A waste product turned environmental resource

A novel research study lead by Dr. Rebecca Cole and researchers from ETH-Zurich and the University of Hawai`i have found that by dumping coffee pulp over deforested areas they can accelerate foliage recovery. Opening up further studies into helping restore our natural rainforests.

After spreading 30 dump truck loads of coffee pulp on a 35 × 40m area of degraded land in Costa Rica and marked out a similar sized area without coffee pulp as a control. 

The results were dramatic.” said Dr Rebecca Cole, lead author of the study. “The area treated with a thick layer of coffee pulp turned into a small forest in only two years while the control plot remained dominated by non-native pasture grasses.”

After only two years the coffee pulp treated area had 80% canopy cover compared to 20% in the control area. The canopy in the coffee pulp area was also four times taller than that of the control area.

The addition of the half metre thick layer of coffee pulp eliminated the invasive pasture grasses which dominated the land. These grasses are often a barrier to forest succession and their removal allowed native, pioneer tree species, that arrived as seeds through wind and animal dispersal, to recolonize the area quickly.

The researchers also found that after two years, nutrients including carbon, nitrogen and phosphorous were significantly elevated in the coffee pulp treated area compared to the control. This is a promising finding given former tropical agricultural land is often highly degraded and poor soil quality can delay forest succession for decades.

As a widely available waste product that’s high in nutrients, coffee pulp can be a cost-effective forest restoration strategy. Such strategies will be important if we are to achieve ambitious global objectives to restore large areas of forest, such as those agreed in the 2015 Paris Accords. 

The study was conducted in Coto Brus county in southern Costa Rica on a former coffee farm that is being restored to forest for conservation. In the 1950’s the region underwent rapid deforestation and land conversion to coffee agriculture and pasture with forest cover reduced to 25% by 2014. 

In 2018, the researchers set out two areas of roughly 35 × 40m, spreading coffee pulp into a half meter-thick layer on one area and leaving the other as a control. 

The researchers analyzed soil samples for nutrients immediately prior to the application of the coffee pulp and again two years later. They also recorded the species present, the size of woody stems, percentage of forest ground cover and used drones to record canopy cover.