Cost Implications of Biodegradation of Khaya Grandifoliola （Dry Land Mahogany） by Aspergillus in Residential Buildings

Degradation of timbers in building due to microorganisms was reported to cause enormous economic loses and species of Aspergillus are among the major cause of degradation of timbers in Nigeria. This research aims at evaluating the cost of implications of biodegradations of Khaya grandifoliola by Aspergiilus spp in residential buildings empirically. Decayed Khaya grandifoliola samples were collected on residential buildings to extract, cultivate and identify the Aspergillus spp present. The cultivation went through serial dilutions and inoculations on sabouraud dextrose agar in petri dishes before incubation for 72 hours at 30 ~C. The species were identified through visual and microscopic observations. Percentage rate of degradation was determined under laboratory conditions by inoculating known weights of Khaya grandifoliola with the Aspergillus and incubating in a minimal medium for 24 weeks at 30 ~C. Weight loses and spore counts were recorded at four weeks intervals. A pattern of the degradation was forecasted. Accumulative weight loss of 16% for this period was obtained. Methods and costs of repair and replacement of decayed portions were evaluated. Residential Buildings constructed of Khaya grandifoliola experienced low cost of maintenance in this region but may not be in wetter regions where the conditions could be more favorable.