1. Integration of life-cycle emissions from power generation into the Global Change Assessment Model (GCAM)-USA
Samaneh Babaee (ORISE), Ozge Kaplan, and Dan Loughlin
U.S. EPA Office of Research and Development
Research Triangle Park, NC
36th USAEE/IAEE North American Conference
September 23-26, 2018 – Washington, DC

2. Objectives
Problem:
Human-earth system models are powerful tools for evaluating the energy and emissions implications of wide-ranging socio-economic-technology-policy scenarios. However, even with these models, it can be difficult to attribute changes in upstream emissions to energy technology decisions.
Life-cycle analysis (LCA) methods have been developed to perform such attributions. However, these methods typically do not consider regional and state conditions (e.g., energy resources and technology mix, turnover, and transitions to cleaner technologies) or the national and state policies that shape energy choices into the future.
Primary Objective:
Demonstrate how inclusion of life-cycle factors into a human-earth systems model can support this attribution of emissions to technologies
Secondary Objective:
For combustion related emissions, show how human-earth system models can improve upon life-cycle-based projections by explicitly accounting for state-specific conditions
Disclaimers
GCAM-USA is a work in progress. These results are intended to be illustrative of capabilities and methodology. This work will be revised as an updated Reference Case is formulated.
Views expressed in this presentation are those of the authors and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency.

3. Approach
Use the Global Change Assessment Model (GCAM)-USA to project nitrogen oxides (NOx) emissions for a Reference Case scenario
For the major sectors of the energy system (electric, transport, industry, and buildings) in Texas from 2010 to 2050
Texas is selected for analysis since it has a broad mix of generation, including coal, gas, wind, and solar, and because it is subject to a cap on electric sector NOx emissions.
Conduct a literature survey on life-cycle emission factors (EFs) for U.S. power generation by power plant type
Add life-cycle EFs to power plants in GCAM-USA (e.g., tons of NOx per PJcoal)
Examine life-cycle NOx emissions associated with various stages of electricity production (fuel extraction, transportation, and combustion as well as plant construction)
Compare these life-cycle emissions to the endogenously-projected NOx emissions in GCAM-USA from 2010 to 2050

4. Approach GCAM-USA Model
GCAM is a technology-rich Human-Earth Systems model developed by the Joint Global Change Research Institute of Pacific Northwest National Laboratories and the University of Maryland (Open source and freely available).
GCAM covers the electric, industrial, commercial, residential, transportation, and agricultural sectors of the global economy.
There are 32 global energy-economic regions in GCAM.
GCAM-USA is a derivative of GCAM in which the US region is further subdivided into 50 US states and the District of Columbia.
GCAM-USA is typically run over the time period from 2010 through in 5-year time steps.
For modeled scenarios, GCAM-USA outputs emissions of GHGs (CO2, CH4, N2O), short-lived climate pollutants (BC, OC, SO2), and air pollutants (NOx, SO2, PM2.5, PM10, CO, VOC, and NH3).

5. Approach GCAM-USA Model EPA has modified GCAM-USA by:
adding emission factors from EPA regulatory activities and models (e.g., IPM, MOVES, GREET, NEI),
incorporating pollutant controls for power plants and industrial technologies,
representing relevant policies and regulations (e.g., CAFE, CSAPR, RGGI, ZEV),
and calibrating coal and nuclear power generation to more closely approximate projections from the Department of Energy.
Abbreviations:
IPM: Integrated Planning Model for future electric sector emissions estimate
MOVES: Motor Vehicle Emissions Simulator model
GREET: Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation
NEI: U.S. National Emissions Inventory for industrial emissions
CAFE: Corporate Average Fuel Economy standard ZEV: Zero emission vehicle program
CSAPR: Cross-State Air Pollution Rule for state-level NOx and SO2 cap on electric sector
RGGI: Regional Greenhouse Gas Initiative to reduce CO2 emissions from power sector

6. Approach GCAM-USA Model GCAM-USA systems and their interactions
Outputs:
Fuel use and prices
Technology shares
Policy cost
Emissions:
Air pollutants
SLCPs
GHGs
Water use
Land use
Ag production
Climate:
Climate change
Sea level rise
Other:
1st order PM health cost
Ammonia deposition
Ozone damage to
crops and timber
GCAM-USA systems and their interactions
Scenario:
Population growth
Economic growth
Technology
development
Resource constraints
Policies:
Environmental
Climate
Energy

