How to Calculate Carbon (CO2) Emissions from Water

Water is an important and precious natural resource in its own right. But beyond that, contrary to what many might initially think, the water we use in our homes and businesses also has a carbon footprint associated with it. In this guide we'll walk you through where water emissions come from, as well as how to calculate the carbon emissions of your water usage.

How Does Water Usage Have a Carbon Footprint?

A lot of energy is used to supply, treat, and use water. This can include electricity used during water purification, or simply heating water when we take a hot shower. According to the EPA, drinking water and wastewater systems account for approximately 2% of energy use in the United States, while some studies estimate total water-related energy use may be as high as 10% of all electricity consumption.

Moreover, as climate change worsens, the carbon footprint of water will increase. Water will need to be pumped farther distances to areas facing draughts or water shortages, increasing energy usage and costs. Water with more pollution and contaminents will also need more treatment processing to purify it.

Calculating Carbon Emissions of Water and Wastewater

Getting Water Meter Data to Calculate Usage and Carbon Emissions

Most buildings and businesses have a water meter, but you may not necessarily have access to yours if you're leasing office space or renting an apartment. If you receive a monthly water bill from your local water utility, you most likely have your own water meter. If you don't get a bill, then you probably don't have your own meter.

If you live in a climate with cold winters, your water meter's likely in the basement of your home or building. In some states like California, Colorado, Florida, and North Carolina water meters are commonly located outside in a cement or metal pit, well, or enclosure near the property. As a last resort, try calling your water utility or district.

How to Get Water Data to Calculate Carbon Emissions and Footprint

Most modern water meters also support automated meter reading (AMR) sent via radio. Some are even connected to the internet. In terms of getting water data, if you don't have direct access to the meter, try talking to the building owner. There are also affordable apps, tools, and converters that can help you collect and digitize AMR meter data electronically.

Calculating the CO2 of Water: Helpful Emissions Factors

The California Energy Commission and researcher Dr. Robert Wilkinson break water energy use down into five steps:

  1. Sourcing
  2. Treatment
  3. Distribution and transport
  4. Usage
  5. Wastewater treatment

Water treatment, is, on average, the most energy and carbon-intensive step in the public water lifecycle.

Water Lifecycle Carbon Emissions Factor

Using a lifecycle analysis (LCA) of water across those steps, measuring average energy usage step-by-step, and then applying an emissions factor, regular use water has an emissions factor of approximately 0.340 - 0.46 kg of CO2 per cubic meter of water, depending on the region. To put that in perspective, the average American uses around 2,000 gallons of water a month, equivalent to 2.5 - 3.5kg of CO2 per person.

Calculating Your Own Carbon Emissions From Water

Using the above guidance and emissions factor should give you all the baseline information you need to calculate the carbon footprint of your water usage. We recommend tracking and measuring your water usage and climate footprint monthly, and remember to classify it as Scope 3 emissions if you're doing full carbon accounting.

If you'd like an automated system for all your carbon calculations, data, and reporting, our award-winning sustainability software is used by hundreds of companies around the world to simplify their environmental reporting and emissions reduction.

Carbon Calculator for Water Emissions

Whichever method you choose, remember that the link between water, energy, and climate change presents us with important opportunities and challenges to better manage one of our most valuable natural resources. If we can be helpful to you or your organizationā€™s sustainability journey, please be in touch.