Flow Control of Methane Fermentation Digested Sludge Applicator

A digested sludge fertilizer applicator was designed and developed to apply concentrated methane digested sludge in a paddy field. The applicator was mounted on a high-clearance vehicle to apply the fertilizer as top-dressing at panicle initiation of rice. It employs three electric-motor-drive pumps to control the flow rate of the digested sludge. The pumps dispense the concentrated digested sludge at 4-15 kg/min. The rotational speed of the pump is controlled by a proportional-integral (PI) compensator with a feedback based on its rotational speed and a pre-filter of the desired rotational speed. The fertilizer applicator was tested using the concentrated digested sludge fertilizer in actual farm work. The error in the application rate was found to be −4.4%. The developed applicator was able to apply digested sludge fertilizer at a reliably uniform rate in the paddy field.