Keywords: ethanol; peak oil; Gaia; James Lovelock; cellulosic ethanol; switchgrass; biomass; greenhouse gas; C02; gasohol; E85; enzymes; Joseph DiPardo; Clostridium; Patricia E. Woertz; Archer Daniels Midland
If not intoxicated, I’m at least giddy with delight about ethanol. I’m no longer convinced that the shortage of fuel will do us in. Of course, there are still plenty of other dangers around; James Lovelock, the Gaia inventor, apparently believes that it’s too late to preserve earth’s homeostasis, and that we must expect climate change to destroy humankind within maybe twenty years, except for a few people in the melting Arctic.
Okay, saving Gaia will have to wait. Today was my day to save us from Peak Oil. (These capital letters are no accident. When any theory becomes all-encompassing, people tend to give it a proper name.) I am no longer afraid of the looming depletion of petroleum, for I have ethanol on my side. For my awareness of its promise, I am still thanking Ted Turner, idealistic huckster par excellence, who set me thinking and Googling about it.
For example, a report by the National Commission on Energy policy recently proclaimed that “biofuels coupled with vehicle efficiency and smart growth could reduce the oil dependency of our transportation sector by two-thirds by 2050 in a sustainable way.” That’s actually a modest projection, for some prophets are expecting equally good results even sooner.
For example, the National Renewable Energy Laboratory (http://www.nrel.gov/) posted for a while a draft of their report, available now at http://www.nirs.org/alternatives/factoid18.htm entitled: “Renewable Resources Could Provide 99 Percent of US Electricity Generation by 2020.” It listed the potential amount of energy available from renewables as a percentage of the total projected US generation in 2020. Here are some of the expected sources:
Biomass: 9- 14 percent of the national petroleum demand in 2020
Geothermal: 4 percent of US electric generation in 2020.
Hydroelectric: 9.4 percent of electric generation in 2020.
Ocean (wave, tidal, and current): 4.5 percent of electric generation projected for 2020.
Solar:12 percent of the total US generation
Wind: 20 percent of total generation.
They also offer projections of longer-term possibilities from these sources, but I won’t copy them down here. However, the ones I’ve shown above don’t add up to 99 percent, as the title of the paper led me to expect, so I may have missed something. Still the report seems, if anything, to project quite moderate estimates rather than overly optimistic ones.
For example, Wikipedia’s entry of “Cellulosic ethanol” projects that ethanol produced from biomass cellulose products “might provide as much as 30 percent of the current fuel consumption in the US — and probably similar figures in other oil-importing regions like China or Europe. Moreover, even land marginal for agriculture could be planted with cellulose-producing crops like switchgrass, resulting in enough production to substitute for all the current oil imports.” This 30 percent is far better than the aforementioned NREL estimate, 9-14 percent. And the Wikipedia writers also cite studies by the US Department of Energy conducted by the Argonne Laboratories.
“One of the benefits of cellulosic ethanol is that it reduces greenhouse gas emissions by 85 percent over reformulated gasoline. By contrast, starch ethanol (e.g. from corn), which uses most of the time natural gas to provide energy for the process, reduces greenhouse gas emissions by 18% to 29% over gasoline. Sugar ethanol, on the other hand, from sugarcane, reduces greenhouse gas emissions by as much as cellulosic ethanol...”
What about the energy efficiency of cellulosic ethanol? Until a few days ago I had dismissed all ethanol fuels as unpromising because, according to Jack Santa Barbara, they offer no net energy gain over fossil fuel. That is, for every unit of ethanol now being produced, one unit of fossil fuel energy is required. (Jack does admit that ethanol makes sense in Brazil, however, where the “feedstock” is sugarcane, which gets five units of energy out for every unit of input.)
Well, according to Joseph DiPardo’s paper, “Outlook for Biomass Ethanol Production and Demand,” ethanol does better than I had understood. Instead of referring to the input-output ratio, he describes the same issue in terms of “net energy balance”:
“The net energy balance is calculated by subtracting the energy required to produce a gallon of ethanol from the energy contained in a gallon of ethanol (approximately 76,000 Btu). Corn-based ethanol has a net energy balance of 20,000 to 25,000 Btu per gallon, whereas cellulosic ethanol has a net energy balance of more than 60,000 Btu per gallon.”
