NOVELTY - A biogas apparatus comprises gas engine generators which burn biogas and air supplied from gas storage apparatus, drives gas engine and drives generator, excessive combustion equipment for fuel gas which burns excessive biogas to gas engine generator, and control apparatus which inputs detected value of pressure detection apparatus and measured value of continuous monitoring apparatus and controls start-up and stop of gas engine generator and excessive combustion equipment for fuel gas.    USE - Biogas apparatus.    ADVANTAGE - The biogas apparatus can prevent discharging of methane gas with high environmental impact in air.    DETAILED DESCRIPTION - A biogas apparatus comprises methane fermentation tank which generates biogas containing methane gas as main component from organic waste, purifier which isolates and removes harmful gas from biogas emitted in methane fermentation tank, continuous monitoring apparatus which confirms concentration of harmful gas and oxygen continuously, pressure detection apparatus which detects pressure of biogas, gas storage apparatus which stores biogas emitted from methane fermentation tank, gas engine generators which burn biogas and air supplied from gas storage apparatus, drives gas engine and drives generator, excessive combustion equipment for fuel gas which burns excessive biogas to gas engine generator, and control apparatus which inputs detected value of pressure detection apparatus and measured value of continuous monitoring apparatus and controls start-up and stop of gas engine generator and excessive combustion equipment for fuel gas. The pressure of biogas detected with pressure detection apparatus is compared with predetermined engine starting pressure, engine drive maximum pressure and engine drive minimum pressure. The gas engine generator of maximum number that can be driven from methane gas in biogas is driven when pressure of biogas is more than engine starting pressure. The excessive combustion equipment for fuel gas is driven when pressure of biogas is more than engine drive maximum pressure. The gas engine generator which cannot be driven from methane gas in excessive combustion equipment for fuel gas and biogas is stopped when pressure of biogas is below engine drive minimum pressure.    DESCRIPTION OF DRAWING(S) - The drawing shows a flowchart of the start-up and stop control of gas engine generator by pressure and ignition control of excessive combustion equipment for fuel gas. (Drawing includes non-English language text).    Starting step of first gas engine generator (S20)    Stopping step of first gas engine generator (S32)    Starting step of second gas engine generator (S40)    Stopping step of second gas engine generator (S52)    Starting step of third gas engine generator (S60)