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suzzane.jpg (6486 bytes) Suzanne Shelley
Guest Columnist and Freelance Technical Writer
Suzanne Shelley is a Manhattan-based freelance technical writer specializing in science, engineering and technology (Email: suzanneashelley”at” A 16-year veteran and former Managing Editor of Chemical Engineering magazine, Suzanne now writes about a broad array of engineering and business topics related to the chemical, petroleum refining, pharmaceutical and related industries, for both corporate clients and technical trade magazines. She currently serves as Contributing Editor to several magazines, including Chemical Engineering, Chemical Engineering Progress, Turbomachinery International, and Pharmaceutical Commerce. Suzanne holds a B.S. in geology (honors) from Colgate University, and an M.S. in geology from the University of South Carolina (Columbia).
Published: January 8, 2008
Biodiesel: The Road Ahead
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Market drivers

The benefits of biodiesel

Improving air quality

Technology innovations

World-class facilities

Advanced reactor designs

Novel catalysts

Pursing non-traditional feedstocks

Sidebar: Converting a glut of glycerin into propylene glycol

In the U.S. alone, biodiesel capacity has grown more than seven-fold since 2004. Today, growing demand for this renewable transportation fuel is helping to drive a flurry of grassroots expansions and technology innovations worldwide, including advanced reactor designs, novel catalysts, and other process improvements.

Market Drivers

With concern over greenhouse gas emissions and global warming reaching a fever pitch, crude oil prices expected to average $75/barrel throughout 2008, and much of the world’s crude oil still coming from geopolitically unstable regions of the globe, it’s no surprise that worldwide demand for, and production of, the biofuels ethanol and biodiesel have been on the rise, as cleaner-burning alternatives to traditional petroleum-derived transportation fuels.

Compared with ethanol, biodiesel is currently produced and used on a far smaller scale worldwide. However, if recent market and technological activity around biodiesel are any indication, biodiesel is clearly poised to occupy an increasingly larger portion of the renewable barrel in the years to come.

For instance, to meet growing demand, biodiesel capacity in the U.S. has grown more than seven-fold in recent years, and European capacity (which already tops U.S. capacity) has been also been rising steadily.

In 2004, just 22 plants in the U.S. were producing biodiesel at a rate of roughly 157 million gallons per year. By June 2007, the number of plants had grown to 105, bringing U.S. nameplate capacity to 1.4 billion gallons per year, according to the National Biodiesel Board (NBB; Jefferson City, Mo.;, the industry trade group representing U.S. biodiesel producers.

In addition, according to NBB’s June 2007
industry update, an additional 97 facilities are currently under construction in the U.S. (representing both new capacity and capacity expansions). Should all of these facilities ultimately come to fruition, they could result in an additional 1.9 billion gallons per year of U.S. biodiesel capacity over the next two years.

(For comparison, as of mid-2007, there were 119 ethanol plants in the U.S., with a combined production capacity of more than 6.2 billion gallons/year, according to the Renewable Fuels Association (RFA; Washington, D.C.;, the trade association for the U.S. ethanol industry. An additional 86 ethanol refineries or expansions are under construction, representing another 6.4 billion gallons/yr of new capacity that is anticipated to come online by 2009. Worldwide, 2006 ethanol capacity (including the U.S.) was 13.5 billion gal/yr, according to RFA.)

In 2006, conventional diesel fuel made up roughly 22% of the ground transportation fuel pool used in the U.S., and

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Download maps of existing biodiesel facilities and new construction.
"diesel makes up 22% of the ground transportation fuel in the U.S., and biodiesel made up just 0.5% of the highway diesel fuel consumed in the U.S. in 2006", according to Kreido Biofuels (Camarillo, Calif.;

biodiesel made up just 0.5% of the highway diesel fuel used, according to Kreido Biofuels (Camarillo, Calif.; However, that figure is on the rise, driven in part by the U.S. Energy Policy Act of 2005, which mandates an increase in renewable fuel use to 7.5 billion gallons/yr by 2012 (up from 4 billion gallons/year in 2006). The bill supports the alternative fuel industry with various production incentives, such as tax credits and other government subsidies.

As noted earlier, European biodiesel production has also been growing a swift clip. For instance, in 2005, the biodiesel production capacity among the so-called EU-25 countries was 960 million gallons./yr — a 65% increase over the 2004 total of 570 million gallons/yr, according to trade group The European Biodiesel Board (EBB; Brussels, Belgium; By 2006, European capacity for biodiesel had grown to 1,832 million gallons/yr.   According to EBB, most of the biodiesel production can be attributed to the leading EU-15 member countries, but the number of EU countries with a biodiesel industry has nearly doubled in recent years, from 11 in 2005, to 20 in 2006.

In Europe, strong growth in biodiesel production is being driven in part by the 2003 European Biofuels Directive concerning biofuels (2003/30/EC Article 3(1)), which aims to replace:

· 5.75% of the overall motor fuel (diesel and gasoline) pool in Europe with biofuels by 2010 (creating estimated demand for 4.2-5.4 billion gallons/yr of biofuels)

· 10% by 2020 (creating estimated biofuel demand of 11.4 billion gallons/yr)

· 25% by 2030, (creating estimated biofuel demand of 22.5 billion gallons/yr)

These goals will spur significant growth, considering that in 2007, biofuel use (including both ethanol and biodiesel) in Europe accounted for less than 2% of the current 300-million-m.t./yr transportation fuel consumed.

The Benefits of Biodiesel (Back to Top)

As an alternative to conventional petroleum-derived diesel fuel, biodiesel is comprised of fatty acid methyl esters (FAME), which are produced via the catalytic transesterification of various renewable feedstocks, ranging from vegetable oils (including soybean, canola, palm, rapeseed and other vegetable oils) to various types of animal fats (even recycled

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Biodiesel is produced via the catalytic transesterification of various renewable feedstocks, most commonly vegetable oils and animals fats. Soybean crops (shown here) are one of the most widely used feedstocks.
Source: U.S. Dept. of Agriculture

cooking grease). Biodiesel is produced by reacting the triglycerides in these renewable feedstocks with an alcohol (typically methanol or ethanol), in the presence of an alkaline catalyst (most often sodium hydroxide or sodium methylate, although several novel alternatives are discussed below). The reaction yields methyl esters (biodiesel) and byproduct glycerin.

