Biofuel from Prickly Pear Cactus

Universidad Mayor in Santiago, Chile is experimenting with the use of plantation-grown prickly pear cactus for use as biofuel. They intend to establish plantations in the Atacama desert, a place that averages 0.004 inches of rain a year, mainly as fog from the Pacific Ocean.

Reporter Anatoly Kurmanaev of the Santiago Times sets the scene:

The driest place on earth, the Atacama Desert in northern Chile, wouldn’t seem an auspicious place for biofuel production.

Biotechnology experts, however, may have found a way to turn one of the desert’s only available plants, the cactus, into energy.

A US$500,000 pilot project in the Río Jorquera Valley in the Copiapó province aims to reduce Nopal cactus stems to high-energy dry briquettes that can be burned in coal-fired thermoelectric plants.

The five-acre experimental plantation will produce sufficient scientific data on cactus biomass production in arid conditions by the end of 2013, and will then begin supplying fuel to a small-scale onsite power station.

The project’s leader, Prof. Alexis Vega of Universidad Mayor’s Biotechnology Institute in Santiago, believes a pilot-scale plantation of 420 acres will be able to sustain 1.5 megawatts per hour (MW/h) of electricity generation.

At an estimated cost of US$112 per MW/h, cactus biofuel is competitive with fossil fuels at current global prices and is much cheaper than other sources of alternative energy in the region such as wind or solar.

“This is an opportunity to diversify the local economy by utilizing marginal soil—land which has little water and few agricultural alternatives,” said Vega.

The researchers hope to develop the plantation to a level where they can begin supplying large electrical utilities in northern Chile.

One of the advantages of the cactus plantations is their proximity to energy-hungry mining operations. Utilizing locally available sources of energy would reduce the need for costly energy shipments from the south, Vega explained.

“Four years ago, when we approached the big power distributors they told us no. Now the moment has arrived—they are keen to participate.”

A law passed in 2010 binds Chile to generate 10 percent of its electricity from renewable, non-conventional sources by 2024.

At present the figure stands at around five percent, and Vega believes the government’s support for alternative energy puts the nation well on course to meeting the target.

Apart from the environmental benefits, researchers believe the scheme also holds substantial economic potential.

Southern Atacama’s traditional crop has been the table grape, the profitability of which has fallen steadily in recent years due to growing competition from Peru and Argentina.

As cactuses require at most a third of the water used by a grape plantation of the same area, there are large potential savings for farmers, as well as stable year-round jobs.

“For the small declining indigenous communities of northern Chile this is a real development opportunity,” said Vega. “These people can stay on the land, produce fuel for their own use, and sell the surplus, instead of migrating to the cities where they will remain poor.”

According to a report from Universidad Mayor, the cactus can be used in two ways: 1) anaerobic bio-digestion can produce methane for use as a feedstock for electrical generation, much as we harvest methane from landfills here in Tucson; or 2) the prickly pear pads can be dehydrated using solar energy, then pelleted and used as a co-combustion fuel in coal-fired plants. The cactus plantations will have to be irrigated and fertilized to allow a harvest every six months. An added benefit, if the project proves feasible, is that this biofuel is produced from a non-food crop and will provide year-round jobs rather than seasonal employment common to most crops. The goal of the project is to produce at least the equivalent of 40 tons dry matter per hectare per year which they deem competitive with other biofuels.