Innovations in market crop waste compost production: Use of black soldier fly larvae and biochar

Authors

• Asiwome Mensah Akumah ¹
• Eric Kwesi Nartey * ²
• Godfred K. Ofosu-Budu ³
• Ebenezer A Ewusie ³
• Benjamin K. Offei ⁴
• Noah Adamtey ⁴

1. Department of Agro Enterprise Development, Ho Technical University, P.O. Box HP 217, Ho, Ghana
2. Department of Soil Science, University of Ghana, P.O. Box LG 245, Legon Accra, Ghana
3. Biotechnology and Nuclear Agriculture Research Institute, Ghana Atomic Energy Commission, P.O. Box LG 80, Legon, Accra, Ghana
4. Research Institute of Organic Agriculture (FiBL), Switzerland

Abstract

Purpose Compost production technology and use are known among Ghanaians farmers. However, the long composting period averaging three months has had adverse effect on adoption. The black soldier fly (Hermetia illucens) larvae (BSFL) feed voraciously and breaks down organic wastes fast. Addition of rice husk biochar (RHB) neutralises acidity and aerates the compost. Combined application of BSFL and RHB to feedstocks could therefore reduce composting period and improve compost quality.
Method Two studies were conducted with market crop waste (MCW) as feedstock. Firstly, feedstocks at two particle sizes (x < 5 mm and 5 mm < x >10 mm), with and without BSFL were evaluated to determine degradability, chemical content of the degraded residue and to select appropriate feedstock size ideal for composting. Secondly, the selected feedstocks size of between 5 mm and 10 mm were inoculated with or without BSFL and RHB of 0%, 5% 10% and 15% added. Composting trials were conducted in barrels inclined at 30^o to facilitate drainage. Physicochemical and biological parameters of feedstock were monitored until maturity.
Results Degradability of MCW by BSFL was feedstock specific rather than feedstock size. Inoculation of BSFL and biochar addition reduced composting period from 76 to 45 days. Biochar addition at 15% increased P availability to 1882 mg kg^-1 but reduced total N to 10.5 g kg^-1. E coli levels decreased in the BSFL-biochar composts to acceptable limits.
Conclusion Composting MCW with BSFL and biochar reduced composting period and improved compost quality.

Highlights

• Co-composting with black soldier fly larvae and 15% biochar matured in 45 days.
• Co-composting with 10% and 15% biochar enhanced P and K concentrations.
• Black soldier fly larvae degradation is feedstock specific and does not depend on feedstock size.
• Black soldier fly larvae reduced E coli levelsin the matured compost. 

• The use of black soldier fly larvae and biochar enhanced compost quality.

Keywords

• Co-composting
• Feedstock
• Inoculation
• Degradation
• Organic waste