Evaluación de la eficiencia de producción de biogás en biodigestores tubulares con estiércol bovino mediante la modificación de temperatura y carga orgánica

Abstract

The manure produced by a beef is equivalent to 8% of its live weight, an amount that, being subjected to anaerobic digestion, can generate biogas as a by-product capable of producing energy. This is why the main objective of this research is to experimentally evaluate three types of semi-continuous feeding tubular biodigester systems, which were subjected to different temperature and organic load conditions, in order to observe in which scenario the biogas production is more efficient.

Within the methodology, three tubular biodigester systems with a capacity of 50 L each were used. The first system was a three meter tubular biodigester which was subjected to environmental conditions and fed with a 1: 3 mixture of manure and water. The second system consisted of three tubular biodigesters of one meter each connected in series and was fed with a 1: 4 mixture of manure and water, operating at ambient conditions. The third system was made up of three tubular biodigesters of one meter each connected in series, where the second biodigester operated at 37 ° C while the other two operated at ambient conditions. This system was fed with a 1: 3 mix of manure and water.

The biogas production of the three biodigester systems was recorded daily. In addition, the tracer test with NaCl was performed on the three systems to obtain hydraulic characteristics of the structures.

In the present investigation with the different configurations of tubular biodigester systems, it was obtained that system 3, which within its configuration, its intermediate part operated at 37 ° C, produced 73.45% more biogas than system 1, the which only consisted of a single biodigester, and 112.18% more biogas than system 2, which consisted of three tubular biodigesters connected in series operating at the same temperature and fed with a lower organic load.

Regarding the operational variables, it was obtained that system 1 has a maximum Specific Biogas Production (SBP) of 0.045 [/kg SV] operating with an average Organic Loading Rate (OLR) of 1,311 [kg SV/*day], reaching a maximum Biogas Production Rate (BPR) of 0.059 [/day]. System 2 has a maximum Specific Biogas Production (SBP) of 0.043 [/kg SV] operating with an average Organic Loading Rate (OLR) of 0.778 [kg SV/*day], reaching a Biogas Production Rate (BPR) maximum of 0.034 [/day]. System 3 has a maximum Specific Biogas Production

(SBP) of 0.098 [/kg SV] operating with an average Organic Loading Rate (OLR) of 1.311 [kg SV/*day], reaching a Biogas Production Rate (BPR) maximum of 0.129 [/day].

Regarding the hydraulic characteristics of the biodigesters, it was determined that system 1 had short circuits, did not have dead spaces and the predominant flow in the structure is of the mixed type. On the other hand, systems 2 and 3 on the other hand presented dead spaces and the predominant flow in the structures is of the mixed type, a characteristic that helped to retain organic matter, favoring the generation of biogas.

In addition, the biomethanization potential test of stabilized cattle manure was carried out in three batch reactors of 500 mL capacity, operating at 37 ° C for 57 days. Subsequently, the bacterial consortium of the resulting material was used to perform the test of the biomethanization potential of cattle manure again, but this time at different temperatures which were: 37 ° C, 23 ° C and at room temperature.

The second round of the test for the biomethanization potential of cattle manure at different temperatures was monitored for 131 days, with the aim of evaluating biogas production at different temperature conditions in order to obtain an idea of the adaptation capacity of bacteria to conditions. different environments.

Subsequently, a third round was replicated in which it was operated at the same three temperatures as the previous round. The material from the predecessor round fed with fresh bovine manure was used to observe the behavior of the bacteria in the course of time for 64 days.

In relation to the BPM test, it was determined that the same amount of biogas can be obtained by working at different temperatures. In the case of the test at 23 ° C, 177 days were required, while in the test at 37 ° C it took 46 days to obtain the same production. This is why it was concluded that the ability to produce biogas by the bacterial consortium depends on the operating temperature and the time given to the bacteria to be able to adapt to a certain environment.

Based on the aforementioned, it can be concluded that it is more efficient to work in a system made up of several linked biodigesters than in a system made up of a single biodigester. It was also verified that the more organic load the biogas production increases.

Likewise, by increasing the operating temperature of the system, the production of biogas is favored.

The biogas production of a bacterial consortium also depends on the time given to the system to adapt to the operating environment.