Want to better understand first generation renewable fuels (corn ethanol and biodiesel) and the brave new world of “next-generation” advanced biofuels? There are significant differences in the fuel chemistry sets, feedstocks and underlying process technologies, as well as how well each fuel performs, and how much each fuel costs to produce. There are also important environmental considerations: There are oil-based fuels that float on water and are toxic (like petroleum oils) on one hand, and there are biodegradable alcohol fuels. There are excellent alcohol fuels beyond ethanol, including butanol and higher mixed alcohols. But in today’s oxygenate fuels market in the USA, only ethanol from corn starch fermentation has thus far made it to market in any significant volume. China is leading with methanol production, which nearly matches the volume of corn ethanol produced in the USA. (15 billion gallons per year.)
Biodiesel: Made from oil crops or animal fats and trans-estrification processes: Converts greases and plant oils into a cleaner bio-oil which has thermal gelling problems in winter and is not highly biodegradable. Biodiesel floats on water just like petroleum oil does. Processes are difficult to scale, cost per gallon highest of all biofuels on the market today. Waste french fry grease and soy beans are the two most prevalent oil feedstocks used to produce biodiesel. There is growing support for cultivating hemp for producing oils which can be converted to usable fuels as well.
Biodiesel combusts cleaner than petroleum-derived diesel, and it can either substitute for petroleum diesel in warmer climates or be utilized as a volumetric blendstock to petroleum diesel, especially in colder climates. Biodiesel like other oils still floats on water and does not readily biodegrade, although biodiesel will break down in the natural environment faster than crude oil or petroleum-derived fuels.
Dedicated Oil Crops to produce Biodiesel: Oil seed crops such as Miscanthus, Jatropha, Soy, Palm, Switchgrass and green Algae are grown to produce vegetable oils which can either be consumed or trans-estrified and converted into biodiesel.
Ethanol Industry Ouput: According to the Renewable Fuel Association (RFA), there are currently 201 corn ethanol facilities with a capacity to produce 13.5 billion gallons per year (RFA, April 27, 2010). In addition, there are facilities under construction that will add another 1.2 bg of capacity of ethanol. As a result, the United States will soon have the installed capacity to produce up to the 15.0 billion gallons of ethanol per year that is allowed by RFS2.
Over 39% of America’s corn crop is currently used to manufacture ethanol.
Of the remaining 21 billion gallons of advanced biofuels needed to achieve the RFS2 total 36 billion gallon goal by 2022, 15 billion gallons is required to be advanced cellulosic biofuels (fuels made from cellulosic feedstocks that reduce greenhouse gas emissions by at least 60 percent relative to gasoline).
But there’s a “small” problem: producers aren’t producing! Most recently, the US Environmental Protection Agency has again cut already greatly reduced expectations for cellulosic biofuels production in its 2011 renewables mandates. Earlier in 2010, EPA dropped the cellulosic target in its renewable fuel mandates by 93% to 6.5 million gallons as companies failed to bring production capacity online. The 2011 production estimate has dropped even further.
Source: USDA Strategic Production Report June 2010
Corn Ethanol: Currently produced via four-day batch fermentation from corn using acidic enzymes and yeasts while offgassing beer fizz CO2. Ethanol is a wonderful fuel, yet fermentation methods most commonly used to produce it are not very energy efficient. Domestic production of EtOH is currently near 12 bgpy and will be capped at 15 bgpy as the current volumes of ethanol which equate to about 6% of the U.S. gasoline volume are consuming 30% of the U.S. corn crop. Ethanol is a heavily subsidized renewable fuel and food vs: food issues have surfaced in the past few years. Ethanol is water soluble, it is highly biodegradable, features a 107 octane rating and EtOH provides 2/3′s of the BTU’s per gallon when compared to gasoline.
Ethanol production capacity has increased nearly sevenfold since 2000, thanks to government mandates, subsidies, trade barriers and facility overbuilding. Now the industry wants regulators to increase the allowable blend of ethanol in gasoline from 10 percent to 15 percent, which would effectively boost ethanol sales by 50 percent.