Byproduct glycerin is widely used during the manufacture of soaps, cosmetics, pharmaceuticals and other products. Today, the rapid expansion in biodiesel production worldwide has saturated the glycerin market — and the anticipated glut of glycerin has spurred parallel technological innovation among a growing number of chemical companies, who are racing to commercialize routes to convert byproduct glycerin into the widely used commodity chemical propylene glycol (as a renewable alternative to the traditional petroleum-derived feedstock propylene glycol).   For more on this, see the sidebar box.

Biodiesel is biodegradable and non-toxic, is essentially free of sulfur and aromatic compounds, and burns more cleanly than its fossil-fuel-derived counterpart, according to the NBB. It can be blended (in any amount) with traditional diesel, or used on its own, in existing diesel (compression-ignition) engines with little or no modifications. Biodiesel blends are denoted as BXX, with the XX representing the percentage of biodiesel in the blend. Today, most biodiesel sold in the U.S. is B20 (a blend of 20% biodiesel and 80% conventional diesel fuel).

In addition to its favorable environmental profile compared to traditional petroleum-derived diesel fuel (discussed in greater detail below, in the section called improving Air

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Quality), biodiesel offers some other positive performance attributes, as well. These include increased cetane (the measure of the combustion quality of the fuel), higher fuel lubricity (which lowers engine friction), higher oxygen content, and the highest Btu content of any alternative fuel, which makes it a "preferred blending stock to produce ultraclean diesel," according to the NBB. A 2000 report produced for the U.S. Department of Energy (DOE) by the National Renewable Energy Laboratory (Golden, Colo.;, entitled "Biodiesel: the Clean, Green Fuel for Diesel Engines," (DOE/GO-102000-1048, May 2000;, shows that even 1% biodiesel blends can improve lubricity by up to 30%, thereby reducing engine wear and tear and enabling engine components to be used longer.

As for cetane numbers, the International Energy Agency (IEA; Paris;, says that in the U.S., typical petroleum-derived #2 diesel fuel has cetane numbers in the range of 40-45, while for #1 diesel, cetane numbers of 48-42 are typical. By comparison, biodiesel from vegetable oils can have cetane numbers ranging from 46-52, while animal-fat-derived biodiesel can have cetane numbers as high a 56-60, according to a 216-page report published in 2004 by the International Energy Agency ("Biofuels for Transport: An International Perspective;"; page 110).

Similarly, biodiesel has the highest energy balance of any liquid fuel currently produced. For instance, for every unit of energy used to make biodiesel, 3.24 units are gained, according to the U.S Dept. of Energy (DOE; Washington, D.C.;

The NBB emphasizes that — despite lingering confusion to the contrary — biodiesel is "not an experimental fuel." Rather, the group notes that biodiesel "has been proven to perform similarly to diesel in more than 50 million successful road miles in virtually all types of diesel engines, countless off-road miles and marine hours." And today, in the U.S. alone, more than 600 major fleets (ranging from school buses and commercial vehicles to government and military fleets) now use diesel blends that incorporate the cleaner-burning fuel. Through all of this experience, B20 has demonstrated similar fuel consumption, horsepower, torque, and haulage rates as conventional diesel fuel.

One potential downside is that pure biodiesel (B100) has a solvent effect, which can lead to the release of deposits that may have accumulated on tank walls, pipes and engine components. To keep such sludge from clogging filters, the NBB recommends that precautions should be taken to replace fuel filters until such buildup is eliminated, but notes that this issue is less prevalent with B20 blends, and says that there is no evidence that lower-level blends (such as B2) have experienced filter pluggage.

This solvency effect has also been shown to soften and degrade certain types of incompatible elastomers and natural rubber compounds over time (i.e., those used for certain fuel hoses and fuel pump seals), although this effect is lessened as the biodiesel blend level is reduced. The group notes that extensive experience with B20 has found that no changes to gaskets or hoses are necessary, and notes that many OEMs have switched to components that are more compatible with biodiesel.

Improving Air Quality (Back to Top)

As a petroleum-free transportation fuel, biodiesel is “less toxic than table salt, and biodegrades as fast as sugar” according to the NBB. The trade group notes that today, biodiesel is the only alternative fuel to have fully completed the Tier I and Tier II health-effects testing requirements of the 1990 Clean Air Act Amendments.  Because it contains no sulfur or aromatic compounds, tailpipe exhaust from diesel engines firing biodiesel contains no sulfate emissions, and has reduced levels of unburned hydrocarbons, carbon monoxide and particulate matter, compared to diesel-fired exhaust. 

In its 2002 report, entitled “A Comprehensive Analysis of Biodiesel Impacts on Exhaust Emissions,” can be found at, the U.S. Environmental Protection Agency (EPA; Washington, D.C.; surveyed a large body of biodiesel emissions studies and compiled average statistics related to both regulated and non-regulated air pollutants. These average values (in terms of emissions reductions compared to petroleum-derived diesel), are shown in Table 1.

Table 1: Average Biodiesel Emissions Compared to Conventional Diesel
Emission Type

B100 (100% Biodiesel)

B20 (20% Biodiesel)

Total unburned hydrocarbons -67% -20%
Carbon Monoxide -48% -12%
Particulate matter -47% -12%
NOx +10% +2% to -2%
Sulfates -100% -20% *
(polycyclic aromatic hydrocarbons) **
-80% -13%
nPAH (nitrated PAHs) ** -90% -50% ***
Ozone potential of speciated HCs -50% -10%
* Estimated from B100 results
** Average reduction across all compounds measured
*** 2-nitroflourine results were within test method variability
Source: EPA's 2002 report entitled "A Comprehensive Analysis of Biodiesel Impacts on Exhaust Emissions," as posted on the Biodisel Board's website (

While EPA’s 2002 analysis showed that NOx emissions in tailpipe emissions can sometimes increase with biodiesel use (depending on the engine family and testing procedures), the fact that biodiesel contains no sulfur allows a variety of catalytic NOx-control technologies to be used, without the poisoning threat that fuel-borne sulfur can pose. Similarly, a number of companies have developed additives to reduce NOx emissions in biodiesel blends, according to NBB.

