USING CULTURES OF "EFFECTIVE MICROORGANISMS" (EM) AS INOCULUM IN SUBSTRATES FOR ANAEROBIC DIGESTION

Abstract

Abstract. In the 1970 's the Japanese horticulturist and researcher Dr. Teruo Higa, initiated the use of a culture of microorganisms beneficial to soil, which he named "Effective Microorganisms" (EM). Currently, research about this culture have not only demonstrated its effectiveness in improving soil characteristics, but also as an alternative way to accelerate the degradation of organic matter in waste treatment systems. That is, it can be inferred that the use of an established culture of microorganisms must accelerate and/or improve the process of digestion of an organic material. Starting from the principle proven in several scientific surveys, that the addition of inoculum to substrate in anaerobic digestion in digesters, increases the process efficiency, the main objective of this study was to test the EM culture, as inoculum, influencing the efficiency of waste treatment and the biogas production. The culture of EM, prepared for this work, was obtained from the colonies captured on the “A horizon" of a forest soil (secondary forest, the Atlantic Forest biome, Brazil) where it was placed cooked rice in contact with the ground, during 15 days. After that, the established colonies were separated according their colors; being discarded all shades of black, gray and white. The selected ones were reproduced in a sugarcane broth medium for 15 days in order to compose the EM. Twelve bench digesters were used, with a total capacity of three liters of substrate, each one. The treatments consisted of different additions of EM (concentrations of 15 %(T1), 10 % (T2) , 1%(T3) and 0 %(T4), as inoculum, to the substrates composed of dairy cattle waste, with three replications each one, being digested under controlled temperature (35oC). The collected data refer to the characteristics of the effluent, inoculum and influent, such as concentrations of total, fixed and volatile solids (TS, VS and FS), pH and Biochemical Oxygen Demand (COD). The pH of the EM was 3.34 and its COD was 24,250 mg.L-1. The accumulated biogas production was 20.601 L biogas per L substrate for T3. The efficiency removing COD and TS were 79.44% and 42.50%, respectively for T4. It was concluded that, aiming energetic improvement, small concentration of EM in the substrate, may be advantageous to the anaerobic digestion.