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Biofuels

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The training page, with links to registration or archive, Links page, and feedback, for the Biofuels course is available at http://www.clu-in.org/conf/itrc/biofuels/

Remaining Simulcast Questions and Answers from March 20, 2014

Question 1: The readily biodegradation of ethanol can lead to anaerobic conditions. But anaerobic conditions are needed to achieve the acetate and H2 degradation. So is bioremediation 2 fold, one with increased O2 levels to push the ethanol to acetate and H2 and then an anaerobic phase to convert the daughter products to methane?

  • David Tsao: ethanol can convert to acetic acid and water in the presence of oxygen (think about wine going bad). Oxygen is often limited in the aqueous phase, but is available at the fringes of the source. Depending on the buffering in the subsurface, the acetic acid forms acetate + hydrogen. Methane forms from acetate via aceticlastic methanogens or from hydrogen via hydrogenotrophic methanogens. All methanogens are anaerobes.

  • Denice Nelson: To add to David's response - the confusion may have been in that we show the anaerobic pathway in the training since that shows the connection between ethanol degradation and methanogenesis. But, per David's response above, there is also an aerobic pathway for ethanol that produces acetate. Acetate can also be consumed/degraded under aerobic conditions in a way that will not produce methane (it will instead be converted to carbon dioxide). So, for remediation - if you add oxygen - you can avoid methane generation all together while still effectively degrading the ethanol and its breakdown products.

Question 2: How are biofuels blended with petroleum before delivery to gas stations?

  • David Tsao: there are multiple methods to blending the bulk petroleum and bulk biofuel into the final blended biofuel: in-tank mixing (flow both componants into an AST at the terminal), in-pipe mixing (flow both components together as it feeds into the tanker truck at the terminal - one pipe), splash blending (both flow separately - two pipes - into the truck at the terminal; blending occurs in the truck itself), etc.

Question 3: slide 64 fatty acid is called as surrogate analyses for biodiesel. however this analyses is not called in 67 and 68. Do you have experience with the analyses of fatty acid. also in relation to saturated and non saturated fatty acids

  • David Tsao: FAME can be analyzed by GC/FID or HPLC methods. Ironically, the FAME that comprises biodiesel rapidly converts to fatty acids when in the environment; the analytical methods for fatty acids often require converting the fatty acid back into a FAME for analysis. Likewise, standard petroleum analytical protocols (SW846) often require a clean-up step (e.g. silica gel clean up of the sample). This is to remove compounds that complicate/interfere with the analyses for hydrocarbons. Those interferences are often fatty acids/FAMES.

Question 4: Recommended parameters/conditions for consistent site closure ? Typical time frame to closure?

  • Mark Toso: There really isn't an easy answer to this question. It depends on the site, potential receptors and regulatory requirements. In general if methane is the risk then you would want to monitor for methane in ground water until levels decrease indicating the source biofuel has been depleted. You should also monitor soil gas for methane at the same time mas it might be possible to document a relationship between groundwater and soil gas concentrations which could allow site closure if the risk to receptors is no longer a concern. Because of the difficulties with monitoring ethanol in the capillary fringe I would never rely on the disappearance of ethanol alone for site closure.

Time to reach site closure is very site specific, and would be dependent on the size of the release. Based on case studies it appears E95 releases will degrade faster than petroleum releases so the time to reach site closure should be shorter. As an example the Balaton MN site which was a 60,000 gal E95 release that occurred in 2004 will be closed this year. We haven?t detected ethanol in groundwater since 2007 but methane levels in groundwater didn't drop off until 2011.

Question 5: So the oil pollution act is triggered by the presence of a sheen. For spilled ethanol what would be be the appropriate regulatory statute to clean up a spill to the environment?

  • Mark Toso: I don't believe ethanol is considered an oil under OPA so I'm not sure of federal triggers for response. In MN the response would be triggered by low DO levels which would affect aquatic life, same as a release of municipal sewage. Also in MN ethanol is considered petroleum under our statutes so it would fall under the same regulatory requirements as petroleum fuels.

