- Road location: Hundreds to thousands of years, as shown by old streets in ancient cities.
- Road surfaces: Approximately 20 years.
- Piping systems: 50 to 100 years.
- Pumps and equipment: 20 to 30 years.
- Heating plants: 20 to 30 years.
- Natural stormwater management systems: no limit.
- Landfills: decades to centuries.
The life cycle impacts of these systems depend not only on the infrastructure design, but are also tied to planning and design choices for buildings and neighborhoods. For example, think of the construction impacts and energy needed to distribute water and convey sewage within a large, sprawling community versus a compact one.
Infrastructure design can also affect greenhouse gas emissions in other sectors. For example, a district energy system can enable cost-effective sharing of renewable energy sources, thus significantly reducing the greenhouse gas emissions associated with buildings connected to the system.
Life cycle impacts can be grouped into three main categories:
- Construction. Infrastructure construction and the embodied energy of materials (for example concrete) may be a significant greenhouse gas contributor; construction also affects land and ecosystems. However, impacts due to operation are probably more significant over the long term, and construction impacts are not as comprehensively documented (nor as easily analyzed) at this time.
- Operations. Operation of infrastructure is probably the most significant source of infrastructure greenhouse gas emissions, due in part to the typically long life of infrastructure systems. Emissions originate from energy consumption of systems such as water distribution and wastewater treatment, and directly from sources such as landfills.
- Decommissioning/demolition. When infrastructure reaches the end of its life, materials are re-used, recycled or sent for disposal. Greenhouse gas reductions at this point require a solid waste management strategy.
Impacts within each specific infrastructure area are discussed further in the technical pages:
