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MICROREFINING OF WASTE GLYCEROL FOR THE PRODUCTION OF A VALUE-ADDED PRODUCT
Impact/Purpose:
Biodiesel is an excellent transportation fuel. It was developed as an alternate or a supplement to diesel fuel. It can be used in any existing diesel engine with little or no modifications. Normal diesel fuel currently powers freight trucks, trains, boats, barges, some sport utility vehicles and lighter trucks, and over two thirds of all farm equipment in the United States. Vehicles that are powered by diesel fuel can claim 20 to 40 percent better fuel economy than the same vehicle powered by gasoline. Because of their higher efficiency, diesel powered vehicles are used in many physically demanding jobs, such as construction work. The production of biodiesel results in a significant byproduct stream of crude glycerol, contaminated with methanol and caustic. In most large biodiesel production facilities, the waste stream is treated in an on-site refinery. However, many Americans produce their own biodiesel in smaller outfits, such as their own garage or in small biodiesel facilities that service a single fleet, such as the UT Biodiesel program on the campus of the University of Tennessee. This often leads to dumping of the waste stream down a drain or into the garbage. This can turn out to be problematic at the wastewater treatment facility, leading to a significant increase in COD in the plant influent. Also, the dumping of the useful byproduct stream wastes energy and increases carbon dioxide emissions. The destruction of potentially useful glycerol hinders the world’s pursuit of sustainability. The work proposed here will develop a prototype system for the small scale, or micro-refining of the glycerol produced locally by micro-manufacturers. We have identified a single point source (the UT Biodiesel program noted above) as an initial supplier of contaminated glycerol.
Description:
As a result of Phase I, a process to refine crude glycerin waste to value-added products was designed. An economic analysis was performed to determine the capital and operating costs for a commercial facility that implements this design. Using the estimated 1,800 gallons of raw material per year, it was determined total annualized cost of glycerol accelerant was found to be $21.18/gallon, the FFA annualized cost was $19.12/gallon, and the annualized cost of producing phosphate salts is $1.91/lb. This results in a manufacturing cost for the glycerol accelerant of $10.60 per five bushels of composting material (based on using 2 liters (~1/2 gallon) per application). The purpose of the experimental design portion of this project was to determine the efficacy of the selected refining technique and to determine the performance of the resultant products. This was carried out by measuring the effect of the glycerol and phosphate salts on a compost pile and the effect of FFA material as weed killer. It was essential that these products perform with minimal environmental impact. In this study, common agricultural activities such as composting waste into a natural fertilizer and the removal of unwanted plants by weed killer are examined. These methods were chosen as a response to the ever-growing need to replenish and aid the degrading environment by recycling waste material back into biodegradable products.
Before determining the efficacy of the compost accelerant and FFA weed killer were in application, an effective way to generate these products from the crude glycerin had to be developed and tested. The chosen method was an acidification reaction. Phosphoric acid was added to the crude glycerin material, vigorously agitated, and then allowed to settle. Through this process, the dark, viscous liquid turned to a lighter color through acidification settled into three distinct layers that could be separated gravimetrically. After accumulating a sufficient amount of each product, performance tests of the product streams were conducted. Two sets of experimental tests were implemented; the first set of tests was to determine the effect of adding glycerol amended with phosphate salts as an accelerant to a compost pile. The second set of tests was to determine the effectiveness of using the FFA material as a weed killer.
Composting is a common agricultural practice that farmers and other agricultural businesses employ to create an inexpensive organic fertilizer. This is carried out by the catabolism of carbon and nitrogen sources via aerobic metabolism by bacteria and fungi. To determine the performance of glycerol amended with phosphate salts as a compost accelerant, a temperature profile was obtained for compost piles to monitor levels of microbial activity. Six compost piles with three treatments were observed and measured for this experiment.
The separated free fatty acid material was tested to determine its performance as a weed killer, and whether a foliage application or soil application showed significant differences in resultant effect. Three treatments were used on four plant specimens to determine if the FFA material would result in significant negative effects to the plants within a week. The FFA material had obvious deleterious effect on healthy plants. During the seven days that elapsed after the application of the FFAs, the plants experienced significant negative effects, with the foliage turning brown. Applying the FFAs to the foliage of the plant was more effective at inhibiting plant growth than applying the FFAs to the soil surrounding the plants.
It was determined that the overall process of recovering crude glycerin by means of acidulation was sustainable. This is from taking a waste product that may accumulate in the environment or be sent in large amounts to waste treatment and converting it into value added products to be used in the environment. In general, a waste product is converted into a useful product used and then used in agricultural actions such as composting and weed killer. In addition, this process eliminates a potentially harmful waste product containing a large amount of methanol and converts it into useful methanol-free products.