Heat Redistribution System for Enhanced Composting


 
 
 
 



 
 
 


Composting Bioreactors 



 
 
 
 
 
 
 
 
 
 
 
 
 
 



 Design
III
Report
 Winter
2011


Jamaleddine,
Eyad

[260282587]


Rainville,
Cloé









[260282662]



 JAMALEDDINE
&
RAINVILLE
2011
 






 2


ABSTRACT
 


Considering
 the
 present
 push
 towards
 greener
 industrial
 and
 residential
 activities,
 composting
 is
 once
 again
 a
 hot
 topic
 amongst
 Ecological
 Engineers.
 Uniform
 composting
 conditions
 are
 necessary
 to
 ensure
 the
 destruction
 of
 pathogens
 and
 maintain
 the
 whole
 system
 at
 the
 same
 composting
 stage,
 so
 it
 is
 essential
 to
 maintain
 a
 homogeneous
 temperature
throughout
the
compost.
In
the
quest
to
accomplish
the
latter,
an
in‐vessel
heat
 redistribution
system
was
constructed
and
tested.
The
system
requires
no
external
inputs
 of
 energy,
 but
 exploits
 the
 principles
 of
 conductive
 and
 convective
 heat
 exchange.
 Once
 composting
 gets
 underway
 and
 temperature
 differentials
 arise
 within
 the
 compost
 bed,
 changes
 in
 buoyancy
 cause
 water
 to
 flow
 through
 a
 closed
 coil
 of
 copper
 tubing,
 redistributing
 the
 core
 heat
 throughout
 the
 medium.
 Heat
 is
 also
 conducted
 along
 the
 copper
 tubing.
 In
 the
 past,
 a
 controlled
 experiment
 was
 conducted
 to
 test
 the
 design.
 A
 statistical
analysis
of
the
experimental
results
demonstrates
that
the
vessels
fitted
with
the
 heat
 redistribution
 system
 exhibit
 lower
 temperature
 gradients
 within
 the
 compost
 bed
 than
in
control
vessels
without
the
system.
The
present
will
deal
with
an
air
redistribution
 system
to
be
fitted
to
the
aforementioned
design.
The
latter
would
permit
warm
air
exiting
 from
the
top
four
inch
whole
to
be
cooled
and
re‐circulated
to
the
bottom
four‐inch
whole
of
 the
 barrel.
 
 The
 overall
 objective
 is
 essential
 to
 reduce
 heat
 losses
 while
 maintained
 the
 replenishing
of
the
oxygen
supply
throughout
the
composting
media.





Introduction





Compost
is
essentially
the
decaying
of
organic
matter.
Primarily,
a
mesophilic
phase
 occurs,
followed
by
a
thermophilic
phase.
For
centuries
man
has
been
utilizing
the
 latter
 process
 to
 increase
 soil
 fertility,
 reduce
 organic
 ordure
 volumes
 and
 treat
 contaminated
 soils.
 Composting
 is
 a
 practice
 gaining
 popularity
 amongst
 the
 agricultural
 community,
 the
 engineering
 realm
 and,
 on
 a
 more
 general
 scale,
 even
 with
the
average
individual.
Essentially,
as
more
applications
involve
utilizing
this
 ancient
 technique,
 one
 must
 account
 for
 the
 numerous
 limitations
 that
 can
 be
 encountered
 when
 composting.
 Of
 the
 latter,
 the
 inability
 to
 ensure
 that
 the
 composting
media
is
fully
cured
after
a
certain
period
or
ensuring
that
the
entirety
 of
 the
 media
 has
 attained
 the
 crucial
 thermophilic
 phase,
 where
 pathogenic
 organisms
 are
 destroyed,
 are
 limiting
 factors
 when
 considering
 composting
 as
 a
 means
 to
 an
 end.
 More
 so,
 the
 production
 of
 volatile
 fatty
 acids
 from
 microorganisms
 is
 the
 source
 of
 unpleasant
 odors
 that
 can
 deter
 individuals
 from
 setting
up
a
composting
bin.
The
aforementioned
limiting
factors
are
due
to
the
non‐

homogenous
 nature
 of
 compost
 and
 the
 presence
 of
 anaerobic
 digestion
 within
 pockets
 of
 the
 compost
 media.
 In
 the
 past,
 a
 heat
 redistribution
 system
 was
 designed
in
the
quest
to
redistribute
the
core
temperature
of
the
composting
media
 uniformly
throughout
the
composting
vessel,
without
any
external
inputs
of
energy.


To
 do
 so,
 the
 heat
 produced
 by
 the
 activated
 microorganisms
 was
 uniformly
 distributed
by
a
watertight
system
consisting
of
copper
and
plastic
tubing
connected
 to
a
heater
core
placed
at
the
center
of
the
composting
mixture.

Next
we
designed
 the
above
mentioned
heat
redistribution
system
and
tested
it
using
six
two
hundred
 liter
polyethylene
barrels.
The
latter
was
done
by
fitting
the
barrels
with
a
four‐inch
 hole
at
the
top
and
bottom
and
a
mesh
grid
at
8
inches
from
the
bottom
to
hold
the
 0.15m³
of
compost.
A
mixture
of
dog
food
and
wood
chips
was
utilized
due
to
their
 low
 cost
 and
 availability.
 To
 insure
 the
 statistical
 validity
 of
 the
 results,
 six
 composting
vessels
were
built,
three
controls
and
three
barrels
fitted
with
the
heat
 redistribution
system;
a
statistical
analysis
was
then
conducted
to
determine
if
we



 JAMALEDDINE
&
RAINVILLE
2011
 






 4


had
 obtained
 valid
 results.
 The
 objective
 was
 to
 test
 the
 effectiveness
 of
 the
 designed
system
to
transfer
heat
throughout
the
compost
media
and
permit
uniform
 composting
 throughout
 the
 latter,
 therefore
 a
 fully
 cured
 final
 product.
 The
 main
 constraint
within
the
design
of
the
heat
redistribution
system
was
the
fact
that
no
 external
 inputs
 of
 energy
 were
 to
 be
 added;
 the
 system
 was
 to
 be
 self‐sufficient.



