Extraction of Humic Acid from Agricultural Crop Residues Conditioned with Cow Dung, Compost from Landfill and Human Waste

Abstract

Rwanda has various sources for humic substances that may be utilized for the large scale production of humic acid which can be used as soil amendment to enhance the plant growth. Humic substance is a dark colored fully decomposed remains of plant and animal organic matter through the process called humification. This work aims of finding the potential source of extracting humic acid for reducing environment pollution and increasing the yield from agriculture in any weather seasons The potential sources that were investigated in this study include 30:70 coffee husk and cow dung named as A, 70:30 coffee husk and cow dung named as C, 30:70 cow dung and rice husk named as B, compost from landfill named as LC and human waste named as HW. All tested samples were treated with 0.1M sodium hydroxide NaOH for dissolving all humic substances. Humic acid was recovered after all sources were allowed to be precipitated with concentrated hydrochloric acid (38%). Analysis was done with UV-visible spectrometer through determining E4/E6 ratio and concentration. Also masses were measured with electrical balance. The results shows that in all tested sample, landfill compost and 30:70 cow dung and rice husks have low E4/E4 which signify high degree of aromatic condensation, high molecular weight compared to the other sources these values are 4.31 and 4 respectively. The concentration also was found to be 770 ppm for landfill compost and 484.54ppm for 30:70 cow dung and rice husks. Finally, in all tested samples landfill compost (LC) and 30:70 cow dung and rice (B) husks found to be considered as potential source for production of humic acid compared to the tested potential source.