As for carbon dioxide (CO2) and other greenhouse gas (GHG) emissions, a variety of studies shown that net GHG emissions reductions from rapeseed-derived biodiesel range from 40% to 60% compared to conventional diesel fuel in light-duty compression-ignition engines, according to the 216-page IEA report (p. 63) cited earlier.

In addition to its potential to improve air quality, the increased use of biodiesel is also expected to provide some advantages for the economy. For instance, in the U.S. alone, the biodiesel industry is expected to add $24 billion to the U.S. economy between 2005 and 2015, and create more than 40,000 jobs, according to Joe Jobe, CEO of the NBB (in remarks made before the U.S. House Small Business Committee on May 3, 2007). That group’s stated goal is to have biodiesel make up 5% of the U.S. diesel fuel market by 2015. Says Jobe: “That may not sound like a lot, but if 5% biodiesel were added to all of today’s on-road diesel in the U.S., it would displace 1.85 billion gallons of petroleum-derived diesel.”

Technology Innovations (Back to Top)

As noted earlier, commercial-scale processes to produce biodiesel react any number of renewable feedstocks based on vegetable oils and animal fats with ethanol or methanol in the presence of a catalyst. In the U.S., fuel-grade biodiesel must be produced in compliance with strict industry specifications (ASTM D6751), to ensure proper performance. While the processes for producing biodiesel are proven, the biodiesel industry is always looking toward the next-generation of biodiesel production routes. For instance, today, a

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Growing worldwide demand for biodiesel has spurred numerous grassroots expansions, and is driving a number of reactor and catalyst innovations, and other process advances.
Source: National Biodiesel Board

number of novel catalysts and advanced reactor designs and non-traditional feedstocks are being investigated and commercialized, to enable greater feedstock flexibility, increase conversion rates and biodiesel yield, allow the reactions to be carried out under increasingly mild operating conditions (i.e., at lower pressures and temperatures), and reduce capital and operating costs.

Many of these promising new advances are discussed later in this article. As with most burgeoning technologies, costs tend to fall as additional facilities are built, technologies are proven and optimized, and economies of scale are exploited.

Speaking for the entire industry at the NextEnergy Biodiesel Summit held in Detroit in March 2007, Donnell Rehagen, NBB’s chief operations officer said: “Our goals for next generation biodiesel are to optimize biodiesel’s fatty acid profile for cold flow and stability, optimize agriculture for higher production of oils and fats from traditional crops, and develop additional, non-traditional crops such as micro-algae for biodiesel, and even crops that can be grown on marginal land or Brownfield sites.”

World-class Facilities (Back to Top)

While it is not possible to profile all of the many grassroots plants that are under development today, a variety of world-class deals are discussed here. Many of these are pushing the envelope in terms of nameplate capacity, and incorporating newer (so-called second-generation) biodiesel technologies.

Lurgi AG (Frankfurt, Germany; has built what it claims is the world’s largest biodiesel plant (although larger pending plants are discussed below) in Piesteritz, (East) Germany, for Neckermann-Renewables GmbH (Wittenberg, Germany), and parent company Global Alternative Energy (GATE) GmbH. The facility, which started up in June 2007, is producing 200,000 tons/yr of biodiesel from rapeseed oil, plus 20,000 tons/yr of pharmaceutical-grade glycerin, and 300,000 tons/year of colza meal.

According to Lurgi, the plant is the first in Germany to integrate field-to-fuel-pump biodiesel production (including seed processing, pressing and oil extraction, processing the crude rapeseed oil, and producing biodiesel). In Europe, Neckermann runs several biodiesel plants with total capacity of more than 350,000 tons/year.

Lurgi is also constructing an even-bigger two-train biodiesel plant in the port of Rotterdam for biodiesel producer Biopetrol Industries AG (Zug, Switzerland, Once online in the third quarter of 2007, annual capacity will be 400,000 tons/yr of biodiesel (with anticipated scale up to 650,000 m.t./yr), plus 60,000 tons/yr of pharmaceutical-grade glycerin and 60,000 ton/yr of fatty acids for re-esterification. This plant will be the third biodiesel plant for Biopetrol (the other two are in Brandenburg, Germany, and Rostock, Germany), bringing its total biodiesel capacity to 750,000 tons/yr of biodiesel in 2007, and 1 million tons/yr by 2008.

Lurgi is also building a 200,000-m.t./yr biodiesel plant for The Victoria Group (Novi Sad, Serbia), to be located in Sid, near Belgrade. The plant is slated for startup in 2007.

Since July 2005, Lurgi has been awarded nine biodiesel contracts, for a total capacity of 1 million m.t./yr. Once these facilities all come online, the company claims that 60-70% of global biodiesel output will be produced using Lurgi technology.

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When it came online in May 2007, the 170,000-m.t./year biodiesel plant at Neste Oil’s petroleum refinery in Porvoo, Finland, became the first commercial-scale facility to use the company’s proprietary NExBTL (for “next-generation biomass-to-liquid”) process. A second, identical facility is under construction at the refinery, and is slated to come online in 2008 .
Source Neste Oil Corp.

The scale of these world-class facilities continues to grow. For instance, specialty and intermediate chemical company Ineos Enterprises (Hampshire, U.K.; is in the process of building a new 500,000-ton/yr biodiesel plant at its petroleum refinery in Grangemouth, Scotland (startup is slated for 2008). The company is also in the process of doubling the output of its biodiesel plant at Baleycourt (France), which has been producing biodiesel for more than 10 years, and it is building a new biodiesel facility at its site at Zwijndrecht, in the Port of Antwerp (Belgium). That facility will have a capacity of 500,000 m.t./yr once it starts up in 2009. The company’s stated goal is to achieve at least 1.2 million m.t./yr of biodiesel by 2020, and 2 million m.t./yr by 2012.

