ENVIRONMENTAL IMPACTS OF UNUTILISED FLY ASH AND ITS POTENTIAL UTILISATION FOR SOIL PRODUCTIVITY AND FOOD SECURITY

Abstract

The combustion of coal during thermal electricity generation produces huge volumes of fly ash solid waste. The disposal and storage of dry fly ash in the environment have resulted in high nutrient concentration levels becoming toxic to humans, air, soil and water environments. Soil nutrient deficiency is limiting sustainable food productivity with soil nutrient deficiencies and limited access to fertilizers or biological options aggravating the predicament of hunger. This study focused on assessing the environmental impacts of fly ash and its potential utilisation in crop production. The study was conducted at Harare Power Station (170 50‘ S and 310 1‘ E) and Harare Experimental Station (170 49‘S and 31o2‘ E). Mixed research methods were used. To unearth the environmental impacts of fly ash qualitative research approach guided by the interpretivism paradigm was applied. Purposive sampling of six key informants was implemented and data was gathered using in-depth and semi-structured interviews. Thematic content analysis was used to analyse the data. To evaluate the potential utilisation of fly ash for sustainable crop production, laboratory analysis of the physical and nutrient composition of fly ash was undertaken. To evaluate the effects of fly ash on tomato, cucumber and rape crops, a field experiment was set up. A Randomised Complete Block Design (RCBD) with five treatments, replicated three times, was implemented on each of the crops. The analysis of variance was used for analysing the results. Results showed that dumped and stored fly ash caused air pollution, groundwater contamination, human health effects and soil pollution. Fly ash can potentially be used in crop production to control soil-borne pests and diseases and improve the physical and nutrient characteristics of soil for improved crop yields. The application of fly ash had a significant effect (P<0.05) on the growth and yield of tomatoes, cucumbers and rape. The highest yields were realised at 25% fly ash soil concentration, while 100% fly ash was toxic.