Higher Blends Require Higher Quality Ethanol

Increasing the amount of ethanol allowed to be blended into gasoline would be beneficial for the ethanol industry and the United States, but it is important that producers be aware of the product quality requirements that higher blends will demand.
By Tom Slunecka | August 10, 2009
Monitoring ethanol quality is nothing new for the industry, but producers must all be aware that adding higher percentages of ethanol to gasoline changes the dynamics of the limits of contaminants that can be accepted in the ethanol. Suppliers, technology providers, plant managers and wholesalers must remain alert to help the industry reduce the occurrences of out-of-compliance blended product. The American Society for Testing and Materials (ASTM) and Original Equipment Manufacturers (OEMs) have set standards for transportation fuel that may cause concerns in the fuel distribution system.

Unintended Consequences
The ethanol production process has many feedback loops due to living organisms (yeast), bacteria, process chemical additions and the recycle of water streams. This means that chemical or biological additives can lead to unintended consequences in other parts of the plant.

The first example of an unintended consequence is the detection of high levels of silicon. In the past, some refiners reported denatured ethanol that contained excessive amounts of silicon. The source of the silicon was traced back to the use of silicon-based antifoam used by an ethanol plant. It was determined that the silicon was a breakdown product from polydimethylsiloxane, an active ingredient in the antifoam formulation. The Renewable Fuels Association was alerted to this and sent a notice to ethanol producers to discontinue the use of any antifoam containing silicon. Current ASTM specifications do not have a limit for silicon. However, section 4.2 from ASTM standard D4806-08A states that customers can hold ethanol producers to lower limits of impurities. General Motors Co. has stated that no level of silicon can be tolerated in automotive fuel because it will cause permanent and irreversible damage to the oxygen sensors in an automobile.

Another example of an unintended consequence is the use of sulfur-based compounds that can contribute to sulfate levels in denatured ethanol. These process-based additives include the water source, sulfuric acid, bisulfites for air scrubbers and sulfamic acid/sodium bisulfate for cleaning heat exchangers. There is speculation that the sulfur in these chemicals forms organic sulfur compounds that are volatile in the distillation part of the process. Over a period of time, these organic sulfur compounds are oxidized to sulfates in the ethanol. Minimizing the use of these sulfur-based compounds will help insure compliance with standards for denatured alcohol and also introduce less sulfur into the distillers grains.

Chlorine dioxide, which could potentially contribute to higher levels of chlorides in denatured alcohol, is another example of a process aid that could have unintended consequences. The presence of higher chloride levels in U.S. fuel supply could greatly damage efforts underway to increase the acceptable amount of ethanol blended into fuel.

When higher amounts of ethanol are blended, the chloride concentrations increase, possibly resulting in higher level blends being out of specification.

Judy LaZonby, an expert in the application of industrial biocides and chlorine dioxide at The MicroStar Lab in Crystal Lake, Ill., said that when ethanol plants are considering the use of older chlorine dioxide technology as an antimicrobial in the fermentation phase, they risk contributing unexpected amounts of chloride ions. LaZonby said that generating chlorine dioxide in the fermentors by using sodium chlorite could open the door to increasing inorganic chlorides in the ethanol. The additional chlorine dioxide flashes overhead with the ethanol distillate and will decompose to oxygen and chloride ion within the distillation process.

Dr. Dennis Bayrock, director of Phibro's research and development, said Phibro has developed a spreadsheet model that can determine the quantity and potential impact of using chlorine dioxide. The modeling reinforces the belief that the use of chlorine dioxide could be an issue with fuel quality. Using an antimicrobial that is not chlorine-based or carefully testing and monitoring chlorides with an ASTM method with a one parts per million (ppm) limit of detection could help remedy the issue.

Chloride Limitations
Current ASTM specifications tightly regulate the amount of inorganic chlorides permitted in E10 and E85 to one ppm. Regulations on chloride limits in denatured fuel alcohol are 10 ppm, thus making all ethanol blends consistent with the one ppm limit in E10, but inconsistent with the E85 limits.

A recent RFA survey shows that while nearly all plants are producing E98 with chloride levels at or below the amount allowed to produce E10, nearly 10 percent of the plants are producing a product that is out of compliance with the limits of higher blends.

Ethanol containing excess levels of chlorides may be problematic for OEMs and car manufacturers due to higher warranty costs from corrosion failure of fuel pumps and fuel injectors. Chloride concentrations as low as one ppm can cause fuel system corrosion in high temperature areas near the engine.

Blender pumps that use one source of ethanol to mix with gasoline to dispense different grades of ethanol from E10 to E85 should meet the current E85 chloride limit of one ppm. This means that, in practice, the 10 ppm limit on denatured alcohol has been reduced to one ppm and any alcohol with unacceptable levels of chloride will be rejected from use in blender pumps.

The continued future growth of the ethanol industry will require a better understanding of the use of different processing aids and their impact within the ethanol process. All stakeholders in the future success of the ethanol industry will need to share information on concerns for potential contaminants to the ethanol process and prevent the industry from harming its image.

Tom Slunecka is the vice president of marketing for Phibro Animal Health Corp.'s Ethanol Performance Group. Reach him at tom.slunecka@phibrochem.com or (402) 575-5855.