Deep decarbonization pathways (DDP) modeling helps us understand how different decarbonization strategies contribute to reducing the carbon emissions intensity of energy that powers a country, region, state, city, or business.
One of the key end products of a DDP modeling exercise is data that show how any entity interested in reducing carbon emissions could pursue five intertwined strategies to achieve a desired greenhouse gas emissions reduction target—the so-called five deep decarbonization pillars.
The figure below depicts the Five Decarbonization Pillar results from the Net-Zero Northwest (NZNW) Energy Pathways Core Case. The Clean Energy Transition Institute (CETI) commissioned Evolved Energy Research, a leading national expert in DDP modeling, to perform this study in 2023 to determine how the four Northwest states might achieve net-zero emissions by 2050.
The five decarbonization pillars depicted above are:
Here is how the five pillars work on their own and in tandem:
Energy Efficiency
Starting on the left of the five pillars figure with the rose/pink bars, energy efficiency is a bedrock decarbonization strategy for the simple reason that the less energy is used, the less is needed, which helps reduce emissions right away if the energy is produced with fossil fuels.
Energy efficiency also helps along the way to decarbonization because the less energy you require, the less you must generate, which saves money and pressure on the grid to deliver power.
In the NZNW Energy Pathways analysis, aggressive efficiency improvements in buildings, appliances, vehicles, and industrial processes cause per capita energy consumption to drop by 50% between 2021 and 2050. The study also found that the more efficient use of energy—largely resulting from fuel switching to electricity—resulted in a 30% decrease in energy demand by 2050 despite population and economic growth.
Clean Electricity
Clean electricity is a core decarbonization strategy that can be deployed to power uses currently supplied by fossil fuels. You see in the gold/yellow bar in the five pillars figure, second from the left, that in the NZNW Energy Pathways analysis, the Northwest’s electricity grid’s carbon emissions intensity declines to zero between 2021 and 2050.
The generation capacity of renewables (solar, onshore and offshore wind, some nuclear) in the Northwest and surrounding region would grow significantly to add to the region’s robust hydropower resources and provide clean electricity. There would also be substantial growth in electricity storage capacity in the West to store electricity produced from intermittent sources, such as solar and wind.
Electrification
We will need a lot of electricity in the future to meet the increase in demand from electrifying end-uses such as vehicles, appliances, and heating and cooling units for buildings. You can see this in the blue bars under ‘Electrification’ in the five pillars figure above.
The NZNW Energy Pathways analysis found a 105% increase in end-use demand for electricity by 2050 throughout the region, resulting in electricity comprising over 60% of the region’s total energy demand by 2050.
Electrification has another decarbonization advantage: it contributes to efficiency gains. Electric drive trains are 4.4 times more efficient compared to the internal combustion engines they replace that run on petroleum products. Fossil-fuel powered residential and commercial appliances also see significant efficiency gains when switching to electric equivalents, such electric heat pumps, which can be more efficient than both electric resistance heat and gas furnaces.
In 2050, electricity will be used not only to power end uses but also to produce electrofuels, which is represented in light blue in the ‘Electrification’ bar of the Five Pillars figure. Electrofuels are another example of how intertwined the five pillars are, which brings us to Clean Fuels.
Clean Fuels
Not all end uses can be electrified and so for those liquid fuels that we will still need for planes, ships, long-haul trucking, or other industrial processes, we must make them as low carbon as possible. You can see in the green bars in the five pillars figure above that the carbon intensity of fuels drops by approximately 90% from 2021 to 2050 due to the production and use of electrofuels, ammonia, and green hydrogen.
An electrofuel, or an e-fuel, is a synthetic carbon-based fuel that can substitute as a so-called “drop-in fuel” for fossil liquid fuels. Electrofuels employ renewable electricity as the primary source of energy, hence their name. The primary type of electrofuel represented in the NZNW Energy Pathways analysis are Fischer-Tropsch liquids, which are produced by combining hydrogen derived from renewable sources with captured carbon and can replace the petroleum products that power ships, planes, or long-distance trucks.
The Haber-Bosch process combines nitrogen and hydrogen to create ammonia that can replace the bunker fuel that powers maritime transport.
Green hydrogen is created using electrolysis to split the oxygen and hydrogen molecules in water. For hydrogen to be produced carbon-free, some form of renewable energy, such as solar or wind, must power the electrolysis process. This hydrogen is called “green electrolytic hydrogen.”
To see how these processes work, please view this step-by step infographic. You will note that captured carbon is required to create carbon-neutral synthetic natural gas and carbon-neutral synthetic liquid fuels, which brings us to the fifth and final pillar.
Carbon Capture
For all energy uses that can be neither electrified nor converted to low-carbon fuels, we must capture emissions and either sequester them or use them to produce clean synthetic fuels as depicted in the purple bar under ‘Carbon Capture’ in the five pillars figure. The “utilized” carbon is deployed to create electrofuels, and the“sequestered” carbon is stored through geologic sequestration.
Initial DDP studies developed in the 2010s did not present this fifth pillar, but the need for carbon capture and sequestration emerged as the role of electrofuels became apparent; some carbon emissions still remained after the other four pillars were deployed; and entities started setting net-zero emission targets. In future Demystifying Decarbonization blogs we will talk about negative emission technologies and why they are needed to achieve net-zero emissions.
So now you understand what the Five Decarbonization Pillars are and how they work in tandem to help decarbonize energy systems.
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