The following was stolen from:
http://www.esrla.com/brazil/frame.htm
Suppose we were asked to imagine the best possible
way to dispose of putrescent waste, to imagine a
totally natural process that would effect an
enormous reduction in weight and volume within a
matter of just a few hours. This process should
require no energy, no electricity, no chemicals, not
even water. It should be totally self-contained and
not emit a drop of effluent, and aside from a small
Simple & Easy to Operate
amount of carbon dioxide, it should not produce
methane or any other greenhouse gases. The unit
housing this process should operate with the
simplicity of a garbage bin. It should have no
moving parts, and it should require very little
servicing and maintenance, very little expertise or
experience to operate. It should not emit offensive
odors, and it should drive away houseflies and
Unlimited Quantities
other filth-bearing flies. The process should not only
generate its own heat, but it should also regulate
heat to assure maximal bioconversion throughout
the winter months. This simple and inexpensive unit
could be situated out-of-doors in a shaded area, and
any number of units could be coupled together to
uhandle unlimited quantities of waste.
On-site Recycling of Food Waste
Since food waste would be rapidly reduced
and recycled at its point of origin, it would eliminate
altogether the collection, transport and land-filling
of food waste. This bioconversion process, however,
should not demand the introduction of anything
foreign or exotic.
No Transmission of Disease
It should be powered by a creature commonly found
throughout the world, and even though this
creature may have lived alongside humans for
thousands of years, it should not be associated in
any way with the transmission of disease. In view of
the wide variability of putrescent waste presented to
it, this benign creature should possess one of the
most robust digestive systems within nature.
Ideal Bioconversion Agent
It must have the ability to thrive in the presence of
salts, alcohols, ammonia and a variety of food
toxins. In addition to food waste, it should also be
able to process swine, human and poultry waste.
Upon reaching maturity, it should be rigidly
regimented by evolution to migrate out of the unit
and into a collection bucket without any human or
mechanical intervention.
Reintegration of Nutrients
This self-harvesting grub should represent a
bundle of nutrients that should rival in
commercial value the finest fish meal. Why not
boldly insist upon the reintegration into the feed
chain of most of the nutrients contained within
uputrescent waste?
Ideal to Real
Is the bioconversion process described above
nothing but a fanciful leap of the imagination?
Hopefully as we proceed, it will become clear that
this process does, indeed, exist, and that it
represents the cleanest, most efficient, and most
economical way to recycle most types of putrescent
waste.
The Black Soldier Fly
The agent chosen for this bioconversion process is
the larva of the black soldier fly (SF) Hermetia
illucens, a tropical fly indigenous to the whole of the
Americas, from the southern tip of Argentina to
Boston and Seattle. During World War II, the black
soldier fly spread into Europe, India, Asia and even
uAustralia.
The Adult Black Soldier Fly
Flies & Bacteria
Many of us panic when we see the word “fly,” just
as we often panic when we see the word “bacteria.”
Yes, there are noxious, filth-carrying flies that
transmit deadly, disease-bearing bacteria. But not all
bacteria and not all flies are harmful to humans.
Without bacteria and flies, life as we know it on
earth could not exist. Both play an essential role in
the recycling of nutrients within the food chain.
Intense SF Competition
Just as benign bacteria compete with harmful
bacteria and block their proliferation, so too, the
soldier fly aggressively competes with filth-
bearing flies and very effectively blocks their
proliferation. Just as certain Calliphorides are used
to clean out necrotic human tissue, SF larvae can
be used to dispose of the large quantities of
put rescent waste generated through human activity.
A Beneficial Fly
Unlike many other flies, SF adults do not go into
uhouses, they do not have functional mouth parts,
they do not eat waste, they do not regurgitate on
human food, and therefore, they are not associated
in any way with the transmission of disease. Adults
do not bite, bother or pester humans in any way.
Even though their larvae have been known to
survive inside the human gut if swallowed whole,
Enteric Myiasis
this only happens under utterly extreme and bizarre
conditions and poses no real danger to humans. True
enteric myiasis does not exist in man through the
agency of SF larvae or any other fly larvae,
whereas pseudomyiasis can occur, even through the
agency of ordinary houseflies. SF adults
congregate near a secluded bush or tree in order to
find and select a mate. After mating, the females
search for a suitable place to lay their eggs.
Life Cycle
A female produces about 900 eggs in her short life
of 5 to 8 days. Housefly adults, by contrast, live up
to 30 days, and during this long period, they must
eat, and in so doing, they are actively engaged in the
spread of disease. SF eggs are relatively slow in
hatching: from 102 to 105 hours. The newly hatched
larvae then crawl or fall onto the waste and eat it
with amazing speed.
