What carbon concepts are useful for sustainability professionals learning about water sustainability?

In a past article, we discussed how GHG accounting and water sustainability differ. This may cause one to ask: is it even worth considering the comparison between Greenhouse Gas (GHG) accounting and water sustainability? We argue: Yes, as water sustainability becomes increasingly important, it pays to learn from one of the most developed environmental impact reduction-focused fields. Some of the similarities include the following:

Embodied carbon / water

In GHG accounting, embodied carbon refers to the GHG emissions needed to create, move, install, maintain, and dispose of an object. Embodied carbon is useful because it helps people and organizations better conceptualize otherwise hidden GHG emissions.

Water has an analogous concept called virtual, indirect, or embodied water. Like embodied carbon, embodied water considers the amount of water used to create, move, install, maintain, and dispose of a product. This concept has most commonly been used in international trade to understand how water-intense goods and services travel between water-scarce and water abundant nations.

Because of water’s Dimensionality, Regionality, and Temporality, creating meaningful embodied water comparisons is very difficult. Further, the usefulness of embodied water as a closely tracked metric can vary widely for different organizations. Still, the concept of embodied water directionally points to important considerations for developing a water stewardship program and prioritizing water sustainability efforts.

(See the previous article for a more detailed description of Dimensionality, Regionality and other distinguishing features of water sustainability.)

When considering water processes:

• Is water used in water scarce regions for products that will be used in water abundant regions?
• Is water used in periods of drought for products that will be used during more normal conditions?
• Is high quality water being used for products with limited water quality needs?
• Are the answers to the questions above driven by organizational needs or by organizational inertia?

Net zero / water neutrality

In GHG reduction efforts, net zero is a commonly discussed goal. Net zero can be defined as the point where an organization’s total GHG emissions are reduced to zero or completely negated. These efforts are often made achievable through some combination of fossil fuel replacement and energy use reduction, with carbon offsets used to make up for any remaining emissions. Net zero is often set as a long-term goal for organizations.

Water neutrality is the analogous concept for water sustainability, specifically addressing water scarcity. Water neutrality can be achieved by balancing organizational water use with water harvesting, ensuring the organization is replacing all water that it uses with water of the same quality level. Water harvesting in this context can be performed by collecting water for direct organizational use or by replenishing the water supply more broadly.

This concept is made more complex by water’s Regionality. Due to long range water transportation’s prohibitive cost, legal complexity, and present lack of infrastructure, moving water from one region to another is generally not a feasible strategy. This makes water concerns much more regional than GHGs - where energy travels more freely and emissions are more broadly distributed. This means that meaningful water neutrality must be pursued at a regional rather than an organizational level – an organization using water in the desert but harvesting water near a lake may technically be net water neutral, but the water harvesting doesn’t meaningfully address the impact of operations on the desert community.

Water neutrality is further complicated by water’s Essentiality. Water neutrality can be achieved in terms of equating water consumption and water replenishment, but there will always be water consumption that must be accounted for.

Considering these complications, it may behoove organizations to consider working towards region-specific science informed water use goals instead of, if not as a precursor to, organizational water neutrality. Where water neutrality sets up a universal target, science informed water use goals help the organization to tailor its water sustainability strategy to meet the needs of the communities where it operates. To be science informed, water use goals must consider local water replenishment, other water uses in the area, local population levels and other organization specific factors to determine an organization-specific fair amount of water use that exists within the natural replenishment rate of the local water system.

Carbon scopes

In GHG accounting, an organization tracks GHG emissions by categorizing emissions as Scopes 1, 2 or 3. Scope 1 emissions are those that occur directly from sources owned by the organization, Scope 2 emissions are those emissions that come from purchased energy for the organization, and Scope 3 emissions are those emissions that are not owned or purchased by the organization but result from upstream or downstream activities within the organization’s value chain. Typically, Scopes 1 and 2 are grouped together, with Scope 3 kept separate due to its position outside the organization’s direct locus of control.

Water does not have complete analogues to Scopes 1, 2 and 3. However, a differentiation in water use can be created similar to that which exists between Scopes 1 and 2 and Scope 3. For water, this distinction takes the form of direct water use, or water use due to operational activities (those analogous to Scopes 1 and 2) and indirect water use, or water use within the organization’s value chain (analogous to Scope 3). Separating water use in this way enables a deeper understanding of how water is used in and around the organization’s operations.

If you consider the reasons behind the use of Scopes 1 and 2, there is an added dimension that can be introduced into water use tracking: that of quality. Scopes 1 and 2 are separated in part to increase the granularity of the organization’s GHG emissions. The distinction between these two scopes provides a way to view and differentiate between GHG emissions and ultimately to highlight alternative solutions based on that distinction.

For water use, consideration of water quality can provide that differentiation for water consumption. For human health, water is typically divided into three categories: clean water, greywater and blackwater. Clean water is water that arrives from a source and is typically treated to drinking water standards. It is safe for human consumption excepting rare cases. Greywater is wastewater that has only been lightly used. Greywater can contain soap, grease, food particles, etc. depending on prior use, but does not contain toxic chemicals or excrement. Blackwater is wastewater that has interacted with toxic chemicals or excrement.

Of the above, clean water is primarily used in buildings and processes today. Greywater may, in certain situations, be substituted for clean water depending on the level of contamination in greywater and the process’s water quality needs. Blackwater generally must be treated due to its contamination level prior to returning to the source.

Differentiation between water quality definitions and water quantity needs across an organization can highlight potential strategies for water reduction, especially those related to water reuse and decreasing the quality of water used where applicable. For example, an organization could save water by rerouting wastewater from washing machines for reuse in toilets.

In summary, while water sustainability does utilize different terminology from GHG accounting, underlying concepts can be loosely applied across domains. Discussion of these concepts by altering pre-existing GHG frameworks can help an organization take a big step up in how it interacts with water sustainability, and consideration of these concepts can highlight areas where water sustainability can be improved.