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Researchers Investigate Supercritical Method of Converting Chicken Fat and Tall Oil into Biodiesel
20 December 2007
Chemical engineering researchers at the University of Arkansas have investigated supercritical methanol as a method of converting chicken fat into biodiesel fuel. The new study also successfully converted tall oil fatty acid, a major by-product of the wood-pulping process, into biodiesel at a yield of greater than 90%, significantly advancing efforts to develop commercially viable fuel out of plentiful, accessible and low-cost feedstocks and other agricultural by-products.
Supercritical methanol treatment dissolves and causes a reaction between components of a product—in this case, chicken fat and tall oil—by subjecting the product to high temperature and pressure. The simple, one-step process does not require a catalyst.
Substances become supercritical when they are heated and pressurized to a critical point, the highest temperature and pressure at which the substance can exist in equilibrium as a vapor and liquid.
Chicken fat and tall oil treated with supercritical methanol produced biodiesel yields in excess of 89% and 94%, respectively. With chicken fat, maximum yield was reached at 325°C and a 40-to-1 molar ratio. The process also produced a respectable yield of 80% at 300°C and the same amount of methanol. At 275°C and the same amount of methanol, the process was ineffective.
Ideal results using tall oil fatty acid were achieved at 325°C and a 10-to-1 molar ratio. At 300°C and the same amount of methanol, the conversion produced a yield of almost 80%. Again, at 275°C, the process was ineffective.Previous efforts to make biodiesel out of low-cost feedstocks as opposed to refined oils have used one of two conventional methods, base-catalyzed or acid-catalyzed esterification. Although successful at producing biodiesel, these conventional methods struggle to be economically feasible due to long reaction times, excessive amounts of methanol required and/or undesired production of soaps during processing.
The supercritical method hit the free fatty-acid problem head on. Because it dissolves the feed material and eliminates the need for the base catalyst, we now do not have the problems with soap formation and loss of yield. The supercritical method actually prefers free fatty acid feedstocks.
—R.E. Babcock, professor of chemical engineering, University of Arkansas
A number of other researchers have also investigated the use of supercritical methanol in the production of biodiesel, using different feedstocks. Examples include:
Researchers at Kyoto University in Japan have applied a supercritical methanol process to the production of biodiesel from rapeseed oil. They obtained their best results at 350°C, 30 MPa and 240 sec with a molar ratio of 42-to-1. According to their calculations, a conventional transesterification process alone consumes 4.3 MJ/l, while the supercritical methanol method requires 3.3 MJ/l, or energy reduction of 1.0 MJ for each liter of biodiesel produced.
The Saka Laboratory at Kyoto has gone on to develop a two-step supercritical process that allows more moderate reaction conditions than those of the one-step method.
Researchers at Chulalongkorn University in Thailand used supercritical methanol to produce biodiesel from coconut oil and palm kernel oil. They obtained their best results at a reaction temperature of 350°C, molar ratio of 42-to-1, and space time of 400 s. The percentage methyl ester conversions were 95 and 96 wt% for coconut oil and palm kernel oil, respectively.
Researchers at Beijing University of Chemical Technology prepared biodiesel from soybean oil using supercritical methanol with CO2 as a co-solvent. With CO2 as co-solvent in the reaction system, there was a significant decrease in the severity of the conditions required for supercritical reaction. Optimal results produced a 98% yield of methyl esters, occuring at a reaction temperature of 280°C, methanol to oil ratio of 24 and CO2 to methanol ratio of 0.1, reaction time of 10 minutes and a reaction pressure of 14.3 MPa.