Remaining Simulcast Questions and Answers from November 19, 2013

Question 1: I believe the ITRC document would be an extremely important document especially with the increase of biofuels usage in the future. For public safety, why not incorporate its recommendations into legislation rather than limit it to a guidance document? - University Participant; London, United Kingdom

  • Michael Maddigan: One of the main goals of every ITRC team is for state governments to not only use the guidance in everyday operations but to also use it to help develop and revise regulations. Each state's laws and regulations are different so ITRC's guidance documents try to appeal to a wide audience. Ultimately it is up to each state government to decide whether or not to implement the methods and recommendations provided in our guidance. This is why ITRC uses an active network of diverse professionals led by members of state government to develop our guidance documents.

Question 2: What is the difference in the overall scale of environmental concerns between standard diesel and bio diesel? Considering all the biodiesel spills is there less of an incentive to use it, and if so why is this not regualted on a larger scale? - University Participant; London, United Kingdom

  • David Tsao: On a global scale diesel dwarfs biodiesel considerably in terms of volume consumed (see Table 1-4 in the document). From an environmental standpoint, neither are exceptionally mobile in the subsurface; however, biodiesel is likely more rapidly biodegradable leading to the methane generation issues discussed during the training. One of the other issues associated with biodiesel is during the production. Glycerol is a byproduct during the esterification process and makes up about 1/3 of the total carbon from the fat and oils used to create the FAME. The volume is large. Because of all of the biodiesel production occurring worldwide, there is a glut of glycerol on the market (more than what is needed in commercial products that use glycerol). This glut makes this a waste stream that has a very high BOD which gives issues to treatment facilities/waste disposal. The high BOD can also lead to fishkills.

Question 3: If Ethanol is detected in LNAPL analyses, should that be considered as strong indication that Gasoline spill is fresh enough to justify ethanol presence, or can this be a consequence of other biological processes occuring in groundwater? - Environmental Consultant; Stockholm

  • David Tsao: Aside from the preference of ethanol to partition into the water phase, it can be an indication, although how strong, I'm not sure without additional lines of evidence or analyses. One of the issues with analyses associated with ethanol is the high propensity for false positives. One issue is the relatively high method detection limits when using analyses for petroleum, but another is the presence of ethanol in many commercial products, particularly those that are used in the sampling process (decon), labs and by technicians, etc. We conducted a study of soil and groundwater samples where we originally detected ethanol and after re-analysis to confirm the hits, we found 48% of the groundwater and 79% of the soil samples were false positives. The ethanol detections were found in the field blanks and other QA/QC samples. This study was done about 10 years ago, so the techniques and awareness has increased since, so this may be less of an issue now.

Remaining Simulcast Questions and Answers from June 7, 2012

Question 1: What is the timeframe for the degradation of methane by methanotrophs in groundwater or soil? - Environmental Consultant; Islandia, NY, United States

  • David Tsao: this is really going to be site specific...influenced by soil type, depth of the vadose zone, moisture content, atmospheric pressure influence, indigenous microbial composition, etc. The reference cited by Dr. Denice during the presentation (Ma, et al: "Methane Bioattenuation and Implications for Explosion Risk Reduction along the Groundwater to Soil Surface Pathway above a Plume of Dissolved Ethanol" in ES&T 2012) provides a rate of 0.51 +/- 0.028 ug CH4/h/g soil. However, this is a sand packed tank study done under highly controlled conditions.

Remaining Simulcast Questions and Answers from December 6, 2011

Question 1: Is the common observation that chlorinated compounds migrate further in soil gas into indoor air than petroleum compounds not (or less) applicable when compared to methanol? - State Regulator, MA, United States

  • David Tsao: First of all, I would refer this question to the ITRC Vapor Intrusion training / team members. One point however is that regardless of which vapor (chlorinated, petroleum, or biofuel), there must be a driving force behind the vapors to cause migration in soil gas. Presumably you mean ethanol or methane rather than methanol as most methanol is not produced biologically for fuel, but chemically, so isn't considered a biofuel (not discussed in our training). Methane migrating in the subsurface may be driven by the high rates of generation due to the biodegradation of biofuels. As Mark mentioned in his portion of the training - slide 64 for biodiesel - (perhaps Denice as well), it appears that the volume of methane produced from biofuels (e.g. 1.4 L creating 600+ L methane) may be sufficient to create that driving force in soil gas.

