While proper use of organic waste to produce an alternative fertilizer use recently also proposed as a renewable energy source, which additionally would provide several benefits such as promoting lower polluting effect, generate usable products and to promote sustainable development.
According to figures from the Ministry of Environment and Natural Resources (SEMARNAT), Mexico is estimated to produce 94 thousand 800 tons of garbage daily, of which at least 40 percent is concentrated in the states of Mexico, Jalisco, Veracruz and Federal District.
Given this scenario, the teacher-researcher Arzapalo Nelson Caballero, Autonomous University of Yucatan (abattoir), conducted a study to extract the energy stored in organic waste (citrus, banana and papaya, among others), in addition to those produced poultry industry, with the aim of utilizing alternative power generation for public consumption and reduce pollution brought about by such waste.
To this end, the team of researchers at the abattoir was based on the anaerobic digestion method, which consists of decomposing the biodegradable material in the absence of oxygen to generate biogas, whose main energy component is methane, also containing carbon dioxide and other trace gases.
Biogas can be used as fuel in cars, factories or at home by way of replacement of butane gas. The quality and quantity of the chemical energy depends on several factors, among them the type of waste used, and also of certain control parameters such as temperature and pH.
To make anaerobic digestion, Arzapalo explained that the waste first goes through an acid phase where all the waste caused by large particles are transformed through a process carried out by enzymes and bacteria, a kind of small molecules from which emerge alcohols, and then converted into acetic acid, which is finally converted into methane gas and carbon dioxide.
In this last stage the more we succeed in cutting the second major component is the amount of methane and biogas quality, he said.
The researcher said the abattoir waste, by their nature, have stored energy that directly or indirectly captured through the Sun prior to the case of vegetable waste is more noticeable the process of saving energy through photosynthesis. Meanwhile, animal waste fuel which is largely acquired indirectly through the consumption of plant-type foods.
Arzapalo Caballero stressed that unlike other similar surveys, the abattoir used the solar energy to provide necessary temperature reactors and makes the process self-sustaining.
He noted that with the help of temperature the process is favored, since streamlines the processing of polymers to alcohols and fatty acids, and finally to methane gas. The study included experiments on two different scales, micro and macro-scale digesters used as roads and special reactors respectively.
In the micro-scale experiments were batch (batch) made to know the main characteristics of the biodegradability of waste, while the macro-scale made were of a continuous supply to resemble an application larger scale.
“By increasing the temperature with solar radiation not only speeds up the process, but the intention is to eliminate pathogens that may be organic waste,” he said.
Also, the specialist said that UADY the results were favorable, with only one gram of papaya generates up to 340 milliliters of the gas. Meanwhile, with banana waste 310 ml was reached in the case of the remains of citrus production, the results were outstanding, as it led to 400 milliliters per gram.
According to the head of the research, energy in the form of biogas produced during the investigation was monitored in terms of quantity and quality with the help of special storage bags and laboratory equipment for analysis, respectively.
“The intention is to use energy in their agricultural fields where waste is generated to run irrigation pumps or machines plow, like any type of conventional energy,” explained the researcher from the abattoir.
It is noteworthy that another peculiarity of this research is that after extracting energy from waste, solid waste can be utilized as compost or manure to crops and gardens, while the residual water after a simple treatment process can reused in irrigation.
“In Mexico, we have plenty of raw material that can be used efficiently and make this transformation in a sustainable development, because much of what we throw away and waste it can be used to produce energy and support energy supply in homes and institutions also contribute to reverse pollution cause the waste,” said Arzapalo Caballero.
The project involved the collaboration of researchers from the Center for Scientific Research of Yucatan (CICY), Technical University of Munich and University of Applied Sciences in Stuttgart, both in Germany and with funding from the National Council for Science and Technology.