Performance evaluation of termite-mound clay, concrete and steel silos for the storage of maize grains in the humid tropics

Authors: OMOBOWALE, M - University Of Ibadan; MIJINYAWA, Y - University Of Ibadan; Armstrong, Paul; IGBEKA, J - Niger-Delta University; Maghirang, Elizabeth

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2015
Publication Date: 7/18/2015
Publication URL: http://handle.nal.usda.gov/10113/61712
Citation: Omobowale, M.O., Mijinyawa, Y., Armstrong, P.R., Igbeka, J.C., Maghirang, E.B. 2015. Performance evaluation of termite-mound clay, concrete and steel silos for the storage of maize grains in the humid tropics. Journal of Stored Products Research. 6(7):56-65. doi: 10.5897/JSPPR2015.1087.

Interpretive Summary: In order to reduce postharvest losses in developing countries, there is a need to design and test appropriate maize storage facilities that can be made from locally- and readily-available materials. This study was conducted in Nigeria where termite mound clay (TMC) can be found in abundance and was used to construct a 3.5 ton capacity round storage silo. Similar capacity silos made from reinforced concrete (RC) and galvanized steel (GS) were constructed and compared to the TMC silo over an eight month storage period using maize with an initial moisture content (MC) of 12%. All three silos were instrumented to monitor temperature and relative humidity and to predict MC. Temperature trends were found to be similar in all three silos for the storage period while relative humidity increased in all three silos, however, the increase was less pronounced in the GS silo compared to the TMC and RC silos and indicates a higher potential for molding in the TMC and RC silos. Moisture permeation through the TMC and RC silos was identified as a possible reason for increased moisture content. The current TMC silo design was found to be applicable for short-term maize storage of up to four months. To address longer term storage needs, design modifications to counter the moisture permeation problem are being considered.

Technical Abstract: Inadequate storage facilities have contributed to severe maize postharvest losses in many developing countries. This study determined the potential of termite mound clay (TMC), a readily-available material in Nigeria, as a construction material for storage silos. The performance of the TMC silo was made in comparison to conventional silos made from reinforced concrete (RC) and galvanized steel (GS) by monitoring temperature and relative humidity inside the grain-filled silos and measuring selected grain parameters including moisture, protein, oil, crude fibre, starch, and ash contents. TMC, RC, and GS silos of 3.5-tonne storage capacity were loaded with 3 tonnes of maize at 11.2% moisture content (MC) for an 8-month storage period. Over the 8-month storage period, monitored temperature range and trends were found to be similar in all three silos. There was a consistent increase in relative humidity for all silo types; the increase in relative humidity was less pronounced in the GS silo (10.6%) compared to the TMC and RC silos at 15.8% and 22.2%, respectively. Changes in quality parameters of maize samples stored for eight months in the TMC, RC and GS silos were found to be similar although to varying degrees, i.e., increasing trends for MC and crude fiber contents and decreasing trends for protein, oil, starch, and ash contents. The three storage silos have comparable performance up to the fourth month of storage, after which MC was significantly different (p<0.05) across silos. The MC on the eighth month in TMC, RC and GS silos were 16.0%, 15.1%, and 12.7%, respectively. Higher MC may be due to moisture permeation. TMC silos should be adequate for short-term storage (<4 months). Construction of silos using local materials has a high potential for adoption. Improved resistance of the TMC silo to moisture permeation may allow for its use for longer periods.