The need to speed up carbon uptake

Last week I gave a talk, entitled "Net Ecosystem Production and Actionable Negative Emissions Strategies," at the American Geophysical Union (AGU) fall meeting in San Francisco. It was presented in a session on negative emissions strategies, which refers to the topic of removing CO2 from the air in order to slow -- and hopefully one day reverse -- the buildup of carbon in the atmosphere.

Net ecosystem production (NEP) is the net rate at which carbon is taken up by a terrestrial ecosystem. It determines the amount of carbon that becomes available for some use (e.g., crop or timber harvest) or for sequestration on the land. Scientifically speaking, any parcel of land with living organisms on it is an "ecosystem," including farm land or managed forests as well as natural lands and parts of the built environment that aren't totally paved with sterile concrete.

Plants and other organisms that carry out photosynthesis in the terrestrial biosphere actively remove CO2 from the air. Thus, they provide a fundamental mechanism for pursuing negative emissions. However, to be meaningful for climate mitigation -- which is the sense in which the term negative emissions is used -- carbon must be removed from the air more quickly than it is already being removed. That's what "the need to speed up carbon uptake" means and for the terrestrial biosphere, that means increasing NEP.

The fact that terrestrial carbon management is an actionable ("here-and-now") strategy and that using it for negative emissions requires increasing NEP are the main points of my talk. It can be download here in PDF format including both the narrative and slide images.

A simple comparison of ABC to LCA results for corn ethanol

Our recent paper [1] provides an example that compares annual basis carbon (ABC) accounting results to typical lifecycle analysis (LCA) results for corn ethanol. As noted in the paper's discussion section, we used the same process GHG emissions as used in a standard LCA but then adjusted for the fact that biofuel combustion is not fully carbon neutral, as LCA assumes. The implication is then that corn ethanol is 27% more carbon intensive than gasoline instead of 44% less carbon intensive as was claimed by the LCA previously published by Wang et al [2]. This post describes how we made that comparison.

Carbon balance effects of real-world biofuel use

Most of the debate about the environmental merits of biofuel use has been based on lifecycle analysis (LCA). Also known as life-cycle assessment, carbon footprint analysis, "cradle-to-grave" analysis, or (in the case of motor fuels) "well-to-wheels" analysis, LCA is a method for adding up all of the impacts of interest associated with a product. It includes the effects of producing a product and its component materials, associated shipping and packaging effects (as relevant), the use of the product and any related disposal effects. For assessing climatic impacts, LCA tallies the greenhouse gas (GHG) emissions associated with the production, use and disposal of the product. When the product is a motor fuel, the numerical result of such LCA modeling is called the fuel's "carbon intensity," as calculated for California's Low-Carbon Fuel Standard (LCFS), for example.

A cornfield does not absorb CO2 from the atmosphere
any more quickly when it is used to make ethanol than
when it is grown for food or feed. This basic fact of 
carbon mass balance is ignored by the lifecycle studies
that claim climate benefits for biofuels. 

The question, "how does the overall emissions impact of using a biofuel such as ethanol compare to that of a fossil fuel such as gasoline?" seems straightforward, and sounds like something that LCA can answer. However, that question is actually ill-posed scientifically speaking. In other words, when one looks carefully at what actually happens when a given biofuel substitutes for a fossil fuel, it turns out that LCA cannot give a straightforward, unambiguous answer. Properly qualified, the answer will always be, "it depends." And it doesn't just depend on the particular fuel and how it is produced; it also depends on the design of the LCA model and the assumptions it invokes.

U.S. biofuel consumption chart through 2015

Just to provide an updated picture of the rise in U.S. biofuel consumption, here's a chart based on the latest annual data from EIA's Monthly Energy Review (MER). 

As of calendar year 2015, U.S. ethanol consumption was 13.9 billion gallons per year, up from 1.7 billion gallons in 2000. In 2000, biodiesel consumption was below the level of significance for EIA reporting (i.e., statistically zero relative to overall U.S. motor fuel use). Biodiesel consumption reached 1.5 billion gallons in 2015, and so total biofuel consumption amounted to 15.4 billion gallons that year.

For context, U.S. motor gasoline consumption was 140 billion gallons and distillate fuel oil (which is mostly but not all highway diesel) was 61 billion gallons last year.

In terms of carbon, biofuels accounted for 4.7% of total direct CO2 emissions from the U.S. transportation sector in 2015.

A short URL for embedding this chart is: https://goo.gl/rM5EpM. If you use it, please credit this blog. The source data can be downloaded as Tables 10.3 (for ethanol) and 10.4 (for biodiesel) from the Renewable Energy section of EIA's MER webpage.

A-\R-\Corn+soy+biofuel_stats

Tailpipes top smokestacks as nation's largest CO2 emitters

Transportation, which runs almost entirely on petroleum fuels, and electricity generation, which had used mainly coal, have long been the largest sources of CO₂ emissions in the United States. Although power plant smokestacks exceeded motor vehicle tailpipes and other mobile sources such as aircraft in terms of CO₂ emissions for nearly forty years, this year brings a crossover of these two emission trends. The CO₂ emitted by the transportation sector has been greater than that from the power sector for seven of the past eight months, and so 2016 is on track to see mobility overtake electricity as the country's biggest contribution to global warming.

