Determination of the levels of inorganic elements in ashes from selected agro-waste biomass from Githurai market, Nairobi

Abstract

The ashes of different types of agricultural biomasses from Githurai market and rice husks collected from Mwea, have been analyzed for their inorganic elements content using both Atomic Absorption and X-Ray Fluorescence Spectroscopic Techniques. The results show that ash content of various agro-waste ranges from 3.31± 0.10% to 23.92±0.39% with rice husks having 23.92±0.39%. Further analysis on the ashes show that some biomaterials contain very high levels of K2O and Na2O, for instance ashes from banana, potato and pineapple peelings were found to have high concentration of K2O at 63.17± 0.09%, 59.48± 0.77% and 47.05± 0.30% respectively. These were however recovered as the carbonates and thus explain why; ashes were used by the ancients for the manufacture of soap. Ashes from onion stock waste and pigeon pea pods gave high concentrations of CaO at 34.95± 2.28% and 15.20± 5.74% respectively. Rice husks and banana leaves ashes contain over 97% and 61% silica respectively and thus, are important raw materials for pozzolanic cement production. The results of the current study show that the current practice of burying ashes as a waste is not therefore justifiable. They should be treated as a resource rather than a waste.