Results
 obtained
 in
 the
 past
 suggested
 to
 a
 99.5%
 confidence
 coefficient
 that
 the
 heat
 redistribution
 system
 was
 meeting
 it’s
 objective
 of
 distributing
 the
 heat
 uniformly
throughout
the
barrel.
We
were
also
able
to
suggest
that
the
system
had
 the
potential
of
accelerating
the
composting
phase
and
producing
a
cured
product
 quicker
 than
 the
 barrels
 not
 fitted
 with
 the
 heat
 redistribution
 system.
 We
 did
 however
notice
that
a
significant
amount
of
heat
was
lost
from
the
four
inch
whole
 at
the
top
of
the
polyethylene
container.
These
wholes,
one
at
the
top
and
bottom
 were
put
in
place
to
insure
that
the
air
would
circulate
throughout
the
composting
 bed,
 favoring
 aerobic
 bacterial
 growth
 and
 reducing
 the
 production
 of
 odorous
 gasses.
Therefore,
in
a
quest
to
reduce
heat
loss
and
favor
higher
temperatures
and
 a
 prolonged
 thermophilic
 phase
 we
 have
 gone
 about
 designing
 an
 air
 exchange
 system.
 This
 system
 (AES)
 should
 be
 able
 to
 permit
 oxygen
 to
 be
 replenished
 throughout
 the
 composting
 media
 while
 minimizing
 losses
 through
 the
 four‐inch
 wholes.

Sketches
of
the
heat
redistribution
system
(HRS)
and
the
air
redistribution
 system
can
be
found
in
Appendix
B,
Figure
12,
and
Appendix
C,
Figure
13.


Design
of
the
HRS
System
 


FUNCTION
 


The
heat
redistribution
system
utilizes
the
heat
produced,
under
the
form
of
 energy
 from
 microorganisms,
 and
 distributes
 it
 throughout
 the
 composting
 media
 permitting
temperature
gradients
to
be
lowered
and
the
compost
to
be
at
the
same
 composting
phase
throughout
the
process.
Essentially,
as
the
heater
core
placed
at
 the
center
of
the
barrel
is
heated
by
the
microbial
activity,
the
density
of
the
water
 within
the
latter
drops.
The
density
gradient
of
the
water
within
the
heater
core
and
 copper
tubing
causes
the
water
to
flow
from
the
heater
core
to
the
plastic
piping
and
 into
the
copper
tubing
throughout
the
compost
heap.

This
process
is
called
thermal
 driving.

The
difference
between
the
forces
of
gravity
exerted
on
the
two
volumes
 will
 cause
 the
 warmer
 fluid
 to
 rise
 and
 the
 colder
 fluid
 to
 sink.
 
 The
 continuous
 warming
of
the
barrel
is
based
on
this
principle.

As
the
microorganisms
within
the
 compost
 bin
 begin
 to
 digest
 the
 nutrients,
 heat
 will
 be
 dissipated
 and
 once
 it
 has
 elevated
 the
 water’s
 temperature
 to
 the
 proper
 level,
 the
 warm
 water
 will
 slowly
 rise
 as
 the
 cold
 water
 spirals
 down
 the
 copper
 tubing
 towards
 the
 bottom
 of
 the
 barrel.

When
the
aforementioned
occurs,
the
heat
from
the
center
of
the
barrel
is
 evenly
distributed
throughout
the
composting
mixture
due
to
the
high
conductivity
 of
 the
 copper
 tubing,
 without
 external
 inputs
 of
 energy.
 The
 latter
 permits
 the
 compost
 to
 be
 at
 the
 same
 microbial
 phase,
 whether
 that
 be
 mesophilic
 or
 thermophilic,
 essentially
 eliminating
 pockets
 of
 undigested
 organic
 mater
 and
 ensuring
that
the
final
product
is
completely
cured.
The
four‐inch
holes,
made
at
the
 top
 and
 bottom
 of
 the
 barrel
 and
 the
 clearance
 produced
 by
 the
 grill
 and
 V‐bent
 steel
 supports
 also
 permit
 air
 to
 flow,
 through
 convection,
 throughout
 the
 media,
 permitting
aerobic
conditions.
The
latter
reduces
the
amount
of
VOA
(volatile
fatty
 acids)
 emitted
 by
 the
 compost,
 therefore
 reducing
 the
 unpleasant
 ammonia
 smell
 caused
by
the
decomposition
process.




 JAMALEDDINE
&
RAINVILLE
2011
 






 6



 


A
 Solid
 Works
 model
 was
 designed
 to
 better
 understand
 the
 layout
 of
 the
 heat
 redistribution
system
and
its
implementation
before
the
construction
and
testing
of
 the
barrels
that
was
done.
From
the
Solid
Works
drawings
and
previous
work,
the
 construction
 of
 the
 vessels
 was
 much
 facilitated;
 see
 figures
 in
 Appendix
 B.
 The
 latter
also
probably
contributed
to
the
final
results
not
being
hindered
by
technical
 errors.
 Furthermore
 another
 simulation
 model
 was
 designed
 including
 the
 ARS
 system
to
establish
a
better
reference
in
terms
of
space
and
sizing.
The
latter
would
 be
used
to
simply
have
a
better
understanding
of
the
way
the
system
would
come
 together
when
the
HRS
and
the
ARS
system
are
implemented.
Note
that
in
Appendix
 B
 Drawings
 1
 to
 6,
 the
 lid
 of
 the
 200
 Liter
 Polyethylene
 barrels
 was
 not
 included.


The
latter
is
to
ensure
that
the
system
can
be
properly
seen.





CONSTRUCTION
 



 As
mentioned
previous,
the
materials
used
within
the
HRS
design
involved
a
 heater
core,
five
feet
(1.50
meters)
of
copper
tubing
and
about
2
feet
(0.6
meters)
of
 braided
plastic
piping.
Therefore,
for
the
barrels
fitted
with
the
heat
redistribution
 system,
 three
 five‐foot
 coils
 of
 copper
 tubing,
 with
 an
 inner
 diameter
 of
 4/8
 inch
 (0.01
meters)
were
used
along
side
three
2‐feet
segments
of
5/8
in.
(0.0158
meters)
 inner
 diameter
 plastic
 piping
 and
 a
 3‐way
 control
 valve.
 A
 zinc
 coated
 mesh
 grid
 would
be
fitted
into
each
of
the
six
composting
vessels.
V‐bent
steel
bars
to
hold
the
 total
weight
of
compost
would
support
the
latter.
A
four‐inch
(0.1m)
hole
would
be
 made
at
the
center
of
the
top
lid
of
the
barrel
and
another
four‐inch
hole
would
be
 made
 8
 inches
 
 (0.2m)
 from
 ground
 height,
 to
 insure
 there
 would
 be
 airflow
 throughout
the
composting
media.

