Biofuel Efficiency

Along with other forms of so called “renewable energy,” I have come to hold a jaundiced view of biofuels, largely because of their inevitable competition with food supplies, as well as some concern about land use and the pressure placed on natural habitats, and finally, maybe most importantly, the long term sustainability of large scale ammonia synthesis coupled with the depletion of phosphate reserves, both of which are required for industrial scale agriculture.

Today, the overwhelming majority of the corn crop grown in Iowa, for instance, is converted to ethanol for use as an oxygenated gasoline additive, where it has replaced MTBE, (methyl t-butyl ether) as an agent to reduce the serious air pollution associated with gasoline. (As is often the case with industrialized “solutions” to environmental problems, MTBE had environmental problems of its own, which led to it being banned in many places as a fuel additive.) The use of the ethanol replacement – which is advertised as “renewable energy” - has helped Iowa corn farmers to sustain high prices for their product.

During a recent lecture at the Andlinger Center for Energy and the Environment at Princeton University,  on the subject of the sustainability of water use for growing biofuels, Jerald Schnoor, who is the Allen S. Henry Chair, Professor of Civil & Environmental Engineering at University of Iowa who is also the Editor of the important journal Environmental Science and Technology - after remarking on how wonderful it is to have tenure given how unpopular his scientific opinions are in, well, Iowa – among other things, noted that water use in Iowa to grow corn for ethanol is responsible for a large dead zone at the mouth of the Mississippi River in Louisiana. This is because of the run off associated with rainfall on, and irrigation of corn fields treated with nitrogen and phosphorous fertilizers in Iowa has led to the eutrophication of a stretch of the Gulf of Mexico roughly the size of New Jersey, where fish, shellfish, well, practically everything (except algae) are unable to survive.   

This problem is not limited to the Gulf of Mexico, agricultural runoff and both treated and untreated sewage have led to the appearance of “green and yellow tides,”[1] massive choking outbreaks of algae blooms, worldwide.

Interestingly, it is algae that are often proposed as a source of biofuels, specifically biodiesel, a widely utilized fuel generally made from palm oil or other vegetable oils  – probably the liquid biofuel that is second to ethanol in scale of industrial use – that is composed of what are widely known as FAME, fatty acid methyl esters. At this point, algal biodiesel, like the much hyped and still industrially unimportant cellulosic ethanol industry remains largely the subject of wishful thinking. That said, given that so many bodies of water around the world are suffering from eutrophication, algae based liquid fuel remains, for me at least, intriguing enough to be worthy of further consideration, not just for the purpose of making biofuels but also for the subsidiary reason of recovering a fraction of run off  phosphorous. (Most of the world’s phosphorous, on which the agricultural green revolution of the 1950’s has depended, is mined from deposits, deposits that are subject to depletion.[2])

As practiced now, again, the biodiesel industry relies on the transesterification of fats and oils from plant and animal sources. Vegetable oils and animal fats are almost entirely triesters of glycerol.   In their native forms vegetable oils and animal fats are marginally useful in most diesel engines – famously Rudolf Diesel ran his first compression engine on peanut oil - but for practical reasons using modern engines the glyceryl triesters are substituted with methanol to give (mono) methyl esters which have superior properties as diesel fuel. Under the conditions under which the monomethyl fatty acid esters are made, glycerol forms an immiscible liquid phase which is separated from the biodiesel fuel.

(Almost all of the world’s methanol, by the way, is produced by the partial oxidation of dangerous natural gas, and thus like the wind and solar industries, the “renewable” biodiesel industry is dependent on access to dangerous fossil fuels.)

Glycerol is therefore a by-product of the production of biodiesel (and, for that matter, soap). Glycerol has three carbons, three oxygen atoms and eight hydrogens, and thus, by weight is 52% oxygen, 39% carbon and 8% hydrogen, meaning that it is highly oxygenated, more oxygenated than ethanol, which is only 17% oxygen. However glycerol cannot be utilized directly as a motor fuel, since, among other things, it is insoluble in petroleum based fuels. This a huge drawback because almost the entire “renewable” corn ethanol business, along with the entire “renewable” biodiesel business functions to provide additives to petroleum based fuels, a very limited number of vehicles burn these fuels exclusively. Moreover the direct combustion of glycerol is difficult because of its viscosity, low heating value, miscibility with water, and high flash point. Concerns exist that a potential oxidation product under some conditions is acrolein, [3]  which is thought to be one of the major carcinogens in cigarette smoke.[4] Thus direct incineration is problematic.

