Major reductions in GHG emissions will require comprehensive changes not just in how we manage energy supply, forest, and agricultural systems, but in how we live and move in urban areas, where most of world’s energy, materials, and products are consumed. The main pathways to a low-carbon future, or “deep decarbonization,” as it is described in the literature are:

• Conservation & Efficiency—Consuming less energy and using energy more efficiently in buildings, transportation, and industry
• Decarbonization—Decarbonizing electricity and other fuels by removing coal from the electricity grid entirely; limiting the use of fossil gas in heating and transportation in the 2030-35 timeframe; and halving the carbon content of transportation fuels by 2030 and getting to zero-carbon fuels by 2050.
• Fuel-Shifting—Switching fossil fuels to low- to zero-emission renewable fuels to power buildings, vehicles, and industry.
• Waste Reduction—Reducing the emissions associated with all waste products, as well as decreasing consumption
• Emission Sequestration—Preserving and increasing natural carbon sinks, such as forests, agricultural land, vegetation, and soils.
• Methane Emission Reduction—Setting methane emission standards for new and existing fossil gas and oil development to reduce methane emissions from landfills, coal mines, and agriculture.

Six Sectors Transitions

There are six key sectors in which to concentrate decarbonization efforts, each of which has a series of critical transitions or actions that need to occur as follows:

Energy Supply Sector Required Transitions

• Ramp up energy efficiency
• Transform utilities and power markets[i] [ii]
• Modernize the grid to integrate renewable energy and demand-side resources
• Replace coal and gas with renewables to reduce fossil fuel emissions and decarbonize electricity generation
• Modernize the grid to integrate renewables and demand-side management
• Increase electricity generation to address fuel switching

Transportation (air, marine, fleet, freight) Sector Required Transitions

• Improve fuel efficiency
• Improve engine efficiency
• Electrify transportation and/or embrace fuel cell vehicles
• Decarbonize liquid and gas fuels
• Reduce vehicle miles traveled

Residential and Commercial Sector Required Transitions

• Improve end-use efficiency
• Conserve energy
• Switch from coal, oil, and gas to electricity for space and water heating

Industrial (manufacturing, construction, agriculture energy transformation, mining) Sector Required Transitions

• Energy efficiency
• Combined heat and power to capture and reuse waste heat
• Switch to lower-carbon fuel sources and electric processes[iii]

Agriculture and Waste Sector Required Transitions

• Reduce methane emissions from land use and agriculture
• Increase nutrient use efficiency/manage nitrogen fertilizer
• Increase carbon sequestration
• Develop manure-to-energy processes

Land Use and Forestry Sector Required Actions

• Maintain and increase carbon sinks
• Reduce logging and forest conversion
• Reforestation
• Afforestation
• Improve management of working lands to increase carbon sequestration
• Manage urban natural areas to increase carbon sequestration

Decarbonization Strategies

1. Building transmission that will carry renewable energy to the loads that need it, addressing the challenges of variability.
2. Developing grid integration strategies to match loads to variable renewable energy
   1. Responses to expected daily patterns in energy supply and demand (e.g., spring evenings when the sun goes down and everyone comes home from work and demand climbs)
   2. Responses to long stretches of cloudy or calm weather
      1. Grid connected-storage (batteries, pumped hydro, etc.
      2. Demand response
      3. Real-time price signals tied to load fluctuations such as those that EV charging would add
3. Protecting and expanding policies that encourage renewable growth
   1. Third-party ownership of rooftop solar
   2. Net-metering (which will evolve to time-of-use or value-of-solar pricing over time)
   3. Renewable Portfolio Standards
   4. Tax incentives
   5. Utility business models that incentivize conservation and renewables
4. Capitalizing the renewable energy sector
   1. Wind power purchase agreements currently 2.35 cents/kW-hr (now competitive with non-RE) and solar below 4 cents
   2. Competitive even without federal subsidies
   3. Costs continue to drop
   4. Accelerate investment now because interest rates are low
   5. Renewables have high capital cost but zero fuel cost so over time the investment pays off hugely
5. Recognize that decarbonizing the electricity grid and the transportation sector go hand-in-hand
   1. Cleaning the grid makes possible “fuel-switching” to electric-powered transportation vehicles wherever technically possible to replace dirty fossil fuel-based vehicles with vehicles powered by clean electricity
   2. To decarbonize the grid, more capacity than will be used at certain times of day and load requires capacity and storage to compensate for the times when less energy is being produced (variability of renewable energy)
   3. When renewables are producing more energy than what is being consumed, storage will be required and electric vehicle batteries or hydrogen for fuel cell vehicles can provide that storage in addition to grid-connected storage
   4. Transportation requires you to store energy anyway, which dovetails neatly with a future in which we sometimes have a surplus of clean electrons
6. Biofuels will be required for marine, aviation, and potentially long-distance freight, but not for cars
   1. Takes 1-2 acres of land planted with canola to keep a Jetta TDI in biodiesel and only 270 ft² of solar panel in Seattle to power a Nissan Leaf, not counting the capital expenses for the biorefinery
7. Interconnection of building energy efficiency and electric vehicles
   1. Replace electric resistance heat in an ordinary Seattle house with a middle-of-the-road heat pump, save 60% (7,200 kW-hr) of the 12,000 kW-hr consumed for home heating in the winter. That energy is enough to drive a Nissan Leaf 24,000 miles