In May 2007, Neste Oil Corp. (Helsinki, Finland; brought online a 170,000-m.t./yr biodiesel plant at its Porvoo, Finland, petroleum refinery. That facility marks the commercial debut of the company’s proprietary NExBTL — for “next generation biomass-to-liquid” — process, which can use a flexible mix of vegetable oil and animal fat to produce premium biodiesel, says the company.  A second, identical plant is being built alongside the original facility at Porvoo, and it is slated for completion by late 2008. To ensure a captive supply of rapeseed oil for the Porvoo facility, Neste also signed a contract in mid-2007 with Raisio plc (Raisio, Finland; to buy 10,000 tons/yr of that renewable feedstock.

Meanwhile, following the signing of a Memorandum of Understanding (MOU) in July 2005, Neste Oil and Total S.A. (France; are evaluating the possibility of jointly building a large-scale biodiesel facility at one of Total’s petroleum refineries. The proposed facility, which is being given a target startup date of 2008, would also use the Neste’s NExBTL process.

In April 2007, ConocoPhillips LP (CP; Houston, Tex.; and Tyson Foods (Springdale, Ark.; — which claims to be the world’s largest producer and marketer of chicken, beef and pork, and produces large volumes of various types and grades of animal fats — announced a strategic alliance to commercialize a proprietary thermal depolymerization process (developed by CP) that produces a product called “renewable diesel (RD),” using a mix of beef, pork and poultry fats supplied by Tyson’s rendering plants and traditional hydrocarbon feedstocks.

According to CP, renewable diesel and biodiesel are not the same. While they are produced from similar feedstocks, they are produced using different processing methods that yield chemically different products. Because RD is chemically equivalent to conventional diesel, CP says it can be shipped via conventional pipelines, along with other fuels.

CP’s thermal depolymerization process using animal fats has been successfully tested at the company’s Whitegate Refinery in Cork, Ireland (which has also been producing 1,000 barrels per day — 150,000 liters — of renewable diesel from soybean oil since late 2006).

Commercial-scale production of renewable diesel from animal fats is expected to be carried out at several CP refineries by the end of 2007, and could reach 175 million gallons/year by mid-2009, says the company. The company’s goal is to have renewable diesel ultimately comprise 3 vol.% of its total biodiesel production.

Meanwhile, in June 2007, Tyson also announced a 50/50 joint venture with Syntroleum (Tulsa, Okla.; The new venture, dubbed Dynamic Fuels LLC, will produce a range of synthetic fuels, including renewable diesel, using Syntroleum’s patented Biofining process. The first facility (at a yet-to-be-decided site in south-central U.S.) will produce about 75 million gallons/yr of synthetic fuel, with startup slated for 2010.

Similarly, UOP LLC (Des Plaines, Ill.; and Eni S.p.A. (Milan, Italy) have jointly developed a process to produce what they call “Green Diesel, a premium, high-cetane diesel blending component for refineries” from various vegetable oils such as soybean, palm or rapeseed oil. The process developers christened their product “Green Diesel” to distinguish it from biodiesel, which is obtained by reacting vegetable oil with methanol (the Green Diesel process is described below).

According to UOP, Green Diesel has cetane values of 70-90 (by comparison, conventional petroleum-derived diesel and biodiesel blends found at the pump today have cetane values ranging from 40-60), providing “significant blending benefits” for refiners seeking to enhance existing diesel fuels and expand the diesel pool.

As reported by Chemical Engineering magazine (May 2007), the Green Diesel product is produced by reacting vegetable oils with hydrogen to remove oxygen from the oil via decarboxylation and hydrodeoxygenation. The reactions occur simultaneously, at roughly 300 deg C and 400-600 psi, over a proprietary fixed-bed catalyst.

All of the olefinic bonds are saturated, so that the product consists only of normal paraffins, plus about 5% byproduct propane. In a second step, the paraffins are hydroisomerized to obtain isoparaffins and produce a fuel with good cold-flow properties. This step also produces a small amount of naphtha. The Green Diesel yield is 86-98%, and hydrogen consumption is 1.5-3.8 wt.%, according to the process developers.

UOP and Eni have tested the process, which UOP says “integrates seamlessly into existing refinery operations,” and they offer it for license.

In June 2007, UOP and Eni announced that Eni will build a production facility in Livorno, Italy, which will produce 6,500 barrels per day of Green Diesel using UOP’s “Ecofining” (catalytic hydroprocessing) technology. It is expected to come online in 2009.

Meanwhile, in late 2006, Uhde GmbH (Dortmund, Germany; was awarded a contract from Thai Oleochemicals Co. (Bangkok, Thailand) and Thai Fatty Alcohols Company Ltd. for the construction of an integrated biodiesel plant, slated for startup from late 2007 to early 2008. It will produce 200,000-m.t./year of biodiesel, 100,000 m.t fatty alcohols and 30,000 m.t./yr of glycerin from a variety of vegetable oils. To be located in Map Ta Phut, Thailand, it will be that country’s first biodiesel plant, and its first to make refined fatty alcohols. The “feedstock-flexible facility” will use process technology licensed from AT-Agrar-Technik GmbH & Co. KG (Schlaitdorf, Germany; to transesterify the feedstocks with methanol at room temperature using a potassium hydroxide catalyst.

In 2006, Chevron USA (San Ramon, Calif.; created a new biofuels business unit. One of its first initiatives, through its Chevron Technology Ventures division, was to acquire a 22% interest in a large biodiesel facility in Galveston, Tex. The facility, operated by BioSelect Fuels LLC (Houston; started up in May 2007, with 20-million-gallons/year, but is expected to undergo expansion to 110 million gallons/yr by 2010, says the company.

