Among those taking the lead in it is the vegetable greenhouse farm in Sapho District, Hamhung City of South Hamgyong Province.

The farm established a process of recycling city sewage for producing electric power and nutrient solution for plants, thus making contribution to preventing river pollution.

The farm operates motor generator with gas produced by fermenting aqueous deposit and turns out nutrient solution and organic fertilizer by separating useful materials from lees.

Meanwhile, the farm produces thousands tons of vegetables with soilless cultivation method every year.