Life Cycle
Under ideal conditions, it takes about two weeks for
the larvae to reach maturity. If the temperature is not
right, or if there is not enough food, this period of
two weeks may extend to six months. The ability of
the SF larva to extend its life cycle under conditions
of stress is a very important reason why it was
selected for this putrescent waste disposal process.
SF larvae pass through five stages or instars. Upon
Tough & Robust
reaching maturity, they are about 25mm in length,
6mm in diameter, and they weigh about 0.2 grams.
These larvae are extremely tough and robust. They
can survive under conditions of extreme oxygen
deprivation. It takes, for example, approximately
two hours for them to die when submerged in
rubbing alcohol. They can be subjected to several
1000 g’s of centrifugation without harming them in
any way.
Texas Experiment
In an experiment conducted in Texas over a period of
one year, ESR LLC determined that SF larvae can
digest over 15 kilograms per day of restaurant food
waste per square meter of feeding surface area, or
roughly 3 lbs per square foot per day. A 95%
reduction in the weight and volume of this waste was
also noted. This means that for every 100 lbs of
restaurant food waste deposited into a unit, only 5 lbs
of a black, friable residue remain!
Nothing More Powerful
Huge Mass of Larvae
Two- to Four-Inch Layer
Over 100,000 active larvae can be found in a typical
waste disposal unit, and in contrast to red worms,
these larvae have the ability to eat and digest just
about any type of putrescent waste, including meat
and dairy products. On the surface of the disposal
unit, we typically see a 2- to 4-inch layer of actively
feeding larvae in all stages of growth. The moment
waste is deposited into the unit, the larvae begin
Powerful Enzymes
to secrete powerful digestive enzymes into the waste
long before it begins to rot and smell. Since
thermophilic and anaerobic bacteria play no part in
this process, these tiny creatures are able to conserve
and recycle most of the nutrients and energy within
the waste. While actively feeding, the larvae secrete
an info-chemical that permits them to communicate
with other species of flies.
Synomone
This synomone allows them to tell other flies that it
makes little sense to lay their eggs within an area full
of actively feeding SF larvae. This interspecies
communication is very effective. In the vicinity of
the disposal unit, we note the near absence of
houseflies and all other flies that are a pest to
humans.
An Ideal Pupation Site
Upon reaching maturity, SF larvae change color
from beige to black, their mouth parts transform into
a digger, they empty their guts of waste, and
they set out in search of an ideal pupation site. SF
larvae will crawl over 100 feet in search of an ideal
pupation site. An ideal pupation site consists of a
dark, dry area providing refuge or cover for the
Exiting the Disposal Unit
mature prepupal larvae. SF larvae are negatively
phototactic (afraid of light), and therefore most of
their migratory activity takes place at night. Their
migration initially appears to be a random search for
a way out of the waste. If a ramp of an upward
inclination lies at the edge of the waste, they will
make every effort to negotiate this ramp. If this ramp
has an angle less than 40 degrees, the larvae will
Steep Angle
have no problem exiting the unit. Such a steep angle
makes it difficult for the larvae to carry along any
adhering residue, and it also serves as a barrier
for the larvae of most other species of fly. Housefly
larvae generally are not able to negotiate a dry ramp
of a 20-degree angle, and if they cannot get out of
the disposal area, they cannot pupate, and if they
cannot pupate, they cannot become adults and
A Fly Trap Set by a Fly
reproduce. The SF waste disposal unit mounted
with steep ramps serves as a very effective sink or
trap for the larvae of just about every species of fly
that ignores the chemical warning to stay away from
the unit. Once trapped within the unit, these
uninvited larvae and pupae constitute one more item
of food for the hungry SF larvae.
Self-Harvesting
At the summit of the ramp, an exit hole is provided,
and this hole discharges into a collection bucket. SF
larvae are totally self-harvesting. They abandon the
waste only when they have reached their final mature
prepupal stage, and they crawl out of the waste and
into a bucket without any mechanical or human
intervention.
Plastic and Concrete
ESR LLC will soon begin the manufacture of
soldier fly bioconversion in both plastic and
pre-cast concrete. These units resemble garbage
bins, but these bins (US patent 6,780,637) are
somewhat special in that they possess evacuation
ramps that permit the larvae to self-harvest into a
bucket. Ramps begin at the bottom of the unit and
spiral up to the top. The next slide shows the path
that the larvae take in exiting the unit
Interior Top View
The Larvae Climb Both Ramps
Side View
And Fall into a Bucket
Small Spiral Ramps
The spiral ramps need not be wider than about one
inch. Consequently they occupy little space and
incur little loss in the holding capacity of the unit.