Cellulosic Ethanol: Produced from ground biomass (corn cobs, corn stalks, wood chips) via a longer, seven-day batch fermentation process converting wood, stalks or cobs into sugars then using yeasts to furither convert sugars into EtOH. Converting biomass cellulose into EtOH requires more acidic, more expensive enzymes plus traditional yeasts. Ligno-cellulosic ethanol fermentation produces only about 1/3 of the alcohol volumes per batch when compared to four-day batch fermentation of ground corn. Mother nature’s biobugs invade seven-day batch cooking processes and typically contaminate every third batch. Ligno-cellulosic ethanol fermentation is not likely to scale, it is far more expensive than batch fermenting ground corn. Two-carbon ligno-cellulosic Ethanol is water soluble and it easily biodegrades.
Synthetic Ethanol: Produced via thermal conversion (gasification) of solid biomass feedstocks, which generates an intermediate synthetic gas (CO and H2) which is then run through gas to liquid catalysis producing a blend of formula-patented C1 to C10 higher mixed alcohols. Ethanol then needs to be fractionalized and distilled out of this blend of alcohols after first removing the C1 methanol portion. It is very expensive to isolate EtOH in this manner. Synthetic ethanol (just like fermented corn ethanol) features 75,500 BTU’s per gallon, about 2/3′s the energy densisty of gasoline and is highly biodegradable.
Methanol: Produced via thermal conversion (gasification) of solid carbonaceous feedstocks or steam reformation of methane natural gas. This GTL process first generates an intermediate synthetic gas (CO and H2) when solids are gasified or CO and H2, H2, H2 when methane gas is steam reformed. This intermediate syngas is then run through gas to liquid methanization catalysts in use worldwide since 1923. Synthesis of single carbon MeOH requires 10-12 passes of syngas across the catalyst which is somewhat process intensive. Methanol contains 56,000 BTU’s per gallon, about one-half the energy density of gasoline yet can be produced commercially from stranded sources of methane natural gas for about 25¢ per gallon. Methanol is the largest volume chemical produced on this planet (used to produce plastics, nylon, rayon, paints, varnishes, thinners, window washing solvent) yet MeOH has been purposefully kept out of the petroleum-derived fuel pool for the past 100 years. C1 Methanol (octane rating 107) was used as a neat, substitute fuel in Indy 500 race cars for 37 years until it was politically replaced about four years ago with C2 corn ethanol. Water soluble and oil soluble, Methanol is highly biodegradable in the natural environment.
Dimethyl Ether: Made via thermal conversion (gasification) of feedstocks, which generates an intermediate synthetic gas (CO and H2) which is then run through gas to liquid catalysis. Dimethyl Ether or DME (formula CH3OCH3) is a pressurized, gaseous fuel (similar to propane) which combusts cleaner than C3 hydrocarbon propane does because the ether molecule contains a missing Oxygen atom. Dimethyl ether is a two-carbon, oxygenated gas which provides less BTU strength than does propane yet it combusts much cleaner than does propane. The use of DME in transport would require tanks of 125 psi pressurized gas to be retrofitted to truck and buses. Conventional autos are presently not being converted to combust pressurized DME.
Butanol: Butanol may be used as a fuel in an internal combustion engine. Because its longer hydrocarbon chain causes it to be fairly non-polar, it is more similar to gasoline than it is to ethanol. Butanol has been demonstrated to work in vehicles designed for use with gasoline without modification. It can be produced from biomass (as “biobutanol”) as well as fossil fuels (as “petrobutanol”); but biobutanol and petrobutanol have the same chemical properties.
Biobutanol can be produced by fermentation of biomass by the A.B.E. process, which uses the bacterium Clostridium acetobutylicum, also known as the Weizmann organism. It was Chaim Weizmann who first used this bacteria for the production of acetone from starch (with the main use of acetone being the making of Cordite) in 1916. The butanol was a by-product of this fermentation (twice as much butanol was produced). The process also creates a recoverable amount of H2 and a number of other byproducts: acetic, lactic and propionic acids, acetone, isopropanol and ethanol.
