Use of bio-enzymatic preparations for enhancement biogas production

VITĚZ, T., HAITL, M., KARAFIAT, Z., MACH, P., FRYC, J., LOSAK, T., SZOSTKOVA, M.: Use of bioenzymatic preparations for enhancement biogas production. Acta univ. agric. et silvic. Mendel. Brun., 2011, LIX, No. 3, pp. 203–208 Biogas is a renewable energy resource with high increasing developed in last few decades. It’s big opportunity for stabilization rural areas, concretely agriculture sector. This technology can decentralize supply of energy. The number of operated biogas plants is rapidly increasing. Biogas plants require a high level of intensity and stableness of the process of anaerobic fermentation with biogas production for effi ciency treatment, also for good quality of development biogas and fertilization eff ect of the rest of fermentation. If this is not completed the operator has problem to keep the process in optimal condition for anaerobic fermentation. Researchers have tried diff erent techniques to enhance biogas production. In order to achieve the aforementioned state, it is essential to ensure increased activity of microorganisms that contribute to the anaerobic fermentation. The metabolic activity of microorganisms is preconditioned by availability of easily decomposable solids. Adding of bacterial and enzymatic cultures into a fermented substrate represents one of the possibilities. The enzymes contained in this preparation are responsible for better exposing methanogenic bacteria to the material. The tested bio-enzymatic preparation, APD BIO GAS, is a mixture that contains bacteria and enzymes which are essential for the effi cient progress of anaerobic fermentation. The reference biogas laboratory of the Mendel University in Brno was used for the purpose of testing of APD BIOGAS in mesophilic conditions of anaerobic fermentation on a substrate consisting of a mixture of maize silage and liquid manure. The producer of this preparation declare enhancement of quality and quantity of developed biogas, elimination of smell level of the rest of fermentation its higher homogenity. For the test were used lab scale fermenters of batch type with work volume 0.12 m3. An increase of biogas production by 15% was determined in connection with addition of the preparation, also with higher decrease of total solids and decrease of organic substance in total solids in the fermenter where were used this preparation. biogas production, anaerobic fermentation, enzymatic preparations Functionality of our society is currently dependent on exploiting of the limited amount of non-renewable resources of energy. The everincreasing energy demands force us to look for a replacement of the non-renewable resources of energy by other (renewable) resources. One of the available alternatives pertains to use of biomass within the process of anaerobic fermentation resulting in creation of biogas that may be further used for energy-related purposes. Anaerobic technologies off er an attractive manner of use of biomass resources for the purpose of partial satisfying of the energy needs of our society (Yadvika et al., 2004). Anaerobic fermentation is a process typical for decomposition of organic matter without in an environment in which air is not present. It consists of four stages: hydrolysis, acidogenesis, acetogenesis and methanogenesis. In the course of individual stages high-molecular substances such as fat, carbohydrates, proteins, nucleic acids, etc., are decomposed into low-molecular substances including their subsequent transformation into the acetic acid, carbon dioxide and hydrogen. 204 T. Vitěz, M. Haitl, Z. Karafi at, P. Mach, J. Fryc, T. Losak, M. Szostkova These intermediate products of the process of anaerobic fermentation are further transformed (using methanogenic bacteria) to biogas, which consists mainly of methane and carbon dioxide. The total production of biogas comprises mainly transformation of acetic acid to methane and carbon dioxide (70%) while 30% represents transformation of hydrogen and carbon dioxide to methane and water (Martin Kaltschmitt et al., 2009). Anaerobic fermentation is a spontaneous process; however, its intensity proves to vary depending on the respective conditions in the environment, properties of the decomposed materials and presence of microorganisms that contribute to it. As regards biogas production equipment, a high level of effi ciency is required as only its high level presents economic benefi ts for operators. Possibilities of increasing the level of biogas production are divided into the following four categories: use of additives, reuse of the fermentation residue and its fi ltrate, change of the process conditions such as the delay time and partially also the amount of the substrate, use of bio-fi lters (Yadvika et al., 2004). Additives might feature an organic or inorganic nature. Organic additives represent mixtures of bacterial strains which have positive eff ects on the activity of enzymes decomposing the organic matter. While mechanical and chemical methods of treatment of substrates have been thoroughly studied and exploited in the practice, there are only very few fi ndings related to positive eff ects of the biological treatment of substrates with the principal objective of increasing the production of biogas (Hendriks and Zeeman, 2009). This fact served as a basis for focusing the submitted paper on the biological manner of treatment of substrates. Possibilities of increasing the level of biogas production are related to decomposition of polysaccharides to biologically easily degradable intermediate products (Egg et al., 1993). In case that they do not degrade, an effi cient production of biogas may not be expected. The degree of decomposition of sparingly degradable substances such as cellulose is also signifi cant. As stated in (Tirumale and Nand, 1994), decomposition of cellulose using actinomycetes and a mixture of bacterial cultures resulted in an increased production of biogas. This fact may be explained by the subsequently better availability of intermediates for methanogenic bacteria, which results in a higher production of methane. Jewell et al. (1976) states that any method that might treat a substrate in a manner ensuring its accessibility to bacteria transforming the substrate to methane features a high potential as regards an increase of the production of energy. Biogas plants operated in the Czech Republic process mainly products of the primary agricultural production, i.e. the substrate comprises mainly a combination of maize silage and liquid manure (pigs or cows). Considering the high content of cellulose in the maize silage as well as other feed materials of vegetable nature such as grass silage and fodder, it is essential to optimize the process of anaerobic fermentation in a manner achieving the highest possible exploitation of the feed material. Use of a preparation containing bacterial and enzymatic cultures seems to be one of the possible solutions. Our objective was to determine (verify) – on the basis of the present fi ndings – the eff ects of APD BIOGAS (featuring the bio-enzymatic nature and containing a mixture of bacterial and enzymatic cultures) on the production of biogas in mesophilic conditions of anaerobic fermentation as well as decrease of the odour level of the fermentation residue. MATERIALS AND METHODS