“Bioethanol is coming to Mexico,” said energy researcher Dr. Arturo Sánchez. “Within a few months, you’ll find it at every gasolinera.”
For the moment, this plant-based fuel is mainly coming from the United States, where 30 percent of its corn production is now turned into ethanol. “We don’t produce enough corn to do that,” said Sanchez, “but our sugar cane and tequila industries do produce great quantities of bagasse and 70 percent of it is sugar that’s just going to waste.”
Discovering a practical way to convert waste products like bagasse, corn stover and wheat straw into alcohol has been Sanchez’ focus for over ten years at Cinvestav (Center for Research and Advanced Studies of the National Polytechnic Institute), located at the northern edge of the Primavera Forest, within sight of the Omnilife Stadium. Recently, the importance of these studies brought twelve institutions together, ten of them based in Mexico, one in Oxford, England and one in Chile. The result, said Sánchez, is “the biggest bio-alcohol project in Mexico,” and the opening of the Bioenergy Futures Lab, inaugurated on the Cinvestav campus in April, 2017 at a cost of 25 million pesos.
“What we are aiming at,” said Sánchez, “is to substitute vegetable fossil fuel with biomass fuel in as short a time as possible. We want to produce bioethanol to use in automobiles and bio-products like plastic. So, we are working along three lines. First, we are mathematically simulating a bio-refinery that could do everything involved in this process. Next, we are trying to find out whether these bio-refineries would really be sustainable, and thirdly, in this particular facility, we are studying how to break down biomass so we can extract the sugars, which will be used in the further processing stages of a bio-refinery.”
Sugar cane and cooked agaves, of course, produce great quantities of sugar which can easily be removed in distilleries and refineries by pressing and rinsing. What is surprising is that that the leftover bagasse, which is considered worthless and typically flushed into the nearest river, still consists of around 70 percent sugar. “Even cornstalks and straw contain high amount of sugars,” Sánchez said, “but the problem has always been getting that sugar out of the fiber.”
The researcher explained that the cell walls of these fibers are made of lignin, which is very tough and resistant to decay. His team has been working for years to find ways to break this down.
“First, we grind the material up,” he said. “Then we cook it, just as you would cook tamales. We use pressure cookers for this and, as a result, much of the fiber is reduced. Next, we discovered that we can submit the biomass to high pressure, to ten times the atmospheric pressure, and then we suddenly release the pressure. This we call a ‘vapor explosion,’ and with it we succeed in utterly destroying the structure.”
Standing in front of a huge machine producing loud chugging noises similar to those of bygone steam engines, Sánchez showed me a sample of what the biomass is finally turned into. You could say it looks like mud, although other comparisons might come to mind.
“What we are working on now,” continued Sánchez, “is figuring out how much time we need to cook and ‘explode’ each type of biomass. It’s tricky. For example, wheat straw from a mushroom farm in La Barca might be structurally different from year to year, even though it comes from the same place.”
The researchers have now liberated the sugars, but they have one more obstacle to deal with. “The molecules of these sugars are in the form of long chains or polymers which we need to break down. The way to do that is through microbes, which produce enzymes. Once we have the smallest components, which we call sugar monomers, we use a certain type of yeast to produce alcohol. But if we want butanol, we use another one. For bioplastics, it’s yet another. Unfortunately, many of these enzymes are patented by companies like Dupont and Monsanto and they are very expensive,” noted Sanchez.
These researchers have obviously overcome many obstacles. Will they reach a point where it is affordable and practical to produce a gasoline substitute from bagasse and other agricultural waste products?
“It would have a positive impact on the environment here in Mexico,” said Sánchez. “As you may have heard, to produce one liter of tequila, you must produce between 10 and 15 liters of liquid waste material. Some distilleries treat this, but the majority don’t. Rivers of waste from Amatitán and Tequila, for example, flow directly into the Santiago River. This pollution problem is very serious. So, this is what we are working on here, a way to turn those liters of liquid waste into something useful.”