203 Frazier Rogers Hall
P.O. Box 110570
Gainesville, FL 32611-0570
(352) 392-1864 ext.203 fax: (352) 392-4092
With his background in chemical engineering, Pratap Pullammanappallil has focused his research and development efforts on waste management and biofuels. If it seems like these are two different things, they really aren't. It's a twenty-first century story as old as human culture -- how to take the waste from one process and generate new and useful products. Ancient, too, are the processes at the heart of his cutting edge work -- digestion and fermentation.
In Pullammanappallil's work on waste management, he studies a process called anaerobic digestion. "Anaerobic" simply means that the process takes place in the absence of oxygen, and digestion is the general word for breaking down and transforming materials into simpler chemicals. In this case, bacteria consume waste materials and produce "biogas," a mixture of carbon dioxide and mostly methane. The carbon dioxide is removed, and what remains is methane, the primary ingredient in natural gas. This biofuel can be used in any process that is set up for natural gas, from industrial-scale boilers to home hot water heaters and form power plants to automobile fuels.
Pullammanappallil takes up the development of anaerobic digester technology where former Professor David Chynoweth left off. Chynoweth developed a process called SEBAC, which stands for SEquential Batch Anaerobic Composting, a patented process now used by several industries and communities as a means of recovering fuel from waste materials. Chynoweth had seen the first large-scale application of SEBAC before he retired a few years ago. The department sought a candidate for this position who could take up Chynoweth’s promising work and continue its development. Pullammanappallil was then working in Australia, but his qualifications and his past work with Chynoweth made him a perfect fit for the job. Pullammanappallil has advanced SEBAC to newer designs by adapting it to more industrial settings, each with its unique challenges.
Currently, his largest partner in this effort is a manufacturer of sugar beets in Minnesota. In Florida, when people think of sugar, they naturally think about sugar cane, but nearly half of the sugar produced in the United States comes from sugar beets. In the northern Midwest, sugar beets are harvested, trimmed, and then pressed to produce a liquid from which sugar is extracted. Along the way, a great deal of waste material is generated in the form of the trimmings (called "tailings"), the pulp left after the pressing, and the waste liquid, which is left after the sugar has been extracted. All of these waste products can be digested using Pullammanappallil’s newer anaerobic digestion design to produce methane.
Methane recovered from sugar beet waste can be used to offset the large amounts of natural gas that are used to extract the sugar. The digester currently operating at the Minnesota plant can handle two tons of beet tailings a day, but that is a relatively small portion of the 60 tons of solid waste they generate daily. Pullammanappallil estimates that if all these wastes were digested, over 60% of the natural gas used to produce beet sugar could be replaced with recovered methane. In this energy-intensive industry, that is a huge savings. An added benefit of the process is an almost 90% reduction in the volume of solid waste.
Pullammanappallil also describes how SEBAC has been used by communities to process the municipal waste that is hauled in by garbage trucks every day. This waste often contains a large quantity of paper, which is primarily made of a natural material called lignocellulosics. This material is an ideal feedstock for anaerobic digestion because the cocktail of natural microbes that do the fermenting thrive on it, not only producing biogas but also a rich compost residue. Considering the amount of waste that communities generate, the potential is vast.
Anaerobic digestion and biogas form one track of Pullammanappallil's work, but a second one is related -- production of biofuels. In this area, Pullammanappallil looks into making the liquid fuel, ethanol. Use of ethanol as a biofuel has been in the news a great deal over the last few years, but people who have followed the stories know that one problem with the production of ethanol is that a lot of it is made from corn. This means that corn for food must compete with corn for fuel.
In a hungry world, the competition over using corn for food or fuel is more than a practical problem; it also has an ethical dimension. Starting again with the concepts of fermentation and digestion, Pullammanappallil is working on processes that generate ethanol from "cellulosic sources," which means making fuel from the cellulose-rich parts of plants that people don't eat. The edible part of a mature corn plant represents a tiny fraction of its total weight. Consider the stalk and leaves, which are left in the field, and the husk and cob that are left in the processing plant. Many field crops produce a fruit or vegetable that leaves this kind of waste, and turning this waste into fuel is Pullammanappallil's specialty.
Plants contain a lot of cellulose. Generally, over 30% of a plant's weight is cellulose, which is basically a long chain of sugar molecules. Making ethanol from sugar is very common; that's how alcoholic beverages are made -- by fermentation in which bacteria turn sugar into ethanol. So, all one has to do is break the cellulose chain into its separate sugar links. It turns out that doing this on an industrial scale is not that easy. The bonds between the sugar molecules in cellulose are difficult to break. That is the main reason that people do not eat grass, because people cannot digest cellulose. However, cows do eat grass, but they have a complicated series of stomachs which act as vessels for the bacteria which digest the cellulose in the grass for the cow. It's a slow process, but a cow has the time.
Pullammanappallil is studying how to break down cellulose efficiently so that the vast amount of waste left from production agriculture and forestry can become a feedstock for a process that produces biofuels. In 2007-2008, a new laboratory dedicated to this project was added to Frazier Rogers Hall, the home of Agricultural and Biological Engineering at the University of Florida. A series of gleaming stainless steel tanks served by complex piping and instrumentation create a small-scale factory for the production of ethanol. In this research facility, Pullammanappallil will investigate the efficient production of several biofuels, including hydrogen, methane, and biodiesel.
Dr. Pullammanappallil specializes in design, modeling, control and optimization of processes for biofuel production and pollution control; wastewater and solid waste management, treatment and disposal; and environmental biotechnology.
- ABE 5442 Bioprocess Engineering
- ABE 5663 Environmental Biotechnology
- ABE 5707c Agricultural Waste Management
Research and Extension
- Conversion of lingo-cellulosic biomass to ethanol.
- Biodiesel production
- Hydrogen from biomass
- Continuous high solids anaerobic digestion of biomass.
- Anaerobic wastewater treatment systems
- Struvite crystallization for recovery of nitrogen and phosphorus in wastewater
- Ph.D. Chemical Engineering, University of Florida 1993
- M.S.Engineering Science, University of Mississippi 1988
- B.Tech. Chemical Engineering, Indian Institute of Technology 1984
Associate Professor, Agricultural and Biological Engineering Department, University of Florida
Assistant Professor, Agricultural and Biological Engineering Department, University of Florida
Director, Centre for Organic Waste Management, School of Environmental Science, Murdoch University, Perth, Australia
Lecturer, Department of Chemical Engineering, The University of Queensland, Brisbane, Australia
Research Fellow, Department of Chemical Engineering, The University of Queensland, Brisbane, Australia.
Awards and Honors
- Nominated for Vice Chancellor’s Excellence in Graduate Supervision Awards, Murdoch University
- Phi Kappa Phi
- Graduate Research Fellowship