The study showed that coffee pulp, a byproduct of the original coffee bean production process, is a great fertilizer that can help barren land quickly recover to grow into dense tropical forests. The finding is a win-win for farmers who need the extra expense of dealing with these byproducts.
Coffee berries are actually cherry-like berries, covered with a skin and pulp. The difference is that cherries are eaten for their skin and pulp, while coffee beans are the inner core of this fruit. The growing industry now widely uses machine processing to remove the outer skin and pulp of the coffee fruit immediately after picking. The industry used to call this part of the material coffee pulp, which is a major by-product of the coffee industry.
Coffee pulp contains some caffeine and tannins, which are toxic and therefore need to be disposed of properly at some cost to the farmer producing the coffee beans.
Researchers from the Swiss Federal Institute of Technology Zurich (ETH Zurich) and the University of Hawaii (UH) collaborated on the experiment in Coto Brus, a beautiful town in southern Costa Rica. Beginning in the 1950s, as the world became dramatically industrialized and urbanized, the native forests here were also rapidly lost to coffee plantations or pastures. By 2014, only 25% of the forest cover was left here.
These tropical plantations can become so barren after years of cultivation that it typically takes decades for them to naturally return to forest.
In 2018, researchers set aside two plots of land here, both 35 meters wide and 40 meters long, for a test to examine how well the land would recover to forest land on its own. About half a meter of coffee pulp was spread on one of the plots, and the other was left unspread as a comparison.
Before spreading the fruit pulp shreds, researchers analyzed samples of the land to record them, and two years later sampled and analyzed the land again and recorded the species of trees in the restored woodland, trunk size, the percentage of tree cover on the ground, and the percentage of tree canopy cover on the ground from the air using a drone.
“The results are so dramatic.” Rebecca Cole, the study’s leader, said, “The land that was covered with coffee pulp has grown into a small forest in just two years, while the other area still grows mostly non-native, exotic weeds.”
The study said that in just two years, 80 percent of the land covered with coffee pulp was covered by a canopy of trees, while only 20 percent of the comparison land was covered by a canopy of trees. Moreover, the height of trees on the former land was four times higher than that of the latter.
The study analysis said that the layer of coffee pulp laid on helped to get rid of the weeds that were previously dominant on the land. These weeds are usually the main obstacle to woodland recovery. By removing them, the seeds of native species that come with the wind or are brought in by animal manure have a better chance of taking root and growing quickly.
Analysis of samples of the land showed that the nutrients carbon, nitrogen and phosphorus in the land covered with coffee pulp were significantly higher than in the other land. This is an important result, because the poor land is in great need of restoring these nutrients.
This experiment shows that agricultural by-products can help speed up the process of rehabilitating poor tropical agricultural land into woodland,” Cole said. Farmers often have to pay extra expenses to dispose of these by-products, and if they can be used to speed up woodland restoration, it’s really a win-win.”
The study also mentions the limitations of using coffee pulp to help restore woodlands, such as the fact that it is best used on gentle terrain so that nutrients are not quickly washed away by rain. Also, plots should be easily accessible for workers to get the pulp material in and spread out.
The study was published March 28 in the journal Ecological Solutions and Evidence.
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