การหมักปุ๋ยระบบเติมอากาศ

Introduction
Composting is a natural process where organic substances are decomposed by aerobic microorganisms under a controlled condition. Aerated Static Pile (ASP) system is a composting process where air is added into ten static piles using an electric blower to ensure sufficient level of oxygen for the digestive activities of microorganisms, making it unnecessary to turn over the piles manually. It involves the chimney convection effect as heat building up inside of the pile (from the digestive activities of microorganisms) rises up and cooler air from outside flows into the pile at all times. This heat also accelerates the decomposition as it is conductive to the functioning of thermophillic and mesophillic microorganisms.
	Factors needed to be controlled are C/N ratio, porosity, moisture content, temperature, microorganisms, and oxygen concentration. The active process requires approximately 30 days. After that the finished compost is piled indoor and left for 2-3 weeks to air dry and to allow microorganisms to be stabilized (stabilization period).
Procedure in composting ASP system:
	1. Mix agricultural wastes and animal manure in 3:1 ratio by volume and moisten the mixture.
	2. Place tree branches on the 4-inch perforated PVC pipe which is connected to a 15-inch, 3-horse power squirrel-cage blower. The branches help the air distribution inside of the pile.
	3. Pile up the mixture into a prism-like pile measuring 2.5x3.5x1.5 meters (WxLxH) on top of the branches.
	4. Blow each pile twice daily for 15 minutes. Maintain the moisture for 30 days. The pile will be reduced approximately 40% by volume at the end of the process as a result of microbial activities.
	5. Move the finished compost into shades and leave for 2-3 weeks to air dry to allow the microorganisms to be stabilized (stabilization period).
The merits of this system lie in the fact that farmers can produce at least 10 piles or 10 metric tons of compost at one time. The investment is minimal at approximately USD 2,860 including (1) a shredder, USD 1,490 (2) a squirrel-caged blower, USD 515 (3) a bag sewing machine, USD 370 (4) PVC pipes, cow manure, etc., USD 485. The return on investment, however, is USD 1,140 worth of compost every month. Electricity cost per metric ton of compost is USD 3. This research has won the third prize in the Social Award of the Thailand National Innovation Awards 2006, held by National Innovation Agency, Ministry of Science and Technology, Thailand, for its incorporation of applied engineering, allowing farmer groups to produce compost on their own, save costs, cut down on the use of chemical fertilizer, and significantly contribute to the community involvement.