Evaluation of the effect of iron oxide waste powder in biogas production from Vegetable waste.
Abstract
Optimization of biogas is a study being explored all over the world and a number of methods are being used to achieve this. This is being done to ensure more sources of renewable energy, reduce and eliminate disposal of wastes in the environment. Vegetable waste from cabbages, nakati (salanum aethiopicum), cucumbers are being generated and landfilled. However, these wastes are suitable for anaerobic digestion because they have organic matter. Anaerobic digestion is just one of the many methods used to produce biogas from wastes. Vegetable wastes compared to other wastes like cattle manure, pig manure and chicken droppings are producing low quality methane. In this study, addition of iron oxide was done to enhance the anaerobic digestion process of cabbage waste to increase biogas production. The iron oxide waste powder used is generated as a by-product from acid regeneration after the spent pickling process. A waste acid liquor is generated from the process of pickling the steel surfaces with acid to remove stains and rust. The waste acid goes through regeneration to regain Hydrochloric acid and iron oxide powder is generated as a by-product. This study investigated the utilization of iron oxide generated in the acid regeneration plant as a catalyst in the production of biogas. Proximate and ultimate analysis were done to determine the chemical composition and biodegradability of the cabbage waste. Iron oxide powder was washed before using it to correct its PH from 2.03 to 6.8. To These experiments that were done in triplicate included varying dosages of 8,10,12,14,18 22 and 24mg/l of iron oxide powder with mesophilic temperature of 370C. In each batch reactor, cabbage waste of 600g/VS and inoculum based on a 1:3 ratio was added. For the first experiment which was run to determine the optimal dosage of iron oxide, doses of 8,12,18 and 24mg/l were used. Results from this experiment showed a higher methane yield from the 18mg/l digestor compared to the rest which either didn’t produce any gas or produced gas with higher percentages of carbondioxide than methane. Gas produced composed of 37.8%, 46.3%, 3.3% and 12.5% of methane, carbondioxide, oxygen and other trace elements respectively. From the final experiment, biogas quality of 35.7%, 40.5%, 46.1%, 58.4% and 55.4% was obtained from the digestor with 0mg/l, 10mg/l, 14mg/l, 18mg/l and 22mg/l respectively.