CMI's Stabilization Categories

Continuing our look at the Carbon Mitigation Initiative, here is a list of the different categories, and the most promising possibilities within those categories, that could be capable of producing a whole or partial wedge of abated emissions. Each wedge effectively prevents 1 billion tons of CO2 emissions per year, or 25 billion tons over the next half century. To stabilize atmospheric carbon concentrations, seven wedges are required.

Wedge Summary Table Category Technology Efficiency Efficient vehicles Reduced use of vehicles Efficient buildings Efficient baseload coal plants Decarbonization of power Gas baseload power for coal baseload power Capture CO2 at baseload power plant Nuclear power for coal power Wind power for coal power PV power for coal power Decarbonization of fuel Capture CO2 at H2 plant Capture CO2 at coal-to-synfuels plant Wind H2 in fuel-cell car for gasoline in hybrid car Biomass fuel for fossil fuel Forests and agricultural soils Reduced deforestation, plus reforestation, afforestation, and new plantations Conservation tillage

The Carbon Mitigation Initiative

In previous posts I have referred to the Carbon Mitigation Initiative, pioneered by Robert Socolow and Stephen Pacala, both of Princeton. As part of their work they have designed a "Stabilization triangle" that illustrates our current emissions trajectory if nothing is done, an increase that will lead to the tripling of CO2 concentration in the atmosphere, and a flat trajectory that will prevent the doubling of concentrations.

In their words:
"In order to avoid a doubling of CO2 and dramatic climate change, society needs to act quickly to deploy low-carbon energy technologies and enhance natural carbon sinks.
The "stabilization wedges" concept illustrates the scale of emissions cuts needed in the future, and provides a common unit for comparing the carbon mitigating capacities of various energy and storage technologies."

Implementing these reductions would prevent 200 billion tons of CO2 emissions between now and 2054. Each of the seven wedges represents reduction in the rate of emissions of 1 billion tons per year by 2054, or 25 billion over the whole period. Their wedges fall into five basic categories: energy conservation, renewable energy, enhanced natural sinks, nuclear energy, and fossil carbon management. All of these reductions can be made using existing and readily available technology, which does not mean that the political and social will is there. In my upcoming posts, I would like to look at some of their numbers, which help illustrate the scope of the challenge and provide a sobering reminder that every nation and sector of society must be involved, and that the average individual only has control over a small part of this effort.

Electricity Factoids

According to the EIA:

In 2005
Emissions from electric plants amounted to 2,513,609,000 Metric Tons of CO2

Electricity Production:
Coal produced: 2,013,179,000 megawatt hours

Natural Gas: 757,974,000 megawatt hours

Nuclear: 781,986,000 megawatt hours

Hydro-electric: 269,587,000 megawatt hours

Renewables: 94,932,000 megawatt hours

Nuclear, hydro and most renewables produce no greenhouse gas emissions.

Between 1994 and 2005:
We increased renewable energy production by 18,400 megawatt hours
We increased coal production by 322,485 megawatt hours

Emissions from Coal

From a National Environmental Trust report on "Sources of Greenhouse Gases in the United States":

Coal accounts for about half of electricity generation in terms of kilowatt hours, but 83% of carbon dioxide emissions from the electricity sector, the largest piece of the pie in terms of U.S. greenhouse gas emissions.

Natural gas, in contrast, generates nearly 20% of the country’s electricity but is responsible for 12% of emissions in this sector because it is a less carbon-intensive fuel.

Targeting Methane: Manure

From the EPA web site:

Methane emissions occur whenever animal waste is managed in anaerobic conditions. Liquid manure management systems, such as ponds, anaerobic lagoons, and holding tanks create oxygen free environments that promote methane production. Manure deposited on fields and pastures, or otherwise handled in a dry form, produces insignificant amounts of methane. Currently, livestock waste contributes about 8 percent of human-related methane emissions in the U.S. Given the trend toward larger farms, liquid manure management is expected to increase.

AgSTAR is an outreach program designed to reduce methane emissions from livestock waste management operations by promoting the use of biogas recovery systems. A biogas recovery system is an anaerobic digester with biogas capture and combustion to produce electricity, heat or hot water.

The AgSTAR Program has been very successful in encouraging the development and adoption of anaerobic digestion technology. Since the establishment of the program in 1994, the number of operational digester systems has grown to more than 125 systems across the United States. This has produced significant environmental and energy benefits, including methane emission reductions in 2007 alone of approximately 80,000 metric tons and energy generation of about 275 million kWh. The graph below shows the historical use of biogas recovery technology for animal waste management.

