Pathways Study Methodology and Emissions Target

Eileen V. Quigley
July 1, 2019
Dock Ship Container

Prior to commissioning Meeting the Challenge of Our Time: Pathways to a Clean Energy Future for the Northwest, the Clean Energy Transition Institute convened a Deep Decarbonization Pathways Working Group (see list of participants) and conducted numerous interviews with Northwest stakeholders about the value of conducting an economy-wide pathways study.

The stakeholder process revealed a clear need for a common set of facts about the decarbonization pathways for the Northwest that legislators and the advocacy community could agree to and developed a set of questions to study.

The Clean Energy Transition Institute commissioned Evolved Energy Research (EER) to develop the pathways to deep decarbonization for the four Northwest states with the following study parameters:

  • Explore how energy sectors and energy supply need to transform in the most technologically and economically efficient way.
  • Examine the extent to which electricity generation needs to be decarbonized to achieve economy-wide carbon reduction goals.
  • Estimate the most cost-effective use of biomass for decarbonizing fuels.
  • Assess the impacts of alternative assumptions and constraints, such as the limits of available biomass or  the failure to achieve a high rate of electrification.
  • Explore the value of increased electricity grid transmission between the Northwest and California.

The modeling process began by creating representations of each of the four state energy systems, incorporating state-specific energy infrastructure data and existing policies and creating benchmarks against historical energy use and emissions.

The modelers then defined the deep decarbonization pathways by identifying plausible technologies for energy supply and demand and creating multiple scenarios that were designed to address the specific regional decarbonization questions, cases, and sensitivities that the Clean Energy Transition Institute wanted to explore.

The model ran scenarios for each pathway through 2050, optimizing energy supply-side decisions within the constraints of the scenario being run and producing outputs of energy, emissions, cost, and infrastructure for different pathways to achieve steep reductions in energy-related CO2 emissions by 2050.

Modeling involved two different models that Evolved Energy Research developed: EnergyPATHWAYS (EP) and the Regional Investment and Operations model (RIO). (See the Full Report, pages 64-66 and the Technical Report, slides 17-26 for a detailed discussion of the modeling approach.)  

The deep decarbonization target was applied to each Northwest state independently and assumes that each state complies with the target individually, although each can also use regional energy resources by importing or exporting clean energy to achieve compliance. One advantage of this study methodology is that it produces deep decarbonization pathways for each individual state.

Greenhouse Gas Emissions Context

Meeting the Challenge of Our Time, page 22.

Energy-related CO2 emissions have historically dominated greenhouse gas emissions in the Northwest, including emissions from fossil fuel combustion in buildings, industry, transportation, and electricity consumption. As the figure shows, energy-related CO2 emissions comprise more than 80% of all GHG emissions in Oregon and Washington. (Data for Montana and Idaho are not available.)

The remaining GHG emissions, colored light blue on the chart, include non-energy CO2 and non-CO2 greenhouse gas emissions from agriculture and industrial processes, such as methane from agriculture and waste, as well as hydrofluorocarbons and other high-intensity industrial emissions.

Meeting the Challenge of Our Time, page 22.

As shown in the figure to the right, energy CO2 emissions are spread across three major sectors: electricity, transportation, and buildings and industry. The transport sector accounts for nearly half of all energy-related CO2 emissions in Washington and Oregon primarily because of liquid fuel consumption: gasoline in passenger vehicles, diesel fuel in freight transport, fuel for marine transport, and jet fuel for aviation.  

Study Emissions Target

Two of the four Northwest states have set mid-century greenhouse gas emissions reduction targets. Washington established limits on emissions in 2008, including a 50% reduction below 1990 levels by 2050, which the Department of Ecology has recommended strengthening to 80%. Since 2007, Oregon has had the goal of reducing GHG emissions by 75% below 1990 levels by 2050.

This study’s analysis uses the carbon emissions reduction target of 80% below 1990 levels by 2050 for all emissions (the global target established by scientific consensus) and assumes that the energy system will need to achieve reductions of 86% in energy-related CO2 emissions below 1990 by 2050 to achieve the overall target that includes other sources of carbon emissions, such as forestry, agriculture, waste management practices, and others.

This target was applied to each Northwest state independently. Targeting an 86% reduction in energy-related CO2 emissions allows for fewer reductions of non-energy CO2 emissions and non-CO2 GHG emissions, where reduction strategies are less well understood.

While achieving the economy-wide target of 80% below 1990 levels by 2050 does not put the Northwest on track to do its part to limit the rise of global temperatures to 1.5oC, it is the standard target that most deep decarbonization pathways studies have modeled to date. An 80% reduction target provides a baseline against which deeper reductions could be measured in future studies.

This study, therefore, represents a floor and not a ceiling for responsible climate action, and while it develops an important pathway, further analysis should be conducted to achieve the targets that scientists recommend for the world to address global warming. This figure depicts the deep decarbonization target for the Northwest energy system to attain:

Meeting the Challenge of Our Time, page 23.

For additional information on the Northwest deep decarbonization pathways study, please see:

Eileen V. Quigley

Founder & Executive Director
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