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Final Report: Process-Intensified Low-Cost Biodiesel Production Using Meat Rendering Waste, Greases, and Food WastesEPA Contract Number: EPD08043
Title: Process-Intensified Low-Cost Biodiesel Production Using Meat Rendering Waste, Greases, and Food Wastes
Investigators: Elliott, Brian E
Small Business: TDA Research Inc.
EPA Contact: Manager, SBIR Program
Project Period: March 1, 2008 through August 31, 2008
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2008) RFA Text | Recipients Lists
Research Category: SBIR - Emission Reductions and Biofuels , Small Business Innovation Research (SBIR)
Biodiesel is a fuel made by reacting vegetable oils and animal fats with an alcohol to form a liquid fuel that can burn in a standard diesel engine with no modifications. Typically, methanol is used with a base catalyst to promote a transesterification reaction to produce fatty acid methyl esters (or biodiesel). This standard process requires a highly refined and expensive feedstock oil. The quality of oil required is similar to edible-grade vegetable oils. The use of this production process, which requires highly refined oils, has caused widely publicized problems relating to commodity price increases for soybean oil and canola oil, questions regarding the use of food as a fuel, and questions regarding the ability to produce a meaningful amount of biodiesel for the effort required. The biodiesel industry would greatly benefit from a new process technology that can convert low-quality, non-edible oils and fats into fuel. By using these low-quality oils and fats (such as waste greases, recycled oils, rendered animal fats, etc.) the industry would not be competing with food for feedstock, and it could produce a renewable fuel that is price competitive with petroleum-derived diesel #2.
Biodiesel is a critical component of our nation’s effort toward energy independence and lowering of our CO2 emissions. The feedstock issues need to be resolved, but there will always be a demand for the domestic excess of soybean and canola oil for producing renewable fuels. The key to expanding the current level of biodiesel production without further competing with food is to develop new technology to take advantage of waste feedstocks and even oils from non-food oilseed crops. For the use of non-food oilseed crops the ideal process would use the crude, unrefined oils. The refining process removes impurities and adds significant cost. The two main goals of this project were to develop a technology that can tolerate these impurities and at the same time lower the production cost of biodiesel.
The impurities found in both crude and waste oils and fats are similar. In particular, free fatty acids and water are particularly problematic for the existing biodiesel production technology. Free fatty acids react with the catalyst to form soap. This reduces the fuel yield by converting a portion of the feedstock into much less valuable soap, and makes it difficult to separate the biodiesel fuel from the soap and glycerol by-products. More product losses result from the difficult separations. Water also contributes to this problem because the oils and fats are hydrolyzed during the esterification reaction and a hydrolysis reaction forms more free fatty acids, which also become soap. It is not uncommon for process yields to be as low as 60-70 percent when using high free fatty acid feedstocks (with at least 5% free fatty acid). This poor yield makes it very difficult to produce biodiesel using conventional technology and make a profit.
This project sought to develop a new process technology that can not only tolerate high levels of free fatty acids and water, but can convert all of the oil/fat as well as the free fatty acids into ASTM-grade biodiesel. Specifically, this project developed, tested, and evaluated a new process for producing biodiesel from low cost (waste) high free fatty acid vegetable oil and animal fat feedstocks. The new process uses a proprietary catalyst and a unique chemical conversion pathway relative to the conventional process that allows it to tolerate waste feedstocks that cannot be converted to biodiesel with current methods.
Furthermore, another goal of this project was to introduce process-intensification into our general biodiesel process technology, and to determine if the process economics could be further improved. Process intensification is a design strategy that attempts to combine more than one function in a single chemical process unit operation. For example, reactions typically involve the use of an excess of one of the feedstock components. After the reaction is completed in a first reactor vessel, the product mixture is sent to a separation unit, such as a distillation column, to remove the excess component from the product. A relatively new process technology called reactive distillation combines the functions of reaction (typically over a catalyst) with separation, all in one process vessel. Thus, process intensification can result in a more physically complex process, but one with fewer major equipment components and a lower capital cost. Also, energy inputs often can be reduced if process intensification can be incorporated into the process design. In this project, two types of process-intensification were studied to improve the economics of biodiesel production. One involved the use of reactive distillation and the other involved a proprietary reactor/reaction design.
TDA used a bench-scale version of the two types of processes to evaluate their performance. Waste oils were obtained (yellow grease) from a recycled oil collector and processor. These oils had a free fatty acid content ranging from 2 to 20 percent. The level of water in these feedstocks was above 0.6 percent. These waste oils would normally have to be refined and purified prior to use as a feedstock for biodiesel production, but we used them as-received with no purification. The process conditions for our two bench-scale units were adjusted and fuel samples were collected and tested for free glycerin and total glycerin, acid number, mono-, di- and tri-glycerides and other specifications outlined in ASTM method D-6751. The kinetics for the reactions were evaluated at varying temperatures using two types of proprietary catalysts. Optimum process conditions were estimated for each type of process and used to design a biodiesel production plant capable of converting 20 million gallons of waste grease per year into biodiesel.
A detailed engineering and economic analysis was performed for the two processes. A separate analysis was performed for each type of process. The analysis included estimating the capital cost for the purchased process equipment, installation, fixed capital costs including the auxiliary facilities, the total capital investment including working capital, and the product cost estimate (or the total cost for producing the biodiesel product on a per gallon basis).
The processes were both very effective at converting oils containing both elevated levels of free fatty acids (2.5% up to 20%) and elevated levels of water (up to 2%) into ASTM-grade biodiesel. Both processes were more attractive (more profitable) than the conventional process. We down-selected to the preferred process based on several considerations. The preferred process was the more physically simple, and more similar in complexity to that found in existing biodiesel production facilities. The preferred process also had a slightly lower product cost as a result of a lower capital investment and lower energy inputs. The preferred process, which uses a proprietary reactor and a proprietary catalyst can produce biodiesel from yellow grease and ethanol at a product cost of $2.63. Wholesale biodiesel currently sells for $4.50 (before the blender’s tax credit), making this a very attractive process investment. This analysis assumed a 20 million gallon per year facility, a cost of yellow grease of $2.05 per gallon and ethanol at $2.30 per gallon (current values for September, 2008).
This project developed a potentially very profitable process for making biodiesel from waste oils and ethanol. Whereas conventional biodiesel production technology cannot convert waste oils or fats with greater than about 5 percent free fatty acids into biodiesel (and generate a profit), the technology developed in this project can not only tolerate such impurities, but it can convert essentially all of the oil fraction and the free fatty acid impurities into biodiesel while generating a profit. The use of ethanol provides a biodiesel fuel that is 100 percent renewable. Methanol is produced from natural gas, thus biodiesel made using methanol contains a fraction originating from fossil fuel, and the rest from a renewable oil/fat source.
The new process developed in this project can convert yellow grease containing 5 to 20 percent free fatty acid and 0.6 percent to 2 percent water into ASTM-grade biodiesel. No pre-treatment of the feedstock is required. The process is based on a proprietary reactor design and uses a proprietary catalyst.
TDA has filed two U.S. patent applications relating to this process technology. The commercial applications for this technology include biodiesel production using a variety of waste oils and fats, not limited to yellow grease, brown grease, tallow, and poultry fat.
The new process will promote increased use of biodiesel by reducing the cost of the fuel, but more importantly it will convert waste oils and fats, which end up in sanitary landfills, into a useful fuel. Also, substituting petroleum diesel with biodiesel reduces CO2 emissions by about 80 percent.