Evaluation of biogas production from co-digestion of organic solid waste ; Avaliação da produção de biogás a partir da co-digestão de resíduos sólidos orgânicos

The anaerobic co-digestion of food waste and grass is a competitive alternative for treatment of the organic fraction of urban solid waste taking into account the context of insufficient and almost null value of this fraction in Brazil contrary to actual legislation and also the typical hard proportion of organic matter on wastes in national and international ambit. About this panorama the present article sought to evaluate the biogas production from the co-digestion of food waste and grass (Zoysia japonica) in 3 proportions (1:1; 2:1 e 3:1 taking as reference 500 ml) in mesophilic temperature (38ºC) during 21 days. The solid content present in the digested mass was evaluated, comparing to the biogas production and the reduction of biodegradable organic matter. The results were analyzed statistically through a variance analysis considering 5% of significance. Co-digestion done, treatment 2 (in other words, the proportion of 2:1 of grass in relation to food waste) presented the best results in terms of biogas generation. It results in maximum biogas production, which was 1440 Nml of accumulated biogas or 25 Nml per gram of volatile solid (VS). These results mean an important verification, because it shows the inherent viability of the use the of grass clippings in the process of sustainable management of solids wastes, guiding the ideal proportion to be used in order to obtain a better biogas production. The results show that further researches are needed for optimize the biogas production since the production obtained during the test is still below the potential of biogas generation through co-digestion with food waste and grass clippings which, according to the literature, indicates values of 500-600 Nml per g.VS. The lower biogas production observed during the experiments is probably due to the accumulation of volatile acids, which inhibits the occurrence of the whole digestion process bearing in mind that the pH of digestate mass presents acid conditions (4.07±0.22). This finding is corroborated by the ...