Germán Buitrón Méndez heads a team of Mexicans who achieved this development. (Photo: UNAM / Art: Tec Review)
From waste from the cheese and wine industries, researchers from the Engineering Institute (II) of the National Autonomous University of Mexico (UNAM), in the Juriquilla Unit, managed to obtain hydrogen and methane, gaseous biofuels useful to generate electricity in a clean process.
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Mexicans get biofuel from cheese and wine
The investigator Germán Buitrón Méndez leads a team of academics using the must or grape juice and its shell, in addition to the whey resulting from the cheese industrialization, to give them added value.
“The wine effluent is collected during the harvest (from June to November) between Tequisquiapan and Ezequiel Montes, an area where the wineries and vineyards are concentrated, while the rest of the year we obtain the whey to work in the laboratory and generate electricity. with biogas ”, explained Buitrón.
Once collected, the waste is taken to the Institute’s laboratory where it is processed with microorganisms (bacteria and archaea) in several reactors and a pilot plant in a serial process.
The vitivinicultural effluents come with an acidic pH, which is ideal to start the process in two stages: in the first we generate hydrogen under acidic conditions in a reactor, and volatile fatty acids.
The material has ethanol, part of it oxidizes and forms acetic, propionic, butyric acid and hydrogen.
The hydrogen is harvested and the fatty acids are passed to the methane-producing reactor, where the organic matter is already more easily assimilated, Buitrón explained.
“In the acidogenic stage, where we produce hydrogen, we use bacteria that like acidic pH, which is how the effluent comes from. In the methanogenic reactor are archaea, which are also microorganisms and like a neutral pH. In the reactor we can give them these conditions ”, he explained.
The process of microorganisms working in the reactors is automated and controlled with a mathematical model that knows how to feed from the first reactor what the second reactor needs, in order to maximize methane production.
The hydrogen process is faster and with acidic pH, while that of methane is slower and with neutral pH. The contribution of Buitrón and his group was to automate it and maximize the production of both gases.
The experts realized that in the first reactor they also obtain fatty acids at a very high concentration, and within them there are medium chain acids, such as caproic and caprylic, which have a much higher added value than gaseous fuels.
To produce caproic and caprylic acids, acetic acid and ethanol are needed, which are present in the vitivinicultural effluents, because the residues continue to ferment. “We have the raw material to form these two medium chain fatty acids that have a high added value,” he said.
For now, the proposal by Buitrón and his group is to use gaseous biofuels in the wine and cheese producers themselves to make them self-sufficient without transporting biogas very far.