The Digestion of Waste from Vegetables and Maize Processing

Abstract

This study was carried out in order to find a possible use for waste produced during the processing of vegetables and maize. Anaerobic fermentation is a suitable way to handle this wet and easily biodegradable organic material. The aim of this study was to evaluate the impact of waste corn kernels, peas, crushed corn kernels, French beans, mixed vegetables (broccoli, cauliflower, peas and carrot), corn leaf and corn husk on anaerobic fermentation. Anaerobic fermentation tests was carried out in batch fermenters (5 dm3) for 21 days at 42 °C. During this period the quantity and quality of biogas produced were monitored. The following substrate parameters were determined: dry matter content, organic dry matter content, nutrients content (protein, fat, fibre, starch, acid detergent fibre, neutral detergent fibre) and elemental composition. The hypothesis predicting the inhibitory impact of substrates on the anaerobic process was not confirmed. Biogas production after 21 days of hydraulic retention time ranged from 0.6773 m3/kg of organic dry matter (peas) to 1.1108 m3/kg of organic dry matter (mixed vegetables). All substrates had the final concentration of methane in the biogas ranged from 59.43 to 65.97%vol. The hypothesis about the impact of pre-treatment of substrates (crushing) on the quantity of the biogas produced was confirmed. The biogas production from the crushed corn kernel was significantly higher than the biogas production from substrates with a similar composition of nutrients (corn kernel, peas). Vegetables and maize waste produced during processing is a suitable substrate for anaerobic fermentation.