This is the first in a series of blog posts about CETI’s Northwest Clean Energy Atlas that offer deep dives into visualizations and energy data displayed in the Atlas. We want to incorporate feedback and questions from our community, so please get in touch if you have questions about the Atlas that you would like us to explore.

This blog post refers to two map visualizations from the Atlas: 1) Northwest Greenhouse Gas Emissions from Large Emitting Facilities by Gas and 2) by Industrial Process. When viewing these maps side-by-side, a few questions emerged:

• What is the difference between emissions by process and emissions by greenhouse gas?
• Why are the reported direct emissions displayed in the map by gas different from the stationary combustion emissions displayed in the map by industrial process?
• For some facilities, why is it that emissions from biogenic CO₂ are more than the total reported direct emissions?

We dug in to understand the underlying dataset better, and this is what we found.

Background on Emissions Data Collection

These Atlas maps use data from the U.S. Environmental Protection Agency (EPA) Greenhouse Gas Reporting Program (GHGRP), which requires large emitters to report greenhouse gas data and other relevant information.

Reporting is required by sources that emit over 25,000 metric tons of carbon dioxide equivalent (CO₂e) annually (equivalent to the emissions from one year of energy use for approximately 3,000 homes). The GHGRP has over 8,000 individual reporters and captures an estimated 85-90% of total U.S. greenhouse gas emissions.

The GHGRP reporting requirements apply to direct greenhouse gas emitters (e.g., an industrial facility), fossil fuel and industrial gas suppliers (e.g., a natural gas distribution company), and facilities that inject carbon dioxide (CO₂) underground.

Some suppliers do not report greenhouse gas emissions at the facility level because the emissions do not take place at their reporting location but rather are distributed throughout the country wherever the fossil fuels are used. The EPA has separate reporting requirements for each type of emitter.

Facilities report combustion emissions and process emissions

In general, direct emissions refer to emissions from sources that are controlled or owned by a reporting entity (e.g., an industrial facility) and are emitted during the production phase(excluding upstream or downstream emissions indirectly related to the industrial process). The GHGRP collects two types of emissions from direct-emitting facilities: stationary combustion emissions and process emissions, which together equal the facility’s total direct reported emissions.

• Stationary combustion emissions occur from the combustion of a fossil fuel or biomass feedstock. In industrial processes, fuel combustion is used to create the heat necessary for industrial processes. The production processes for aluminum, cement, glass, and steel, for example, involve melting materials at high temperatures (between 1,000-2,500 degrees Fahrenheit).

• Process emissions include emissions from the chemical transformation of raw materials during the industrial process. For example, the production of cement (the binding agent in concrete), involves a process called calcination to turn limestone into clinker, the material that gives cement its binding properties. The calcination process turns ground limestone (CaCO₃) into lime (CaO) and then into clinker while also releasing CO_2. Approximately two-thirds of total direct CO₂ emissions from the production of cement come from calcination, while the remaining emissions are due to fuel combustion.

Facility Emissions by Greenhouse Gas Type

The first map, Northwest Greenhouse Gas Emissions from Large Emitting Facilities, by Gas, shows each facility’s total reported direct emissions, categorized by greenhouse gas type. The total reported direct emissions are equal to the total of emissions by all gas types, except for biogenic CO₂, which is not included in the total. According to the EPA, that is because fossil and biogenic carbon interact with the carbon cycle on different timescales.  

The omission of biogenic CO₂ is particularly apparent in industries that rely heavily on biomass as fuel, such as pulp and paper. To see this, we can look at the WestRock Tacoma Mill in Tacoma, WA in Figure 1 below, where the total reported direct emissions in 2019 were 129,143 MT CO₂e, comprised of non-biogenic CO₂, methane (CH₄), and nitrous oxide (N₂O)emissions. The emissions from biogenic CO_2, however, seen in Figure 2, totaled 958,705 MT CO₂e (over seven times as much as the other greenhouse gas emissions from pulp and paper combined).

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Facility Emissions by Industrial Process

The second map, Northwest Greenhouse Gas Emissions from Large Emitting Facilities, by Industrial Process, shows each facility’s emissions by process. This map shows both the stationary combustion emissions and process emissions that the facility reports. The total direct reported emissions are equal to the sum of the industry’s stationary combustion emissions plus the emissions by the process that pertains to that industry.

To use WestRock Tacoma Mill as an example again, the stationary combustion emissions are 73,214 MT CO₂e, seen in Figure 3. When filtering for “pulp and paper manufacturing,” the emissions are 55,929 MT CO₂e, seen in Figure 4. Together, the two values equal 129,143 MT CO₂e, which is the same total seen in the first map (the total of all greenhouse gas emissions, excluding biogenic CO₂).

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The visualizations above demonstrate how to use the Atlas to answer questions about industrial emissions. We encourage you to share how you are using the Atlas and any questions you would like to see explored in future posts.