Thus, as a result of the “renewable” biodiesel business, a glut of glycerol has appeared. Although glycerol does have some economic value as an additive to pharmaceutical and cosmetic products as well as other specialized uses, such as the manufacture of the explosive nitroglycerin, none of these current industrial uses can consume the amount of glycerol produced by the biodiesel production industry, leading to prices so low that it is not worth transporting. Often the “solution” to the question of what to do with it is to dump the glycerol in local landfills, where the biodiesel industry likes to tell everyone it will “biodegrade.”  This is undoubtedly true, which is not to say that glycerol dumps are ideal. Indeed, the 39% carbon in glycerol represents concentrated carbon captured from the air and it seems a shame to throw it away where it will ultimately end up back in humanity’s favorite waste dump, the planetary atmosphere, as carbon dioxide.

Chemists around the world have recognized this problem, and have come up with many interesting solutions to the problem, one of which is to deliberately convert it to acrolein,[5], [6] ,[7], [8], [9] , [10] , [11] which despite its toxicity turns out to be a useful synthon (starting material) in organic chemistry, a potential non-fossil fuel path, for example, to methacrylate and other related acrylic polymers, displacing some of the petroleum requirements of this multi-billion dollar market. Acrylic polymers so prepared actually would represent sequestered carbon if the ultimate fate of the polymer is not to be incinerated. Be this as it may, these types of applications are probably not economic for a variety of reasons. One concerns the fact that for economic reasons probably all of the world’s methylacrylate polymer processes are continuous, and plants for producing operate on a scale of hundreds of thousands of tons per year. The installation of the complex machinery associated with these plants at biodiesel production facilities – some of which may be subject to sporadic seasonal operations would tend to make acrylic polymers so prepared relatively expensive. Also, the plants would need to be multistage plants, conducting the dehydration of glycerol to acrolein, oxidation of the acrolein to acrylic acid, functionalization of the acid, and finally polymerization. On the other hand, transport of glycerol to large existing plants for carrying out these functions without access to pipeline transport would impact both the economics and carbon signature of any resulting manufactured material.

It would be better to convert glycerol into a useful material using simpler processes, and happily such a material exists, it’s called “solketal.” Solketal is formed when glycerol and acetone react in the presence of acid to form a five membered ring containing two oxygen atoms and three carbon atoms – called a 1,3-dioxolane, – chemically bonded to a methanol molecule, releasing a molecule of water in the process of formation. (The formal descriptive name of solketal is 2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane, not to be confused with toxic dioxins.)  In order to drive the reaction to completion, it is necessary to remove the water from the reaction mixture, as well as to develop approaches to addressing issues of multiple liquid phases, but happily many approaches to solving the problems of solketal synthesis have been developed.[12], [13], ,[14] ,[15] , [16]

As a motor fuel, solketal has much to recommend it.    It has been shown to be soluble in gasoline, including gasoline containing a high proportion of ethanol, as much as 25%, and to increase the octane number of fuels by as much as 2.5 octane units. Added to biodiesel, it’s t-butyl ether derivative resolves the problem that biodiesel has with a relatively high melting point which is problematic in winter conditions.[17]

While one portion, the glycerol portion is clearly biological in origins, it is reasonable to ask from whence the acetone portion of the molecule comes. Acetone, of course, is the major constituent of nail polish remover, but it is also a molecule of industrial importance as a solvent, as a synthon, and as constituent of many commercial products for example, varnishes and paints. Almost all of the acetone on earth is currently made via the partial oxidation, with air, of cumene, which has formal chemical name of (1-methyl)ethyl benzene or the more descriptive trivial name isopropylbenzene, to give an unstable compound, cumene hydroperoxide, which on heating decomposes to give one molecule of phenol and one molecule of acetone[18]. The industrial product demand for each of the two molecules is happily quite evenly matched on a molar basis. Cumene itself was developed during the Second World War as an octane enhancer for aviation fuel: It is derived by the alkylation of benzene with propene, benzene and propene both being products of the dangerous fossil fuel industry. Thus the question of whether or not solketal is really a “renewable” biofuel under current industrial practice is certainly open to debate, given that in the case of solketal, exactly half of the carbon content is derived from dangerous fossil fuel sources.

