Some green initiatives are successfully generating electricity in Mexico using legendary and ancestral nopal cactus with a promising future in the industry. Producing biogas and electricity from this plant is up to 40% cheaper and has been proven to be non-polluting.
The projects to produce energy from nopal could turn Mexico into a global benchmark in renewable bioenergies. Indeed, ecologists estimate that 15% of the energy generated in the country comes from natural sources. China and Chile have also made remarkable efforts to utilize nopal in clean energy production.
Natural resource and national symbol
Also known as opuntia or cactus, nopal is a type of plant that belongs to the Cactaceae botanical family. It is a succulent plant that can grow to up to 5 meters high. Its stems or stalks are oval-shaped, flat, green, and prickly. This is a perennial plant that generally blooms between June and December, growing a reddish, purple, and yellow flower.
Less than one hundred of the two hundred species of Cactaceae known worldwide grow in Mexico, with more than sixty of them being endemic to the Mexican soil. Its humidity, proteins, vitamins, sugar, minerals, alkaloids, and fiber make it one of the marvels of nature.
Cacti cultivation contributes to soil conservation in highly eroded areas. It is typical of arid zones, which cover 52% of the Mexican territory, not including the highly saline areas in the country’s northern coast. Nopal can develop at up to 3,000 meters above sea level.
In addition to being delicious, it has been used by indigenous communities for generations to purify water.
The plant is also one of Mexico’s symbols. In fact, its national coat of arms depicts an eagle devouring a rattlesnake while perched on a nopal on a small rock in the water.
From cultivation to methane gas
The process to produce energy from this plant begins with crushing nopal pads in containers known as industrial biodigesters – hermetically sealed during the process–. Simply put, this generates biogas with methane content of 65% that can be transformed into electric energy.
The waste is diluted into a substance formed by different microorganisms. The anaerobic processing, made at 55 °C, produces methane gas (biogas), as well as a mud rich in nitrogen, phosphorous, and potassium that can be used as a fertilizer. This gas is used to power an internal combustion engine that generates electricity, which is then injected into the National Electric Grid.
Nopal cactus treatment yields water residue after the fermentation process. The reutilization of this water has been studied and assessed to make isolating containers, as well as to use as biofertilizers.
The Institute of Electric Research (IER) found that the energy content in nopal is similar to that of corn. The study determines that one hectare that yields about 800 tons of corn can produce 40 cubic meters of gas. The maximum biogas and energy productivity from said land extension could be 32,000 cubic meters and 56 megawatts per hour and per year, respectively.
The idea of transforming nopal into energy has generated international interest in Mexico, so much so that United Nations delegations have visited the country with the purpose of getting familiar with and certifying some of the projects.
Estimates indicate that half of the deserts in Mexico would suffice to produce its own energy, while the rest would be used for gas exports. A large project could contribute to the industrialization of the fields and transforming dry environments into gardens. Regarding economy and employment, farmers would ensure jobs at their homes, contributing to drastically reduce illegal immigration.
Energy specialists insist that the Mexican state must support alternative energies research and technological development, since the current energy reform excludes them.
The Suema project in Milpa Alta
Mexico is developing important energy projects with the nopal cactus. One of the most relevant is located in Milpa Alta, south of the capital, where about 2,800 hectares are being used to cultivate nopal for energy purposes. The 200,000 tons of waste produced annually in this site are reutilized at a rate of ten thousand tons per day.
Suema, the company in charge of this project, says it hopes to process three to five tons of nopal waste per day. With this, it can produce more than a ton of fertilizer and generate 170 cubic meters of biogas that will be converted to 175 kilowatts of energy, enough to light 9,600 lightbulbs simultaneously.
Nopalimex’s progress in Michoacán
Another important project is managed by Nopalimex in Michoacán, located in the municipality of Zitácuaro, where it operates Mexico’s first nopal processing plant that generates biogas and electric energy.
The complex was first commissioned in January 2016, with plans to produce eight tons of biogas per day to power the municipality’s street lighting system. The project met some hurdles to operate at full capacity due to a lack of agreement between the company and the farmers and peelers. In February, authorities gave the green light for the plant’s reopening for fuel production, even for vehicles.
According to Nopalimex, one cubic meter of biogas is equal to one liter of gasoline, except 40% cheaper. The process also generates other by-products like ethanol, nopal for human consumption, organic hummus, and nitrogen-rich water that can be used as a fertilizer.
Additionally, in Zitácuaro, a corn supplier joined Nopalimex in producing biogas for its production processes, vehicles, and electricity generation. The project operates with collaboration of the IIE and the United Nations Industrial Development Organization (UNIDO).
Being self-sufficient, the project would eventually enter a new phase of selling excess electricity and biogas. With the latter, the biogas produced could serve to fuel the vehicles of the Zitácuaro municipality.
With regards to electrical power, Nopalimex technical manager Miguel Aké Madera informed that one watt from the Federal Electricity Commission costs one peso, while his company would sell it at 15 cents, evidencing the project’s profitability. Similarly, and given that this technological development is 100% Mexican, there is no need to import equipment, as is the case with solar generation projects that requires generators.
In the laboratory, Nopalimex is producing 13,000 liters per hectare of nopal, enough to replace gasoline with non-polluting natural gas for vehicles with the purpose of using it in urban and extra-urban transport.
Cruz Azul in Cavillo managed by Conacyt
Also in the Cavillo municipality, in Aguascalientes, there is a one-of-a-kind plant that generates electric energy from nopal pads and manure.
This site has 70 hectares that yield 100 to 150 tons of nopal cactus per day. The project is funded by the National Council for Science and Technology and Cruz Azul, with participation from the National Institute of Forest, Agricultural, and Livestock Research, the El Llano Technological Institute, and the Technological University of Northern Aguascalientes. This project has enabled to produce up to 920 kilowatts in an hour.
For more information, check Energía16