The ramps are created by means of a fold in the
wall of the container. In this way, there is no
underside of the ramp within the container where
migrating larvae might uselessly congregate.
Right & Left Ramps
The round shape of the unit greatly assists the
mature larvae in exiting the unit. As they randomly
orient toward the periphery of the waste, they
encounter the rounded wall of the container, at
which they may turn either right or left. If they turn
right, they eventually come to the base of the right
ramp, and if they turn left, they eventually come to
the base of the left ramp.
High Crawl-off Efficiency
Since the total distance that the larvae must travel
in exiting a unit is very small, the efficiency of
larval crawl-off is fully optimized. Let us look at
some of the main features of the 2-ft unit:
Small Swivel Lid for Waste Input[br]Large Lid for Servicing[br]Indented Handle[br]Ramp: a Fold in the Wall[br]Collection Bucket[br]Bulkhead Hose Fitting[br]Flexible Hose
Underside of Lid
Lip to Prevent Unwanted Crawl-off
Underside Showing Vent & Access Holes
Capacity
This 2-foot unit has an average feeding surface
area of 0.34 M2. At a disposal efficiency of 15 kgs/
m2/day, it can handle over 5 kgs of food waste per
day. It can hold or contain over 144 liters of larval
residue, and with a reduction in weight and volume
of 95%, it must be emptied after receiving a total
of 2.89 m3 of food waste.
Frequency of Clean-Out
This unit serving a family of four people would
have to be cleaned out once every 8 years.
With this larval bioconversion process, the costly
transport of food waste to landfill is completely
eliminated.
Pre-cast Concrete
The most inexpensive way to manufacture
soldier fly bioconversion units is by means of
pre-cast concrete. But a pre-cast unit molded as a
single part will be difficult to handle and
transport. However, if molded in three vertical
sections of 120 degrees, these sections are easy to
handle, and they can be stacked against one
another to reduce transport volume. Another
advantage of molding the unit in three sections: no
metal reinforcement of the concrete is required.
Since the three sections are held together by three
nylon straps in much the same way that an oak
barrel is held together by bands of steel, stress on
the unit is relieved at the points of intersection of
the three sections. All that is needed for the
fabrication of the unit is a dollar or two of cement,
and recycled materials such as stone, brick or
broken glass can serve as aggregate or filler.
To reduce the weight of pre-cast concrete, a
lightweight aggregate such as perlite and
vermiculite can be used. If this results in a
reduction in strength, a small quantity of polyvinyl
alcohol fibers (0.5 % by volume) can be added.
The construction of bioconversion units could
take on many of aesthetic qualities of
Hypertufa: lightweight, artificial stone containers.
See
http://www.backyardgardener.com/tufa.html
The following slides show how the parts of a
2-foot bioconversion unit are assembled:
Pre-cast Concrete
No Bottom
Note that the unit has no bottom. The unit can
be situated above a bed of sand that would serve
as a partial filter, and any nutrients that escape this
filter could be absorbed by the roots of plants
situated around the perimeter of the unit. In this
way any free liquids liberated by the larvae in
the digestion of the waste do not necessitate
the introduction of bulking materials. This greatly
simplifies the operation of the unit.
A Simple Lid
If left out in the open, the unit must have a lid to
prevent rainwater from coming in. A lid
could consist of nothing but a sheet of plastic or
plywood. The fasteners that hold down the metal
strips at the top of the unit create sufficient space
in between the unit and the lid to allow soldier
fly access into the unit.
Exit Pipe
Less Than $10
Our goal is to sell a unit
capable of disposing of all the putrescent waste
from a single household for less than $10 US
dollars. Larger units could be easily constructed
in the same simple manner as indicated above by
changing the angle from 120 to 60 degrees, and
by increasing the number of ramps from two to
four.
Bioconversion
What percentage of fresh food waste bio-converts
into fresh prepupae? Over a period of one year,
ESR LLC noted that roughly 20% by weight of the
fresh food waste converted into fresh larvae. This
food waste had an average dry matter content of
37%, and the prepupae had an average dry matter
content of 44%. On a dry matter basis, the
bioconversion of food waste situates at almost 24%
100 kg Food Waste per Day
The following flow diagram is based upon an input
of 100 kg of food waste per day. Less than three 6-
foot bioconversion units can handle this input.
