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Compost Production Using Windrow Method Disposal and recycling methods of municipal solid wastes (MSW) are various and influenced by some factors such as: the amount and source of waste production; waste composition; ecological, economic, social, cultural and technological conditions of the region. Biogas production, energy recovery using incinerator, RDF production and composting are some usual methods to reuse the produced waste stream. Existence of natural energy resources in the country, on one hand, and shortage of organic materials in agricultural soils in Iran, on the other hand, justify composting process, as a reasonable strategy to modify MSW management problems and reduce the waste disposal on landfills. Analyzing the composition of MSW in Iran confirms that composting should be considered as an important plan among other plans for waste material management. The major issue is adoption of the selected method of composting to specific conditions of the region. Compost production will be safe and useful only if the selected method is performed taking into account all the effective factors in composting process; otherwise installation of an improper composting plant will result in extra financial and environmental expenditures and the product will be necessarily sent to landfills. Basically composting methods are divided into two categories: reactor and non-reactor composting. In non-reactor method, the fermentation process takes place in open air, so the composting process in not completely controllable. Windrow and aerated static pile composting are the most common reactor methods. In windrow method, the pile dimensions are 2.4-3.6 m in width and 1.8 in length and are created by MSW organic waste and aeration is carried out by loader or specific topturn machines. The drawbacks of such systems include: flow and penetration of wastewater at the beginning of the composting process an then dryness of the waste pile, excessive nutritional elements losses especially nitrogen from the composting pile, diffusion of obnoxious odors, attractiveness to insects and noxious animals and impressing by environmental conditions. In aerated static pile method, waste pile would not be turned and aeration is done by perforated pipes placed under the pile and joint to a blower. This method has some drawbacks: non-uniformity of air distribution and, as a result, anaerobic area formation and production of greenhouse gasses, prolonging the composting period, need for excessive land and defection in killing the pathogens and inactivating the weed seeds. However, because of specific ecological conditions in some regions in Iran, like provinces in northern and southern coasts, production of utilizable compost is not possible using outdoor methods. The high moisture and dense residential areas and dearth of land, besides water table level, in these regions are the problems that have restricted outdoor composting. So, for such areas, we suggest controlled and integrated composting plant. In outdoor windrow, which is a reactor composting method, two types of aeration are used in order to speed up the composting process. In this method, besides turning of composting materials, aeration takes place from the bottom of the composting materials simultaneously, so microorganisms are exposed to oxygen permanently and minimize methane and obnoxious odor production odor risks. Meanwhile uniformity of materials as well as meeting thermophilic temperature are guaranteed. In this method, wastewater of composting materials circulate to the fermentation room and prevent contaminant diffusion resulting wastewater turning and cause material moistening and increase the fertility value of compost. A filtration system is used in this method that treat effluent gasses from fermentation room.
The advantages of this system are: reducing the composting process duration, uniformity of composting materials, controlling the process and obviation of insect interest, reducing labor demand and N losses, independence of environmental conditions, acceptable vies of composting plant and finally producing safer and more nutrient finished compost that is beneficial to be used in agricultural and other applications.
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