Interview with Rafael Ayala Magdaleno, Director of Cuervo Distilleries.
(June 1st, 2011 14:00 GMT+6)
What is your job position at Cuervo Distilleries, and what are the main responsibilities?
Cuervo Distilleries has two locations: the biggest one is located at La Laja, at the municipality of Zapotlanejo, near the exit to Guadalajara Mexico Road. The other location is at tequila (actually two distilleries at the same location).
My main responsibility is to coordinate the activities on both locations, all the tequila productive chain since the agave “piña” is received until tequila is ready to be bottled. I report to the Operations Director. There are other divisions, as the Agriculture Division, which manages the company agave fields and the planning of crop cultivation and harvesting, according to the tequila demand.
In our distilleries we receive the agave piña with the base of the leaves. Roots and leaves are left at the field. Average measurements allocate 51% of weight to the agave piña and 49% to leaves and roots *but basically roots are too shallow and small, so it’s mostly the weight of the leaves). When harvesting the agave, the field worker known as “jimador” removes the agave core with the “coa” and manually cuts the leaves and piñas are piled up to be taken to the distillery.
From your perspective, would it have any impact on agave yield and soil fertility if leaves were not sent back to the fields as organic matter?
Honestly, there is no real benefit for the next crop cycle to leave them on the field. Agave leaves have a very fibrous structure, that takes a lot of time to degrade as organic matter, so there is no significant impact on yield or pH adjustment.
What is the current use given to the tequila co-products, agave bagasse and vinasses?
80% of Mexico total tequila production is from the biggest distilleries: Cuervo, Sauza, Herradura, Patron and Cazadores. Regarding tequila vinasses, there has been investment from the biggest firms towards vinasse treatment, since there is a regulatory framework opposing to discharge it to rivers or sewage.
Small and medium tequila producers are somehow reluctant to perform vinasse treatment due to its cost. Vinasses have a high organic matter concentration (COD and BOD). The biggest companies are performing treatment so vinasses are not discharged to effluents. They are also working on other projects, as:
- La Laja plant is currently the biggest distillery plant, and they already have installed a vinasse treatment plant consisting on several steps: 1) anaerobic stage (to degrade organic matter producing methane and CO2, as a biogas), 2) aerobic stage (to deplete the rest of organic matter) and disinfection.
Biogas contains around 66 – 70% of methane to be burned and generate renewable energy, and to be used instead of fuel oil, which is obtained from petroleum refining.
Another use for vinasses is to be used on agave fields for irrigation purposes. Once agave is harvested, field is prepared for next cycle adding vinasse. Maximum allowed is 1000 m3 of vinasse per year per ha. Vinasse contains both organic matter and minerals. COD and BOD depends of the cooking process, but based on the cooking step used by Cuervo, Patron and Herradura distilleries average values for COD are 75000-78000 ppm, and BOD are 48000-50000 ppm. The practice of using vinasse for field irrigation has been questioned lately due to potential lixiviation of aquifers.
Bagasse and vinasse is also used to generate compost. Most of vinasses at Tequila factories have been used for compost generation. Bagasse is mixed with vinasse, in order to help fiber degradation (fibrous structure) with nutritional value. This is the only use of bagasse currently.
There have been several attempts, not successful at a larger scale, like producing bagasse pellets as fuel, compacted via extrusion). Another use could be package tubes. Bagasse has a very high calorific power which makes it a good prospect for combustion to generate heat. Even though it has a very high humidity, there is no problem; it can be dried off through several techniques, like furnace heating via recirculation of hot air, etc. There have been also attempts to make paper, construction materials, and mattress filling. But the main problem is that there are not a lot of people interested on investing to make these projects to go on a larger scale.
Lately Cuervo Distillery has been working on the project of using agave bagasse as fuel to replace fuel oil. In order to be used as fuel, humidity needs to be reduced from 65% to at least 50% (mainly by furnace recirculation heating or hot air process, simultaneous drying and burning). This project is already proposed and by the end of this year it’s intended to have bagasse used as fuel and methane generated from vinasse.
Advantage for bagasse as fuel are: reduced carbon emission by not using fuel oil, eliminate sulphur issues carried with fuel oil usage, reduced corrosion in burner exhaust, and it’s also a cost-effective strategy since cost reduction by buying less fuel oil.
Another potential use for bagasse and vinasse is to generate electricity. This would reduce both direct (process-related emissions) and indirect emissions (those from electricity consumption).
For company-owned agave fields, do you use fertilizers? Herbicides, weed control?
Currently our division is working on synergy with the Agricultural Division, which manager is Fernando Lozano. Cuervo has some fields for agave crop, but the rest are leased. There is a R&D department for soil management techniques. With time, soils get more acid, so lime is added to get pH adjusted between 5 – 7.
Fertilizer is being used, according to the nutritional analysis carried on the fields, to determine which kind of minerals is required. Main soil nutrients are potassium, phosphorus and nitrogen. Also zinc, magnesium, manganese and boron are monitored.
Regarding weed control and use of herbicides, it has decreased due to the following situation: it was performed before, but studies showed agave surrounding weeds is actually an indicator of current nutritional deficiencies for agave plant based on color of weeds. What is currently being performed is a set of “good agriculture practices” which is a exchange of good practices between companies, related but not limited to cleaning, disinfection, etc.
