Composting of abattoir waste and river reed: effect of feedstock and aeration mechanism on process efficiency
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Date
2015-04-22
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Abstract
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.
Description
A thesis submitted to the Agricultural Engineering Department,
Kwame Nkrumah University of Science and Technology in partial fulfilment of the
requirements for the degree of
Doctor of Philosophy, 2014