Evaluación del pretratamiento térmico de residuos alimenticios, para la producción de biogás mediante digestión anaerobia

Abstract

The constant increase in population requires an increase in the demand for food. In response to such consumption, a large amount of waste and waste is generated, in addition to the impacts caused on the natural resources used to produce them. At the same time, the use of nonrenewable energy sources generates the search for alternatives of renewable sources, which can use waste or scrap from other products. As a contribution to the objectives of sustainable development, including the use of renewable and non-polluting energies; in the city of Ouro Petro, Minas Gerais-Brazil, the high generation of food waste in the university restaurant of the Federal University of Ouro Preto, demands the treatment of these, although they are currently taken for the consumption of animals, this study has the objective is to evaluate the use of food waste in the production of biogas, with visas for the energy use of the establishment itself. The food wastes were characterized physicochemically before and after applying a hydrothermal pretreatment at temperatures of 125 ° C, 160 ° C and 180 ° C, which was intended to solubilize the organic matter contained in the substrate for greater biogas production efficiency, in addition, it accelerated the hydrolysis stage of DA. He raw substrate had TS = 19.3%, VSS = 18.3%, C / N = 30, lipids = 25.4%, carbohydrates = 22.8% and proteins = 10.7%. After the substrate was pretreated, these characteristics were altered with the increase in temperature such as COD, the C / N ratio and the appearance of significant concentrations of 𝑁𝐻4+. However, the high concentration of lipids and proteins, generated inhibition of methanogens by the accumulation of fatty acids that caused acidification in the environment, achieving only values of 1.97 NmL𝐶𝐻4/ g of VSS at temperature 125 ° C and A / M = 0.5. Thus, the accumulation of fatty acids allowed microorganisms to have a large amount of food to produce intermediate products such as acetic and propionic acid, which in their transformation generate 𝐻2 obtaining values for the raw substrate of 11,59 NmL𝐻2 /g de VSS and for the pretreated substrate of 5,82 NmL𝐻2 /g de VSS a 125°C, 4,21 NmL𝐻2 /g de VSS a 160°C y 60 NmL𝐻2 /g de VSS a 180 °C, all values were obtained with the ratio A / M = 3. Therefore, it was concluded that although food residues were not positive for biomethanization, they were an excellent acidifying substrate for the production of hydrogen and volatile fatty acids, which can be products of high added value in the green industry.