Photo credit: RENEWABLE ENERGY WORLD
Image: Cultivated Opuntia (prickly pear cactus)
Prickly Pear Cactus: Nuisance or Bioenergy Opportunity?
The beauty of this hardy, drought-resistant cactus, which can tolerate surprising bouts of cold weather, is that it can be grown on veritable desert-like wastelands, where conventional crops would wither and die.
“Opuntia pads have 8 to 12 percent dry matter which is ideal for anaerobic digestion,” said Axel Tarrisse, managing partner in Zoe Biotech, a two year-old Marseille, France-based agricultural and environmental tech company.
Tarrisse notes that with a rainfed climate, there’s no need for extra irrigation or extra water to facilitate the anaerobic digestion process. In fact, with only 300 millimeters of precipitation per year, he says, Opuntia can produce 12,000 kilograms of dry matter feedstock and still retain enough moisture to facilitate biogas production.
By some estimates, Prickly Pear cactus pads degrade five to ten times faster than manure. Thus, only 4 hectares of the Opuntia crop can produce an estimated 800 cubic meters of biogas per day. Although the cactus is native to semi-arid regions with stifling hot temperatures, it can also survive and even thrive in mountainous areas that can have temperatures as low as minus 15 degrees Celsius.
“The world has millions of hectares of land prone to drought and desertification,” said Tarrisse. “Opuntia helps create a vegetative cover, which enhances soil regeneration and improves the infiltration of rainfall back into the soil.”
The idea of using Opuntia feedstock to generate methane-based biogas first took root in Chile. Although the process had been observed as early as 1984 in the lab, its commercial application was actually first realized by environmental engineer Rodrigo Wayland Morales, the owner and current manager of Elqui Global Energy in La Serena, Chile.