Composting of abattoir waste and river reed: effect of feedstock and aeration mechanism on process efficiency

Few successful composting facilities exist in Ghanaand there is limited information and experience in composting abattoir waste and river reed. These wastes are deemed to be potentially suitable for composting but not much has been reported on the composting dynamics when they are composted with different amendment materials and aeration mechanisms. Therefore, this research sought to investigate opportunities that exist for compostingin Ghana based on experiences of currently and previously operational composting facilities in Ghana and evaluate the effect of feedstock formulation, turning frequency, and aeration mechanisms on process efficiency and nutrient quality during windrow composting of abattoir waste and river reed. The state of composting facilities in Ghana was assessed through questionnaires and interviews with managersof such facilities. Two composting experiments were undertaken. The first one was conducted utilizing abattoir waste as the common substrate with source separated market/commercial waste, cocoa pod husk, corn cob and straw, yard trimming and sawmill wood shavings waste as other feedstock materials in the formulation of different composting piles. The second experiment was conducted to assess the effect of four aeration mechanisms on the composting process under an already existing formulated feedstock compositions using river reed (as main substrate), cocoa seed husk, poultry manure, clay soil, cow dung and banana waste. Parameters monitored in the piles include: Temperature, Moisture Content, Organic Matter, pH, Electrical Conductivity, Total Carbon and Total Nitrogen, Macro-nutrients (N, P, K, Mg and Ca) and heavy metals (Pb, Cd, Cu, Zn, Ni, and Cr). It was found that private agro-based facilities were the only operational composting facilities at the time of the study. Opportunities exist for investigating passive aeration mechanisms in some of iv these facilities to reduce the cost mainly due to the use of mechanical turning equipment. Analyses of physicochemical parameters confirm that feedstock composition or turning frequency had significant effect on physicochemical parameters studied. Final C/N ratio of the abattoirwaste compost ranged from 17.03 - 20.09, with no significant difference between the treatments and the interaction of feedstock and turning frequency. Organic matter degradation was influenced by both feedstock composition and turning frequency; difference in degradation data was also observed when fitted to afirst or zero order kinetics, with co-efficient of correlation (r) > 0.918. Analysis on composting of river reed, however, revealed that the kinetics of degradation could be represented by a first order rate equation. Also, findings from the studysuggest that compost maturity should be assessed by measuring two or more compostparameters, and that parameters of compost maturity need to satisfy the following threshold values: NH4 + /NO3 - ratio < 3.5, C/N ratio < 15; stable OM Loss, Temperature < 50 0 C). Passive composting showed comparable characteristics with mechanically aerated systems from this study. Multi-regression equationswere produced to predict nutrient (T, P, K) levels during composting using physicochemical parameters that are easy to measure.

Source: KNUST