Are there industrial examples of biological sources of acetone? The answer to this question is yes, and in fact, the process has been industrialized on a very large scale, and then abandoned – in favor of the petroleum based route – but it seems to have returned to industrial practice in recent years.[19]   This is known as the ABE process, the Acetone, Butanol, and Ethanol process, which for many years in the early twentieth century worldwide, and the mid twentieth century in both China[20] and the former Soviet Union,[21] was the world’s largest industrial fermentation process. In the Soviet case, the feedstock was not corn – as it was in other places where the ABE process was industrialized – but rather “waste” feedstock, notably corn cobs.[22] 

Butanol (and to be clear this is the 1-butanol isomer) and ethanol are both biofuels in their own right, with the former being somewhat superior to the latter in terms of utilization in internal combustion engines, even though the latter is produced and utilized in vastly larger quantities.   

Nevertheless, it is not clear that the ABE process can ever be scaled up even to match the current supply of the glycerol biodiesel waste product with sufficient acetone to make solketal, and the dirty secret of the biofuel business is its water demand, not just to grow the stuff, but to ferment it. All fermenting organisms require water. Add to this the intrinsic cost of separating the organic products from water – an energy intensive process - and one comes away immediately with a sense that the entire enterprise is quixotic.

This brings me, in a convoluted fashion, to my point.

To anyone who is familiar with my writings over the years in various places around the internet will recognize that I am a critic of the so called “renewable energy” industry as a whole. I have argued repeatedly that there are zero forms of so called “renewable energy” that can be as clean, as safe, as sustainable and as economically viable as nuclear energy.

So what is a nuclear advocate doing carrying on about improved biofuels?    

I note, in the nuclear context, among my fellow nuclear advocates, I often complain about the “thorium folks” who want to “throw out the baby with the bath water” by focusing on the drawbacks – drawbacks that I insist are minor – of the uranium/plutonium fuel cycle.  

There is one thing that biosystems probably do far more successfully than nuclear systems are likely to be able to do, and that is to remove carbon dioxide from the atmosphere. This is because biological matter is self-replicating, and thus is able to cover huge surface areas - surface area is a key component of effective processing of dilute species like atmospheric carbon dioxide – this with minimal investment. In fact this state of affairs will usually occur with and without human intervention, often at cross purposes with human goals, witness the algae based sometimes toxic and often destructive red and green tides to which I referred in the opening of this diatribe. Thus it is possible to argue that in rejecting biofuels wholesale, I may be accused with some reason of “throwing a baby out with the bathwater” myself.

Perhaps the problematic red and green tides represent themselves a possible key to the biofuel problem. The mechanism by which these tides destroy ecosystems, denuding them of both vertebrae and crustaceans goes like this: The growth of the organisms is vastly stimulated by the presence of nitrogenous and phosphate species, and begin to grow rapidly. These are photosynthetic organisms and of course, in the process of growing they release oxygen, but only some of this oxygen remains in the seawater; some of it escapes to the atmosphere. The organisms in the tides grow so thick that they actually begin to obscure sunlight, creating what is known as a “twilight zone.” A paper just published in the current issue of Nature[23] as of this writing, March 30, 2014, discusses what happens in oceanic “twilight zones” albeit not specifically in the context of eutrophic ocean. Some of the photosynthetic organisms, lacking light, or dying from some other cause, begin to sink to the ocean bottom. As it sinks and after it sinks, this biomass is decomposed by bacteria, and in this process of decomposition, oxygen is consumed at such a rate that it is effectively depleted. This of course makes it impossible for fish and crustaceans to survive, and thus a dead zone is created, of which the dead zone at the mouth of the Mississippi River is just one example.