The
heat
redistribution
system
was
assembled
 and
 tested
 by
 inserting
 the
 heater
 core
 into
 a
 water
 bath
 and
 increasing
 the
 temperature
of
the
water
bath
until
water
motion
could
be
observed
throughout
the


clear
plastic,
care
was
taken
to
ensure
flow
was
occurring
throughout
the
piping
and
 the
 water
 motion
 did
 not
 only
 consist
 of
 localized
 turbulence.
 It
 had
 been
 determined
that
around
35°C
water
would
start
flowing.
After
testing
all
three
of
the
 heat
redistribution
system,
frames
were
designed
to
hold
the
latter
and
insure
the
 heater
core
would
be
at
the
center
of
the
two
hundred‐liter
polyethylene
barrels,
as
 shown
 in
 Figure
 2.
 
 The
 heat
 redistribution
 systems
 were
 then
 fitted
 to
 their
 respective
barrels.
The
200L
plastic
vessels
were
then
insulated
with
mineral
wool
 and
 bubble
 rap
 to
 minimize
 heat
 losses
 from
 the
 sides
 of
 the
 barrels.
 All
 vessels
 were
 then
 transported
 to
 the
 Bioresource
 Engineering
 Laboratory
 for
 further
 testing.





 
 
 
 
 



 



 
 






 
 
 


Figure
1:



Picture
 of
 the
 heat
 redistribution
 system,
 before
 being
 placed
 into
 the
 insulated
compost
barrel.



 JAMALEDDINE
&
RAINVILLE
2011
 






 8


HRS
CALCULATIONS
 





Thermal
Driving


Thermal
driving
head
is
the
force
that
causes
natural
circulation
to
take
place.

It
is
 caused
by
the
difference
in
density
between
two
bodies
or
areas
of
fluid.

When
we
 have
 two
 volumes
 that
 are
 at
 different
 temperatures,
 then
 the
 volume
 with
 the
 higher
temperature
will
have
a
lower
density
and
hence
less
mass.

The
inverse
is
 also
 true,
 which
 is
 why
 the
 volume
 with
 a
 lower
 temperature
 will
 have
 a
 higher
 density
 and
 a
 greater
 mass.
 
 The
 higher
 temperature
 will
 not
 only
 bring
 about
 a
 lower
 mass,
 it
 will
 also
 lower
 the
 force
 exerted
 on
 the
 fluid
 by
 gravity.
 
 The
 difference
between
the
force
of
gravity
exerted
on
the
two
volumes
will
cause
the
 warmer
fluid
to
rise
and
the
colder
fluid
to
sink
(Munson
et
al.,
2005).





The
 continuous
 warming
 of
 the
 barrel
 is
 based
 on
 this
 principle.
 
 As
 the
 microorganisms
within
the
compost
bin
begin
to
digest
the
nutrients,
heat
will
be
 dissipated
and
once
it
has
elevated
the
waters
temperature
to
the
proper
level,
the
 warm
 water
 will
 slowly
 rise
 as
 the
 cold
 water
 spirals
 down
 the
 copper
 tubing
 towards
the
bottom
of
the
barrel.





Friction
in
the
pipes


Two
main
factors
were
considered:
the
Reynolds
number
and
the
head
loss
due
to
 friction.
 
 The
 former
 is
 necessary
 to
 determine
 whether
 the
 flow
 is
 laminar
 or
 turbulent
 and
 the
 latter
 to
 establish
 the
 losses
 in
 the
 system
 due
 to
 the
 choice
 of
 material.


It
is
important
to
maintain
a
laminar
flow
because
it
is
more
stable
and
it
 will
lower
the
pressure
drop
in
the
pipes.

Turbulent
flow
is
a
much
more
complex
 process
 although
 it
 should
 theoretically
 enhance
 the
 heat
 and
 mass
 transfer
 processes.


Materials
 


HOMOGENEOUS
COMPOST
 


Two
options
were
available
for
the
organic
waste
material:
dog
food
and
chicken
or
 cow
manure.

Dog
food
was
chosen
over
manure
chiefly
for
its
conformity.

Since
the
 experiment
will
be
repeated
in
the
future,
a
more
conform
material
was
favored
to
 avoid
discrepancies
between
experiments
and
between
the
6
barrels
that
were
set
 up
 for
 this
 design.
 
 Additional
 features
 include
 the
 greatly
 reduced
 amount
 of
 pathogenic
organisms
and
its
FDA
approval
(FDA
2010).

Another
beneficial
aspect
 is
the
dog
food’s
water
absorption
capacity.

Several
materials
were
also
considered
 for
 the
 bulking
 agent:
 sawdust,
 shredded
 paper,
 straw,
 and
 wood
 chips.
 
 Sawdust
 was
rejected
since
we
needed
a
material
that
could
provide
structure
to
the
mixture.



The
use
of
shredded
paper
was
an
interesting
option
since
it
permitted
the
recycling
 of
old
material,
but
as
with
sawdust,
it
wouldn’t
provide
adequate
structure.

When
 comparing
the
remaining
two
materials,
as
with
dog
food
and
manure,
the
issue
of
 availability
was
noted.

Since
another
experiment
run
is
scheduled
for
this
spring,
 similar
 materials
 must
 be
 available
 at
 that
 time.
 
 Straw
 would
 have
 been
 more
 difficult
to
obtain
than
woodchips
at
that
point,
and
if
obtained
would
have
been
of
a
 different
 quality
 than
 the
 fresh
 straw
 collected
 in
 the
 fall.
 
 Wood
 chips
 were
 also
 favored
for
their
larger
size,
providing
suitable
structure
to
the
compost,
as
well
as
 their
availability
and
consistency.





In
order
to
determine
the
total
mass
of
compost
materials,
a
volume
and
density
had
 to
be
established.

The
height
of
compost
was
chosen
to
be
26
inches
(0.6604
m)
and
 the
diameter
of
the
200‐litre
polyethylene
barrel
was
21
inches
(0.5334
m).
From
 this
 information,
 the
 volume
 of
 compost
 material
 was
 found
 to
 be
 0.15
 m³.
 
 The
 density
 of
 the
 mixture
 was
 assumed
 to
 be
 550
 kg/m³,
 after
 consultation
 with
 an
 expert
on
the
matter
(Dr.
S.
Barrington, PhD,
Agr.
Eng.,
McGill
University),
yielding
a


wood
chips
accounted
for
4.9
liters
of
water
(based
on
information
in
Table
1)
and
 so
44.6
liters
of
tap
water
theoretically
had
to
be
added
to
the
compost
mixture.
To
 ensure
that
such
a
large
quantity
of
water
would
remain
within
our
system
rather
 than
 leak
 out
 through
 the
 bottom
 4‐inch
 hole,
 the
 wood
 chips
 were
 soaked
 for
 3
 days
in
a
white
plastic
bin
with
a
depth,
width,
and
height
of
0.57,
0.86
and
0.58
m.





