Waste to protein: nutrient cycling through integrated farming

Thesis (MScAgric)--Stellenbosch University, 2021.

ENGLISH ABSTRACT: This study addressed the sustainability of our food system with specific focus on nutrient wastage and the treatment or recycling thereof. Black soldier fly (BSF) farming is a well-known method for treating organic waste to produce protein, fat, and fertilizer. Using BSF to recycle wasted nutrients has been proven effective. The complex problem is that insects are not considered as food in most South African diets. Aquaponics involves the simultaneous cultivation of plants and fish in a recirculating aquaculture system. In this project, the integration of aquaponics and black soldier fly farming was proposed as an instrument to recycle organic waste into food production systems , growing food that are well accepted in the South African market. This project entailed the design, construction, and operation of two identical aquaponics systems and a BSF rearing unit. The control aquaponics unit (termed the two-tier system) received a pelleted BSF diet as input while the integrated BSF and aquaponics unit (termed the three-tier system) received live BSF larvae and a filler feed as input. The BSF larvae were reared on a formulated diet made from raw materials in the feed industry and not organic waste. Both systems were primed for 12 weeks before being operated for a trial period of 31 days. Both system were compared considering the performance of African sharp-tooth catfish (Clarius gariepinus) and the culinary herb, basil (Ocimum basilicum L.). Both systems showed comparable results in terms of fish growth rates, feed conversion as well as plant growth curves and biomass yields. The environmental parameters monitored for both systems were indicative of a stable nitrogen conversion cycle and resilience against abrupt environmental stimuli in the form of power outages and changes in temperature, pH and dissolved oxygen. The integrated black soldier fly and aquaponics system displayed technical feasibility for Nutrient recycling through the integration of BSF farming and aquaponic farming. This farming method proved to be feasible in recycling food waste to food production on a small scale and shows promise for scalability to large scale food waste recycling. The project also showed potential in decentralised community food production systems on the same scale or smaller units.

AFRIKAANSE OPSOMMING: Met hierdie projek is die volhoubaarheid van ons voedselsisteem, met spesifieke fokus op nutrient afval en die behandeling óf herwinning daarvan aangespreek. Venstervlieg (BSF) boerdery is 'n alombekende metode om organiese afval te behandel en proteïene, vet en kunsmis te produseer. Dit is bewys dat die gebruik van BSF vir die herwinning van voedsel afval effektief is, Die ingewikkelde probleem is dat insekte in die meeste Suid - Afrikaanse diëte nie as voedsel beskou word nie. Akwaponika behels die verbouing van plante en vis in 'n hersirkulerende akwakultuurstelsel. In hierdie projek is die integrasie van akwaponika en BSF boerdery gebruik as 'n instrument om organiese afval te herwin en in voedsel produkte, wat aan die Suid Afrikaanse mark bekend is, te omskep. Hierdie projek het die die ontwerp, konstruksie en werking van twee identiese akwaponika stelsels en 'n BSF eenheid behels. Die kontrole-akwaponika-eenheid (wat die tweevlakstelsel genoem word) het 'n verpilde BSF- dieet as insette ontvang, terwyl die geïntegreerde BSF- en akwaponika-eenheid (die drievlakstelsel genoem) lewendige BSF-larwes en 'n vulvoeding as inset ontvang het. Die BSF -larwes is gekweek op 'n geformuleerde dieet wat van roumateriale in die voerbedryf gemaak is en nie van organiese afval nie. Beide stelsels is vir 12 weke in werking gestel voordat dit vir 'n proeftydperk van 31 dae gebruik is. Die tweevlakstelsel en die drievlakstelsel is vergelyk deur die prestasie van Afrika-katvis (Clarius gariepinus) en die kulinêre krui, basiliekruid (Ocimum basilicum L.) in elk te meet. Beide stelsels het vergelykbare resultate getoon in terme van visgroei, voeromsetting sowel as plantgroei kurwes en opbrengste van biomassa. Die omgewingsparameters wat vir beide stelsels gemonitor is, was 'n aanduiding van 'n stabiele stikstofomskakelingsiklus en veerkragtigheid teen skielike omgewings stimuli. Die geïntegreerde venstervlieg- en akwaponika-stelsel toon tegniese haalbaarheid vir die herwinning van voedselafval deur die integrasie van BSF -boerdery en akwaponika. Hierdie boerderystyl was haalbaar om voedselafval op klein skaal na voedselproduksie te herwin en toon belofte vir skaalbaarheid tot grootskaalse herwinning van voedselafval. Die projek het ook belowende resultate getoon vir gedesentraliseerde voedselproduksiestelsels in die gemeenskap op dieselfde skaal of kleiner eenhede.

Masters