By Annel K. Greene, PhD
Center Director, Clemson University
Animal Co-Products Research and Education Center
Clemson University bioenergy researchers Dr. David A. Bruce and Dr. Dora E. Lopez are studying the utilization of animal fats for the production of biodiesel. Members of the Clemson University Animal Co-Products Research and Education Center (ACREC) team, Bruce and Lopez seek to answer the question, “How much energy input is required to produce biodiesel from animal fats versus vegetable oils?” They are using a technique known as the Life Cycle Analysis (LCA) methodology, which looks at all energy inputs and outputs to derive a final energy balance for the product.
An associate professor in the Clemson University Department of Chemical and Biomolecular Engineering, Bruce and his group conduct research in a variety of areas including biofuels, catalysis, kinetics, pollution abatement, molecular modeling, and the syntheses of novel molecular sieves for automotive exhaust and fuel conversion processes. Lopez, a post-doctoral fellow in the Department of Chemical and Biomolecular Engineering, investigated the chemical reactions utilized in making biodiesel during her PhD degree program. She has studied the mechanisms of the reactions as well as developed more economically efficient methods of catalyzing the formation of biodiesel. In their project for ACREC, Bruce and Lopez are evaluating the energy balance for a variety of rendered products including tallow, poultry fat, and yellow grease for conversion and utilization as biodiesel fuel.
The U.S. biodiesel industry experienced rapid growth between 1999 and 2006 when production capacity increased from one million gallons to greater than 240 million gallons per year. However, due to rising prices for soybean oil feedstocks, the biodiesel industry has greater potential production capacity than it is utilizing. It is estimated that the currently installed biodiesel plant equipment has the capacity to produce three times the actual 2007 biodiesel production volume. However, operation at full capacity will require a more economical and readily available feedstock. Competition for current agricultural land among bioenergy and food crops is becoming more serious. Crops such as soybeans have multiple potential end uses – from foods to commercial products to biofuels. Supply and demand are causing crop prices to soar and, as fat feedstock prices rise, production costs for biodiesel from these feedstocks rise. For 2008, this trend is expected to continue.
Rendered animal fats are suitable alternatives to vegetable-based feedstocks and may lower the cost of the production of biodiesel when compared to that of dedicated crops. Additionally, the use of rendered animal fats for fuel does not represent a direct competition with the human food chain.
Any raw material to be used in the renewable fuels feedstock portfolio must be assessed for sustainable production and effectiveness to combat climate change. The LCA fossil fuel energy ratio (ER) is a research tool used to rate the renewability of a potential feedstock. ER is defined as the amount of thermal energy that a biofuel can produce divided by the total amount of fossil fuel energy (petroleum products, coal, and natural gas) required to produce it.
An “ER = 1” means that the biodiesel provides an amount of energy equal to the amount of fossil fuel energy that was needed for its production. Thus, there is no environmental emissions advantage to using a bio-derived fuel where the ER is equal to or less than one.
The ER value is dependent on the particular boundaries selected for consideration. For instance, in the production of biodiesel from vegetable crops, all energy inputs from planting to crop maintenance to harvest to transport to biodiesel conversion must be considered. For rendered animal fats, the primary use of the animal was for food and the fats are by-products. The calculation of the value of the ER will depend on the point at which energy inputs are allocated to the food industry as opposed to the rendering industry. These assumptions are often a subject of great debate among stakeholders. For this reason, the Clemson researchers are working on a combination of different system boundaries (animal production, rendering, biodiesel conversion) and allocation methods (mass and price) in an attempt to provide a better assessment on case-specific situations. In addition, the team is evaluating the different energy costs of using various types of rendered animal fats, of selecting different co-feedstocks (methanol versus ethanol), and the rendered fat conversion process.
It has been shown by several previous studies that the ER ratio for converting tallow to biodiesel can range from slightly above one to almost four. Unfortunately, little data is available for other animal fats. This disparity of values and the lack of information about poultry fat and lard feedstocks make it difficult for regulatory bodies to make appropriate decisions. Therefore, Bruce and Lopez are working to determine this information and believe it will clearly define the environmental advantages associated with the conversion of animal fats to transportation and heating fuels.
In order to obtain key LCA input information at the rendering stage (raw and final material characteristics, process energy requirements, emissions, and transportation), Bruce and Lopez have surveyed the rendering industry with the assistance of Dr. David Meeker of the National Renderers Association. Individual company results will be kept confidential but the averaged survey results are being used to obtain representative energy estimates for different rendered products, such as tallow, poultry fat, and yellow grease.
For the conversion of rendered animal fats and grease into biodiesel, the team is evaluating the energy balance of a conventional biodiesel conversion process as well as the energy balance for a state-of-the-art recyclable solid catalyst process. Emeritus Professor Dr. Joe Mullins, also with the Clemson University Department of Chemical and Biomolecular Engineering, is combining his vast thermodynamics and process modeling expertise to assist in analyzing these systems using computer modeling. The use of solid catalysts for biodiesel synthesis not only may reduce the number of processing steps needed for the conversion of animal fat into biodiesel (and thereby reducing the energy demand of the process), but also represents a more economical production method that yields fewer by-products. Recently, new ventures and academic reports have shown that this modern production method may provide savings ranging from 10 cents per gallon to 50 cents per gallon of biodiesel. Upon completion of the study, the ER data will be a useful marketing and economic evaluation tool.
The Clemson University Animal Co-Products Research and Education Center is very pleased to have Dr. David Bruce and Dr. Dora Lopez working on the assessment of animal fats and grease in the manufacture of biodiesel.
ACREC Solutions - February 2008 Render