Once
the
materials
were
purchased,
they
were
analyzed
in
a
laboratory
for
moisture
 content,
 density,
 percent
 total
 solids
 and
 percent
 ash
 content.
 
 To
 determine
 total
 solids,
three
samples
of
each
material
were
weighed,
placed
in
an
oven
at
103°C
for
 24
 hours
 and
 weighed
 once
 more
 (see
 Sample
 Calculations,
 Eq.
 5).
 
 The
 remains
 were
 then
 placed
 in
 a
 furnace,
 set
 to
 a
 temperature
 of
 550°C
 for
 5
 hours,
 to
 determine
 the
 ash
 content
 of
 both
 materials
 (see
 Sample
 Calculations
 Eq.
 6).
 
 Ash
 content
is
expressed
as
a
percent
of
the
total
solids.

The
density
was
measured
by
 weighing
 the
 samples
 in
 a
 crucible
 of
 known
 volume.
 
 Characteristics
 of
 the
 final
 compost
mixture
were
analyzed
in
the
same
manor
as
the
dog
food
and
wood
chips,
 however
6
samples
were
tested
instead
of
3.

Results
from
the
laboratory
analysis
of
 the
compost
materials
will
be
further
discussed
in
the
Analysis
section.
With
these
 results,
calculations
were
verified
and
iterations
were
conducted
once
more
to
yield
 more
accurate
masses
of
each
ingredient,
based
on
measured
parameters.





Once
the
materials
were
purchased,
three
samples
of
each
dog
food
and
wood
chips
 were
 analyzed
 according
 to
 the
 aforementioned
 methods.
 
 The
 data
 obtained
 is
 presented
 in
 Appendix
 C:
 Tables
 5,
 6
 and
 7.
 
 In
 tables
 2
 and
 3,
 results
 for
 mean
 moisture
content,
mean
total
solids
content
and
mean
ash
content
are
presented
for
 both
dog
food
and
wood
chips.

The
moisture
content
and
total
solids
content
were
 close
 to
 the
 values
 that
 had
 been
 initially
 assumed.
 
 This
 indicates
 that
 the
 calculations
made
to
arrive
at
desired
masses
dog
food
and
wood
chips
based
on
a
 theoretical
 C/N
 ratio
 respected
 the
 characteristics
 of
 the
 chosen
 composting
 materials.

However,
the
densities
were
quite
different
with
341.3
and
162.0
kg/m³
 for
 dog
 food
 and
 wood
 chips
 respectively.
 
 Also,
 the
 moisture
 content
 of
 the
 wet


A
 Hewitt
 Packer
 Data
 logger
 (Model
 #:
 34970A)
 was
 used
 to
 acquire
 the
 temperature
readings
from
the
three
pre‐determined
heights
previously
mentioned.


The
latter
was
set
to
take
temperature
readings
at
fifteen‐minute
intervals
and
the
 data
was
extracted
from
the
data
logger
every
day.



The
 data
 was
 collected
 for
 a
 period
 of
 thirty
 days,
 running
 three
 control
 barrels,
 labeled
 CX‐#
 and
 three
 barrels
 fitted
 with
 the
 heat
 redistribution
 system,
 labeled
 HR‐X#
(X
varies
from
A
to
C
and
#
vary
from
1
to
3)
as
shown
in
figure
3.














 












Figure
3:
Labeling
schematic
of
the
thermocouples.



 





Three
 things
 are
 apparent
 when
 evaluating
 the
 graphs
 above
 (Fig.
 4).
 One
 of
 the
 latter
would
be
the
fact
that
the
green
lines
on
all
of
the
charts,
representing
the
top
 thermocouples,
seem
to
have
more
aggressive
and
unpredictable
variations
than
the
 other
lines.
This
is
due
to
the
unforeseen
effects
of
compaction.
It
was
not
taken
into
 account
that
compost
volume
would
be
reduced
to
that
extent
(70
mm
decrease
in
 height),
 exposing
 the
 top
 thermocouples.
 The
 aforementioned
 lead
 the
 top
 thermocouples
to
measure
ambient
air
within
the
composting
vessels
instead
of
the
 actual
temperature
at
the
top
of
the
compost
media.

Another
aspect
worth
noting
is
 the
 higher
 temperature
 that
 the
 vessels
 fitted
 with
 the
 heat
 redistribution
 system
 (HRS)
 attain.
 The
 preceding
 is
 assumed
 to
 be
 due
 to
 the
 heat
 being
 uniformly
 distributed
 throughout
 the
 composting
 vessels
 fitted
 with
 the
 HRS,
 favoring
 the
 microorganisms
 of
 thermophilic
 nature,
 permitting
 the
 latter
 to
 attain
 full
 maturation
and
in
the
process
permitting
the
vessels
to
attain
higher
temperatures.






The
 third
 phenomenon
 that
 can
 be
 observed
 involves
 the
 smaller
 temperature
 differences
 noticed
 between
 the
 center
 and
 bottom
 thermocouples
 (Red
 and
 Blue
 lines
 respectively)
 in
 the
 vessels
 fitted
 with
 the
 HRS,
 notably
 between
 35
 and
 50
 degrees
 Celsius.
 More
 so,
 after
 400
 data
 acquisitions,
 it
 can
 be
 noticed
 that
 the
 temperature
 starts
 decreasing
 in
 the
 control
 barrels,
 whereas
 the
 HR
 vessels
 temperatures
continue
to
rise.
This
also
can
be
attributed
to
the
heat
redistribution
 system
and
will
be
discussed
further
in
the
discussion
section.
A
better
depiction
of
 the
 latter
 can
 be
 observed
 in
 Figure
5
 and
 Figure
 6,
 where
 the
 difference
 of
 temperatures
between
the
center
and
bottom
thermocouples
were
averaged
out
for
 the
control
and
HRS
vessels.
It
can
be
observed
that
temperature
of
the
HRS
vessels
 do
not
attain
as
large
differences
as
the
control,
demonstrating
that
over
the
period
 of
nine
days
and
861
data
acquisitions,
the
vessels
fitted
with
the
heat
redistribution
 system
seem
to
have
a
more
uniform
temperature
gradient.