Will car companies do better than coal companies in embracing the climate challenge?

Today in Slate, Daniel Gross published a thought-provoking piece entitled "Could Coal Have Survived by Going Green?" It highlights how the industry itself contributed to its own demise not only by fighting environmental policies but also by failing to invest in ways to utilize coal much more cleanly.

The Cadillac Escalade: this one is as black as coal and its
tailpipe spews nearly nine tons of CO2 into the air per year.

Coal fueled the industrial revolution and even in this post-industrial era it still provides a bedrock source of energy for much of the world. Although now overtaken by natural gas for generating electricity in the United States, coal remains second only to oil as the world's largest source of commercial energy. Its low resource cost could give it a role even in an increasingly climate-constrained future. But for that to happen, the industry's leaders would have had to embrace carbon mitigation as a worthy, investment-stimulating challenge instead of spending down their dwindling political capital to fight the inevitable.

One can see some parallels here to the recent near-death crisis of U.S. domestic automakers. Although General Motors, Ford and Chrysler had often talked a green line and showed off a few token green-branded products, for many years their major investment and lobbying strategies emphasized evading energy and climate policies instead of embracing them.

Latest tweak to U.S. biofuel mandate is politically correct and ecologically cruel

EPA's new Renewable Fuel Standard (RFS) proposal modestly increases the amount of biofuel that America's cars and trucks have to consume next year but still keeps the total renewable fuel mandate below the Congressionally scripted target.

In the plan released on May 18, ordinary corn ethanol gets a 300 million gallon boost, biodiesel is bumped up by 100 million gallons and other so-called advanced biofuels see a 200 million gallon increase compared to last year's regulation. Nevertheless, the proposed 18.8 billion gallon total remains significantly lower than the 24 billion gallon goal for renewable fuel in 2017 that Congress wrote into law back in 2007.

EPA's approach reflects a compromise worked out last year after several tortuous years of regulatory delay. This "politically correct" strategy has the agency taking a middle road that balances the money-making interests of the biofuel industry and the corn and soybean lobbies against the engineering and economic realities that render ethanol and biodiesel such inferior motor fuels. Reactions to the proposal were predictable. The renewable fuel lobby and its allies complain "that's not enough" while the oil industry and other critics say "that's too much" biofuel.

House Oversight Testimony on the RFS

This post is a transcript of my oral testimony at the U.S. House of Representatives as delivered on March 16, 2016. 

I wish to thank the Chairs, Ranking Members and other members of the committee and subcommittees for inviting me to today’s hearing.

My name is John DeCicco and I am a research professor at the University of Michigan Energy Institute. My main focus is transportation fuel use and its environmental impact. I hold a doctorate in engineering from Princeton University and have worked on America's energy challenges for nearly 40 years, including 21 years at environmental organizations before returning to academia in 2009.

My recent research has included scientifically rigorous evaluations of the Renewable Fuel Standard (RFS) and other policies that promote biofuels such as ethanol and biodiesel. RFS proponents claim that the policy reduces CO2 emissions. I have found that it does not. In fact, from its inception, the RFS has increased rather than decreased the amount of CO2 entering the atmosphere compared to petroleum fuels such as gasoline.

Fuel Economy Matters

Pump prices are down and given the outlook of a weak global economy, a strong dollar and a lingering oil glut, they could drop even more as the year goes on. The U.S. average retail gasoline price fell below $2.00 per gallon in January and as of last week it averaged $1.93 per gallon. For over a year now, it's been significantly lower than the roughly $3.50 per gallon average of the previous few years, let alone the brief spike to over $4.00 per gallon in summer 2008. 

Consumers respond to gasoline prices and so it's no surprise that new vehicle sales are at a record high while the vehicle mix has shifted away from compact segments and back to trucks, larger SUVs and more luxurious cars. The amount of driving is back up as well. 

The fuel economy of the vehicle fleet doesn't totally backslide even when the price of fuel does. Most efficiency gains are due to improved technology; once such engineering refinements are made they don't get undone. Corporate Average Fuel Economy (CAFE) standards prop fuel economy up even when consumer interest fades, and that policy is now reinforced with greenhouse gas (GHG) emissions standards that limit the amount of carbon dioxide (CO₂) and other GHGs exhausted from tailpipes. 

Average new car and light truck fuel economy (right-hand axis) 

compared to nominal and inflation-adjusted gasoline prices. 

The adjoining graph compares the average fuel economy of new cars and light trucks to the price of gasoline since 1970, shown as both nominal "dollars of the day" and inflated to 2015 ("real") dollars. It's clear how fuel economy ratchets up as fuel prices rise. We can also see the slow backsliding that happened from the late 1980s until a decade ago. Although fuel economy has been climbing since 2005, we may be in for a serious tug-of-war between the need to keep fuel economy heading up and weakened consumer interest due to lower gasoline prices.