Advanced Reactors (Back to Top)

As for advanced reactor designs, Kreido Biofuels (Camarillo, Calif.; has developed a new, high-shear reactor, whose commercial debut is being made in the production of biodiesel. The company claims that its STT (for “spinning tube-in-tube”) process intensification reactor can speed chemical reaction rates by up to three orders of magnitude.

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The patented Shock Wave Power Reactor (SPR) from Hydro Dynamics is said to cut the residence time required for the transesterification of vegetable oils and animal fats from hours to seconds, using what the company calls “process intensification through controlled cavitation.” It made its commercial debut in 2007 at a grassroots biodiesel plant operated by Memphis Biofuels LLC

Source: Hydro Dynamics

Biodiesel producer Foothills Bio-Energies (Lenoir, N.C.; is currently using Kreido’s STT reactor to add one million gal/yr of capacity to its existing 1-million-gal/yr capacity (which it produces by transesterifying vegetable oil using a sodium hydroxide catalyst).

Kreido's patented STT reactor consists of a 4.5-in-dia. cylindrical vessel (which functions as a stator tube), and an inner rotating cylinder (which functions as the rotor) that is driven at up to 5,000 rpm by a variable-speed motor. Reactants are fed into the narrow annulus between the rotor and stator at one end of the reactor, and exit at the other end, with a residence time of less than 1 second. According to its inventor, the STT reactor not only accelerates chemical reaction rates (especially those processes that have mass transfer, temperature control, viscosity or solids issues), but can also increase selectivity, conversion rate and yield.

The novel reactor is said to achieve these advantages by inducing faster, more-uniform mixing in the narrow annual gap between the stationary stator and the rapidly rotating, concentric, internal rotor, so the reactants move as a coherent thin film in a high-shear field. The equipment is available at working volumes from 1.5 milliliters to 1 liter. A 1-liter system can produce as much as 50 million pounds/year, says the company, with larger production capacities available through the use of parallel STT reactors.

Similarly, Hydro Dynamics (Rome, Ga.; has developed the patented ShockWave Power Reactor (SPR), which, according to the company, cuts the residence time required for the transesterification of vegetable oil or animal fats from more than an hour to just several seconds through process intensification.

The company claims to have “harnessed the destructive force of hydrodynamic cavitation, and applied it for useful purposes, after years of intensive research.” Inside the reactor is a cylinder that contains numerous cavities, and rotates at about 3,600 rpm. As the liquids pass through the SPR, tiny bubbles continuously form and collapse generating shockwaves. This “controlled cavitation” breaks the fluids into microscopic droplets (thereby increasing the overall surface area of the liquids and achieving higher mass-transfer rates, and more-efficient mixing and heating compared to traditional reactors that rely on bladed or impeller designs, says the company). Faster reaction times also help to reduce unwanted saponification and emulsification during the transesterification of vegetable oils and animal fats, according to Hydro Dynamics.

The SPR is making its commercial debut at a grassroots biodiesel plant that was started up in 2007 by Memphis Biofuels LLC (Memphis, Tenn.; Using the new reactor, Memphis Biofuels is able to drive the transesterification reaction used to produce biodiesel in a matter of seconds. The 50-million-gallon/year facility is currently using a 3-gallon SPR to produce 100 gallons/minute of biodiesel. In general, the SPR can be used in either batch or continuous mode, to produce up to 150-million gallons/yr of biodiesel, according to its manufacturer.

Novel Catalysts (Back to Top)

In an attempt to improve yield and allow for more favorable processing conditions, a variety of process developers are pursuing (and commercializing) advanced processes based on novel catalysts. For instance, in late 2006, engineering and construction firm Technip (Paris; was awarded two contracts by Paris-based Diester Industrie S.A. for two new biodiesel plants in France. The first is for a new production unit near Bordeaux. The second will double the capacity at Diester’s existing facility near Rouen. Each facility will have a capacity of 250,000-m.t./year, and both are slated to go online by the end of 2007. Both facilities will use process technology from Axens (Rueil-Malmaison France;, and vegetable oil as the feedstock.

Technip has already built three other biodiesel units for Diester in France (at Rouen, Séte and Compiegne), and is currently constructing another 250,000-m.t./yr unit, in Montoir-de-Bretagne (France), which is also slated for startup in 2007.

The 160,000-m.t./yr facility at Séte is the first commercial plant to use the newEsterfip-H biodiesel process, which was initially developed by the Institut Français du Pétrole (IFP; Rueil-Malmaison, France;, and commercialized by Axens. The Esterfip-H process is a fixed-bed process that is based on a heterogeneous catalyst, rather than the traditional Esterfip process, which uses a homogeneous catalyst and has been in commercial use since 1992 (the first commercial application of the traditional, homogeneous-catalyzed Esterfip process is at Diester Industrie’s Venette, France, site).

The newer heterogeneous catalyst in use at Diester’s Séte location is a spinel mixed oxide of two non-noble metals, as reported in Chemical Engineering magazine (October 2004). According to Axens, the continuous Esterfip-H process carries out the transesterification reaction at a higher temperature than that used by the homogenous-catalyzed process, with an excess of methanol, which is later removed by vaporization and recycled to the process. The use of the solid, heterogeneous catalyst “enables a significant reduction in waste streams compared to other processes,” says the company. This is possible by eliminating the need for catalyst recovery and aqueous neutralization and washing steps (and the waste streams associated with them) that are required when biodiesel is produced using conventional homogeneous catalysts (most often sodium hydroxide or sodium methylate).

In addition, Axens says the methyl ester purity exceeds 99%, with yields close to 100%, the glycerin byproduct that is produced using the Esterfip-H process has a purity on the order of 98%, compared to about 80% using the homogenous-catalyst routes.

Perstorp Oxo (Perstorp, Sweden; has also selected Axens’ Esterfip-H biodiesel technology for a 160,000-ton/year plant it is building in Stenungsund, Sweden (about 50 km north of Gothenburg). That facility is slated to come online by late 2007.