Resources
Biodiesel fuel for diesel fuel substitute prepared by a catalyst-free supercritical methanol (Kyoto University)
Kunchana Bunyakiat, Sukunya Makmee, Ruengwit Sawangkeaw, and Somkiat Ngamprasertsith. “Continuous Production of Biodiesel via Transesterification from Vegetable Oils in Supercritical Methanol” Energy Fuels, 20 (2), 812 -817, 2006. 10.1021/ef050329b
Weiliang Cao, Hengwen Han and Jingchang Zhang. “Preparation of biodiesel from soybean oil using supercritical methanol and CO2 as co-solvent” Process Biochemistry Volume 40, Issue 9, September 2005, Pages 3148-3151
December 20, 2007 in Biodiesel | Permalink | Comments (10) | TrackBack (0)
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Comments
This could be important since a lot of fire-prone plants and weeds are like tall oil insofar as they contain a mixture of fatty acids and turpentine (terpenes). I wonder how this compares with Nextbtl or other processes that can use chicken fat.
I don't know what to believe on the energy/CO2 balance of paper mills as I see coal trains visit regularly.
Posted by: Aussie | Dec 20, 2007 6:26:03 PM
Take a closer look at the by product and tell me if it wont be a host to bacteria's and cause major influenzia outbreaks to increase? And any other deadly living virus that feeds on animal fat by-products.
Posted by: Nick | Dec 20, 2007 10:49:47 PM
Nick wrote:
Take a closer look at the by product and tell me if it wont be a host to bacteria's and cause major influenzia outbreaks to increase? And any other deadly living virus that feeds on animal fat by-products.
Way to be positive, Nick! Maybe there is a solution to that problem, such as burning the waste directly or co-firing it with coal/biomass to produce electricity. Or even better, to use as feedstock somewhere else, if possible...
Posted by: | Dec 20, 2007 11:50:48 PM
I don't think many bacteria could survive the pressure cooking. It's not living so viruses won't survive long. I don't know such much about prions that cause mad cow disease. When you store biodiesel keep the moisture out or use an antifungal additive so it is completely microbe free. When and if biodiesel is spilled it should biodegrade quickly. That's a good thing for tugboats for example working around harbours.
Posted by: Aussie | Dec 21, 2007 1:54:12 AM
Fantastic news. The Maine logging truckers have been badly hurt by recent diesel prices, and something like this could allow a waste product of the paper mills to be turned into a useful fuel to be sold back to the truckers, helping to close a carbon loop in the process.
Posted by: rob | Dec 22, 2007 3:11:34 PM
And any other deadly living virus that feeds on animal fat by-products.
Since viruses don't feed on anything, I have to wonder if you even know what a virus is.
Posted by: Paul F. Dietz | Dec 23, 2007 5:23:01 AM
Are you worried about your vehicle coming down with the flu? Unless someone is drinking the biodiesel, or rubbing it on open wounds, I fail to see the problem.
The only objectionable part of the whole process is the morbid source of the fatty acids (chicken entrails). It's just a little bit too "Soylent Green" for me, that's all.
Posted by: Bike Commuter Dude | Dec 23, 2007 1:48:54 PM
Didn't Changing World Technologies already do this?
Posted by: swen | Dec 25, 2007 5:47:52 PM
Changing World is/was certainlly doing something similar. Most of it was with chicken fat and other unusable parts from big producers such as Tyson.
The were making the astonishing claim of being able to use any organic input in their process. But as someone said or should have 'claiming is easy, comedy is hard.'
CWT caught my eye because I held some Conagra stock a few years ago and Conagra owned most or all of CWT.
Posted by: K | Dec 26, 2007 11:51:18 AM
Changing World Technologies is making "green" diesel (chemically speaking: hydrocarbons) as opposed to biodiesel (CS: FAME). CWT has a superior product.
Unfortunately, CWT made the classic mistake of overpromising (claiming they would make diesel fuel for ~$15/bbl) and underdelivering (actual cost ~$80/bbl).
The process at Carthage consists of two steps: (dilute acid) hydrolysis and decarboxylation. So, great for lipids, not much use for anything else.
Posted by: Engineer | Dec 26, 2007 1:31:10 PM
