The large amounts of the agricultural wastes remaining after the harvesting operations of the different crops represent a great challenge facing farmers, where they are estimated at 25 million tons annually. The farmers have to burn these wastes. This behavior leads to serious problems including the air pollution. Composting is considered the other choice to get rid of the agricultural wastes. It aims at both conservation of the environment, human safety and economically convenient production. The current investigation aims at:
1- Designing a network for forcing air through the compost pile to facilitate production of a good compost.
2- Studying the effect of both type of tube and rate of forcing air through it on the end-product, i.e. the compost beside of saving labor and time of production.
A direct ventilation system has been designed. It works on the basis that there is no turning but through forced air for the purpose of producing the compost from a mixture of rice straw and cattle dung at ratio of 2:1.
For fulfilling these purposes four networks were designed as follows:
1- Transversal system.
2- Longitudinal system.
3- Width and length system.
4- Reciprocal system.
The whole system was designed using PVC pipes with a 6.35 cm diameter, 3.9 mm thickness, a 262 cm length and a 130 cm width. The length and width were drilled with holes at equally divided distances of 30 cm (center to center) in two parallel rows.
The used types of tubes and the rate of air forced through them were evaluated according to the compost quality standards and guidelines which depend on determining quality parameters of the compost to be used in agriculture.
The obtained results indicated that the most suitable design for a network to produce compost of acceptable quality is the "width and length system" within which air is forced at rate of 0.0196 m3/min.Moreover, a comparative study conducted among this system and both of natural conveyance system and self propelled machine systems illustrated that although the natural conveyance method gave the highest profit, yet the system depended on forcing air through width and length system seemed more preferable owing to the more favorable quality of the compost obtained by this method and also its relatively high profit.