The nopal option to reduce CO2 emissions in Mexico City

The phase of loss of organic carbon has been occurring in the country in corn monocultures and in areas with high tillage rates, however, perennial species, including cactus-nopal and agave, would contribute to the maintenance of total organic carbon (TOC) in the plant and soil.

In addition to contributing to food production, nopal provides ecosystem services. Photo: Agencies
In addition to contributing to food production, nopal provides ecosystem services. Photo: Agencies

Cactus cultivation has the same potential to capture carbon (C) as a pine and oak forest in the Milpa Alta region of Mexico City, so in addition to contributing to food production it would provide ecosystem services, reported Mariela Hada Fuentes Ponce, professor at the Autonomous Metropolitan University (UAM).

In the cultivation of the cactus as an option to reduce carbon dioxide (CO2) emissions, in a soil with low fertility, carried out in the Milpa Alta Mayor's Office, a group of UAM researchers compared the patterns of CO2 and TOC projection in a mountainous area of central Mexico, she explained.

The member of the team of scientists who won the Research Award 2019, in the area of Biological and Health Sciences, granted by the Open House to Time, said in an interview that rural soils tend to lose organic carbon, which contributes greatly to increased CO2 emissions into the atmosphere.

Fuentes Ponce explained that the phenomenon of climate change intensifies the occurrence of rains, droughts, and frosts due to -among other factors- the increase in greenhouse gas emissions, including CO2, whose main source is the burning of fossil fuels, said the academic from the Department of Agricultural and Animal Production of the Xochimilco Unit.

In agricultural systems, the gas has several origins: the production of agrochemicals, including nitrogen fertilizers; procedures with excess tillage; the burning of crop residues; the use of tractors; and even the breathing of plants, basically made up of C, like the rest of living beings, which when they die are incorporated into the soil and become organic matter.

Agricultural complexes can generate carbon dioxide and nitrous oxides -- a gas that also triggers the greenhouse effect -- but at the same time they can become a reservoir of C, since plant species in the process of photosynthesis integrate what is in the air into their tissues, and if they are perennial, the C will remain in their stems, so when they die they will be incorporated as fertilizer on the surface, which will capture that element, the teacher explained.

A rational and more thoughtful agricultural management would keep the C longer in the soil as stable organic matter, instead of converting it back into CO2, however, conventional agriculture -which uses agrochemicals and is highly technology-, has increased the dispersion of pollutants to the habitat and now contributes 25% of CO2 to the planet; in Mexico, this sector participates with more than 6%.

The phase of loss of organic carbon has been occurring in the country in corn monocultures and in areas with high tillage rates, however, perennial species, including cactus-nopal and agave, would contribute to the maintenance of total organic carbon (TOC) in the plant and soil.

The management systems selected were corn monoculture with conventional tillage and synthetic fertilization; corn associated with Vicia faba and the addition of manure; cactus-nopal without and with manure in compost; pine-oak forest and fields that were planted by the cereal and had four years of rest without control of arvenses; in all of the CO2 and volumetric humidity measurements were made every 15 days in five points of each plot.

The doctor in agronomy from the Colegio de Postgraduados and member of the Crop Physiology Laboratory of the UAM explained that the pine-oak forest showed stable C-CO2 dispersions throughout the year; in the cornfields, they were unstable, with several peaks of respiration, while in the case of the nopal there was a very close pattern of respiration to the forest.

The Intergovernmental Panel on Climate Change has recognized that not only forests, but also agriculture have important carbon sequestration capacities, "provided that more thoughtful management is done", so "our team is working on implementing mechanisms that not only consider obtaining food -although this is the central objective of such activity- but also provide ecosystem services".

"If what we are going to do with the farmers implies that there is no food self-sufficiency for the production unit, it will not be viable, no matter how much carbon capture we achieve," unless there is a public subsidy policy that allows these practices, and "in that sense, the Mexico City government could provide resources to the nopal agrosystem," with more planning, he said.

MEXICAN STUDENT MANAGES TO PURIFY WATER USING A NOPAL COMPOUND

The creation of a capsule that takes advantage of a nopal compound can now make the water drinkable. The best thing is not only that a product from Mexico is used, but it was developed by Shirley Kimberly Enríquez, a Mexican student of Energy Engineering and Sustainable Development of the Universidad del Valle de México (UVM).

Shirley Kimberly Enríquez. Image: Agency
Shirley Kimberly Enríquez. Image: Agency

Only one capsule of cactus mucilage can purify one liter of water; if it was not enough, its elaboration is from beginning to end it is free of CO2 emissions since it does not use fuels in any part of the process.

Enríquez has called it Noptec, which is 100% sustainable and is a proposal to solve the problem of access to drinking water that Mexico and other nations in marginalized communities suffer from.

According to the United Nations Children's Fund (UNICEF), drinking non-leg water for consumption and lack of water for personal hygiene are factors involved in the rates of loss of life due to diarrheal diseases, especially in children.

Shirley Kimberly Enríquez stressed that thanks to Noptec people could have easy and affordable access to drinking water. The capsule was able to purify the water of bacteria, mineral salts and heavy metals such as selenium and lead.

The history behind noptec

The creation of Noptec is based on the process of dehydrated cactus. In conjunction with UVM Mechatronics students, Abdiel Acosta, Julián Mora, Alejandro Trejo, and César Ramírez was built a solar stove, which was composed of waste ensuring low cost.

For the development of the capsule, a cactus compound called mucilage is used and it is achieved due to the grouping of suspended colloidal particles. The process begins with the separation of the epidermis from the cactus; Subsequently, the cladode is blanched and a solar cooker is used for this. Then filtering is carried out, the remaining material is placed in a water bath, and finally, the precipitation and drying of the mucilage are done to crush it and place it in capsules.

The nopal was obtained through an agreement with a producer community of Milpa Alta.
The nopal was obtained through an agreement with a producer community of Milpa Alta.

"The alliance consists in that they will provide us with some of their crops and we in return give them the product for their consumption and, in turn, we train them so that they can also do it. With this union, a great benefit is obtained for both parties and a value chain is achieved ", explained Enríquez.

Mechatronics students will also make their contribution by implementing the use of solar cookers in the Community of Milpa Alta. A great achievement that bears the "made in Mexico" stamp thanks to the young talent of Mexican minds.

by Mexicanist