Stabilization Wedges

Three categories, 15 options (Pacala & Socolow, 2004):

Key Point: A portfolio of technologies currently exist that would allow us to "solve the climate problem" in the next half a century. In this article, solving the climate problem is defined as stabilizing atmospheric CO2 at 500 ppm, which means to hold emissions near the current level of 7 billion tons of carbon per year (GtC/year) for the next 50 years.

Category I: Efficiency and Conservation (Offers the greatest potential to stabilize atmospheric CO2, but requires hundreds of innovations and less tangible than the options in other categories)
1) Improved fuel economy (60 mpg by 2054)
2) Reduced reliance on cars (more greenways, trails, and bicycles?)
3) more efficient buildings
4) improved power plant efficiency

Category II: Decarbonization of Electricity and Fuels
5) substitute natural gas for coal
6) Storage of carbon captured in power plants
7) Storage of carbon captured in hydrogen plants
8) Storage of carbon captured in synfuels plants
9) Nuclear fission (but what do we do with the nuclear waste? risk of nuclear weapons proliferation and hazardous waste issues)
10) Wind Electricity
11) Photovoltaic Electricity
12) Renewable Hydrogen
13) Biofuels (however, recall that Professor Currie pointed out that this would require cropland the size of India- feasible? hmmm…)

Category III: Natural Sinks
14) forest management (Land demands of agriculture, reduced deforestation benefiting biodiversity)
15) agricultural soils management (Reversibility and verification)

These options are proven ideas, and currently available and implemented. Solving the climate problem is possible; the call to action is to scale up these options to stabilize emissions to "less than double the preindustrial concentration of 280 ppm".

S. Pacala & R. Socolow (2004)
Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies
Science 305, 968

Below is an overview of the reading that was assigned on Stabilization Wedges and how these wedges can be realized using current technology

Overview of “Stabilizaion Wedges: Solving the Climatge Problem for the Next 50 Years with Current Technology S. Pacala and R. Socolow

Overview: Technology already exists to solve carbon/climate problem, specifically the goal to reach a stabilization of 500 ppm of CO2 emissions by 2054, which would require keeping emissions at current level of 7 billion tons of carbon per year

The authors talk about the stabilization triangle which which removes a third of BAU emissions

The article details opportunities for creating 7 equal wedges from existing technologies. “A wedge respresents an activity that reduces emissions to the atmotsphere that starts at zero today and increases linearly until it accounts for 1 GtC/year of reduced carbon emissions over 50 years” leading to 25 GtC of reduced emissions over 50 years.

Next they discuss 15 examples of technologies that currently exist that would fill a wedge.

Category 1 Efficiency and Conservation (clearest way to reduce emissions)
Option 1 Improved fuel economy (e.g. if in 2054 2 billion cars (4 times the number of today) Average 10k miles a year but fuel efficiency doubles to 60 mpg
Option 2 Reduced Reliance on Cars (Only drive 5k a year instead of 10k)
Option 3 More efficient buildings – Reduce building emissions by ¼
Option 4 Improved Power Plant Efficiency – A wedge created if “twice today’s quanity of coal-based electricity in 2054 were preduced at 60% instead of 40% efficiency
Category 2: Decarbonization of Electricity and Fuels
Option 5 Substituting natural gas for coal – Carbon emissions are half as much from natural gas power plants than from coal plants
Option 6 Storage of carbon captured in power plants Installation of Carbon Capture technology (CCS) lead to a wedge if installed at 800 GW of baseload coal plants by 2054 or 100 GW of basload natural gas plants. Talks about different options most likely being precombustion CO2 capture and hydrogen burned for energy, as well as other storage parts of this wedge including Co2 injection, etc
Option 7 Storage of Carbon Captured in hydro plants (e.g. offsite electricity capture) This would require CCS installation by 2054 of CCS at coal plant producing 250 MtH2/year or natural gas plants producing 500/MtH2/year
Option 8 Storage of carbon captured in synefuels plants - Synthetic fuel from coal For it to be a wedge (capture and storage) require 200 Sasol scale (165,000 barrels day) by 2054
Option 9 Nuclear fission would require twice current level of nuclear power at 90% capacity to replace coal
Option 10 Wind electricity Would require 50 times current (2004) wind deployment of 40 GW p
Option 11 Photovoltaic electricity requires same amount as above but currently on 3 GWp installed (but growing at 30% a year)
Option 12 Renewable hydrogen If byproduct of renewable energy were used to power cars from 4 milion 1-MWp windmills in 2054, could lead to wedge of displaced gasoline or diesel.

Option 13 Biofuels Wedge from 34 million barrels a day of ethanol could displace gasoline if ethanol were fossil-carbon free. Warns about issue of “compromising agricultural productivity,”

Category 3: Natural Sinks (focusing on options for creating a wedge that are already demonstrated scaleability)
Option 14 Forest Management reduced deforestation and reforestation
Half wedge=rate of clearcutting of primrary tropical rain forest were reduced to zero by 2054 instead of halfed.
Half wedge=reforesting or afforesting 250 million hectares in tropics or 400 million hecatares in temperate xone
Half wedge=Create 300 hectares of plantations on non-forested lands
Option 15 Agricultural Soils Management e.g. Conservation tilling, and enforcement could lead to ½-1 full wedge

Technologies exist and are in use at a large scale. If you implemented solutions could lead to a wedge in effort to address climate change.

Some of the problems with this article:
Wedge effects are helpful, but doesn’t address additional pollutants that might enter the environment as a result of some of these solutions (e.g. agriculture, nuclear fission). Even the article admits that current scalability is small in terms of what is required for large scale reduction of CO2. Also, agricultural solutions and ethanol solutions lead to serious challenges. While this is just a summary of the issue, doesn’t fully account for negative feedbacks among different options.

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