U.S. CO2 Emissions by Sector and State

Lowering CO2 emissions is increasingly becoming a goal of Corporate America. The CEO's of 10 major corporations are calling on the Bush administration and Congress to pass some " ... serious global warming legislation as quickly as possible." Evangelical Christians, an important constituency inside the Republican party, are also beginning to take environmental issues more seriously. Throw in the 2008 Presidential primaries early next year, and this could be the year of serious global warming legislation.

So what are the primary sources of CO2 emissions in the U.S.? What states and regions have the highest CO2 emissions per capita? I turned to data published by the Environmental Protection Agency (EPA). The EPA data spans 1990-2003, and is broken down by "sector". While composing this post I came across similar data (Wall St. Journal, subscription required) from the International Energy Agency (IEA).

(To enlarge a particular image, click on it.) In the U.S., 33% of CO2 emissions come from the Transportation sector, world-wide, Transporation accounts for only 20%. Americans tend to drive less fuel-efficient vehicles, and tend to drive more miles. Interestingly, while the fast-growing economies of India and China are increasing their share of emissions from the Transportation sector, the U.S. seems to be trending towards less driving, and lighter and more fuel-efficient cars. With the growing popularity of hybrids, bio-diesel, and the possibility of plug-in hybrids, I expect the Transportation sector in the U.S. to see large reductions in the next decade. The other notable difference: the U.S. Residential sector accounts for about 7% of CO2 emissions, compared to 13% world-wide.

Which sectors have shown the fastest growth from 1990-2003? Again we normalize all the time-series, so they start at a common value (say 100), then use their respective year-over-year growth rates to plot the rest of the graph:

From 1990-2003, emissions from the Electric Power and Transportation sectors grew 24% and 20% respectively. Not only are these the largest sources of CO2 emissions (accounting for 71% of total emissions in 2003), they are also the fastest-growing. Policy-makers in the bellwether state of California have long focused their efforts on these sectors, and recently two key initiatives garnered bi-partisan support: utilities must produce 20% of their electricity from renewable sources by 2010 AND refineries and gas stations must reduce by 20% the carbon content of fuel they sell by 2020. As the " ... world's ninth largest emitter of the greenhouse gases that trap heat in the atmosphere", California is ground zero for innovation in renewable energy.

In the U.S., emissions from the Industrial sector declined by 5% from 1990-2003. This drop is probably a reflection of the fact that the U.S. manufacturing sector has declined significantly during that time period.

Finally we use heat maps to present state level emissions. To account for the size of a state, we compare emissions-per-capita. Our benchmark will be the U.S. per capita emissions: Green means a state has lower per capita emissions than the U.S., Red means it has higher emissions per capita.

In 2003, Wyoming had the highest TOTAL CO2 emissions per capita. The above map is somewhat reminiscent of the 2004 Presidential Electoral College map :-)

Next we examine state level emissions data for the two largest sources of CO2 emissions in the U.S. (Electric Power and Transportation).

The Western states rely more on hydro-electric power compared to the rest of the country. The "red" states are most likely those that lean heavily on coal powered plants. In a previous post, I highlighted the fact that California used the least amount of electricity per capita. In the graph below, we look at a simple linear relationship, between electricity consumption per-capita AND per capita CO2 emissions due to electric power:

WY, ND, WV are states whose per capita CO2 emissions are high relative to their per capita electricity consumption. These are states whose electric power comes largely from coal powered plants.

Turning to the Transportation sector:

We expect California (home to over 1 in 10 new cars sold in the U.S.) to be about average, and the Northeast (home to mass transit) to have less emissions per capita. In a previous post, I noted that California is among the states that used the LEAST amount of gasoline per capita (here is a map). Below is a scatterplot of 2004 Gasoline consumption per capita vs. 2003 CO2 Emissions from Transportation. Unfortunately, data for the variables represent two different years:

Using this "weak" linear relationship, we uncovered some interesing outliers: AK, WY, and to a lesser extent HI and LA. These states have CO2 emissions (from Transportation) higher than what one would expect from their repective per capita gasoline consumption. AK is a huge state, and transportation between some areas is limited: to get to the state capital you have to fly or take a ferry! I suspect that gasoline consumption-per-capita is largely based on data from gas stations, while the Transportation emissions-per-capita captures more forms of transportation.

Sound energy policy pays off relatively quickly. Consider the case of California:

Power use per person has remained roughly stable in the state since the 1970s, even as it has doubled in the rest of the country (see chart above). As a result, California's greenhouse-gas emissions per person are on a par with those of Denmark. Relative to the size of its economy, they are lower.

In the next few weeks, I will try to focus on the Transportation and Electric Utility sectors: the reasons behind the high amounts of emissions, and the solutions currently being developed.

UPDATE: The SJ Mercury News has a great article on the steps California took to become the most energy efficient state in the US.

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U.S. Renewable Energy Consumption

I recently came across data sets on Renewable Energy Consumption from the U.S. Census. Besides recent Consumption rates, we will examine historical rates and trends. Consumption gives a good proxy for the growth in investments in particular types of renewables: the more projects get funded, the more energy is available for consumption.

The U.S. Census defines renewable energy as:

... obtained from sources that are essentially inexhaustible unlike fossil fuels of which there is a finite supply.

