"Carabao Models Commercial Bio-Ethanol Production"
By Melpha Abello
Manila Bulletin


There’s more to carabao than its meat, milk and being a dependable draft animal. Soon, scientist say, this sturdy animal can be key to commercial production of cellulosic or biomass ethanol from agricultural wastes.

How can this be possible? Carabao has micro-organisms in its rumen that transform lignocellulose into ethanol, says Dr. Fiorello B. Abenes, an emeritus professor of the CalPoly State University Pomona in California, and a Balik Scientist Program (BSP) awardee of the Department of Science and Technology (DOST).

Dr. Abenes together with Dr. Perla C. Florendo of Central Luzon State University (CLSU) and a research team from Philippine Carabao Center (PCC), have developed a method of producing bio-ethanol from lignocellulose using the carabao as a model as validated by their research titled “Validation of a Paradigm: The Philippine Carabao as a Model for Cellulosic Ethamnol Production”.

The research has bagged the third place at the recently concluded competition in energy and industry R&D conducted by the Philippine Council for Industry Energy Research and Development(PCIERD) of the DOST.



The Philippine carabao, explains Dr. Abenes, is known for its ability to subsist on low-quality forage like rice stubbles and straw. Such ability is conferred upon the animal by rumen (one of the four compartments of the ruminant’s stomach) micro-organisms that digest cellulose and hemicellulose, turning them into methane CH4, carbon dioxide (CO2) and volatile fatty acids (VFAs). CH4 and CO2, are expelled when the animal eructates, while the VFAs are shared between the host animal (carabao) and micro-organisms.

He said that the carabao uses VFAs as a source of energy, while the micro-organisms use them to support their life functions including growth and reproduction by synthesizing glucose and proteins and storing them as bacterial starch which can be turned into alcohol using common yeast.



Biomass ethanol is a type of biofuel produced from lignocellulose which makes up the structural materials in plants. It is composed of cellulose, hemicellulose and lignin. Agricultural wastes such as rice straw, corn stover, sugarcane bagasse, grasses and wood are some of the cellulosic feedstocks which can be considered for this purpose.

Lignocellulose is nature’s most abundant molecule. Although its advantage as raw material for bioethanol lies on its high abundance, it has a rigid structure which requires pre-treatment and enzymatic hydrolysis to convert this molecule into alcohol. These processes are very expensive, that is why “commercialization of this technology is not fully achieved,” Dr. Abenes said.

Typically, producing ethanol from biomass feedstocks using a biological approach involves several stages. These are: pre-treatment phase, which makes the lignocellulosic material amenable to hydrolysis; cellulose hydrolysis, wherein the molecules are broken down into sugars; microbial fermentation which converts the sugar into alcohol; and distillation to produce 99.5 percent alcohol.

Dr. Abenes cited that the existing technology uses hydrolyzed glucose using specific enzymes which requires pre-treatment technique involving the costly acid acid hydrolysis, and the hydrolysis of cellulose that uses purified enzymes. He added that the cost of enzyme alone makes up 60 percent of the total processing cost.



Using the rumen fluid from carabao as a source of cellulosic and hemicellulosic enzymes simplifies the process of producing biomass ethanol. Dr. Abenes said that this method eliminates the acid pre-treatment, suggesting only particle size reduction or grinding of the materials as the pre-treatment method used to simulate rumination that occurs naturally during digestion. Aside from being costly, acid pre-treatment of biomass. He says, has destructive environmental effects due to acid disposal.

It also eliminates the need for enzyme production and enzyme delivery systems because rumen fluid has micro-organisms that generate powerful enzymes. There’s no need to separate the hydrolysate from undigested biomass prior to fermentation, provided that the system is abiotic.

In their experiments conducted between November and December 2007 to validate the carabao paradigm, Dr. Abenes said that anaerobic rumen micro-organisms could be propagated and anaerobically cultured in plastic bioreactors. Quantitative studies showed a microbia1 enzymatic hydrolysis of rice straw with high efficiency within seven days : incubation in vitro at a rate of 84.5 percent. The hydrolysates containing sugars and lysed microbes were successfully converted to ethanol using ordinary yeast.

