Cocoa pod husk wastes derived biochar for overcoming potassium deficiency in organic agriculture

• Published in: International journal of recycling of organic waste in agriculture 2024-10
• Main Authors: Murali Gopal, Elain Apshara S., Sathyaseelan Neenu, Alka Gupta
• Format: Article
• Language: English
• Subjects: Cocoa pod husk biochar; Organic farming; Organic wastes; Potassium nutrition
• ISSN: 2195-3228; 2251-7715
• DOI: 10.57647/ijrowa-tyz5-1967

Purpose: Potassium (K) deficiency is emerging as a significant global agricultural challenge impacting 20% of farming areas and posing a threat to food security. In India, the potassium deficit has aggravated due to a focus on nitrogen and phosphorus application, with the net potassium balance declining from -3.29 million tonnes in 2000–01 to -7.2 million tonnes in 2015–16. Cocoa cultivation in Southern states of India like Kerala, Karnataka, Andhra Pradesh, and Tamil Nadu, produce substantial biomass waste, including cocoa pod husks, which are rich in potassium. Method: This study explores the conversion of cocoa pod husks into biochar as a sustainable potassium source. Cocoa residues, including leaves, pod husks, and bean shells, were sun- and polyhouse-dried before being pyrolyzed in a single-drum charring kiln. The biochar produced from cocoa pod husks was selected for further analysis due to its superior quality, with a conversion efficiency of approximately 40%. Results: The resulting biochar had a potassium content of 10.9%, with 60% of it being water-soluble, and also contained 13% organic carbon along with nitrogen, phosphorus, and micronutrients. Physico-chemical and microbiological analyses revealed the biochar's alkaline pH (10.7) property, low bulk density (0.41 g/cc), and low native microbial activity, with Bacillus spp. being the dominant microbe. An ecotoxicity assay using earthworms indicated no acute toxicity, although earthworms took longer to acclimatize to the cocoa pod husk biochar compared to coconut residue biochar. Conclusion: Thus, cocoa pod husk biochar, with its high potassium content, organic carbon, and non-toxicity to earthworms, offers a sustainable solution for potassium deficiency in soils, particularly in organic agriculture. Research Highlights • Cocoa farmers in India find it difficult to dispose of pod husk wastes generated @ 15-17 tonnes/ha • Recycling this waste via pyrolysis to produce biochar was attempted • Biochar produced from cocoa-pod husk wastes had 10-11% readily available potassium • Cocoa-pod husk biochar can help overcome potassium deficiency in organic agriculture