The development of anaerobic digesters for livestock manure treatment and energy production has accelerated at a very fast pace over the past few years. Factors influencing this market demand include: increased technical reliability of anaerobic digesters through the deployment of successful operating systems over the past five years; growing concern of farm owners about environmental quality; an increasing number of state and federal programs designed to cost share in the development of these systems; increasing energy costs and the desire for energy security; and the emergence of new state energy policies (such as net metering legislation) designed to expand growth in reliable renewable energy and green power markets.

Since 2003, methane reductions from operational digester systems have increased almost four fold.

Comment: As with landfill gas, the beauty of the manure digesters is that they not only trap a potent greenhouse gas, but they use that gas to generate electricity--electricity that might otherwise be generated by burning coal.

While the EPA is on the right track, at 125 systems they have just gotten started. According to their own numbers, an 80,000 metric ton reduction represents only about .2% of the 41 million metric tons of methane emissions that come from manure every year. But by some estimates, digesters would be cost-effective on about 7000 dairy and pig farms. These would have a generating capacity of about 722 MW, enough to power about 144,000 homes, and would reduce greenhouse emissions by about 30 million metric tons--the same as removing 4.7 million cars from the road.

One policy point: Given how important the agriculture sector is to tackling climate change, it is especially important that the environmental movement give farmers our support when our interests align. We will need their good will to push more far-reaching changes such as conservation tillage. We should strongly support greatly increased subsidies for biogas digesters--we will be giving farmers another source of income while at the same time preventing water and air pollution as well as methane emissions.

Targeting Methane: Turning Landfill Gas Into Electricity

Most of us love wind (unless we own a house on Nantucket), but let's not forget about the much less glamorous landfill gas, which offers a cheap source of power that puts to use what is now a nuisance gas. Landfills are already there, so using the gas presents far fewer problems with NIMBYism or people worried about their views.

According to these EPA numbers, we are currently exploiting about half the landfill gas potential in the U.S.:

As of December 2006, approximately 425 landfill gas (LFG) energy projects were operational in the United States. These 425 projects generate approximately 10 billion kilowatt-hours of electricity per year and deliver 230 million cubic feet per day of LFG to direct-use applications.

Of the 2,300 or so currently operating or recently closed MSW landfills in the United States, about 400 have LFG utilization projects. We estimate that approximately 560 additional MSW landfills could turn their gas into energy, producing enough electricity to power over 870,000 homes.

Comment: Burning methane produces CO2, but it counts as a renewable energy source since it is basically recycling carbon that was absorbed by (now decomposing) plants and animals. Targeting methane produces a double benefit first by preventing the methane emissions and second by using the methane as a substitute for non-renewable energy sources like coal.

Here are a few back-of the-envelop calculations: Generating 10 billion kWh of electricity from coal would produce more than 10.26 million metric tons of carbon emissions (assuming 2.3 lbs of CO2/kWh).

Using LFG to power another 870,000 homes--roughly another 9.5 billion kWh--would prevent another 9.7 million metric tons of emissions.

In 2006, methane emissions from landfills decreased by 20 million metric tons. If we were to take complete advantage of this resource, we could reduce methane and non-renewable emissions by about 60 MMT of CO2 equivalent--or about 5% of the total emissions from the residential sector (1197 MMT).

In contrast, according to industry numbers, wind currently generates about 17 billion kWh and prevents about 19 million tons of CO2 emissions each year.

Targeting Methane: Landfill Gas

The EPA is working to reduce landfill gas (LFG) emissions, which represent about 25% of human caused methane emissions. Whether through their program or through other means, U.S. LFG emissions are significantly down. Between 1990 and 2004, landfill methane emissions declined by 18%, or 31.4 million metric tons (CO2 equivalent) per year--that represents about .5% of total U.S. greenhouse gas emissions for 2004.

