Biogas Digester Technology: LPG from Piggery Waste
by Mancielito S. Tacadena
Foul odour coming from the piggery is a common cause of misunderstanding between neighbours. To solve the enigma, the University of Northern Philippines in Vigan City came out with a technology they called Biogas Digester Technology which will utilize the waste from piggeries and convert it into energy. The by-products that can be produced from organic wastes of swine are biogas. It is a very stable gas which is non-toxic, colorless, odorless, inflammable gas produced from biomass decomposition. The composition of different gases in biogas: methane (CH4), 55-70%; carbon dioxide (CO2), 30-45%; hydrogen sulphide (H2S), 1-2%; nitrogen (N2), 0-1%; carbon monoxide (CO), traces; and oxygen (O2), traces. In other words, you did not only solve the problem of air pollution but also saved from buying LPG. If you are going into a higher form of energy, you can also produce electricity using this kind of technology.
In 2008, with the funding support from the Philippine Council for Agriculture Resources Research and Development (PCCARD) and Ilocos Agriculture Resources Research and Development Consortium (ILARRDEC), Dr. Alfredo Rabena, Engr. Mario Guzman, Engr. Norma Esguerra and Dr. Manuel Bajet designed an 8 cubic meter digester where the gases will be contained and a 1.34 cubic meter waste receptacle which will accumulate the liquid effluent. This was built at the farm of Maximo Rabanal located at Pantay Fatima, Vigan City. Mang Maximo became the farmer-cooperator after he agreed that a biogas digester will be developed at his piggery. A minimum of 7 pigs is needed to produce enough methane gas that will supply the cooking in a day. In the case of Mang Maximo, he is raising 10-15 heads in his piggery.
According to Dr. Rabena, they spent P71, 123 in the construction of the digester, waste receptacle and pipes that were connected to the gas stove placed in the kitchen of Mang Maximo. The concrete digester needs to be finished with untainted plastering to prevent gas leak that will cause possible explosion. Avoid using nickel, chrome or metallic pipes as some chemical reactions will take place and will cause delay in the production of methane gas and Sulfur disulfide. It will also shorten the life span of the tubing. The life span of the project can go up to 50 years if you used standard materials and follow the specifications in building it. It is therefore necessary to consult experts before going into the project.
Dr. Rabena futher explained that you need to wait for a month after the waste were deposited at the digester before gas is produced. But you can use initiators or microorganisms that will facilitate the decomposition of the waste and gas is produced after 2-3 weeks. Aside from the fact that this will give you free LPG for cooking you can also use this for business since you can cook your products using this. Here in Ilocos Sur for example, you can make bagnet or longganisa. This is an additional product value to farmers if they process their own products.
Free LPG is not the only benefit you can get with this technology. As said, the liquid effluent is separated from the gas through a receptacle. This can be used to water vegetables like eggplant, bell pepper, bitter gourd and others and serves as organic fertilizer thus it will cut your production cost in farming. Remember that organically produced vegetables are of higher market value since consumers prefer non chemical vegetables for their consumption.
“You are able to reduce your budget utilizing the waste coming from your piggery and able to help prevent air pollution that contributes to climate change” Dr. Rabena said.
Before the biogas digester was built in his farm, the family of Mang Maximo uses a tank of LPG for cooking in just 20 days. It is understandable that they saved some the amount when they started using the gas coming from the biogas digester. According to him, when the University of Northern Philippines offered the project, he never hesitate to accept it become at that instance, he know this will solve his problem with the foul odour coming from the piggery and this will mean higher profit for him in hog raising.
“I am very thankful that UNP entrusted the project to me. I am now recommending this technology to my fellow hog raisers in order for them to enjoy the benefits it will provide for them.
To those who are interested with the Biogas Digester Technology, you can visit the University of Northern Philippines Research and Development Office in Tamag, Vigan City. You can also call telephone number (077) 722-2810 or text Dr. Alfredo Rabena at cellphone number (0917) 2027696.