Thus the corn-based ethanol does better than 1:1, and cellulosic ethanol does far better than that — though of course it cannot compete with petroleum (a new well of sweet crude oil has a 100:1 ratio of output to input energy).
The greenhouse gas emissions also vary according to the source (“feedstock”) of the ethanol, and the composition of its blend with regular gasoline. After a little mechanical tinkering, it is possible for ordinary cars and trucks to use gasohol (or “E10”) — a blend containing 10% ethanol. Some other blends are higher in concentration, such as E85, which is 85 percent ethanol, 15 percent gasoline. As DiPardo reports,
“Argonne National Laboratory estimates that a 2-percent reduction in greenhouse gas emissions per vehicle mile traveled is achieved when corn-based ethanol is used in gasohol (E10), and that a 24- to 26-percent reduction is achieved when it is used in E85. Cellulosic ethanol can produce an 8- to 10-percent reduction in greenhouse gas emissions when used in E10 and a 68- to 91-percent reduction when used in E85. ”
This estimate seems consistent with the one I quoted above — 85 percent reduction, when cellulosic ethanol is “straight”— not mixed with gasoline at all. (I’m not sure whether it is ever used straight in cars, though.)
These papers assume more scientific knowledge of the reader than I actually bring to the task. For one thing, they describe the various processes that are being developed for making ethanol from cellulose, but I don’t follow the narratives. Evidently one process involves the use of enzymes to break down the cellulose into glucose molecules — a reaction that takes place in the stomachs of ruminants such as cows and sheep, which is why they can eat grass but you can’t. An alternative technology converts the carbon in the raw material into a gas, which is fermented by the action of a microorganism named Clostridium Ijungdahlii. (That name doesn’t look plausible but I think I copied it down right.) Apparently there’s a new strain of Clostridium bacteria that’s twice as efficient in producing ethanol than this current one.
There’s something else that I don’t understand fully either: the basis for the reduction of greenhouse gas emissions in ethanol as compared to fossil fuels. Most of the time the articles imply that alcohol’s superiority is simply because of its chemical composition. However, there seems to be another reason as well (or maybe instead of the former one): that it comes from renewable products. Yes, its combustion does produce greenhouse gasses; however, while it is doing so, the next crop of biomass plants is growing and absorbing an equivalent amount of CO2. These absorptions offset the emissions.
Now, is this THE reason why ethanol is better than gasoline? Or is it an additional reason, beyond the superiority that derives from its chemical composition? I don’t know. (If a reader can help me comprehend this, I’ll appreciate your commenting below.)
In any case, the main advantage of cellulosic ethanol seems perfectly clear: It enables us to use ingredients that are otherwise wasted. For one thing, we can recycle industrial wastes and municipal solid wastes, including paper sludge. This eliminates the landfilling of wastes. One of the byproducts is lignin — a material that can be recycled to make the plant self-sufficient in energy.
Agricultural wastes are abundant, for now they are simply burned or plowed back under. Some crops can be used for dual purposes: both food and fuel. Thus corn can be harvested for human or animal food, and the stover then used for ethanol, greatly increasing the farmers’ income. (As Ted Turner argues, this will enable governments to reduce or eliminate agricultural subsidies, thus giving developing countries the new opportunity to export their own products and escape from poverty.)
One of the most promising new crops for cellulosic ethanol feedstock is switchgrass (see photo), a perennial grass with a deep root system that prevents erosion and improves soil fertility. It can be raised in many unproductive areas without fertilizers or pesticides. It is also a superior feed crop, producing more protein for animals than corn.
I’m not the only person who is changing her mind about ethanol. In yesterday’s New York Times Business Section, Alexei Barrionuevo presented a big story about Patricia Woertz, who, as the head of refining at Chevron, used to argue against “mixing agricultural policy with fuels policy.” She has now become the CEO of Archer Daniels Midland, the biggest ethanol producer in the United States, which is investing heavily in its future production. Woertz expects ethanol to make up 10 percent of the country’s gasoline supply by sometime next decade, still using the same corn feedstock that is the mainstay for the current technology. When cellulosic ethanol technology is fully developed, she sees the possibility that it may one day replace more than half of gasoline. She is developing a collaborative relationship with Vinod Khosla the CEO of Sun Microsystems, which is investing in cellulosic ethanol. On Wednesday she is to give a major address in St. Louis at a conference promoting biofuels.
Well, good for her!