Abstract: Processed coconut outer husk chops, including coconut outer husk chops produced by compressing coconut outer husk at substantially right angle to the directions of coirs and chopping the compressed coconut outer husk. A reference sample of a resulting coconut outer husk chop which was left at 20.degree. C. at 50% relative humidity for three days contains 0.01-2 wt % tannin and 0.15-0.6 wt % Fe.sub.2 O.sub.3. Each processed coconut outer husk chop is sufficiently porous, and has a shape holding power, a good drainage, a low tannin content and a high iron content. A process for producing processed coconut outer husk chops is disclosed. The processed coconut outer husk chops are suited to a planting material, an inert medium for hydroponics and a microorganism propagating bed for propagating a decontaminating microorganism nurtured with a malodorous substance and trace pollutant in air.