## 3 Results  
StEWI v1.0 was used to produce the flowbyfacility, flow, and facility files for the inventories presented in Table 7.  
StEWI provides a meaningful way to track facility-based emission, energy, and waste flows over time and across inventories. Assessment of flows across inventories allows for a more thorough understanding of trends that are agnostic to any particular inventory. As an example, changes in selected flows from selected inventories since 2014 are shown in Figure 2.  
Visualizing the same flow from multiple inventories demonstrates the benefit of using _stevicombo_ to combine inventory data for the same or related flows. Ammonia, nitrogen dioxide, nitrogen oxides, and nitrogen are all nitrogen-derived pollutants that can have negative impacts on human and ecosystem health. While some of the air and ground-based species show relative stability with annual fluctuations or a slight decline over 2014-2018, the nitrogen released to water as reported in the DMR shows a large relative increase. Similarly, three inventories report releases of carbon dioxide (CO\({}_{2}\)) from facilities (Figure 3). The eGRID only includes emissions from electricity-generating units, which are also covered in the GHGRP. Since 2016, facility emissions in the GHGRP have also been included in data made available through the NEI. The use of _stevicombo_ provides increased certainty that these emissions are not double-counted across the inventories, while also providing a more consistent time series, since data are not available in all inventories each year. Under the default settings for _stevicombo_, emissions from facilities are sourced first from the eGRID (i.e., for electricity-generating units), and then from the GHGRP, prior to \begin{table}
\begin{tabular}{c c} \hline
**Compartment** & **Inventory Preference** \\ \hline air & (1) eGRID, (2) GHGRP, (3) NEI, (4) TRI \\ water & (1) DMR, (2) TRI \\ soil & (1) TRI \\ waste & (1) RCRAlInfo, (2) TRI * \\ \end{tabular}
\end{table} 
Table 6: Default inventory preference by compartment, as documented in the parameter INVENTORY_PREFERENCE_BY_COMPARTMENT. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline
**Source** & **2008** & **2009** & **2010** & **2011** & **2012** & **2013** & **2014** & **2015** & **2016** & **2017** & **2018** & **2019** \\ \hline Discharge Monitoring Reports * & & & & & & & x & x & x & x & x & x \\ Greenhouse Gas Reporting Program & & & & x & x & x & x & x & x & x & x & x \\ Emissions \& Generation Resource & & & & & & x & & & x & & x \\ Integrated Database & & & & & & & & & & & & \\ National Emissions Inventory ** & & & & x & \(i\) & \(i\) & x & \(i\) & x & \(i\) & \\ RCRA Biennial Report * & & x & & x & & & x & & & x & & \\ Toxics Release Inventory * & x & x & x & x & x & x & x & x & x & x & x & x \\ \hline \hline \end{tabular}  
* Earlier data exist and are accessible but have not been validated. ** Only point sources included at this time from the NEI; \(i\) interim years between triennial releases, accessed through the Emissions Inventory System, have not been validated.  
\end{table} 
Table 7: USEPA inventories accessible by StEWI. including any remaining GHG emissions from the NEI not already included. With the exception of the first year of inclusion for the NEI, all three datasets show a very similar trend of decreasing facility emissions across the time period. Figure 4 highlights the reduction in total flows using _stewicombo_ in comparison with the data reflecting the original reformatted and harmonized totals from the inventories, represented in the StEWI bar. The equal or lower total amounts reflected in the _stewicombo_ results show the effect of the removal of overlapping flows. For example, based on the default preference of NEI data over TRI data for emissions to air, the vast majority of TRI-sourced ammonia emissions to air are removed from the combined inventory (the first pair of bars).