What about micro-propagation? I read an article by Rosalba Casas mentioning that one of the biggest distilleries developed this kind of techniques.
Sauza was the only company to perform micro-propagation. Cuervo has a “mother plant” system, which generate around each “mother plant” several smaller plants called “hijuelos” (baby plants). This baby plants depend a lot on the mother’s growth, and when they are 2 years old they are transplanted and after a full life cycle of 7 years they are ready for harvesting. Baby plants need to be separated in order to allow the mother plant to concentrate all its sugars and stop feeding the baby plants.
Do you use mechanical or manual harvesting?
All the industry uses manual harvesting. There have been several attempts to move towards mechanical harvesting but there is a lack of will.
Several years ago, I went to a forum in Irapuato, and met some Polish entrepreneurs from a company with very strong mechanical expertise. They were developing a system to run mechanical harvesting, but it is still under construction.
Do you use tillage for your fields? Which kind of tillage is used?
Tillage is being used currently. There have been several trials to run mechanical planting. Tractors are use to open “surcos”, to plow the fields then apply nutrients and vinasses. Mechanical tillage is not very feasible on hills, steep slopes, etc.
Which kind of energy supply is being used for tequila production?
All the industry uses fuel oil (price around 7 pesos a liter). Diesel is the second alternative but it’s more expensive (price around 10 pesos a liter). Both products are quoted every 15 days. Ther are used mainly for vapor generation.
I read on Lucie Leclert’s thesis about tequila denomination and she mentioned that some distilleries add citric acid or glycerol at their process. Is this practice performed by Cuervo?
Glycerol is used at the final stage of the process in order to increase softness of the finished product (as an additive). Some producers add syrup or caramel color as well.
Citric acid could have been used for acidulation purposes for fermentation process where glycerol is not too convenient to be added since it could lead to loss of sugars. Actually at fermentation, glycerol formation is being measured, since it is not convenient to have it in excess to avoid loss of sugars.
How agave maturity is being monitored regarding optimal sugar content in order to be harvested?
Basically, that would be something desirable to be measured, but for harvesting purposes, agave lifecycle is followed, which is 7 years.
R&D and Operations are working together to determine factors to help to harvest at the optimal sugar (inulin) content. Maturity is relative, since there are plants that at 5 years could be harvested. Currently there is a project about to be developed, which scope is to develop decision criteria based on historical data to measure certain factors as humidity, fiber and inulin content on the plant and develop statistical models. But so far havesting cycle is 7 years.
After 7 years, a long stem starts to grow in the middle of the plant from the core. If it starts growing and it’s not cut, a flower develops using all the sugars in the plant as a source of energy, reducing the available inulin to be processed for tequila. If by the time of harvesting the long flower stem is present (known as quiote), it is discarded with leaves and roots at the field.
In your company, has been any research about obtaining tequila from leaves. I found a US patent for a process of tequila making from agave leaves.
Legally tequila manufacturers are forbidden by law to produce tequila from leaves, based on Mexican norm. Harvesting of agave core must be made cutting leaves totally from it, just leaving base attached to the core. Several years ago, due to the shortage of agave supply, some producers used to leave 5 to 8 cm extra from base. But from 2004, last modification to the Tequila norm states that only agave core can be used to produce tequila.
Which kind of energy supply is used for distillation?
Fuel oil. The distillation uses vapor produced from water heated with fuel oil.
Which types of distillation do you use for tequila making?
In our distilleries we have two kinds of distillation: column and using copper or stainless steel stills (“alambiques”) Still distillation includes double distillation, column distillation is a single step.
On the industry there was a popular belief that still distillation needed to be made on copper stills as synonym of quality. It has pros and cons, for example using stills of stainless steel have the advantage of durability. Currently this kind of distillation equipment is made of stainless steel, with copper serpentines (internally) which is enough to eliminate sulphur generated by fermentation. Active copper absorbs sulphur and make it to react. This was found on a study in Scotland for whisky distillation, which if copper is not cleaned it can generate another kind of compounds.
One disadvantage for stills distillation is that there is no way to fraction; column distillation alcohol gets more concentrated and undesired compounds can be eliminated. Regarding energy consumption, column distillation is more efficient. Still distillation has public preference since it is thought by consumers that tequila has better flavor.
Which pH do you use for inlet stream for fermentation? Do you use S. cerevisae?
Inlet stream for fermentations starts with pH=4.2 and process basically is acid, since outlet flow has a pH of 3.8. Most of the industry uses S. cerevisae.
Rosalba Casas in her article mentiones that Cuervo distillery was the first tequila producer that started to use diffuser to process agave prior to fermentation. Is that correct?
Traditional tequila process uses cooking to hydrolyze inulin and then milling to separate agave bagasse from extracted fructose juice to be fermented. La Laja distillery plant uses a modified process where agave core is milled on diffuser, where fiber is washed on a countercurrent extractor with water. Diffuser has 24 stations, and station 1 receives the agave core, while clean water is entered at station 24. Then at the first stations there is n enriched juice, and is being recollected on a tank with a content of 12% inulin not hydrolyzed.
This has been a discussion topic within the industry, since actually efficiency is higher with diffuser; it creates less furfural (which is a toxic compound for the process).