The difference from ethanol production is primarily in the fermentation of the feedstock and minor changes in distillation. The feedstocks are the same as for ethanol: energy crops such as sugar beets, sugar cane, corn grain, wheat and cassava as well as agricultural byproducts such as straw and corn stalks.
Higher Mixed Alcohol Fuel: Produced via two “front end” methods:
Synthesis method 1. Clean, thermal conversion (gasification) of solid and liquid feedstocks, which generates an intermediate synthetic gas (CO and H2) or;
Synthesis method 2. via steam reformation of methane and CO2 greenhouse gas which produces an intermediate synthetic gas containing CO and H2, H2, H2.
With either method, the syngas is then run through a proprietary gas-to-liquid catalyst, generating a blend of C1-C5 or C1-C8 or C1-C10 higher mixed alcohols requiring only 2.5 passes across the catalyst. (By comparison, basic synthesis of methanol requires 10-12 pressurized passes of syngas across a fixed bed, pelletized catalyst.) This blend of synthetically-produced alcohols include methanol, ethanol, and (n) normal propanol, butanol, pentanol, hexanol, heptanol, octanol, nananol and 10-carbon decanol.
Higher mixed alcohol fuel features a 138 octane rating and 90,400 BTU’s per gallon, which is 20% stronger BTU energy content than fermented corn ethanol. In large, commercial GTL facilities this stronger BTU blend of higher mixed alcohols can be produced for less than 50¢ per gallon using a methanol chemistry set used worldwide since 1923. Like methanol and ethanol, the blend of higher mixed alcohols is both water soluble and oil soluble, plus it is coal soluble andeasily biodegrades in the natural environment.
One important environmental aspect of all biofuels is their relative biodegradability.
- Oil-based fuels float on water when spilled and pollute water, land, and the atmosphere when combusted, regardless of their origin (petroleum oil or bio oil).
- Alcohol fuels such as ethanol and higher mixed alcohols are completely water soluble and biodegradable.
Greenhouse Gas Emissions Comparison
Note: Graph does not contain specific references to higher mixed alcohols, however the emission reduction would rank better than Cellulosic Ethanol.
For more information about higher mixed alcohols, please view this NREL presentation (June 2010 – PowerPoint)
Further Advantages of Higher Mixed Alcohol Fuel
In addition to direct economic benefits on investments, mixed alcohol fuel use will reduce industry and social costs by:
- Reducing volatile organic compounds (VOCs), particulate exhaust, carbon monoxide, Benzene, 1,3 Butadiene and other harmful emissions.
- Reduce problematic cost-consuming waste by turning it into a high-value biodegradable fuel.
- Utilize carbon dioxide as a low-cost carbon feedstock rather than venting it as a costly pollutant.
- Production of mixed alcohol fuel will be clean, having nitrogen as the only major process effluent, unlike oil refineries and ethanol plants which generate large volumes of air pollutants.
- If ignited, mixed alcohol fuel can be immediately quenched with water. Spills of this fuel in waterways will feed living phytoplankton at the base of the planet’s food chain. Thus mixed alcohol fuel is very attractive in reducing environmental liabilities.
- Allows countries to build self-reliance using existing resources, improving infrastructure, creating jobs and reducing imports of foreign energy sources.
Global Market: “Biofuels (global production and wholesale pricing of ethanol and biodiesel) reached $83 billion in 2011, up from $56.4 billion the prior year, and are projected to grow to $139 billion by 2021. However, this increase was mostly due to an increase in ethanol and biodiesel prices. The continuing trend of rising biofuel prices, up 10 to 20 percent in 2011, is the result of higher costs for feedstock commodities – mainly sugar for ethanol and rapeseed and other vegetable oils for biodiesel. Between 2010 and 2011, global biofuels sales remained relatively flat, expanding from 27.2 billion gallons to 27.9 billion gallons of ethanol and biodiesel production worldwide.”
Source: CleanEdge Trends 2012