Experiments also showed that using the micro-organisms from carabao’s rumen fluid could yield more fermentable material than using a purely enzymatic process.

Dr. Abenes stressed that since this is done in a closed system, the micro-organisms do not have to compete with a host animal for the VFAs produced.



Dr. Abenes obtained his doctorate degree in animal science and master’s degree in animal industries both from the University of Connecticut in 1975 and 1971, respectively. He worked for many years in the field of animal science at the University of the Philippines in Los Banos, in the University of Connecticut and in Alberta before moving to CalPoly University Pomona where he served as a professor of animal and veterinary sciences from 1986-2004.

Dr. Abenes was among the first Filipino scientists abroad who responded to the government’s Balik-Scientist Program when it was established in 1975. BSP seeks to encourage overseas Filipino Scientist to return or reside in their country and share their expertise to accelerate the country’s scientific, agro-industrial and econimic development.

He came back to the Philippines as a visiting professor in CLSU from October 2007 to January 2008. In March 10 this year, he availed again of the BSP, this time the Short-term Program which he will carry out up to June 7, 2008.



With optimizing biomass ethanol production model as one of his tasks to be accomplished as a Balik Scientist, Dr. Abenes has proposed in collaboration with PCC and CLSU to establish a bio¬mass ethanol research and development experiment station.

The establishment of an R&D experi¬ment station; whose proposal was submitted to the DOST, will require P102 million as funding according to Dr. Abenes. It will be located in CLSU and will focus on improving ethanol yields from biomass feedstocks.

He said that the technology is now at the optimization stage. Based on their preliminary calculations, a 1,000-kilogram of biomass can yield 117 liters of ethanol using the carabao paradigm, but he said that this rate could change with the continuous improvement of the technology.

At the station, the feedstocks will be digested in bioreactor containers using whole rumen fluid from native carabaos. The resulting “bacterial beer” will be cooked to inactivate the micro-organisms and then yeast will be added to start the fermentation process. The alcohol that will be collected will be distilled in a solar distiller designed by engineers from CLSU.

A unique feature of the system will be that the container used in the collection of biomass is the same container used for microbial digestion, fermentation and distillation, allowing a “factory assembly line” process.

They will also consider the environmental impacts of the project that is why scientists and engineers from CLSU will be working together to refine the bioreactor system. Part of the optimization also suggests engineering designs for the collection of methane gas for power generation. In addition, they will also study possible uses of spent biomass.



Several issues were raised on the effect of biofuel production such as it might compete with food production because it will require conversion of some arable lands into plantation for feedstocks. The carabao paradigm, according to Dr. Abenes, could be a very good alternative to bioethanol produced from foodstocks such as sugarcane because it uses farm wastes as sources of lignocellulose which is found in the biomass sources that are widely available in the Philippines.

Data show that 4,046,318 hectares of rice land generate 13 million metric tons of rice straw each harvest season. Added to these are 2.9 million tons of biomass from sugarcane tops and trashes from sugarcane farms. These resources are usually burned which results in environmental pollution.

This project, once commercialized, also aims a partnership with small hold farmers as well as local government units that will be involved in the digestion process. They will be provided with containers where they can collect the biomass feedstocks and start the digestion process right at their own farm using the rumen fluid that will be supplied to them by PCC at CLSU. This way, they will earn additional income.

Dr. Abenes and his team believe that by adopting the carabao paradigm, they can significantly lower the cost of producing biomass ethanol thus allowing commercialization economically feasible. He added that full development of this technology could result in the production of enough ethanol to meet, or even exceed the goals of Philippine Biofuels Act of 2006 and allow the use of 85 percent ethanol for flexible fuel vehicles (FFV).

With these developments, the native carabao is seen to have a new role in the near future