EFFECTIVE MICROORGANISMS (EM) AS BIOFEEDERS FOR ANAEROBIC DIGESTION

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). Research about this culture has demonstrated its effectiveness in improving soil characteristics, and also as an alternative means of accelerating organic matter decomposition in waste treatment systems. To test whether addition of EM inoculum to substrate in anaerobic digesters increases methane conversion efficiency, the objective of this study was to test the EM culture as inoculum, for its efficiency of waste treatment and biogas production. The culture of EM was obtained from colonies captured within the "A-horizon" of a soil in a Brazilian forest. They were grown in cooked rice in contact with the soil for 15 days, after which the established colonies were separated according to their colors, discarding all shades of black, gray and white, according the recommendation. The remaining colonies were further grown in a sugarcane broth medium for 18 days. Twelve bench digesters were used, with a total capacity of three liters each. Four treatments were applied, consisting of different additions of EM inoculum [mixture concentrations of 15% (T1), 10% (T2), 1% (T3) and 0% (T4)], to dairy cattle manure, with three replications per treatment. Anaerobic digestion was carried out under controlled temperature (35 oC). Data collected included concentrations of total, fixed and volatile solids (TS, FS and VS), pH and Chemical Oxygen Demand (COD). The pH of the EM inoculum was 3.34 and its COD was 24.25 mg L-1. The maximum accumulated biogas production was 20.60 L biogas L substrate-1 for T3 after 99 days, approximately. The efficiencies removing COD and TS were 79.44% and 42.50% respectively, for T4. It was concluded that use of EM in low concentrations as an inoculum may be advantageous to anaerobic digestion.