Evaluation of windrow composting pilots for domestic organic waste amended by horse manure and biosolids

Abstract

The current solid waste management in Palestine is unsustainable due to inefficient resources recovery, weak institutional capacity, limited financial resources and severe environmental impacts. To achieve sustainability in Palestinian communities and enhance the protection of environment, recycling of organic waste using windrow composting warrants further exploration. Windrow composting of domestic organic waste forms an environmentally sound technology to alleviate the challenges facing waste management in Palestine. The specific aim of this research is to operate and evaluate two composting experiments including assessment of finished products. The conduction of composting pilots was performed in two stages. The first stage was during the winter season. Five composting piles with different mixtures (ratio 2:1 wet weight) were prepared as follows: - Pile No. 1 (2 Domestic organic waste + 1 Horse manure and saw dust spared through laying the mixture), pile No. 2 (2 Domestic organic waste + 1 Horse manure), pile No. 3 (2 Domestic organic waste + 1 Sludge and saw dust spared through laying the mixture), pile No. 4 (2 Domestic organic waste + 1 Sludge) and pile No. 5 (Domestic organic waste only and saw dust speeded through laying the mixture). All piles were prepare inside soil trenches. The second experimental run was made during the summer period. Carbon to nitrogen ratios (C: N) were tested for four mixed samples as follows: - First (1 Organic+ 1 Horse manure+ 1 Sludge), Second (1 Organic+ 2 Horse manure+ 1 Sludge), Third (1 Organic+ 1 Horse manure+ 2 Sludge), Fourth (2 Organic+ 1 Horse manure+ 1 Sludge). Two mixture samples with the highest C:N ratios were selected to conduct the second experimental trials. The mixtures formed two compost piles: Pile No.1 (2 organic + 1 horse manure + 1 sludge) and pile No.2 (1 organic + 2 horse manure + 1 sludge). The various mixtures were processed using plastic containers in the greenhouse at university campus. The composting process was controlled regularly (moisture content, temperature and pH). In both experimental stages, no major deviations in moisture content and pH values, but larger deviations were recorded in temperature measurements. Over the 100 experimental days VII during winter first composting stage, the temperature ranged from 7 °C to 41 °C. Through summer second composting stage, the temperature ranged from 23 0C to 66 0C and at the end of composting process temperature values dropped down to be close from ambient temperature which considered indication of finishing composting process. Lab analysis for compost quality parameters were made at Birzeit University Central Labs, tested parameters included heavy metals, nutrients and pathogens for the raw and finished compost. Compost maturity was performed for finished compost obtained from the first and second composting experiments. Results for heavy metals contents revealed that the compost quality for the both experimental stages complied with US EPA regulations. All samples of raw and finished compost were free from the Salmonella. For the first experiment there were no major differences in the content of microorganisms (fecal coliforms and E. coli) in the finished compost obtained from all compost piles which were less than 100 CFU/g except pile No. 3 (Organic + Sludge with Sawdust), this might be attributed to a low degree in sludge stabilization reflected in a higher microbial indicators content. For the second experiment, pathogens content in the finished compost were match US EPA standards were the fecal coliform less than 1000 CFU/g and Salmonella absent in the produced compost from the two piles. E.coli was within the international limits in the second pile but not in the first pile which could be affected by moisture content and nutrients content. Reduction in mass weight of raw compost materials reached to 58% for pile No.2 during summer experimental stage, for winter experiment pile No.5 presented 56 % weight reduction. Pile No. 4 (2 Domestic organic waste + 1 Sludge) that processed during first experiment and pile No. 2 (1 organics, 2 horse manure, 1sludge) which processed during second experiment, presented results more comply with USEPA 40 CFR Part 503 standards than other piles in two the experiments. This research study demonstrates operational methods that will aid in the design, operation and control of diverse windrow composting piles, especially those treating organic mixtures of different origins. To promote an integrated solid waste management in Palestine, the results obtained showed that windrow composting is an environmentally sound technology for resource recovery and waste reduction considering using compost for land reclamation and limited capacity of current landfills.