The growing concern over heavy metal contamination in Nigerian cocoa farms—particularly from long-term use of copper-based fungicides—has also led to new remediation technologies.

Dr Paul Aikpokpodion developed phosphate rock-based materials designed to immobilize copper contaminant in soil and minimize its uptake by cocoa plants.

The black pod disease is a major limiting factor that affects cocoa production in Nigeria. The disease is caused by the infestation of Phytophthora megarkaya and P. palmivora.

The black pod disease if left uncontrol can lead to a 100% yield loss. For the control of the disease, cocoa farmers in Nigeria and other cocoa producing countries where the disease is prevalent use copper-based fungicides for the control.

Over the years, Nigerian cocoa farmers were used to the application of Bordeaux-mixture which was mainly copper sulphate before its ban.

After the global ban of the fungicide in cocoa disease control, agrochemical manufacturers introduced various copper -based fungicides which were less hazardous to plant and the environment.

Among the copper -based fungicides for the control of black pod disease are Fungoran -OH, Ridomyl gold, Copper Nordox 50WP, Kocide 101 and Kocide 2000 among others.

The application of these copper-based fungicides is done by farmers annually to minimize yield loss at the end of the year.

Consequent to continuous application of fungicides in cocoa plantations, most cocoa farms in Nigeria are contaminated with copper due to the non-biodegradability of copper as a heavy metal.

The accumulation of copper in soil can be a source of abnormal level of copper in cocoa beans exported to Europe, Asia and America.

To reduce the amount of copper accumulated in cocoa within the safe limit set by the European Union, Dr. Paul Aikpokpodion an industrial and environmental chemist at the Cocoa Research Institute of Nigeria designed phosphate rock-based materials ladened with ligands that bind with copper contaminant in soil thereby limiting their transport within the soil as well as plant-soil interface.

“The materials bind with copper contaminants, limiting their mobility in the soil and reducing the risk of heavy metal accumulation in cocoa beans,” he said.

“This will help Nigerian cocoa meet the European Union’s strict residue limits and safeguard export integrity.”