Effect of Insulation on the Performance of a Rotary Bioreactor for Composting Agricultural Residues

Fahad N. Alkoaik, Ahmed M. Abdel-Ghany, Ibrahim M. Al-Helal, Mohamed A. Rashwan, Ronnel B. Fulleros and Mansour N. Ibrahim
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Fahad N. Alkoaik: Department of Agricultural Engineering, College of Food and Agriculture Sciences, King Saud University PO. Box 2460, Riyadh 11451, Saudi Arabia
Ahmed M. Abdel-Ghany: Department of Agricultural Engineering, College of Food and Agriculture Sciences, King Saud University PO. Box 2460, Riyadh 11451, Saudi Arabia
Ibrahim M. Al-Helal: Department of Agricultural Engineering, College of Food and Agriculture Sciences, King Saud University PO. Box 2460, Riyadh 11451, Saudi Arabia
Mohamed A. Rashwan: Department of Agricultural Engineering, College of Food and Agriculture Sciences, King Saud University PO. Box 2460, Riyadh 11451, Saudi Arabia
Ronnel B. Fulleros: Department of Agricultural Engineering, College of Food and Agriculture Sciences, King Saud University PO. Box 2460, Riyadh 11451, Saudi Arabia
Mansour N. Ibrahim: Department of Agricultural Engineering, College of Food and Agriculture Sciences, King Saud University PO. Box 2460, Riyadh 11451, Saudi Arabia

Energies, 2019, vol. 12, issue 2, 1-13

Abstract: Rotary drum composters are used to produce high-quality, pathogen-free compost without weed seeds. Insulation is usually applied to small-scale composters to warm up the composted materials and enhance metabolic reactions to produce stable and mature compost within a short time. However, the relationship between the composter size and the heat loss rate is still unclear. In this study, the relationship between the composter size (designated as the ratio of surface area to volume, A s / V ) and heat loss was analyzed and identified. To show the effect of insulation on the composting performance, two identical rotary drum bioreactors (each of A s / V = 9) were used to compost tomato plant residues, one insulated and the other kept without insulation. Results showed that insulation increased the overall resistance against heat loss from the bioreactor from 0.37 (m 2 °C W −1 ) to 1.12 (m 2 °C W −1 ), quickly increasing the compost temperature, and a temperature of 55–67 °C could be achieved and remained for three days. Therefore, mature, stable, well-aged, and high-quality compost was obtained. In the non-insulated bioreactor, the compost temperature did not exceed 37 °C; this caused a decline of microbial activity and the composting process temperature was only in the mesophilic range, leading to a high risk of the existence of weed seeds and pathogens in the final immature compost. Insulation is necessary for laboratory-scale and small pilot-scale bioreactors ( A s / V ≥ 6), because heat loss is high as A s / V is high, whereas it is not necessary for commercial full-scale bioreactors ( A s / V ≤ 4), because heat loss is minor as A s / V is low. For larger pilot-scale bioreactors ( A s / V : 4–6), insulation cost must be considered when comparing the impact of energy saving on the composting process.

Keywords: Compost; tomato plant residues; energy generation; insulation; heat loss; rotary drum bioreactor (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
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