Anaerobic digestion of food waste for biogas production in glass bot-tles

Abstract

The generation and inadequate disposal of urban solid waste have been a major environmental problem worldwide. The management of solid urban waste generated in large urban centers is problematic and concerning globally. Alternatives are being developed for the treatment of organic solid waste. Brazil has great potential for biogas production, more precisely, biomethane, a component of raw biogas that needs to be purified. Considering the large daily volume of municipal solid waste (MSW) generated in urban centers, the main objective of this study is to develop a biodigestion technique for organic food waste from restaurants, specifically the university restaurant (RU) of UFPR. The experiments were conducted with homogenized and non-homogenized waste with quantities of recyclables added such as plastic, paper, and cardboard at proportions of 0%, 1%, and 5% in the waste mass, and the temperature of 35 and 45°C was controlled for the system's biodigestion. The data were presented as means ± standard deviation. To compare response variables, normality and homoscedasticity were checked, and mean values were evaluated by the one-way analysis of variance (ANOVA) tool. The experiments conditioned to a temperature of 35°C showed statistically significant higher cumulative biogas values when compared to 45°C. As for the experiments that varied the percentage of recyclables inside the biodigester, only 12.5% of the experiments conducted with 1% of added recyclables showed higher cumulative biogas volumes in 30 days of production, followed by 37.5% with 5% of recyclables and 50% with 0% of recyclables (control). Compared to the waste treatment experiments (with 2mm treatment ≠ without 2mm treatment), 21% of the experiments that were not treated with 2mm showed statistically significant higher values (p<0.05) for accumulated biogas in 30 days when compared to their respective treated experiments. This study allowed the development of a biodigestion system using glass bottles and demonstrated the behavior of biodigestion when recyclables are added, conditioned to different process routes (wet and dry), in terms of granulometry and temperature (mesophilic and thermophilic).