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What do you think of this?
Hi closetfarmer, - This (from the abstract & not Time's gotcha' journalist): "...crickets fed minimally-processed, municipal-scale food waste and diets composed largely of straw experienced >99% mortality without reaching a harvestable size" ... is not what a cricket really would eat (ie: they are not ruminants with straw degrading digestive tracts).
While this (also from the same abstract & Time's omitted): "...crickets fed ... food waste processed ... via enzymatic digestion ... achieve feed and protein efficiencies similar to that of chickens"... indicates a cricket does not have to be fed on the same cost food as chickens.
Later I'll read the whole "Crickets Are Not a Free Lunch: Protein Capture from Scalable Organic Side-Streams via High-Density Populations of Acheta domesticus"
Meanwhile, in gringo-land my neighbors chickens eat bugs they find in the ground, wander into covered shelters & get a bit of cracked maiz corn; this makes them cheap to raise. The commercial operations have had various serious problems over the decades & several have closed down; in some cases commercial feed costs were a factor.
Now, if you want to do what PLOS describes as "enzymatic digestion" on a small scale this can be done; however, you'd use different technology & micro-organisms than theirs. On the other hand if you think industrial scale is just too imposing bear in mind that fermentation technology is already a massive money making field (ie:
you can do it quite repeatedly once the equipment is set up).
Another aspect to consider is how much water is needed for commercial chicken rearing & processing in comparison to producing the equivalent in cricket protein; of course, I am overlooking the water involved in enzymatic digestion for cricket. Then there is the cost analysis of transportation & storage without spoilage involved getting the respective feedstocks into use; consider that conceivably a chicken farm can't grow all the grain next door & clean it but that enzymatic digestion tanks can be installed in a small area next door to the cricket farm.
Here are 2 examples of what "enzymatic digestion" equipment would be built around: http://www.ebay.com/itm/390709691050?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT ... & ... http://www.ebay.com/itm/141637108053?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT
These look complicated but they are really a simple design; there is a stirrer that comes down from the lid & the lid has a place for a motor to drive the stirrer. Since the enzymes come from specific microbes their "fermenting" creates pressure inside the chamber & so the lid needs to be able to be clamped down tight.
The top piece is not as intimidating as it looks; all those holes are just ports so various monitors can be inserted (ex: thermometer, dissolve oxygen, CO2 meter), places for tubing to cycle water in/out at controlled rate (ie: via peristaltic pump), pump in oxygen or CO2, add stuff, withdraw samples, etc, etc. But, not all kinds of
techniques require all these things & so a lot of used units' tops have design features that you might not need (they can be plugged closed), like ports through the bottom.
Fancy operations connect a computer monitor to track one's variables & even
automatically do specific tasks that use the lid's ports. But this is not required for
all techniques & since we are concerned with bug food a somewhat passive technique would work (ie: batch fermentation, what goes in stays there in fairly
set conditions, is accomplished in a standardized time span, gets taken out & then another batch goes in).
Since the bug food substrate is, in this case, waste plant matter this doesn't require
such fancy equipment - the glass just makes things inside visible for monitoring; you can retro-fit anything that can withstand expanding internal gas which supports a tight fitting lid. As for the lid your biggest challenge is adapting the stirrer drive shaft so that a seal is pretty well assured; a 120 rpm motor is usually a good rate to turn the stirrer at & this doesn't even have to be continuous in some tactics (so could run this off a 12 volt or 24 volt re-chargeable battery bank).
There are different stirrer designs, but the linked pictures give a good idea that these do not operate with just the bottom being stirred; baffles along the inner sides also create the best conditions. Grinding/homogenizing the waste plant matter before putting it into the apparatus is obviously going to work best; when you take the end-product out it would need some low tech filtering/drying.
There are commercial suppliers of specific strains of microbes that have specialized enzymes for different substrates. Since we are not concerned with pharmaceutical grade end-products if one uses some basic quality control it should be possible to maintain cultures for successive batches; the genetic drift is not likely to matter.
Just be aware that scaling up is not always straight-forward; but this is a nuance that can be resolved. A decent welder can take steel drums, re-inforced thick plywood with a metal plate for a top, afix some bolt down toggles, create a rod with staggered side paddles, drill through ports & make a few internal baffles - it won't clean up as easily as a laboratory grade unit due to materials' irregularity.
These are not exactly the same beer & alcohol fermentation vessels, although conceivably one of those could be adapted. Here is a monster unit & it shows a massive hatch for a top plate while placing the through ports off to the side (instead of through the top plate); a welder could also follow this design - http://www.ebay.com/itm/1500-Gallon-5000-Liter-Sanitary-Reactor-Vessel-Fermenter-Bioreactor-Tank-in-NJ-/200717303845?hash=item2ebbaf0025
A schematic biological reactor picture - http://cellator.com/db1-main/internet/foto/thm000001_1182.jpg
Labeled pictures: - http://1.bp.blogspot.com/-jReoY1VxrRU/UNFsYSt8JhI/AAAAAAAAAC0/bQiI8q1aJg8/s1600/Bioreactor+parts.jpg ... http://www.smccd.edu/accounts/case/indmic/images/biorxt.gif ... http://www.mrcorfe.com/KS4/Edexcel/Biology/B2-1-LivingCells/images/Fermenter.gif
A twist on top for a vessel with sealing gasket can have holes drilled for whatever ports you require (ex: stirrer, thermometer); the gadgets hanging on tubes in this 1st picture are just ways to keep out contaminants & syringe in/out things (ex: pH adjusters or when filter disk removed suck out samples) - this could be a recycled bucket with a gasketed lid (ex: 6 gallon volume buckets swimming pool chlorine tablets come in) --- http://img.directindustry.es/images_di/photo-g/biorreactor-multiplaza-22548-8358220.jpg ... & this simpler way of sealing off ports could be adapted (vessels don't need to be glass): https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQHbft4dF2H7mghCa9q2iaqTASWdM2urkBrL3ZRiU7L_w-xqCzEqg ... & this might help envision a basic assembly (vessel & ports can be your design) - http://www.bio-link.org/home/content/lab-equipment/spinner-bottle-bioreactor
Operating several smaller units avoids big bathes ( individual computerized operating systems are not needed for our purposes) - http://www.cytovance.com/portals/0/Images/SubPageHeaders/Process_Development_Cytovance_180h.jpg ... http://broadleyjames.com/images-slideshow/bioreactors/bioreactors3.jpg ... https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcS5A4qUEN7uhRSvS0ENFZdrFUpXms_8ViNUPfjlOhyZFwjlCwHoZA ... http://www.sciencephoto.com/image/211833/large/G2550030-Experimental_AIDS_vaccine_process_bioreactors-SPL.jpg
When you scale up consider: total volume of the vessel, diameter of the vessel, working volume, level of the liquid (called broth), diameter (& height) of the stirrer, number of stirrers (1-3 common), position of each stirrer from the bottom of the vessel, number of baffles in the vessel, power that can move the stirrer(s), etc.
Some nice dynamic conceptualization pictures in Figures 1-10 (don't get hung up on the technical formulas, all kinds of products have different levels of complexity) ... http://2010.igem.org/Team:UCL_London/Fermenter_Mechanics