But suppose this biomass were physically removed by the action of ships using pumps, filters, nets or a suitable combination thereof, what then? Conceivably, this might restore, at least partially, the ecological health of dead zones, including the important fisheries in Louisiana, among other places.    But simply dumping the biomass so skimmed is hardly satisfactory or, as they sometimes emit hydrogen sulfide in the process of rotting – safe, but they are a carbon source. From the mouth of the Mississippi, they might well be transported to the giant petrochemical complexes of Houston and Louisiana, complexes that might well be retrofitted or rebuilt to handle a new carbon source quite different from the dangerous fossil fuels processed there now.    

I noted above that algae can be used to obtain biodiesel, and there are, in fact, many species of algae growing in uncontrolled conditions, in seawater for instance, that make the oils and fats that are starting materials for biodiesel quite well. I am not however, recommending, at least as a general approach, the preparation of things like biodiesel, glycerol, solketal, etc., etc., etc., from oceanic biomass so collected from dead zones, although there are probably many high value chemicals that might be produced for specific products. (For a recent review among the hundreds, if not thousands, that have been published on the valorization of biomass to make specific chemicals, because I just happen to have it handy in my files, I direct the interested reader to a reference[24] which focuses on biomass as a source of relatively pure products described as “fuel additives” although the chemicals explored have many other applicationsbeyond fuel additives . There are some chemicals that can be obtained from biomass, exclusively, that are likely to be of industrial importance to, for instance, specific industries, such as the pharmaceutical industry)

The high temperature treatment of biomass with steam – or interestingly enough  carbon dioxide itself, of which we have a glut far more serious than any glut of glycerol can be - will give a mixture of hydrogen and carbon oxides, we call “syn gas” – as well as some other fixed carbon stuff like asphaltenes. (Asphaltenes are also found in petroleum, as a “nuisance” side product which is nonetheless used to pave roads, where it represents sequestered carbon. Biomass derived asphaltenes would represent fixed carbon obtained from the atmosphere.) In the golden age of chemistry, in which we live, there are very few important organic chemicals that we cannot make with access to syn gas.  Archimedes famously said, "Give me a place to stand, and I can move the Earth!"   The modern chemist might say, without too much exaggeration, "Give me some 'syn gas' and I can make any organic chemical industrial commodity there is!" We can make “FT” (Fischer-Tropsch) gasoline, diesel fuel, kerosene, jet fuel if we still want any of that awful stuff, or things like my favorite “one size fits all” wonder fuel, dimethyl ether. Hell, we can make anything and everything we make from dangerous fossil fuels using syn gas or carbonized biomass, including I think, with due respect to the great mind of Vaclav Smil,[25] even perhaps steel[26].

Another residue of this process, besides asphaltenes, and maybe some minerals would be an important material on which our entire agricultural productivity depends and which is decidedly not renewable, specifically, phosphorous. I note that one chain by which oceanic phosphorous returns to land is the activity of birds and other organisms which eat fish; but as fish stocks are under threat, and the process is slow in any case, this chain risks being seriously broken. Of course the biomass responsible for eutrophication exists precisely because of phosphorous (and nitrogen).

And how would I recommend this kind of process be done? There is one thing that the United States manufactures probably better than anyone else, devices we still train young people to use: Nuclear ships. Of course, all of the nuclear ships we build are intended for warlike purposes, but there is no technical reason that we cannot divert this technological expertise to peaceful purposes, as we’ve been building and using these ships for more than half a century. Nuclear biomass collecting ships would by definition, immediately render the collection of biomass from the sea a carbon negative technology.   Indeed, things like polymers, carbon fibers, and the like made from such collected carbon would represent usefully sequestered carbon, not carbon that one pays to dump, but rather carbon that one is paid to make.

And the heat for this gasification of biomass to make syn gas?