Using this definition, the U.S. Census included the following sources:

• Biomass: Organic nonfossil material of biological origin constituting a renewable energy source.
• (Conventional) Hydroelectric: Power produced from natural streamflow as regulated by available storage.
• Geothermal: As used at electric power plants, hot water or steam extracted from geothermal reservoirs in the Earth's crust that is supplied to steam turbines at electric power plants that drive generators to produce electricity.
  
• Wind: Energy present in wind motion that can be converted to mechanical energy for driving pumps, mills, and electric power generators. Wind pushes against sails, vanes, or blades radiating from a central rotating shaft.
  
• Solar: Includes small amounts of distributed solar thermal and photovoltaic energy.
  

We quickly plot the total consumption (in Quadrillion BTU's) over the 2003-2004 period. (To enlarge a particular image, click on it.)


A drawback in the U.S. Census data set is that it ends in 2004: there has been a surge in interest in renewables, over the last 2 years, among the general public, policy makers, and the private sector. Rising oil prices, articles about "peak oil", instability in oil producing regions, and increasing concern about climate change have all contributed to the overall interest in renewables. I'm particularly interested in Wind and Solar, which the graph shows are small relative to the other sources. How fast have consumption in Solar and Wind grown in the last decade? Recent media coverage in Wind and Solar energy included pending/current projects, interesting start-ups, and increased interest from VC's. Based on the volume of media reports, one gets the sense that Wind and Solar projects and companies have gone mainstream.

The bar graph gives us an idea of the total 2003-2004 consumption in the different sources of renewable energy. What about growth rates and recent trends? The problem with using regular time-series graphs is that the difference in magnitudes (Biomass is much larger than Solar) will hide trends for the smaller energy sources (Geothermal, Wind, Solar). A common trick is to normalize all the time-series, so they start at a common value (say 100), then use their respective year-over-year growth rates to plot the rest of the graph:


Using the normalized values, we expect the smaller sources to display faster growth rates. Nonetheless, Wind Energy consumption has skyrocketed since 1998. The American Wind Energy Association has an "installed capacity" graph which shows a similar post-1998 growth spurt. What happened in the Wind Energy sector during the late 1990s? A combination of contract negotiations with Utilities, new turbine technology, and geographic diversification:

In the 1990s, the California wind farm market began to be affected by the expiration or forced re-negotiation of attractive power purchase contracts with the major California utilities: Southern California Edison and Pacific Gas and Electric. And much of the existing inventory of 1980's wind turbines were really an albatross around the wind industry's neck. Renewal was needed, and -- bouyed by "green power" initiatives in Colorado, Texas and elsewhere -- U.S. wind energy development resumed in 1999, with a much broader geographical base.

Since the growth in Wind Energy distorted the graph, here is a view minus Wind Energy:


I was suprised by the slow growth in Solar Energy consumption. From 1989 to 2004, Solar Energy consumption grew a paltry 15%, compared to a 550% increase in Wind Energy consumption. Based on tax incentives made available over the last two years, I am inclined to believe that Solar Energy consumption grew rapidly in 2005-2006. I look forward to updating these charts to include years after 2004.

So which states are the leading producers of renewable energy? In an earlier post, I listed the top ethanol producing states. The American Wind Energy Association has a nice map showing Texas and California as the top 2 states in terms of megawatts derived from Wind Energy. I hope to address this question in more detail in future posts. For now, here is renewable energy production, as compiled by the U.S. Census:


Given that production was measured in millions of kilowatt hours, I wonder if this data came from utility companies. Note that the aggregation by type, looks quite different from the earlier consumption bar chart.

Holy Mackey: Whole Foods Reader Comments

Whole Foods Market CEO John Mackey started blogging in September 2005, and while I counted only 9 posts, they are all thoughtful and well-written. Equally interesting are the comments left by readers of his blog. Are there particular topics that emerge as important to the blog's readers?

Reprising an earlier post, I used recent developments in (unsupervised) machine learning and bayesian computation. These new techniques allows one to analyze text data, uncover latent topics, and measure the relative sizes of the topics. I was able to identify 473 comments, from the 9 blog posts. While the number of comments is relatively small for an algorithm of this type, I decided to forge ahead and see if what type of results I would get. Using this text mining algorithm, I uncovered 25 topics/subjects from the readers' comments.


As usual, to enlarge an image, click on it. If the topics where equally sized, one expects about 4% of the words found in readers comments to be devoted to each of the 25 topics. Interestingly, the Top 10 topics (in blue) were those with size clearly above the benchmark 4%. For completness, I included some other smaller but notable topics (in yellow).

Not suprisingly, the most popular topic was locally grown and organic food. Related topics include, Michael Pollan's recent book and sustainable agriculture: combined these 3 topics accounted for about 1 in 7 words found in the readers comments. Another popular subject centered around alternatives to purely profit-driven models of business ("good corporations", "the business world and company purpose", "social responsibility", "new capitalism"): these three topics accounted for about 1 in 7 words found in the readers comments. Animal Welfare, as represented by the lower ranking topics, "treatment of animals" and "organic dairy and farms", combined to account for about 1 in 14 words found in the readers comments. Topics that address Whole Foods culture ("team members and culture", "people and vision", "stock and investors", "company/leadership") accounted for about 1 in 6 words found in the readers comments.

SUMMARY: CEO John Mackey's blog elicited comments touching on some of the most interesting (green) topics of the day. Such serious exchanges, provide yet another sign that Whole Foods is different from other large corporations. Can you name another major public company with a CEO who blogs and generates responses which address these topics?