As noted earlier, when it comes to biodiesel production, the desired fatty acid methyl esters (FAME) are typically made by the transesterification of vegetable oils with an alkaline catalyst. As an alternative, Kansai Chemical Engineering Co. (Amagasaki, Japan;, in cooperation with Japan’s Kobe University, has developed a process that uses whole-cell biocatalysis for the transesterification of vegetable oils. The novel process, as reported in Chemical Engineering (March 2005), is said to be simpler and more cost-effective than the traditional catalytic approach to biodiesel production, because it does not generate the large volumes of wastewater that are typically produced using traditional alkali-catalyzed routes. Because no free acids or catalyst residue remains, no purification process is required for the product FAME or the glycerin byproduct, according to the process developer.

Other novel catalysts are also being pursued. For instance, according to reporting in the December 2005 issue of Chemical Engineering magazine, Toshikuni Yonemoto, professor of chemical engineering at Tokohu University (Sendai, Japan) says that to sidestep the need to remove alkaline catalysts from co-product glycerin, and treat alkali-laden wastewater prior to disposal, biodiesel routes based on supercritical alcohol or enzymes have been attempted but not successfully deployed, mainly because of difficulties that arise from the need for high-pressure/temperature equipment or highly stable and active enzymes.

Yonemoto’s research group has developed an alternative catalytic process for biodiesel is said to eliminate the problems associated with alkali catalysts, while operating at mild (50 deg C and 1 atm) conditions. In the new process, a mixture of vegetable oil, animal fat, and alcohol (ethanol or methanol) is fed to a fixed-bed reactor that is packed with a cation-exchange resin, which serves as the catalyst to esterify the free fatty acids.

According to the magazine, the product is then pumped to a second fixed-bed reactor that is packed with an anion-exchange resin, which catalyzes the transesterification of the triglycerides. The transesterification is carried out in a pair of reactors, which alternate in either reactor mode or catalyst-regeneration mode. The catalyst, once contaminated by byproduct glycerin, is regenerated by rinsing with an organic acid solution and then an alkaline solution. The researchers are optimizing the process and working to commercialize it.

Meanwhile, in October 2006, Verenium (formerly Diversa Corp.; San Diego, Calif.;, announced that its Purifine enzyme had received EPA approval for use in non-food applications, including its use to increase the efficiency of oilseed processing during the production of biodiesel fuel. According to the company, enzymes have not been widely used in the vegetable-oil-refining processes. However, Verenium’s new enzyme is said to reduce the need for harsh chemicals to remove unwanted oil phospholipids (to “de-gum” the oil). This improves biodiesel yield and quality without requiring major changes to conventional processing conditions, says the company.

In August 2007, Chemical Engineering reported another catalyst breakthrough related to biodiesel fuel production. The new catalyst, developed by Victor Lin, a chemistry professor at Iowa State University (Ames, Iowa; was developed as an alternative to the soluble, sodium methoxide catalyst that is now widely used for the transesterification of oils during biodiesel manufacture.

Lin’s catalyst consists of 1-micrometer-dia. honeycomb spheres of mixed oxides, which incorporate both acid and base sites. According to the magazine, the acidic sites convert the free fatty acids to biodiesel by esterification, and the base sites convert oil to fuel by transesterification.

The catalyst is said to be preferable for animal fats (which tend to be considerably less costly than vegetable oils), and because it is a solid, it can be recycled (whereas sodium methoxide is dissolved in the process fluid). Production of the catalyst is being scaled up by Catilin Inc. (, a startup company formed by Iowa State University and others, which is also building a 300-gal/day biodiesel plant near Ames, to demonstrate the process.

Pursuing Non-Traditional Feedstocks (Back to Top)

The cost of biodiesel production varies widely by feedstock, conversion process, scale of production and proximity to renewable feedstocks. While costs can be expected to fall as larger-scale plants are built with further design optimizations and economies of scale, most industry observers agree that the cost of feedstocks such as oilseed crops and animal fats is still the dominant factor in the overall economics of the biodiesel flowsheet.

Today, steep growth in worldwide biodiesel production is sending the cost of many traditional feedstocks through the roof. For instance, as reported in the July 2007 issue of

biodiesel_road_ahead7.gif (103402 bytes)
While vegetable oils and animal fats have been the traditional feedstock of choice for producing biodiese, a number of process developers are also developing routes based on other sustainable biomass sources, such as wood, which are cheaper and do not compete for food-based agricultural resources.

Source: Stora Enso

Biodiesel magazine (“A Hard Row to Hoe,” by Jerry W. Kram), despite the fact that soybean stocks in the U.S. are at their highest level in three years, and soybean production in Brazil, Argentina and other South American countries are projected to set records this year, soybean oil prices are at near-record highs. “At more than 30 cents a pound, prices are higher than any time in the past 10 years,” says the article’s author. And, according to the U.S. Dept. of Agriculture (USDA; Washington, D.C;, soybean oil prices are projected to keep rising, and could average as much as 33.5 cents per pound in 2008.

Prices have been on the move not because of tight supply, but because of strong anticipated demand, in the face of the existing and announced expansions in biodiesel production capacity. According to the Biodiesel article, 2006 soybean oil production in the U.S. alone was more than 20 billion lb/year —enough to manufacture 2.6 billion gallons of biodiesel (considerably more than the current biodiesel capacity of 1.4 billion gal/yr), and in 2006, the U.S. biodiesel industry consumed just 10% of the soybean oil produced.

Meanwhile, rendered animal fats generally cost about 10 cents less per pound than virgin soybean oil (according to reporting on the Editor’s Page in the July 2007 issue of Biodiesel magazine), so they may emerge over time as preferred feedstocks, but they often require more purification and pre-processing.

Cost increases are just one reason why a number of biodiesel producers are pursuing non-traditional feedstocks. For instance, in mid-2007, Neste Oil joined forces in mid-2007 with forest products company Stora Enso (Helsinki, Finland;, to establish a 50/50 joint venture to “broaden the feedstock base” for biodiesel by developing what it calls “next-generation biodiesel technology.” Answering the call to pursue biodiesel routes whose low-cost feedstocks that don’t compete with food-based raw materials, the companies are working to develop a biodiesel route that uses cheap and plentiful forest-derived biomass as the feedstock of choice, instead of the traditional vegetable oil and animal fats.

