The Life and Times of BSF (Black Soldier Flies)
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Scaling Up BSF Production| Integration of BSF Workstation Elements

by Terry Green on 03/27/17

There are a number of important considerations to take into account in scaling up BSF production in incorporating workstations into a modular designed BR1/BR2 production train concerning farming larvae grown off food scrap and other biodegradable waste (see Modular Farming of Black Soldier Fly (BSF) | Scaling Up - Schematic Overview, Farming BSF on a Commercial Scale | Calculating BSF Larval Outputs, Waste Inputs and Larval Replacement Requirements and Commercial Black Soldier Fly (BSF) Production in 2016 | Where Are We Today?). This blog provides an example of how the essential workstations used in growing larvae off food scrap waste can be efficiently integrated into a 10 MT (wet weight) per year larval producing modular unit in managing waste and larval throughput at a plant facility.

Under optimal conditions the dry weight feed conversion ratio in harvesting BSF larvae off food scrap waste relative to larval yield appears to be in the range of about 0.25 to 0.30 (see BSF Metrics & Yields| Scale Up Production of Black Soldier Flies).  In practical terms this means it takes about 20 tons wet weight food scrap (average moisture content, 80%) to produce 1 ton of prepupae (dry weight).  Larval yield appears moreover to be markedly dependent upon designing a production facility that maximizes the two-dimensional footprint of the bioreactors underscoring the importance of incorporating vertical stacking in the design of bioreactors in accommodating the processing of large quantities of waste required in growing larvae on a large scale (see Scaling Up BSF Production | Theoretical and Practical Effect of BSF Bin Space Surface Area and Food Scrap Load Rate on Larval Yield and Modular Farming of Black Soldier Fly (BSF) | Scaling Up - Schematic Overview ).

Schematic image of integrated BSF workstations
Fig. 1. Outline of waste flow in the BSF Processing Train – Integration of farming workstations (Copyright (c) 2017, Terry Green, All rights reserved).

Fig. 1. illustrates how the varying workstations can be integrated into a processing train in managing the varying tasks needed in achieving a scaled up operation. Incoming waste mixed in combination with bulking agents (leaves, straw, shredded wood chips, etc. as required to impart good drainage to the waste), delivered in trash cans/bins, totes, etc., and larval-seeded waste, first gets mixed together on a flat concrete floor in the Mixing Workstation using a front loader, or forklift, fitted with a shovel attachment.

Four critical tasks must be integrated seamlessly for a plant facility to efficiently produce BSF larvae year round without sacrificing larval output. Failure to coordinate these tasks into the processing train will inevitably lead to a shut down in larval output.

The first and foremost task is to ensure that young larvae are propagated on a continuous basis to ensure that there is a steady supply of larvae available in replacing those harvested from the BR1/BR2 bioreactors.  Operations involved in propagating and sustaining a steady source of young larvae entail management of the Propagation Workstation.

The second task (carried out in coordination with the first) involves mixing incoming waste with larval-infested waste drawn from the larval BR1/BR2 bioreactors, recycling a portion of the mixed waste back through the Propagation Workstation to restock the waste coming from and to be returned to the BR1 Workstation with another generation of larvae, followed up thereafter by transporting waste treated in this manner back through the Mixing Workstation and on to the BR1/BR2 bioreactors. These operations are all coordinated as waste gets passed through the Mixing Workstation positioned centrally between the Propagation and BR1 Workstations.

The third task involves operation of the BR1/BR2 bioreactors which entails growing larvae off the waste and managing the composition of the waste in maintaining optimal growth conditions in the bioreactors. This includes loading and unloading waste from the bioreactors and overseeing collection of larvae self-harvesting free of the bioreactors.

Lastly, the fourth task, which is vital in sustaining larval growth, involves removal of spent waste no longer providing nutrients for the growth of larvae occupying space in the bioreactors. Failure to systematically remove spent waste causes a shut down in larval output because the accumulation of spent waste, unchecked, displaces the quantity of fresh waste that can be added to bioreactors. This task can be carried out by systematically removing a portion of the waste going in and out of the Mixing Workstation by diverting it, for example, to an externally operated composting facility.

Below in bullet format, taking into consideration the characteristics of food scrap waste, is an example of the type of equipment and operating steps one might want to anticipate illustrating the setting up of a modular unit having the capacity to produce ~10 MT (wet weight) prepupae per year:

  • Food Scrap Density ranges from about 500 to about 1000 Kg (for very compact waste) per cubic meter (compacted waste is about the same density as water, ~ 1 Kg/L).
  • Food Waste Requirements (300 Kg/day; ~660 lbs/day) - approximately 100 MT food waste per year (ww) required in operating a BR1 Workstation at full capacity having 40 BR2s (8 columns, each with 5 bins per column stacked atop BR1s).
  • Commercial agricultural bins (40) - heavy duty rectangular plastic agricultural bins with vented walls and floors (see, for example, Tranpak  “Macrobin 14 series” or their equivalent).
  • 121 L (~32 gal.) trash cans (or equivalent) - three trash cans filled just under 2/3rds full per day passed through the Propagation Workstation and held in transit a minimum of about a week in allowing for spontaneous seeding of the waste with larvae and larval eggs. 
  • A forklift having a rechargeable battery for operating in an enclosed facility without adequate ventilation, or a propane powered forklift where ventilation is adequate, to lift and restack BR2s atop BR1s and for mixing operations, or a front loader tractor with forklift adapters mounted on the front shovel substituted in place of the forklift.
  • Forklift front end bin and barrel/trash can front end dumper attachments for carrying out mixing operations in the Mixing Workstation.
  • A heavy duty food waste shredder saw tooth type or less expensive high RPM shearing shredder for the same purpose in preparing waste for larval feedstock – only if a shredder is deemed necessary in processing incoming waste depending upon the physical properties and condition of the incoming waste passing through the plant facility.
  • Bilge or sump pumps and IBC storage tanks –for collection of BSF leachate and pumping of leachate from BR1 drain reservoirs into IBC tanks for transport and shipment to field application sites.
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