensive bidder that meets the expected quality. Less attention is paid to how sustainably the supplier or manufacturer procures the material. Selecting the material supplier is a multi-criteria decision [26, 27]. Selection criteria of material supplier or manufacturer must modify and include the following criteria (**Figure 9**).

• Extraction methods used by the supplier. This explains the policies the manufacturer uses in extraction to maintain the balance of resources in nature and what measures they utilize to minimize the negative impacts on the ecosystem. There are six principles of green extraction [28]: 1) using renewable plant resources, 2) using alternative solvents, 3) reducing energy consumption by energy recovery, 4) converting wastes to co-products, 5) reducing unit operations, and 6) maxi-

• Green processing of the raw materials. This defines how sustainably the extracted materials are processed by the manufacturer. There are multiple criteria to measure this. Some of these criteria are as follows: (1) Compliance to physical safety (safety measure regarding flammability, explosivity, corrosion, oxidation, and radioactivity), (2) compliance to air pollution reduction (meeting the allowable impacts on air, water, and soil), and (3) sustainable waste management (waste generation reduction, green recycling methods, recyclability of products).

• Green shipment. This defines the measures the manufacturer utilizes to minimize the pollution generated in the shipping process. Some criteria to measure this are as follows: (1) using low polluting vehicles and (2) efficient shipment

design (to minimize the number of trips).

*Selection criteria of material supplier or manufacturer.*

mizing non-denatured and biodegradable uncontaminated extracts.

*2.4.1 Selecting sustainable material suppliers and manufacturers*

and 6 million tons of steel is in place in interstate highways of the USA [25].

**Figure 8.** *U.S. apparent consumption of raw materials (courtesy of USGS).*
