Science —

How California can hit its mid-century emissions reduction goals

California can still meet its 2050 emissions reduction goals if it focuses on …

How California can hit its mid-century emissions reduction goals

If California wants to reach its goals for greenhouse gas emissions—80 percent below 1990 levels by 2050—it must replace most direct fossil fuel use with electricity, according to a new analysis published in Science. In addition, energy efficiency needs to rise steadily and most electricity generation needs to be decarbonized. Since the state is the world’s sixth-largest economy and 12th largest greenhouse gas emitter (its per capita numbers are similar to those of Japan and Europe), strategies developed specifically for California are likely applicable to many large, developed nations.

The study was performed by a team from Energy and Environmental Economics, Monterey Institute of International Studies, UC Berkeley, and Lawrence Berkeley National Laboratory (all located in CA). Its authors took a much more detailed and accurate approach than previous work on the topic.

They built a model that broke down the CA economy into six energy-demand sectors (residential, industrial, transportation, agriculture, and petroleum) and two energy-supply sectors (fuel and electricity). The work also examined some cross-sectorial activities that produce nonenergy greenhouse gas emissions, such as cement production. The backbone of the model, explained in detail in the paper’s 117 pages of supporting material, involved calculating the rollover of infrastructure stocks, like cars, buildings, factories, and coal plants, across their planned lifetimes. It took into account turnover rates, realistic technological progress, and resource availability.

Now, if everyone in California stopped eating meat or switched from driving cars to riding bicycles, or if fusion energy suddenly became feasible, meeting the emissions goals would become a whole lot easier. However, this study left out drastic and probably unrealistic changes like these.

With their model in hand, the team essentially back-calculated what would have to happen to reach the target emissions goal, 85 Mt CO2e, meaning greenhouse gas emissions equivalent to that amount of CO2. They found that three major transformations to the current energy system are required to meet that goal: increasing energy efficiency 1.3 percent each year over the next 40 years; decarbonizing electricity generation with renewable energy, nuclear, and carbon capture and storage; and electrifying most direct uses of oil and gas (such as gasoline and diesel in cars and trucks).

The analysis found that, at best, renewables could provide only 74 percent of electricity demand, while others had previously claimed that renewables could meet all the future demand, due to CA’s high solar and wind resources. In the current study, they found that nuclear power, hydro (not considered renewable here), and natural gas with carbon capture and storage are still needed to meet growing demands.

Most importantly, they found that CA could not meet its emissions reduction goal without electrifying most direct uses of gas and oil. Electricity constitutes about 15 percent of end-use energy now, and this needs to be at 55 percent in 2050. Without this, the best the state can do is lower emissions to about 50 percent of 1990 levels (210 Mt CO2e). 

Most of this change needs to happen in the transportation sector, where in the proposed 2050 scenario, electricity powers 70 percent, biofuels 20 percent, and traditional fossil fuels 10 percent of miles driven. Liquid fuels are still needed for applications like aircraft and long-distance freight trucking, where electrification isn’t feasible. The authors emphasize "smart charging" of electric vehicles (charging the vehicles when demand is low, such as at night) will be needed in order to keep electricity demand steady and costs low. Other important areas where electricity needs to replace fuels include heating and industrial processes.

The pragmatists in the room are probably asking the big question: how much will all this cost? This is a bit tricky to answer, since predicting fuel and technology prices 40 years from now involves some speculation. The authors estimate cumulative costs from 2010 to 2050 of $1.4 trillion, with yearly costs starting at 0.5 percent of the gross state product (GSP) in 2020 and increasing to 1.3 percent of GSP in 2050. This study did not focus on optimizing for cost, however, only on reaching the emissions goal.

Like anything that tries to predict the future, there are some obvious limitations to this study. For instance, the scenario involves a steady 1.3 percent energy efficiency increase every year—this is unprecedented over such a long period of time, but it falls within the range of potential increases in efficiency shown by other recent papers. It also assumes that we can focus technology development, which isn't always guaranteed; it's certain that we'll make technological advances, but they may not be the advances we want or need.

Regardless, this study should be useful to help direct funding and plan infrastructure development to meet the emissions reduction goal—which is still possible, according to the authors, but we need to start now.

Science, 2011. DOI: 10.1126/science.1208365 (About DOIs)

Further reading

Listing image by Photograph by ca.gov

Channel Ars Technica