Phase 1 of the j.v. project will be to build a pilot plant (to be commissioned in 2008) at Stora Enso’s Varkaus Mill. The pilot plant will demonstrate the various process steps, including feedstock drying, gasification, gas cleaning, and Fischer Tropsch synthesis, that the companies are pursuing to convert wood-based biomass into biodiesel.

Phase 2 of the Neste/Stora Enso venture will be to build a full-scale production plant, with 100,000 m.t./yr capacity, and to eventually expand production, as needed.

Along that same vein, BP (London; has formed a 50/50 joint venture with D1 Oils plc (Middlesbrough, U.K., to accelerate the planting of Jatropha curcas — a drought-resistant tree that produces inedible oilseed, in order to make a sustainable, non-food-based biodiesel feedstock available on a much larger scale. Jaropha trees can be grown on land of lesser agricultural value with lower irrigation requirements compared to many other plants, according to the companies, which intend to invest $160 million over the next five years to plant Jatropha seedlings produced through D1 Oils’ plant science program, mostly throughout southeast Asia, southern Africa, central and south America, and India. The goal is to plant 1 million hectares over the next four years, and 300,000 hectares per year thereafter.

In another interesting development, Aspectrics, Inc. (Pleasanton, Calif.; has developed a measurement device that can accurately measure the biodiesel content in any biodiesel blend. The device is based on the company’s  patented Encoded Photometric Near-Infrared (EP-NIR) spectroscopy technology. When coupled with an external halogen NIR source, and an extended range 2-mm path-length process-transmission probe, the MultiComponent 2750 EP-NIR analyzer can determine the precise percentage of biodiesel in various blends within the B0 to 100 range,, with a measurement accuracy of +/- 0.27% volume, with 99.9% confidence level, says the company.

SIDEBAR (Back to Benefits of Biodisel)
** Note: This sidebar was adapted from a longer article by this author entitled: A Renewable Route to Propylene Glycol, which appears in Chemical Engineering Progress, AIChE's monthly magazine, August 2007, pp 6-9,
Turning a glut of glycerin into propylene glycol

The main byproduct of biodiesel production is glycerin, a key ingredient in soaps, hand lotions and other products. During the transesterification of feedstock vegetable oils, every nine pounds of biodiesel yields one pound of glycerin (or, expressed another way, 1.25 lb of glycerin is produced for every gallon of biodiesel). In the U.S., demand for glycerin is currently about 600 million pounds per year. However, market analysts project that the current surge in biodiesel production will yield an additional 1 billion pounds of glycerin over the next two years — essentially flooding the market.

This sudden glut of glycerin is creating a parallel — and perhaps unexpected — opportunity for a number of global chemical producers to improve their environmental profiles by enabling them to produce the widely used commodity chemical propylene glycol (PG; 1,2 propanediol) using inexpensive, environmentally benign glycerin as the starting material, instead of propylene oxide, the traditional petroleum-derived feedstock. Specifically, since 2006, Dow Chemical Co. (Midland, Mich.;, Huntsman Corp. (The Woodlands, Tex;, Ashland (Covington, Ky.;, Cargill (Minneapolis, Minn.;, Archer Daniels Midland (ADM; Decatur, Ill.;, Senergy Chemical (Gig Harbor, Wash.;, Virent Energy Systems, Inc. (Madison, Wisc., and others have either announced plans or broken ground on new plant construction, to commercialize process routes that will convert biodiesel-derived glycerin into PG, most of which are slated to come online by 2008.

PG is a commodity chemical that is widely used during the manufacture of a broad array of industrial and consumer products, including unsaturated polyester resins, plasticizers and thermoset plastics, antifreeze products, heat transfer and coolant fluids, aircraft and runway de-icing products, solvents, hydraulic fluids, liquid detergents, paints, lubricants, cosmetics and other personal care products. Today, global demand for PG is between 2.6 and 3.5 billion pounds per year, according to various industry estimates.

"As with most commodity chemicals, the overwhelming majority of the cost is associated with the raw materials(s). Because crude glycerin is currently abundant and cheap, this process technology will remain competitive as long as that remains the case," says Mark Tegen, president of Senergy Chemicals. "The glycerin-to-propylene-glycol route uses a combination of conventional technology and equipment with some novel process concepts, and generates expected capital expenditures that are substantially less than conventional propylene oxide to propylene glycol processes." Senergy has licensed a patented process route for converting biodiesel-derived glycerin into PG (discussed below) that was developed by Galen Suppes, a professor of chemical engineering at the University of Missouri, Columbia ( Suppes’ patented process was awarded the U.S. Environmental Protection Agency’s 2006 Presidential Green Chemistry Award.

Overall, Tegen of Senergy Chemical says that the production of PG from biodiesel-derived glycerin "is a very clean process, which generates no appreciable emissions other than salts and water."

Harvesting ‘the green,’ in two ways

In additional to its favorable environmental profile, the glycerin-to-PG route offers financial advantages for producers, as well. For instance, while the actual production economics associated producing PG from biodiesel-derived glycerin will not be known until the pending fleet of facilities comes online in 2008, the use of glycerin as a feedstock "could reduce the cost of PG by as much as 40 cents per gallon," according to Suppes.

The patented technology developed by Suppes, and being commercialized by Senergy Chemical, uses hydrogen as a co-reagent in the presence of a copper-chromite catalyst — rather than a conventional precious-metal catalyst — to perform a hydrogenolysis conversion of glycerin. In the course of the reaction, the process first removes a water molecule from the glycerin, and then adds a hydrogen molecule, yielding two products (acetol and propylene glycol), as well as a water byproduct

"Our highly selective processes has multiple advantages over other published technologies," says Suppes. For instance, the process "has higher yields (in excess of 90% to produce a mixture of acetol and propylene glycol, where other published processes tend to have a PG yield around 80%), and very low conversion to unwanted ethylene glycol (typically less than 1.5%, while most competing processes yield PG with 10% ethylene glycol content)," says Suppes. He notes that ethylene glycol is not only undesirable because of its toxicity, but each pound of ethylene glycol produced also yields another 0.5 pounds of unwanted byproducts.

