Odor-Eating Ostriches (and Other Scientific Breakthroughs)

Armando González Sánchez and Juan Manuel Morgan Sagastume, scientists from the UNAM Institute of Engineering (II), created a hybrid odor eliminator (EHLMO), useful in wastewater treatment plants and in landfills or sewers.

The innovation, which obtained the patent title from the Mexican Institute of Industrial Property, eliminates the aromas generated in wastewater treatment plants, drains, manholes and especially can be used to desulfurize biogas, which is why it is possible to give it a new use: supporting the generation of clean and renewable energy.

The university researchers explained that technological progress is unique in Mexico and Latin America, and is less expensive than those developed in developed countries, so its benefits are multiple.

EHLMO is the product of several years of research and great accumulated experience, which complements a technological package from the University in the matter.

The goal is to properly manage gases so that they do not have negative impacts and can be used, especially in a biogas that is primarily a mixture of methane, carbon dioxide and, in smaller quantities, hydrogen sulfide (H2S). This last compound is the cause of the bad smell and also corrodes the equipment used for energy generation, which is why it must be eliminated, explained Morgan Sagastume.

González Sánchez added that a process of desulfurization or elimination of hydrogen sulfide from biogas was considered using an optimized and regenerable reagent based on iron. “The H2S is eliminated and, chemically speaking, it is partially oxidized to elemental sulfur.”

By recovering the latter, EHLMO obtains hydrogen sulfide as sulfur, that is, a solid that is easily separated from the liquid and that, in turn, can be used in other industries, such as cosmetics. “What was a stinky gas is transformed into a solid that is recovered to give it other uses,” he emphasized.

After successfully passing the laboratory tests, the odor eliminator also passed the pilot evaluations, and “desulfurizes very well,” said the doctor in engineering.

The university student explained that because this process is not 100 percent efficient, since there are remnants of hydrogen sulfide in concentrations that are not harmful for the use of biogas as clean and renewable energy, but that are still perceived by the human sense of smell (around 1 part per billion), a biological procedure was added (in addition to the physical-chemical process based on iron).

That is, a biofilter was added consisting of an organic bed (compost) whose microbial diversity is wide and capable of removing H2S, as well as other types of organic and inorganic compounds that generate bad odors.

EHLMO is hybrid because it has these two configurations: to eliminate the largest amount of hydrogen sulfide, and to bring its concentration levels to one so low that it is not perceptible by smell. Furthermore, it is not necessary to add reagents to the eliminator; consequently, its operating cost is reduced, and it is beneficial for the environment, “because we are not contaminating with a process to decontaminate another.”

Morgan Sagastume recalled that we are suffering from a water crisis, so it is time-sensitive to take action to address it. This technology complements a package for the treatment of wastewater created at the II, which contributes to this goal.

In this regard, he stressed that biological means are basically used to treat them. One of the processes used is anaerobic, that is, without oxygen; as it is low cost, its use is essential in countries like ours, with a shortage of resources and, above all, in the municipal and industrial sphere.

At the II, another patent was obtained years ago for the development of anaerobic reactors or systems; now, this new research complements the water treatment part with that of biogases, including methane, which can function as fuel for electric generators. In this way, the operation of the plants becomes cheaper. But to use the biogas available in the generators, “we must eliminate the H2S,” Morgan reiterated.

Organic waste can be processed in anaerobic digesters that produce biogas, but, he warned, with a high content of H2S, which is a reduced form of sulfur, polluting and even poisonous, which when burned produces sulfur dioxides, which cause acid rain.

With the innovations of UNAM experts, pig farms, for example, that use anaerobic digesters for the disposal of organic waste from animals, could be self-sufficient in energy because they would have a system available that removes the H2S from the biogas and leaves it ready to be used in motor generators, without resorting to expensive foreign technology.

The device's capacity in the pilot phase to eliminate bad odors, Armando González said, is 100 liters of gas per minute with a hydrogen sulfide content of up to 5,300 parts per million. "So that people have an idea of ​​what that represents, we can say that if we perceive the foul smell of H2S like rotten eggs, it is because the biogas has concentrations greater than 1 part per billion of hydrogen sulfide."

These concentrations of thousands of parts per million are typical in biogas from anaerobic digesters or wastewater treatment plants, which is why this development is efficient and competitive.

At EHLMO, the biogas is fed from the bottom to make it "bubble" in a liquid that contains iron and other elements; there it is oxidized and most of the H2S is eliminated, then it goes to the biofilter, where it is clean of that compound and free of odor, according to the measurements of H2S concentrations and smell.

This technological innovation is ready to be transferred to a company or technology providers. Those interested can get in touch.