Nuclear of course. The kinds of reactors we build now are not suitable for this purpose; they are mere electricity making machines. But I note that there are reactors suitable for the job close to commercialization. I’ll mention one because, as a nuclear thinker, I’m a lead coolant kind of guy, the Gen4 modular reactor.[27] The people making this reactor are advertising it to do dubious things, for instance, the processing of tar sands, which I oppose on the grounds that I oppose all dangerous fossil fuels, but there is no technical reason in the world that a few hundred, even a few thousand, of these reactors installed along the Gulf of Mexico could help move the world in the opposite direction, toward the immediate phase out of dangerous fossil fuels. And frankly I’m convinced that even this fine reactor is not the best possible reactor for these purposes. With a little creativity it is possible to think of superior reactors that might do a similar thing better.

How much biomass is there in the ocean? I recently attended a lecture with my sons by the oceanographer Kay Bidle of Rutgers University at the Princeton Plasma Physics laboratory’s wonderful “Science Saturday” series which is held each winter. He had some beautiful graphics on oceanic carbon flows, but of course, I don’t have them, but you can watch the lecture yourself on the internet,[28]  - it’s fascinating - and even hear me, at the end of the lecture, ask a question of Dr. Bidle, not the one about space aliens. According to Dr. Bidle, the mass of biomass carbon at the surface of the ocean is about 900 gigatons, roughly about 28 times more massive than the amount humanity routinely dumps each year, with the amount that has fallen to the bottom of the ocean over millions of years easily dwarfing that. According to the note I attached to reference 23, about 100 gigatons are fixed each year by photosynthesis.

Obviously only a small portion of this is in the Gulf of Mexico, but still…

The latest IEA figures for carbon emissions (2011) suggest that 32.6 Gigatons of carbon are dumped each year, of which 14.4 Gigatons come from dangerous coal. The dangerous coal figure is low hanging fruit, and could sensibly be eliminated by using the “French solution,” replacing all coal facilities with nuclear facilities. This leaves dangerous natural gas, and dangerous petroleum, which combined, equal about 18.2 Gigatons with which to deal. By eliminating the world’s dangerous fossil fuel powered ships and replacing them with nuclear powered ships, we can address about 10% of the total petroleum fraction of dangerous fossil fuel waste, which is 11.4 Gigatons, thus leaving 18.2 – (0.1*11.4) = 17 Gigatons.

Can seaweed address the bulk of this? Probably not. Even the ocean is not big enough to do this, never mind whirligigs and cadmium coated glass in California deserts.

To wit:

In reference 1, the authors suggest that a single species responsible for green tides off the coast of China, Ulva prolifera can grow from 500 MT to over 1 million metric tons over a period as low as six weeks: In 2008, according to the authors, 3500 square kilometers of the Yellow Sea were covered by algae patches of this species, although no estimate is made of the total mass represented. Several other million ton outbreaks were suggested, in places as varied as the Gulf of Mexico, the Sargasso Sea and even the Venice lagoon. But these numbers are trivial when compared with the carbon budget of dangerous natural gas and petroleum. Nevertheless, were it only for the phosphorous and the protection of economically important oceanic ecosystems, the effort might well prove worth it, particularly if captured carbon dioxide were used as the oxidizing species rather than water. It certainly seems that we could knock off a gigaton or two worldwide with carbon fixed at sea, collected by nuclear powered ships, and processed with nuclear heat.

Would it be easy? No, of course not. Is it possible? I think so. Could such a scheme be made economically viable? Possibly, depending on the internal and external costs of dangerous fossil fuels. In any case, it could be no worse than the impossibly bad choice of doing nothing, even if doing nothing seems to be exactly what humanity’s policy is.

 

Notes and References



[1]  Victor Smetacek & Adriana Zingone, Nature 504, 84–88 (05 December 2013)

[2] An interesting case showing a profound early effect of phosphate ore depletion is the dire situation on the island nation of Nauru.    In the 1980’s Nauru went from being the nation with the highest per capita income in the world – because of the export of phosphate deposited on the island by bird droppings over millennia – to one of the poorest nations in the world, with the entire nation now representing essentially a depleted strip mined wasteland.   Unemployment on Nauru now approaches 90%, and the national economy now depends on holding, as prisoners, refugees who have attempted to illegally enter Australia by boat.   (Cf, The New York Times Magazine, November 15, 2013)