ANALYSIS
OF
RESULTS

 


Having
plotted
the
average
difference
between
the
middle
and
bottom
temperature
 readings
 of
 both
 the
 control
 barrels
 and
 the
 heat
 redistribution
 barrels,
 it
 is
 essential
to
establish
whether
the
sample
means
for
temperature
differences
of
the
 control
 and
 heat
 redistribution
 systems
 are
 significantly
 different.
 
 Using
 a
 right‐

hand
one‐tailed
test
about
the
equality
of
two
population
means,
it
was
found
that
 the
 average
 temperature
 difference
 in
 the
 control
 barrels
 was
 significantly
 larger
 from
the
average
temperature
difference
in
the
heat
redistribution
system.

It
may
 be
 affirmed
 that
 the
 average
 temperature
 difference
 in
 the
 heat
 redistribution
 system
 is
 in
 fact
 smaller
 than
 the
 average
 difference
 in
 the
 control
 barrels
 with
 a
 confidence
interval
of
99.5%.

This
confirms
that
the
design
is
functional
in
that
it
 succeeded
in
warming
the
compost
mixture
in
a
more
uniform
manner
and
attaining
 higher
temperatures
than
the
controls,
without
any
external
inputs
of
energy.
This
 test
 was
 based
 on
 the
 sample
 means:
 5.493°C
 for
 the
 control
 and
 4.742°C
 for
 the
 heat
 redistribution
 system,
 and
 the
 sample
 variances:
 9.652
 for
 the
 control,
 5.019
 for
 the
 heat
 redistribution
 system.
 Detailed
 calculations
 are
 presented
 in
 Sample
 Calculations
set
b,
Appendix
G.





From
the
above
analysis,
the
HRS
has
demonstrated
its
effectiveness
in
permitting
 the
 barrels
 to
 attain
 higher
 temperatures
 than
 the
 controls
 and
 to
 have
 a
 more
 uniform
 temperature
 gradient
 throughout
 the
 compost
 media.
 This
 more
 uniform
 temperature
 gradient
 could
 be
 effective
 in
 destroying
 pathogenic
 organisms,
 increasing
 the
 quality
 of
 the
 final
 cured
 product
 and
 potentially
 reducing
 the
 composting
time.
It
should
be
mentioned
that
even
without
the
top
thermocouple,
 the
 results
 are
 valid
 and
 statistically
 sound.
 
 The
 comparison
 between
 center
 and
 bottom
 thermocouple
 readings
 to
 determine
 temperature
 distribution
 and
 uniformity
 is
 statistically
 sound.
 More
 so,
 in
 the
 controls,
 midway
 through
 the
 experiment
 it
 seems
 that
 the
 temperature
 stabilizes
 and
 starts
 to
 decrease.
 The
 latter
is
most
likely
due
to
the
compost
not
being
able
to
attain
the
second
tier
of
the



 JAMALEDDINE
&
RAINVILLE
2011
 






 22


thermophilic
phase
due
to
pockets
at
lower
temperatures
inhibiting
the
growth
of
 the
 required
 thermophilic
 bacteria
 and
 slowing
 down
 the
 composting
 process.


Whereas
 the
 barrels
 fitted
 with
 the
 HRS
 are
 able
 to
 continue
 their
 gains
 in
 temperature
 and
 also
 maintain,
 on
 a
 general
 basis,
 a
 smaller
 overall
 temperature
 gap.
 When
 evaluating
 Figure
 5
 and
 Figure
 6,
 it
 was
 observed
 that
 overall
 the
 temperature
 difference
 within
 the
 control
 vessels
 is
 higher
 than
 the
 temperature
 difference
 within
 the
 barrels
 fitted
 with
 the
 HRS.
 
 One
 also
 has
 to
 take
 into
 consideration
 that,
 as
 mentioned
 previously
 temperature
 starts
 decreasing
 in
 the
 control
 vessels
 around
 the
 four
 hundredth
 scan,
 whereas
 the
 temperature
 within
 the
 HRS
 barrels
 continues
 to
 increase
 even
 after
 the
 last
 data
 scan
 that
 was
 recorded.

The
latter
could
explain
the
second
half
of
Figure
5,
where
temperature
 differences
 within
 the
 controls
 seems
 to
 drop,
 but
 this
 may
 be
 explained
 by
 the
 general
decrease
within
those
barrels
as
microbial
activity
diminishes.


Relying
 on
 the
 statistical
 analysis
 procured
 in
 the
 Sample
 calculations
 set
 b,
 it
 is
 possible
 to
 declare
 that
 the
 heat
 redistribution
 system
 has
 attained
 the
 set
 out
 objective
 of
 homogenizing
 the
 temperature
 throughout
 the
 composting
 media,
 increasing
 the
 speed
 of
 composting
 and
 permitting
 the
 barrels
 to
 attain
 higher
 temperatures
 possibly
 destroying
 pathogenic
 organisms
 throughout
 the
 compost.


The
 speed
 of
 the
 composting
 process
 will
 be
 further
 discussed
 in
 the
 next
 report,
 since
 data
 gathering
 is
 still
 underway.
 
 The
 latter
 gives
 a
 strong
 argument
 to
 continue
the
development
and
ameliorations
procured
in
the
improvements
section
 and
 the
 possible
 implementation
 of
 the
 HRS
 on
 a
 larger
 scale,
 increasing
 the
 efficiency
 of
 composting
 and
 it’s
 applications
 in
 a
 residential,
 industrial
 and
 commercial
basis.



 
 
 


Risk
Assessment
&
Failure
Mode
 


A
limitation
of
the
design
would
be
the
potential
failure
of
the
heat
redistribution
 system.
 Failure
 could
 occur
 during
 the
 filling
 phase,
 where
 the
 dumping
 of
 the
 compost
onto
the
HRS
could
cause
a
water
leak
and
hence
disrupt
the
flow
in
the
 copper
tubing.