Flow Diagram
Analysis of Dried Soldier Fly Prepupae
42.1% crude protein[br]
34.8% ether extract (lipids)[br]
7.0% crude fiber[br]
7.9% moisture[br]
1.4% nitrogen free extract (NFE)[br]
14.6% ash[br]
5.0% calcium[br]
1.5% phosphorus
SF Fed to Catfish
Studies were conducted at the Coastal Plain
Experiment Station in Tifton, Georgia, to examine the
suitability of SF prepupae as a feed source for
channel catfish and tilapia. The tests concluded that
soldier fly larvae should be considered a promising
source of animal protein in fish production. Taste tests
were also conducted, and the results of these tests
indicated that fish fed SF larvae are acceptable
Menhaden Fish Meal
to the consumer. About half of SF fresh weight
translates into a dry meal or pellet, and two nutrition
studies done under the supervision of Dr. Craig
Sheppard suggest that this dry matter has roughly the
same value as Menhaden fish meal valued at over
$500 US dollars per ton. Live SF prepupae have
been successfully fed to bull frogs, tropical fish,
reptiles, snakes and many other creatures that have a
Living Food
strong preference for living food. Here the value of
fresh SF larvae ranges from $4 to $20 /lbs, or
$8,000 to $40,000 per ton. If a unit is installed at a
residence where the weekly or bi-monthly
collection of larvae might be somewhat
expensive, the larvae can be placed outdoors in a
shallow plastic pan where birds will readily feast
upon them. Chickens are especially fond of live
SF larvae
As Temperatures Drop
SF larvae have an amazing ability to dispose of
putrescent waste. But as the temperature drops
below 21˚C, their ability to digest waste
progressively grinds to a halt, and if they should
freeze, they die. This tropical fly larva needs to be
sustained at temperatures above 30˚C if it is to
continue to digest putrescent waste at the standard
rate of roughly 15 kgs/m2 of unit surface per day.
A Winter Strategy
To bring bioconversion units indoors during
winter would be costly, and to equip them with
heating coils is not necessary. The strategy
proposed here involves nothing more than placing
a styrofoam sheet on top of the larval residue to
retain the heat generated by larval movement. If
this heat is not allowed to escape, the temperature
on the surface of the residue easily exceeds 35˚C.
Graphs
The following graphs plots daily temperature
readings both outside the unit and underneath the
sheet of styrofoam. Note that outside temperatures
may fluctuate dramatically, but the temperature
underneath the styrofoam sheet remains relatively
constant. The difference in temperature between
inside and outside the unit can exceed at times
u82˚F or 45˚ C.
Jan 14, 2003 Washington La[br]
January 15, 2003[br]
January 16, 22003[br]
Larvae at Minus 1˚ C
Larvae at Minus 1˚ C
During summer, the conversion rate of fresh food
waste into fresh larvae runs as high as 20%, but
during winter, this conversion drops to less than
5%, in spite of the fact that the larvae digest
roughly the same daily quantity of food waste per
unit surface area. Under ideal summer conditions,
it takes about two weeks for newly hatched larvae
to reach their mature prepupal form,
Far Easier Than Imagined
but during the cold of fall and winter, this two-
week period may extend to six months. If SF
larvae are able to generate their own heat
throughout winter and if they are able to extend
their life cycle until more favorable conditions
return in spring, then the management of SF
larvae becomes far easier than anyone had
previously imagined.
Further Research
If disposal units are well insulated, then SF
technology could be introduced to some of the
coldest regions of our planet. If so, the supply of
eggs to such extreme areas will become an
important technical issue, and all aspects of larval
maturation must be researched in a definitive and
conclusive manner.
Heat of Summer
During the hot summer months, overcrowding can
easily occur, and this overcrowding gives rise to
relatively high temperatures within the unit. In
order to cool down, some actively feeding larvae
are forced to exit the unit. This migration continues
until the density of larvae and temperature within
the unit drop to an acceptable level.
No Over-heating in Winter
But during the winter months, larvae can thrive in
very large numbers without overheating, and as the
mass of larvae increases in winter, so too, the
amount of waste consumed within a given unit.
Paradoxically it would appear that this
bioconversion unit functions far better in winter
than in summer.
Conclusion
In our search for an ideal bioconversion unit for
putrescent waste, we do not have to go far to find
what we are looking for. Nature freely gives us a
voracious grub that is by far the pre-eminent
recycler of the fresh putrescent waste generated by
human activity. All that this fascinating creature
demands of us is an appropriate apparatus and
environment to do its job.
The Best that Nature
Has to Offer
uIf we do not take our cue from the best that nature
uhas to offer us, when will we ever learn?
Backyard Aquaponics
