BIOSOLIDS COMPOSTING

Cairo, Egypt

A composting project in Cairo has the goal of processing one million tons/year of biosolids using rice straw and "recycle cake" to dry down the material and provide pore space. Resource Recovery Systems International ? RRSIl is a consultant to the project. "Many years ago. sludge with a very high moisture content was delivered to large ditches dug in the desert," savs Pes Kuhlman of RRSI. "Because of the sandy soil, the liquid portion soaked away quickly. This system was discontinued 12 years ago." Currently, biosolids are pumped to a drying bed covering about 800 acres. Drying occurs slowly, reaching about 75 percent moisture. "The drying bed is full now," adds Kuhlman. "When composting a million tons of biosolids annually, one bay would be emptied and refilled every day."

A small composting project is operating at the site. Biosolids are removed from the drying beds, mixed with shredded rice straw and composted in open windrows for six to eight weeks. After the windrow phase, the compost is placed in curing piles, screened and bagged. Compost is sold for use in the production of numerous agricultural crops. A small amount of dried biosolids is also sold to farmers, a practice likely to be discontinued. Kuhlman explains that the common practice in Egypt is to burn rice straw, which causes considerable air pollution during the season of rice straw burning. "This will likely lead to a ban on this practice," he says. "Incorporating rice straw in the composting process is seen as an excellent way to utilize large amounts of straw and reduce air pollution."

RRSI is also involved in the manufacture of windrow turners in Egypt. It supplies component parts to an Egyptian company that builds the frame and assembles the turners. Thus far. the partnership has completed 20 turners used for composting MSW throughout Egypt.