[3] César A.G.Quispe, ChristianJ.R.Coronado, João.Carvalho Jr. Renewable and Sustainable Energy Reviews 27 (2013) 475–49  

[6]  Chun-Jiang Jia, Yong Liu, Wolfgang Schmidt, An-Hui Lu, Ferdi Schüth  Journal of Catalysis 269 (2010) 71–79

[7] Hanan Atia, Udo Armbruster, Andreas Martin Journal of Catalysis 258 (2008) 71–82

[8] Avelino Corma, George W. Hube, Laurent Sauvanaud,Paul O’Connor Journal of Catalysis 257 (2008) 163–171

[9] Abdullah Alhanash, Elena F. Kozhevnikova, Ivan V. Kozhevnikov Applied Catalysis A: General 378 (2010) 11–18

[10] Feng Wanga, Jean-Luc Dubois, Wataru Ueda Applied Catalysis A: General 376 (2010) 25–32

[11] Song-Hai Chai, Hao-Peng Wang, Yu Liang, Bo-Qing Xu Applied Catalysis A: General 353 (2009) 213–222

[12] Li Li, Tamás I. Korányi, Bert F. Sels and Paolo P. Pescarmona Green Chem., 2012, 14, 1611

[13] Gemma Vicente,Juan A. Melero,Gabriel Morales,Marta Paniaguaand Eric Martın Green Chem., 2010, 12, 899–907

[14] Chun-Ni Fan, Cheng-Hua Xu, Chuan-Qi Liu, Zun-Yu Huang, Jian-Ying Liuk  Zhi-Xiang Ye, Reac Kinet Mech Cat (2012) 107:189–202 References in this paper describe the use of solketal as a fuel additive, the subject of this article, and also its use as a pharmaceutical intermediate, a plasticizer, a solvent, a medical treatment, a surfactant, and a flavoring agent

[15] P. Ferreira, I.M. Fonseca, A.M. Ramos, J. Vital, J.E. Castanheiro Applied Catalysis B: Environmental 98 (2010) 94–99

[16] Jay S. Clarkson, Andrew J. Walker, and Michael A. Wood Organic Process Research & Development 2001, 5, 630-635

[17] Jean-Christophe M. Monbaliu, Marc Winter, Bérengère Chevalier, Frank Schmidt, Yi Jiang Ronald Hoogendoorn, Michiel A. Kousemaker, Christian V. Stevens, Bioresource Technology 102 (2011) 9304–9307

[18] A good review of this process is found in Robert J. Schmidt, Applied Catalysis A: General 280 (2005) 89–103

[19] Ye Ni & Zhihao Sun, Appl Microbiol Biotechnol (2009) 83:415–423 Appl Microbiol Biotechnol (2009) 83:415–423  

[20] Jui-shen Chiao,  Zhi-hao Sun, J Mol Microbiol Biotechnol 2007;13:12–14

[21] V. V. Zverlov . O. Berezina . G. A. Velikodvorskaya .W. H. Schwarz, Appl Microbiol Biotechnol (2006) 71: 587–597

[22] Commercial utilization of corn cobs (and oat hulls) as a feedstock for chemicals was widely practiced in the United States, using a process developed by the Quaker Oats company, for the manufacture of the important industrial compound furan, obtained by the decarboxylation of furfural (furan-2-aldehyde).    Furan synthesis today is mostly carried out with a butadiene feedstock, with the butadiene being obtained from dangerous fossil fuel sources.

[23] Sarah L. C. Giering, Richard Sanders, Richard S. Lampitt, Thomas R. Anderson, Christian Tamburini, Mehdi Boutrif Mikhail V. Zubkov, Chris M. Marsay, Stephanie A. Henson, Kevin Saw, Kathryn Cook & Daniel J. Mayor Nature, 507, 480-482, 27 March 2014   The paper gives an estimate of 100 gigatons as the amount of carbon fixed each year by oceanic photosynthesis; this is roughly just three times the rate at which humanity dumps the dangerous fossil fuel waste carbon dioxide into the atmosphere.   If this doesn’t disturb you, it should.

[24] Maria J. Climent, Avelino Corma and Sara Iborra  Green Chem., 2014,16, 516-547