Greenhouse Gas Management of Water

Water usage in health care organizations is a less obvious source of carbon emissions. In the health care physical environment, water is used for indoor plumbing, irrigation, process heating and cooling, and the heating, ventilation and cooling (HVAC) system.

When evaluating carbon emissions, water usage can be broken down into two main categories. The first is the energy associated with delivering the water to the site, as the energy associated with pumping the water to the site or to the water tower serving the site generates carbon emissions. The second category is the emissions associated with wastewater treatment generated by the building, which includes water treatment as well as the management of wastewater. 

How to measure and report: 

To precisely determine the greenhouse gas emissions due to water for a health care organization, the water usage of a health care facility must be measured. The easiest way to measure the emissions is to simply aggregate the organization’s water bills. Water sub-meters may also be installed for individual water systems to enable the organization to determine major sources of water usage and help identify issues sooner. Water that is used for irrigation, boiler makeup and cooling tower makeup generate emissions associated with the delivery of water to the site, but do not generate emissions associated with wastewater treatment.

The energy and carbon intensity of delivered water (measured in carbon dioxide equivalents per milligal, or CO2e/Mgal) varies by location and must be derived from the local utility company. For example, Southern California has a reported intensity of 9,374 CO2e/Mgal. Where site-specific or regional data is unavailable, use the national average. The grid carbon intensity will then be utilized to determine the carbon emissions associated with water delivery.  

The carbon intensity of wastewater transport and treatment can vary greatly from municipality to municipality depending on a number of factors, such as population and geographical region. The carbon intensity of wastewater can be established using industry averages to help create a better picture of the life cycle carbon emissions, or evaluation of inputs and outputs through the entire procurement, treatment, and distribution process, of water use. A better solution is to work with the local utility company to determine the emissions.  

How to manage:  

The best way to manage and reduce greenhouse emissions from water usage is to reduce the overall water usage of the facility. For a typical health care organization, cooling towers and irrigation account for a significant amount of water consumption. Using air-cooled equipment that does not utilize evaporation cooling technology can eliminate water usage from cooling towers. If this is not possible, utilizing good water treatment strategies can reduce water lost due to cooling tower blowdown, which is the input of freshwater to avoid the buildup of concentrated total dissolved solids. Water usage from irrigation can be greatly reduced by using native plants and reducing sod or other water-intensive vegetation.

Reducing overall water usage for indoor plumbing and process equipment is another way to manage emissions. Implementing low-water plumbing fixtures where appropriate and replacing old steam boilers with closed-loop hot water systems can greatly reduce the water usage of a health care organization.  

On-site water harvesting, water treatment and reuse are other potential solutions. Harvesting rainwater or recycling and treating on-site grey water for reuse can both eliminate carbon associated with the delivery and wastewater treatment process.  

Creating a water measurement and verification plan to identify leaks and consumption rates that do not match up with expectations is another way to cut waste, save money, avoid damages, and reduce the emissions tied to water consumption.1  

©2023 The American Society for Health Care Engineering (ASHE) of the American Hospital Association

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