In addition, it is carried out "at temperatures lower than the conventional 500°F, and pressures considerably lower than the conventional 2,170 psi," says Suppes. "Both of these advantages help to reduce both capital and operating costs."

According to Suppes, the ability to use a catalyst that is based on copper and chromium "helps to reduce costs compared to competing processes that rely on precious-metal catalysts." Following a commercial trial in January 2007, Senergy Chemical is now on constructing its first 65-million-pound/year (7.5-million-gal/yr) facility in the Southeast U.S. to produce PG from biodiesel-derived glycerin, says Tegen, the company’s president.

Dow Chemical claims to be the world’s largest producer and marketer of propylene glycol, with 2007 production capacity of 705 kilotons per year (KTA; the equivalent of 157 million gallons per year) — a 140-KTA increase over 2006. So it’s no surprise that the chemical giant has introduced a glycerin-derived PG product, dubbed "propylene glycol renewable" (PGR). The company’s Dow Haltermann Custom Processing (DHCP) business unit is currently conducting pilot PGR trials with customers, and expects to have limited commercial-scale quantities available by late 2007. Full-scale commercial production of PGR will eventually be carried out at DHCP’s Houston facility, which already produces biodiesel.

According to Dow, one particular environmental benefit of Dow’s PGR production route is that it consumes "considerably less fresh water" compared to the conventional, petroleum-based route for producing PG (although the company declined to be more specific).

Meanwhile, Huntsman Corp., which currently produces 145 million pounds per year of conventional PG at its Port Neches, Tex., facility, is currently scaling up a proprietary glycerin-to-PG process at its development facility in Conroe, Tex., and expects to begin production in 2008. Eventual capacity is slated for 100 million pounds per year.

According to the company, Huntsman’s process first involves the cleanup of the crude glycerin, which is then hydrogenated to 1,2 propylene glycol in a reaction that is "high in conversion and highly selective to PG," (although the firm declined a request to share specific conversion rates or yields). Distillation is then used to purify the PG.

"The projected oversupply of glycerin resulting from biodiesel production was a key element in our decision to develop this technology," says David Hester, Huntsman’s global business development director for performance products. "Having a glycerin-based technology as an alternative to the propylene-oxide-based route will not only ensure a sustainable process, but will provide us with a hedge against higher oil prices," he adds.

In May 2007, Ashland and Cargill announced the formation of a joint venture that will be devoted solely to the development and production of chemicals made from renewable resources. Its first venture will be the production of PG from biodiesel-derived glycerin. The j.v. company is planning a 65,000-m.t./year plant — with startup slated for mid-2008 — which will use both licensed and proprietary (Cargill) technologies, at an as-yet-undisclosed location in Europe. Startup is anticipated for 2009.

The Ashland-Cargill process is said to lower manufacturing costs, improve yields, and yield fewer byproducts than other renewable and non-renewable routes to propylene glycol, according to the company, although few details have been published to date.  The Ashland-Cargill facility will be using new biodiesel process technology from Davy Process Technology Ltd (London;, a Johnson Matthey company. As reported in the August 2007 issue of Chemical Engineering, Davy’s new glycerin-to-propylene-glycol (GTPG) process reacts glycerin in the gas phase with hydrogen over a heterogeneous, copper-based catalyst, at “moderate” pressure and temperatures. This produces propylene glycol via a two-step reaction: First, glycerin is dehydrated into water and acetol, and then, in the same reactor, PG is formed by the in situ hydrogenation of acetol. According to the company, vapor-phase conversion allows moderate operating conditions and relatively low temperature rise over the reactor, which favors high selectivity and increased yield. Davy’s per-pass glycerin conversion is around 99%, according to the magazine.

Meanwhile, in November 2006, Virent Energy Systems, developer of the patented BioForming technology platform for converting biomass into renewable fuels and chemicals, was awarded a $2-million grant from the U.S. Dept. of Agriculture (USDA; Washington, D.C.; and the U.S. Dept. of Energy (DOE; Washington, D.C.; to further its capabilities to convert biodiesel-derived glycerin into PG. The grant was awarded as part of the joint USDA-DOE Biomass Research and Development Initiative.

Virent is working in conjunction with FutureFuel Chemical Co. — formerly a subsidiary of Eastman Chemical Co., — which will supply the glycerin, and help design and then test the first prototype system, at its Batesville, Ark., biodiesel plant.

After establishing anew business unit — Renewable Energy and Chemicals — in December 2007 to pursue promising technologies for converting renewable feedstocks into value-added chemicals and plastics, UOP LLC (Des Plaines, Ill.; announced plans to expand its existing efforts to produce biodiesel from vegetable oils, and to pursue technology to convert biodiesel-derived glycerin into propylene glycol, although company spokesperson Susan Gross says it is premature to comment on any scaleup plans at this time. UOP has been working on several biodiesel-related initiatives with the U.S. Dept. of Energy’s Pacific Northwest National Laboratory (PNNL; Richland, Wash.; since 2004.

Similarly, in 2005, Archer Daniels Midland also announced plans to build its own glycerin-to-PG process, at a polyols facility that will produce both PG and ethylene glycol, to be built at an as-yet-undisclosed location. ADM has also declined to comment further on its process technology at this time.

Rapid growth in biodiesel production — and that industry’s pending surplus of byproduct glycerin — has provided the chemical industry with an opportunity to commercialize sustainable technologies will allow the it to produce a more environmentally benign version of the widely used commodity chemical PG, using renewable feedstocks that demand for costly, environmentally undesirable petroleum-based feedstocks.



By: Suzanne Shelley, Guest Columnist and Freelance Technical Writer


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