However,
care
was
taken
when
the
latter
was
done.
More
so,
another
 factor
that
cannot
be
fully
remediated
for
or
observed
during
the
running
phase
of
 the
 compost
 would
 be
 the
 reduction
 or
 stoppage
 of
 flow
 throughout
 the
 piping
 of
 the
HRS.
The
latter
could
occur
if
an
air
bubble
were
to
enter
the
system,
causing
 blockage,
or
if
a
kink
was
caused
by
the
weight
of
the
compost
itself.
However,
one
 must
 take
 into
 consideration
 that
 even
 if
 there
 were
 to
 be
 some
 sort
 of
 limiting
 factor
 that
 would
 cause
 the
 stoppage
 of
 flow,
 the
 high
 conductivity
 of
 the
 copper
 tubing
 could
 still
 permit
 the
 heat
 to
 be
 transferred
 from
 the
 center
 of
 the
 barrel,
 through
the
heater
core,
into
the
water
within
the
latter
and
throughout
the
rest
of
 the
 piping
 and
 fluid
 by
 conduction.
 The
 latter
 should
 be
 taken
 into
 consideration,
 because
 uniformity
 in
 the
 temperature
 gradient
 does
 not
 necessarily
 imply
 flow
 within
the
piping.

It
is
important
to
mention
that
the
HRS
was
tested
by
inserting
it
 in
a
heated
water
bath
set
at
20°C
and
increasing
the
temperature
in
increments
of
 five
degrees
until
flow
could
be
observed
throughout
the
transparent
plastic
tubing,
 therefore
 demonstrating
 that
 the
 design
 was
 sound
 and
 able,
 under
 ideal
 circumstance
 to
 transmit
 warmed
 water
 throughout
 the
 piping.
 Flow
 occurred
 around
35°C
in
all
three
of
the
HRS
systems.
A
method
of
reducing
kinks
and
leakage
 would
involve
reducing
the
length
of
the
plastic
braided
piping
to
avoid
excessive
 twisting
motions,
and
evaluating
the
copper
tubing,
before
filling,
ensuring
there
are
 no
apparent
or
hidden
kinks
and
avoiding
any
abrupt
changes
in
the
direction
of
the
 copper
 tubing.
 Another
 important
 aspect
 to
 mention
 is
 the
 environment
 in
 which
 the
barrels
are
run.
The
location
where
the
units
were
placed
was
maintained
at
a
 temperature
of
20
degrees
for
the
first
two
days
(192
scans)
and
then
at
25
degrees
 Celsius
 for
 the
 rest
 of
 the
 experiment.
 The
 latter
 should
 be
 taken
 into
 account
 in



 JAMALEDDINE
&
RAINVILLE
2011
 






 24


future
 runs.
 
 To
 avoid
 additional
 discrepancies
 in
 the
 future,
 a
 logbook
 should
 be
 kept
with
the
date
and
time
at
which
the
Bioresource
Engineering
Laboratory
was
 accessed
since
it
was
brought
to
our
attention
that
fellow
students
who
had
work
to
 complete
in
the
Engineering
Lab
would
leave
the
door
open
in
an
attempt
to
reduce
 the
fowl
smells
emanating
from
the
compost
barrels.

The
breeze
created
in
the
barn
 could
 be
 responsible
 for
 the
 erratic
 behavior
 of
 the
 top
 (exposed)
 thermocouple
 readings.
 
 Finally,
 in
 terms
 of
 risk
 assessment
 it
 is
 important
 to
 have
 respiratory
 protection
 when
 dealing
 with
 any
 types
 of
 large
 volumes
 of
 compost.
 For
 the
 purposes
of
this
experiment
data
was
uploaded
once
a
day
and
a
respiratory
safety
 device
was
used.
Another
important
safety
aspect
would
involve
contact
avoidance
 with
compost
that
is
left
as
residue
on
the
sides
of
the
barrels.




 ISSUES


During
the
testing
of
the
HRS,
a
multitude
of
issues
were
encountered.
Of
the
latter,
 heat
loss
from
the
top
four‐inch
hole,
made
for
aeration
was
probably
of
the
highest
 significance.
 Other
 issues
 include
 the
 large
 amount
 of
 leachate
 produced
 by
 the
 compost
and
the
fact
that
it
had
to
be
manually
collected
and
resupplied
to
the
top
 of
the
compost
pile.
The
loss
of
nitrogenous
compounds
during
the
decomposition
 process
occurs
mainly
through
emission
of
gases
such
as
NH3
and
NOx,
as
previously
 mentioned.
 This
 loss
 of
 nutrients
 may
 have
 a
 significant
 impact
 on
 the
 nutrient
 balance
of
our
system.

Since
the
compost
vessel
is
well
isolated,
it
is
assumed
that
 the
majority
of
nitrogenous
emissions
are
exiting
through
the
4‐inch
hole
at
the
top
 of
 the
 barrel.
 
 Heat
 is
 also
 lost
 through
 the
 same
 opening.
 
 These
 issues
 will
 be
 addressed
by
recirculation
the
warm
air
produced
by
the
compost
by
means
of
an
 air‐to‐air
 heat
 exchanger.
 
 Also,
 the
 reduction
 in
 compost
 volume
 was
 not
 anticipated
to
be
so
large.


Air
Redistribution
System
 ARS
INITIAL
DESIGN


To
deal
with
the
heat
loss
from
the
top
four
inch
whole,
we
had
to
find
a
method
to
 keep
the
process
aerobic
while
reducing
heat
flow
from
the
top
of
the
container.
To
 achieve
the
aforementioned
an
Air
Redistribution
System
(ARS)
was
designed.
The
 latter
would
simply
consist
of
a
chimney
that
would
be
able
to
re‐circulate
the
air
 into
 the
 bottom
 four‐inch
 hole
 while
 maintaining
 the
 oxygen
 supply.
 The
 initial
 design
is
depicted
in
Figure
7.



 
 
 
 
 
 
 
 
 
 
 
 
 
 
 


Figure 7: Sketch of the design III concept.

inflow
 of
 ambient,
 quiescent
 air
 due
 to
 kinks
 that
 might
 occur
 during
 the
 construction
or
assembly
processes.





Since
 the
 designed
 system
 has
 no
 external
 input
 of
 energy,
 it
 relies
 on
 free
 convection
to
drive
the
heat
exchanger.
This
free
convection
originates
when
a
body
 force

acts
on
a
fluid
in
which
there
are
density
gradients.

The
net
effect
is
known
as
 buoyancy
force
and
it
induces
free
convection
currents
(Incropera
et
al.,
2007).

In
 this
 case,
 the
 body
 force
 is
 gravity
 and
 the
 density
 gradient
 is
 temperature.
 The
 process
begins
as
the
warm
air,
resulting
from
the
microbial
activity,
rises
through
 the
inner
cylinder
due
to
buoyancy
since
the
density
of
the
warm
air
is
lower
than
 that
of
the
ambient
air.

