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Effect of Inoculum Size on The Composting of Greenhouse Tomato Plant Trimmings

Compost Science & Utilization, (2005), Vol. 13, No. 4, 262-273

F. Alkoaik and A. E. Ghaly

Biological Engineering Department, Dalhousie University, Halifax, Nova Scotia, Canada
A laboratory-scale bioreactor was used to investigate the influence of inoculum size on the composting process of tomato remains-wood shavings mixture. Urea (as a nitrogen source) was added to correct the initial C: N ratio (30: 1). The average temperature in each bioreactor was strongly influenced by the size of inoculum. Maximum temperature of each mixture correlated with the reduction of Volatile solids (VS), total carbon (TC) and Total Kjeldahl Nitrogen (TKN). Volatile solids losses were in the range of 16.9-44.7 %, while total carbon losses were in the range of 9.4-28.4 % and TKN losses were in the range of 3.4-25.4 %. Neither the nitrogen nor the moisture content were limiting factors as the C: N ratio remained in the range of 28: 1 to 29: 1 and the moisture content remained within the optimum ranged of 57-61%. Carbon availability appeared to be the limiting factor in these set of experiments. Since wood shavings, which made 65% of the total mixture, contain no bioavailable carbon, another bulking agent should be considered. The addition of another source of readily available carbon to the tomato should also be investigated.