7. Approach GCAM-USA Operation
GCAM-USA operates by determining the prices at which supply meets demand for hundreds of markets in each modeled time period. The current time period solution serves as the starting point for solving the next period. Technology and fuel choices are determined as a function of the relative cost of competing technologies.
For more information about the GCAM formulation and solution process, please see:

8. Approach LCA Assumptions
LCA-S1: Extraction and processing of the primary fuel and raw material
LCA-S2: Transport of the primary energy source
LCA-S3: Combustion of the fuel in the power plant
LCA-S4: Construction of the power plant
Power plant construction S1 S2 S3 S4

9. Approach LCA Assumptions The LCA factors obtained from the literature:
are in units of metric tons of NOx per PJ fuel input to the power plants
vary by power plant type
are constant from 2010 to 2050
are national averages that do not explicitly represent state-level conditions nor policies (e.g., CSAPR, RGGI,….)
We multiply these by PJ of fuel input to the power plants, obtained from GCAM-USA, to provide technology- and stage-specific emissions

10. Approach Assumptions Run Reference Case in GCAM-USA:
includes CSAPR, RGGI, Tier 3, CAFE, various NSPSs for air pollutants
does not at this time include RPS and CPP
Compare GCAM-USA’s projected NOx emissions with LCA NOx emissions from 4 stages:
Coal and natural gas power plants
Texas chosen for example application
- Subject to CSAPR
Mix of electric generating technologies includes large portions of coal, gas, and wind
Tier 3: Vehicle emission and fuel standards RPS: Renewable Portfolio Standard
NSPS: New Source Performance Standard CPP: Clean Power Plan

11. Electricity generation
Preliminary results
Electricity generation
CHP: Combined Heat & Power
Natural gas and coal are the dominant means of electricity production in Texas in the Reference Case
Note: we are currently revising the Reference Case and expect the growth in electricity demands to increase at a slower rate after that revision

12. NOx emissions: GCAM-USA
Preliminary results
NOx emissions: GCAM-USA
Electric sector NOx emissions are relatively constant due to the state-level cap under CSAPR
Much of the increase in industrial NOx is due to increase in refined liquids production
NOx reductions from the transportation sector are predominantly from the Tier 3 standards

13. NOx emissions: GCAM-USA & LCA
Preliminary results
NOx emissions: GCAM-USA & LCA
GCAM and LCA NOx emissions from fuel combustion in power plants (EGUs) are very close.
LCA-fuel extraction and transportation are significant.
In the next slides, EGU emissions are examined in more detail, including from coal and gas.

14. NOx emissions: coal power plants
Preliminary results
NOx emissions: coal power plants
GCAM and LCA difference shows the effect of emission regulations (CSAPR)
Combustion-related NOx at coal plants is much higher than NOx from the other LCA categories.
NOx emission reduction after 2040 is due to increasingly efficient coal plants and lower coal use.
Differences are largely due to:
In 2010: GCAM-USA is reflecting the emission controls that are in place in Texas in 2010
For projected years: GCAM-USA reflects the EGU NOx cap for Texas that is specified by the CSAPR
The graphic to the right compares emission intensity over time, illustrating how the addition of controls to meet the cap is reducing the emission intensity.

15. NOx emissions: natural gas plants
Preliminary results
NOx emissions: natural gas plants
GCAM and LCA factors need to be calibrated
The high NOx from NG extraction is being driven by the low efficiency and high NOx rate of compressors used in onshore wells
Similarly, the high NOx from NG transportation is from natural gas-powered compressors, needed every miles along with NG pipelines.
The reduction in GCAM-USA’s NOx from NG combustion over time is a result of the introduction of lower-emitting combustion turbines and retirement of older units.
The LCA NOx from NG combustion assumes constant EFs (as opposed to EFs that decline with fleet turnover) and does not appear to represent the higher EFs of the existing capacity in 2010.

16. Conclusions Lessons learned: Next step:
Incorporating LCA emission factors in GCAM-USA enabled us to:
- Quantify upstream emissions related to electricity production
- Identify source categories (e.g., fuel extraction and transportation) for which GCAM-USA emission estimates could be improved
GCAM-USA-produced electric sector combustion emissions would be an improvement over those often used in LCA analyses by considering:
- Existing technology stock and stock turnover
- Access to renewable resources
- State- and region-specific policies
Next step:
Revise Reference Case to incorporate RPS and updated end-use energy demands

17. Questions?
Thank you!

18. Extra Slides