A by-product of the coffee production process has the potential to speed up restoration of former areas of tropical forest, degraded by deforestation and land conversion.
New research has demonstrated the benefits of coffee pulp — also known as ‘husk’ — in making speedy and significant improvements to the condition of the soil on these lands, which can otherwise take decades to recover to a standard suitable for growing trees.
The promising results — details of which were published in Ecological Solutions and Evidence — are great news for coffee growers and foresters alike. By utilising a resource that’s produced in such large quantities and was previously considered a waste product, the technique offers environmental advantages and aligns with the principles of a circular economy.
The research was conducted on degraded land in Costa Rica by a team from ETH Zurich and the University of Hawaii. They spread a layer of husk half-a-metre deep, across an area measuring 35 x 40 metres. A similarly sized plot was left untreated for use as a control.
When tested, the treated soil was found to contain heightened levels of carbon, nitrogen and phosphorus, all known to support plant growth. According to the researchers, the addition of coffee pulp had a dramatic impact on trees.
“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,” said lead author, Dr Rebecca Cole.
Pasture grasses are a known impediment to the regeneration of forests in tropical areas and, together with the elevated nutrient levels, their suppression in the husk-treated plot facilitated the growth of a 60 per cent greater canopy cover than the control, with trees four times the height.
“This case study suggests that agricultural by-products can be used to speed up forest recovery on degraded tropical lands,” said Cole.
The researchers noted that while the study represented a good starting point, ongoing monitoring across a number of sites would be required to understand the long-term impacts of coffee pulp treatment on soil and vegetation. They also indicated a keenness for more by-products to be examined for similar purposes.
“This concept could be tested with other types of agricultural non-market products like orange husks. We hope our study is a jumping off point for other researchers and industries to take a look at how they might make their production more efficient,” concluded Cole.
