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The astonishing power of orange peels

Posted on 22 May 2018.

Researchers at Princeton University analyzed samples collected on a plot of land in Costa Rica where waste oranges had been dumped fifteen years earlier. They made a surprising discovery...

“An awful lot of those problems can be alleviated if the private sector and the environmental community work together.”

“In the mid-1990s, the equivalent of 1,000 truckloads of orange peel and pulp were purposefully unloaded onto a barren pasture in a Costa Rican national park. Today, that area is covered in a lush, vine-laden forest.”

This is the amazing story of an abandoned and almost forgotten experimental restoration and reforestation project that resulted in a real environmental success story. A story that demonstrates the power of waste to ‘resource’ the world and, in this case, the power of agricultural waste to regenerate the rainforest.

This story, told on Princeton Environmental Institute's website, began like this: in 1997, Daniel Janzen and Winnie Hallwachs offered a very interesting deal to Del Oro, an orange juice manufacturer in Costa Rica.

The married couple are ecologists at the University of Pennsylvania and have spent a major part of their careers preserving the rainforest and its biodiversity. At the time, they were working as researchers and consultants in the Guanacaste Conservation Area in northwestern Costa Rica.

12,000 tons of orange peel

Del Oro had just opened a new production facility at the park's northern border. In exchange for donating a piece of wooded land to the Guanacaste Conservation Area, the company was allowed to dump its orange waste, free of charge, onto a barren pasture on the site. The researchers hoped that this nutrient-rich organic matter would feed the soil.

As a result, 1,000 tractor-trailers transported and spread 12,000 tons of orange peel over the area in the Guanacaste Conservation Area.

Unfortunately, shortly afterwards, TicoFrut , a rival company, accused both partners of disfiguring the Guanacaste National Park. The case was brought before the Supreme Court of Costa Rica and TicoFrut won the proceedings. The deposits stopped, and the pasture covered with orange peels was forgotten.

It resurfaced fifteen years later, in 2013, during a discussion between Timothy Treuer, a researcher at Princeton University, and Daniel Janzen. The latter explained that no one had ever made a complete inventory of the site's biodiversity.

During a scientific expedition to Costa Rica, Timothy Treuer decided to visit the site. “It was so completely overgrown with trees and vines that I couldn’t even see the 7-foot-long sign with bright yellow lettering marking the site that was only a few feet from the road.” he said.

Spectacular results

A research team was then formed to try to determine by how much the citrus waste had enriched the soil and influenced the growth of vegetation by comparing samples taken in the area with those collected on another plot on the other side of the road which had not been covered with peel and pulp.

The difference was astounding. Researchers found a 176% increase in biomass above the soil. The fertilized area had richer soil, more tree biomass, more species diversity, and greater canopy closure.

Published in the Restoration Ecology review in August 2017 [], this result “showcases the unique power of agricultural waste to not only regenerate a forest but also to sequester a significant amount of carbon at no cost.”

“Recycling at its best”

For David Wilcove, the study's co-author, it also reveals the importance of cooperation between the private sector and the scientific community, “an awful lot of those problems can be alleviated if the private sector and the environmental community work together.”

He added, “I’m confident we’ll find many more opportunities to use the ‘leftovers’ from industrial food production to bring back tropical forests. That’s recycling at its best.”