Potential of Producing Compost from Source-Separated Municipal Organic Waste (A Case Study in Shiraz, Iran)

Abstract

Developing countries face serious environmental, social and economic challenges in managing different types of organic waste. Proper treatment strategies should be adopted by solid waste management systems in order to address these concerns. Among all of the treatment options for organic waste, composting is the most approved method as an effective strategy to divert solid waste from landfills. This experimental research aimed to examine the potential of producing compost from source-separated municipal organic waste in Shiraz, Iran. Market waste (fruits and vegetables) and garden waste (plant residues) were used as the raw input materials. They were subjected to the windrow pile composting method in an open site area. The process was monitored against several physical, chemical and biological parameters. In-situ measurements (temperature and moisture content) were carried out on a daily basis. Sampling and lab analyses were conducted over the period of the biological treatment. The final product was of acceptable moisture and nutrient levels, pH, Electrical Conductivity (EC), and Carbon/Nitrogen ratio. All of the analyzed compost samples had lower concentrations of heavy metals than the Iranian and German standards. Overall, the results obtained revealed that composting is a promising method for municipal organic waste treatment. The findings also imply the effectiveness of the source-separation collection method in the production of high-quality compost.

Transformation of Biodegradable Organic Municipal Solid Waste to Compost Using Stationary and Rotary Units

“…The temperature was decreased to reach the ambient temperature (28-31 °C) at end of the composting, which is in full agreement with literature [11,18]. The composting process is based on the self-heating of waste and therefore, it is characterized as bio-thermal process.…”

“…These results are attributed to the consumption of the carbon and nitrogen during the biodegradation of organic substances with microorganisms in composting process. For EC values, the obtained results are 5.5 mS/cm for rotary unit and 6.04 mS/cm for stationary unit, which is in the range of the recommended standard EC values (0-10 mS/cm) [11] where EC value ranges from 2-5 mS/cm and it is considered an average salinity and must be mixed with soil with a ratio of 2:5 for all farming applications, while EC values (5-10) mS/cm is considered medium to high salinity and must be mixed with a ratio of 3:10 where soluble salt level (salinity) in the sample is estimated based on the measurements of the electrical conductivity [20]. Low values of NPK can indicate a lack of available minerals, while high values are indicating a large amount of soluble minerals that may inhibit biological activity or cause problems with land applications if large quantities of the materials are used [16,17].…”

“… Compost production stage: This stage is started at the end of the above three stages, where the temperature reaches to ambient conditions, and pH is at neutralization range.  Composting process is influenced by oxygen levels, particle sizes of the feedstock material, nutrient levels, moisture content, temperature, and pH value [10,11,12].  The composting process can occur under aerobic or anaerobic conditions, where aerobic condition is faster than anaerobic with an average of 15 times due to the availability of free oxygen.…”

Influence of Microbial Inoculant on Composting of Biodegradable Domestic Solid Wastes

“…The volume reduction is a result of the organic matter degradation by microbial activity during the composting process has also been pointed out by several investigators [10,32]. Additionally, previous studies investigating the change of physical properties of organic wastes during the composting phase have demonstrated that high levels of biodegradable organic matter increased the capacity of the microorganisms to oxidise the material, and consequently reduced the volume [17,33].…”

“…Although several studies have addressed the optimization of composting of various organic wastes [7,10,11,[14][15][16][17], information on composting of biodegradable domestic solid wastes using effective microorganism inoculants as an accelerator to speed up the composting process and increased nutrients in the compost has not been well documented. Therefore, it is essential to study the effect of microbial inoculant on the composting process.…”