At
this
point,
we
have
assumed
that
the
warm
air
is
evenly
 distributed
 throughout
 the
 entire
 cylinder,
 up
 until
 the
 point
 where
 it
 leaves
 the
 inner
cylinder
through
a
similar
4
inch
diameter
(101.6
mm).


The
inner
cylinder
 should
be
composed
of
a
highly
conductive
material.

Below,
in
Table
5,
are
a
list
of
 metallic
and
non‐metallic
materials
with
relatively
high
conductive
properties.


Metal

Conductivity, k (W/m*K)

at 330 K

Silicon Carbide 490

Silver 428

Copper (pure) 399 Beryllium Oxide 247 Aluminum (pure) 238

Magnesium 155

Tungsten 141

Zinc 114.3

Iron 77

Tin 65

Commercial Bronze (09% Cu, 10% Al)

52 Chromium steels 48.2

Diamond 2047


Table
5:
Conductive
properties
of
metals
and
non‐metal
materials.



 
 Source:

Incropera
et
al.,
2007.



 JAMALEDDINE
&
RAINVILLE
2011
 






 28


Obviously,
 diamond
 and
 pure
 silver
 are
 not
 in
 our
 budget.
 
 Silicon
 carbide
 can
 be
 purchased
 in
 Canada
 at
 a
 price
 of
 277.00$
 for
 a
 50mm
 by
 50mm
 sheet
 ():
 110’800$/m².
 This
 is
 much
 more
 expensive
 than
 copper,
 which
 can
 be
 purchased
 for
26$,
for
a
1ft
x
2
ft
sheet
(www.whimsie.com/coppersheetwire),
around
140$/m².

 Thus,
copper
is
more
affordable
and
still
has
very
high
conductivity,
k.

As
for
the
 outer
cylinder,
the
same
polyethylene
material
that
compost
vessel
is
made
of
will
 be
 used,
 along
 with
 the
 same
 insulating
 materials,
 which
 were
 mineral
 wool
 and
 bubble
foil
insulation
with
thermal
conductivities
of
0.042
W/mK
and
0.034
W/mK
 respectively
(Incropera
et
al,
2007,
Appendix
A).



 


DETERMINING
THE
BOUNDARY
LAYER



As
 the
 ambient
 air,
 approximated
 at
 20
 °C,
 
 comes
 into
 contact
 with
 the
 warm
 surface
of
the
inner
cylinder,

a
thermal
boundary
will
develop
due
to
the
difference
 in
temperatures.

The
fluid
particles
coming

into
contact
the
metallic
surface
will
 achieve
thermal
equilibrium
at
the
solids
surface
temperature.

These
particles
will
 then
 exchange
 energy
 with
 those
 adjacent
 to
 them
 in
 the
 fluid,
 creating
 a
 temperature
 gradient
 in
 the
 fluid.
 
 The
 region
 in
 which
 this
 gradient
 occurs
 is
 defined
as
the
thermal
boundary
layer,
at
the
leading
edge
of
which
the
temperature
 profile
will
be
uniform,
with
T(y)
equating
T∞
(defined
as
the
ambient
temperature).



However,
the
standard
equations
do
not
apply
in
this
case,
since
there
is
no
forced
 convection
 and
 the
 plate,
 or
 rather
 cylindrical
 surface,
 is
 vertical.
 As
 a
 result,
 the
 governing
equation
will
involve
the
dimensionless
parameter
Gr
(Grashoff
number),
 whose
 function
 may
 be
 compared
 to
 that
 of
 the
 Reynolds
 number
 in
 situations
 of
 forced
 convection,
 and
 that
 measures
 the
 ratio
 of
 buoyancy
 forces
 to
 the
 viscous
 forces
acting
on
the
fluid
(Incropera
et
al.,
2007).





The
5mm
distance
will
be
the
length
between
the
inner
cylinder’s
surface

and
the
 perimeter
of
the
outer
insulated
cylinder.

It
is
also
important
to
note
the
state
of
the
 fluid.

Flow
is
considered
laminar
if
the
product
of
the
Grashoff
(Gr)
and
Prandtl
(Pr)
 numbers
are
below
1x10⁹
(Incropera
et
al.,
2007).

In
our
case,
Gr0.8m

and
Pr
were


1’970’259’723 and 0.706 respectively,
 which
 yields
 a
 value
 of
 1.3
 x10⁹.
 Since
 the
 value
obtained
is
very
close
to
the
10⁹limit,
this
indicates
that
at
the
height
of
0.8
 meters,
 the
 flow
 is
 beginning
 to
 transition
 from
 laminar
 to
 turbulent.
 However,
 throughout
 most
 of
 its
 length
 (0m
 to
 0.7m),
 the
 air
 redistribution
 system
 demonstrates
 laminar
 flow
 patterns,
 according
 to
 the
 equations
 previously
 mentioned.





Additionally,
 in
 order
 to
 increase
 the
 surface
 area
 of
 the
 inner,
 heat
 conducting
 cylinder,
two
options
were
available:
vertically
aligned
fins
(straight,
triangular
or
 parabolic)
or
folding
the
copper
sheet
to
create
ripples
along
the
surface.

Although
 the
fins
might
generate
a
slightly
larger
surface
area,
it
was
more
realistic
to
create
 the
folds
on
the
surface
of
the
copper
sheet
than
to
firmly
attach
60
individual
fins.


To
 determine
 the
 amount
 of
 folds
 required,
 the
 perimeter
 of
 the
 inner
 cylinder
 (319.9
 mm)
 was
 divided
 by
 the
 number
 of
 spacings.
 
 In
 the
 table
 below,
 several
 spacings
were
calculated.



 
 
 
 



 JAMALEDDINE
&
RAINVILLE
2011
 






 34


Number of

Spacings Width of spacing

(mm)

Length of Fold (mm)

New Perimeter (mm)

Perimeter with Fins

(mm)

10 31.92 5.00 99.92 346.19

15 21.28 4.43 132.95 361.19

20 15.96 4.12 164.83 376.19

25 12.77 3.92 196.11 391.19

30 10.64 3.78 227.05 406.19

35 9.12 3.68 257.77 421.19

40 7.98 3.60 288.33 436.19

45 7.09 3.54 318.79 451.19

50 6.38 3.49 349.17 466.19

55 5.80 3.45 379.49 481.19

60 5.32 3.41 409.76 496.19

65 4.91 3.38 439.99 511.19

70 4.56 3.36 470.20 526.19

75 4.26 3.34 500.38 541.19

Table
 8:
 Values
 for
 the
 perimeter
 of
 the
 inner
 cylinder,
 dependant
 on
 the
 number
 of
 spacings
assigned.