  • Denice Nelson: I would also add that similar to petroleum compounds, methane is aerobically biodegradable. So if the mechanism behind why petroleum compounds tend to migrate less is because they are more susceptible to aerobic biodegradation, then methane may be similar. Echoing David's response - I would refer this to the ITRC VI team.

Question 2: Could you briefly review some effective remediation approaches for ethanol release to surface water ? Private Sector Participant, OK, United States

  • Denice Nelson: Generally surface water mitigation methods focus on supplying dissolved oxygen to the water body in order to prevent a DO drop that can negatively impact fish, etc. This will also enhance the biodegradation of the ethanol. Technologies such as air sparge curtains or floating surface aerators can be used to achieve this.

  • Mark Toso: In the case of the Wild Turkey Bourbon fire/spill they used floating aerators to supply oxygen, but it is unknown how effective they were. The key to responding to any surface water spill would be to deploy the aeration equipment as soon as possible. The state of MN is looking at for places where we can access this equipment quickly. Wastewater treatment plants would be a good source for aerators which could be used in a surface water response.

Question 3: Is there any difference in behaviour and remediation strategy between corn-based and sugar cane-based biofuels? Government Participant, Canada

  • Mark Toso: I don't think so since they are both at least 96% ethanol (I think that's the ASTM standard for fuel ethanol). With corn ethanol we have seen trace amounts of other alcohols such as octanol and hexanol which could also be present in sugar cane ethanol. However the affect these trace amounts would have on behavior, if any, would be minor.

Question 4: If a pure ethanol aboveground tank had a subsurface release on top of other fuel releases would you still expect as much methane generation as discussed today? GW is 7ft below ground surface... - State Regulator; San Diego, CA, United States

  • Denice Nelson: Yes, I would expect the same amount of methane as discussed within the presentation, unless there was something present related to the other fuel release that is toxic or inhibitory to bacteria (generally not the case). You may have a much shorter lag time to see methane since the groundwater is probably methanogenic already.

Question 5: How long does it take from the biodiesel release to the methane formation in concentrations dangerous for explosion in buildings over the plume? Government Participant; Rome, Italy

  • Mark Toso: That?s a good question because we have little experience with actual biodiesel releases, but I would expect that methane generation would happen quickly, perhaps faster than an ethanol release because there are no toxicity issues with biodiesel. This is one of many areas where more research on biofuel releases would be helpful.

Question 6: Are there any phytoremediation experiences for biofuels? Government Participant, Canada

  • David Tsao: First I would refer this person to the ITRC Phyto training course (Feb 28, 2012). Three aspects that might answer this question: 1) the vegetation on landfill covers often have "dead patches" that form due to methane being released from the landfill. It is actually not a toxicity issue but rather an exclusion of oxygen to the plant roots that are causing the die-off. If you were to use plants to phytoremediate the methane, then the potential dropoff in oxygen would need to be considered. 2) If you were looking to use phyto to capture the dissolved phase of a biofuel release (i.e. ethanol in the groundwater), the miscibility means that the plants would take up the ethanol, but the ethanol would likely be bio- or phyto-degraded completely to CO2 and H2O. Just like with microbes, there would be a level (in the % range) considered toxic to the plants too. Depending on the mass load into the rhizosphere, the biofuel may never actually enter into the plant and be biodegraded. The rhizosphere is essentially a highly active bioreactor. 3) There have been studies looking at the impacts of biofuels on wetland systems. As with any organic load into these systems, the biofuel can be converted to a BOD loading that can then be used to determine what the system could handle or should be designed to handle.

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