The EPA's Landfill Methane Outreach Program:

Accomplishments since program launch in 1994 include the following:

• As of December 2006, LMOP has more than 600 Partners that have signed voluntary agreements to work with EPA to develop cost-effective LFG energy projects.
• LMOP has developed detailed profiles for over 1,300 candidate landfills.
• There are approximately 425 operational LFG energy projects in the United States. In addition, about 120 projects are currently under construction or are exploring development options and opportunities.
• To date, LMOP has assisted in the development of approximately 330 LFG utilization projects - including 32 new projects and 9 project expansions that went online in 2006. These 330 projects have prevented the release of over 24 million metric tons of carbon equivalent (MMTCE - the basic unit of measure of greenhouse gases) into the atmosphere over the past 12 years.
• In the year 2006, all operational LFG energy projects in the United States prevented the release of over 20 MMTCE.
• This reduction is the carbon equivalent of removing the emissions from nearly 14 million vehicles on the road or planting nearly 20 million acres of forest for one year.
• These reductions also have the same environmental benefit as preventing the use of over 169 million barrels of oil or offsetting the use of over 356,000 railcars of coal.

The graph below illustrates the growth of LFG utilization projects before and after LMOP’s inception. The first LMOP-assisted projects started in 1995, as illustrated by the shaded portion atop the 1995 bar. After 1995, the projects are divided into two categories, those that fall under the New Source Performance Standards/Emission Guidlines (NSPS/EG - in blue) and those that don’t (in yellow). Within those two categories, the shaded lines illustrate LMOP assistance. Since 1995, there has been growth in all of the above mentioned areas.

The graph below illustrates LMOP's emission reduction goals as well as performance in relation to these goals. In 2001-2006, LMOP met its goal and anticipates that in future years will continue to meet increasing emission reductions. For 2006, we have broken down the source of the reductions into its three primary components - electricity generation, direct-use, and flaring.

Sources of Methane Emissions

from the EPA:

Human-related Sources

In the United States, the largest methane emissions come from the decomposition of wastes in landfills, ruminant digestion and manure management associated with domestic livestock, natural gas and oil systems, and coal mining. Table 1 shows the level of emissions from individual sources for the years 1990 and 1999 to 2003.

Table 1 U.S. Methane Emissions by Source (TgCO₂ Equivalents)

Source Category	1990	1999	2000	2001	2002	2003
Landfills	172.2	134.0	130.7	126.2	126.8	131.2
Natural Gas Systems	128.3	127.4	132.1	131.8	130.6	125.9
Enteric Fermentation	117.9	116.8	115.6	114.5	114.6	115.0
Coal Mining	81.9	58.9	56.2	55.6	52.4	53.8
Manure Management	31.2	38.8	38.1	38.9	39.3	39.1
Wastewater Treatment	24.8	33.6	34.3	34.7	35.8	36.8
Petroleum Systems	20.0	17.8	17.6	17.4	17.1	17.1
Rice Cultivation	7.1	8.3	7.5	7.6	6.8	6.9
Stationary Sources	7.8	7.1	7.3	6.7	6.4	6.7
Abandoned Coal Mines	6.1	7.3	7.7	6.9	6.4	6.4
Mobile Sources	4.8	3.6	3.4	3.1	2.9	2.7
Petrochemical Production	1.2	1.7	1.7	1.4	1.5	1.5
Iron and Steel	1.3	1.2	1.2	1.1	1.0	1.0
Agricultural Residue Burning	0.7	0.8	0.8	0.8	0.7	0.8
Total for U.S.	605.3	557.3	554.2	546.7	542.3	544.9

Methane Factoids

According to the EPA:

Methane (CH₄) is a principal component of natural gas. It is also formed and released to the atmosphere by biological processes occurring in anaerobic environments. Once in the atmosphere, methane absorbs terrestrial infrared radiation that would otherwise escape to space. This property can contribute to the warming of the atmosphere, which is why methane is a greenhouse gas.

Methane has more than 20 times the heat-trapping capacity of CO2.
The largest human source of U.S. methane emissions are landfills, with 34% of the total.

Other key human sources of methane are natural gas systems, cattle and other animals, wastewater treatment facilities, rice paddies, and coal mines.

Methane represents 7.9% of U.S. global warming gas emissions--these percentages are given in CO2 equivalents, and have already factored in methane's higher Global Warming Potential (GWP).

We reduced emissions of methane by about 10% between 1990-2004; during that period CO2 emissions grew by 20%.

Comment: methane reduction is the ultimate low-hanging fruit. Unlike CO2, which is produced by many necessary and beneficial human activities, a lot of human generated methane comes from poorly managed waste facilities such as landfills, farms, and sewage plants, or from things like leaky gas systems and old coal mines. Often, reduction strategies turn a waste or nuisance gas into an economic asset--as when manure or landfill gas is used to generate electricity. Also, it is much easier to target a few dozen natural gas companies, a few thousand landfills, or even the nation's dairy farmers, than to change the behavior of hundreds of millions of drivers or light bulb users.