Examination of Operational Plans for a Methane Fermentation Plant during Developing Phase on Application of Digested Slurry to Farmlands

Abstract

In this paper, the authors considered operation planning of a methane fermentation plant that applies digested slurry to farmlands as fertilizer in the start-up years of the plant. An evaluation tool was developed to conduct the planning. The tool estimated the input weight of raw materials to the plant and the volume of digested slurry applied to the farmlands based on annual and daily material balances. The tool also calculated annual COD_Cr volume load of methane fermentation reactors.
According to estimates, the plant should start to operate a day before the digested slurry farmland application period each year because the plant can apply digested slurry to the farmlands in the first year of start-up.
The trial calculation that predicted a longer start-up period of 8 years found that the accumulated load of COD_Cr of the methane fermentation reactor during the start-up period was less than half of the design value. This case suggested that it would be possible to divide the methane fermentation reactor tank into 2 tanks and respond to the spread of the use of digested slurry as fertilizer by separately improving each tank.