Maturity and Safety of Compost Processed in HV and TW Composting Systems

Abstract

Two composting systems: passive aerated system, horizontal-vertical system; active aerated system, turned windrow system was designed, constructed and studied for thirteen weeks to compare the maturity and safety of compost processed in them. Waste materials with the following percentage composition: river reed (75%), clay (10%), banana stalk / stem (5%), cow manure / dung (4%), rice chaff (4%), cocoa seed husk (1%), and poultry manure (1%) was processed in the two different systems. Compost materials were weekly sampled from top, bottom and mid portions of the compost masses in each of the systems and bulked to constitute a representative sample for the respective systems. From the weekly representative samples for the two systems, 5g subsamples were used for the determination of the germination index and microbial load for the compost masses. However temperature readings of the compost masses in both systems were recorded insitu daily at three different points using a long stem thermometer and the their respective averages used as the weekly readings for the systems. Temperature and the germination indices of composts processed in the two systems were used as parameters to assess the maturity; and the microbial load and its survival to assess the safety of the compost churned out. There were significant differences in the temperatures recorded in the two different systems during the composting period (p-value = 4.75 x 10-7, at α = 0.05). The total viable counts recorded in HV and TW ranged between 6.90-7.75logCFU/g of compost and 7.11-7.79logCFU/g of compost respectively which were significantly different (p-value = 0.027, at α = 0.05). The total fungi counts recorded in HV and T-W ranged between 1.11-2.32logCFU/g of compost and 1.68-2.40logCFU/g of compost respectively. Compost masses in all the systems had germination indices more than 150%.T-W had a higher rate of decomposition and maturity comparatively, hence a better composting system based on compost maturity. Penicillium spp. survived the process and it is known to produces mycotoxins which cause illnesses in humans. It is recommended that compost end-users, farmers, and producers use protectives and observe good hygiene in order to safeguard their health.