 


Evidently,
 the
 new
 perimeter
 has
 to
 be
 larger
 than
 the
 perimeter
 of
 the
 4
 inch
 diameter,
discarding
all
spacings
under
46.

Once
again,
feasibility
of
construction
is
 key;
we
need
the
highest
number
of
spacings
possible
without
it
being
too
small
for
 us
to
actually
build.
We
decided
on
60
spacings,
yielding
a
new
perimeter
of
409.76
 mm,
 a
 29%
 increase
 compared
 to
 the
 initial
 4
 inch
 diameter.
 
 From
 Table
 8,
 the
 column
on
the
complete
right
indicates
what
the
perimeter
could
have
been,
had
we
 chosen
 the
 impractical
 fins.
 
 It
 is
 higher
 than
 the
 folds,
 however
 if
 both
 are
 compared
 at
 60
 spacings,
 the
 difference
 is
 less
 noticeable
 than
 at
 15
 spacings.
 
 A
 graphical
 depiction
 facilitates
 the
 comparison:
 the
 perimeter
 with
 folds
 increases
 more
rapidly
that
the
perimeter
with
fins
(Figure
11).






 JAMALEDDINE
&
RAINVILLE
2011
 






 36


VELOCITY
AND
MASS
FLOW
RATE
OF
WARMED
AMBIENT
AIR
 


The
 mass
 flow
 rate
 of
 the
 warmed
 air
 was
 also
 determined.
 Mass
 flow
 rate
 is
 a
 function
 of
 the
 air
 density,
 velocity
 and
 cross
 sectional
 area
 of
 flow
 (Incropera,
 2007).



 


ρ
=
1.0682
(at
328
K)
 A
=
(πD²)/4







=
(π
*
(0.1016
m
)²
)/4
 



=
0.008107
m²



 
 
 



where:



 ν:
velocity,
m/s



 g:
gravitational
acceleration,
9.81m/s²

L:
vertical
distance
from
bottom
of
the
 surface,
m.


ΔT:
Temperature
difference,
 
 Ts‐T∞
=35
K


T∞:
Ambient
“room”
temperature,
293K
 ν
=
0.6
m/s



 


Hence,
the
mass
flow
rate
of
the
fluid
at
room
temperature
(293K)
has
a
velocity
of
 0.6
m/s
and
a
mass
flow
rate
of
0.005196
kg/s
as
it
comes
into
contact
with
the
hot
 metallic
surface
that
the
inner
cylinder
consists
of.

ARS
SUMMARY
 


The
air
redistribution
system
consists
of
two
vertical
concentric
cylinders,
both
of
 0.8m
in
height.
The
inner
cylinder
will
be
constructed
using
a
thin
copper
sheet
to
 enhance
the
conduction
of
heat
from
the
exhaust
air
of
the
compost
and
will
be
left
 open
at
the
end.

The
inner
cylinder
will
have
a
star
formation
with
60
spacings
of
 5.32
mm
each,
providing
a
perimeter
of
409.76
mm
and
a
surface
area
of
contact
of
 327’808
mm²
(0.328
m²).

Additionally,
the
length
of
each
of
the
120
folds
will
be
of
 3.41
mm.



The
 outer
 cylinder
 will
 be
 made
 of
 polyethylene,
 covered
 in
 the
 appropriate
 insulation
 as
 described
 above,
 and
 the
 top
 surface
 will
 not
 be
 left
 open
 since
 the
 fresh
incoming
air
will
be
directed
towards
the
bottom
of
the
compost
vessel,
rather
 than
lost
to
an
opening
at
the
top.

To
ensure
inflow
of
fresh
air,
the
outer
cylinder
 will
 be
 punctured
 5
 cm
 intervals
 from
 the
 bottom,
 2
 cm
 intervals
 along
 the
 horizontal,
 and
 a
 well
 insulated
 2
 inch
 diameter
 piping
 system
 will
 connect
 the
 bottom
section
of
the
outer
cylinder
to
two
the
2
inch
openings
that
will
be
present
 on
either
side,
at
the
bottom
of
the
vessels.

See
Appendix
C.



 


TESTING
&
SIMULATION


Construction
and
testing
of
the
air
redistribution
system
should
begin
this
summer.



These
results
should
help
better
determine
the
precision
of
our
calculations
and
the
 overall
efficiency
of
the
system
itself.

During
the
experiment,
we
intend
on
inserting
 3
thermocouples
within
the
inner
copper,
star‐shaped
cylinder:
the
first
just
above
 the
compost
vessel’s
4
inch
opening,
the
second
at
0.4
m
in
height
and
the
third
at
 the
exit
(0.8m).

Thermocouples
will
also
be
placed
in
the
section
between
both
of
 the
vertical
cylinders,
at
the
same
heights.

The
last
pair
of
thermocouples
will
be



 JAMALEDDINE
&
RAINVILLE
2011
 






 38


measuring
the
temperature
of
the
air
as
it
leaves
the
insulated
piping
and
enters
the
 compost
vessel
from
the
opening
at
the
bottom.



Essentially
 the
 testing
 is
 a
 process
 where
 calculation
 methodologies
 will
 be
 compared
to
their
empirical
standings
and
adjustments
will
be
made
to
mend
the
 discrepancies.

Economic
Overview
 


The
 fact
 that
 the
 HRS
 and
 ARS
 system
 can
 be
 implemented
 on
 a
 small
 scale,
 for
 example
on
a
municipal
level,
on
a
medium
or
large
industrial
level
for
a
number
of
 reasons
increase
the
probabilities
that
such
a
system
might
be
commercialized.
The
 purpose
of
our
design
being
a
proof
of
concept
we
concentrated
on
demonstrating
 that
the
system
was
functional.
However,
considering
the
increasing
prices
of
land
 filling
 and
 the
 popularity
 of
 bioremediation
 the
 system
 could
 be
 a
 cost‐effective
 solution
for
the
latter.


Note
 that
 the
 approximate
 cost
 of
 the
 HRS
 &
 ARS
 systems,
 including
 the
 two
 hundred
 litter
 vessels
 hovers
 around
 90$,
 that
 said
 one
 could
 cut
 costs
 and
 used
 recycled
material
to
build
and
implement
the
Composting
Bioreactors.
Land
filling
 in
 Canada
 has
 an
 average
 cost
 of
 around
 85$
 per
 ton,
 however
 the
 total
 environmental
cost
of
the
latter
including
the
eco‐system
benefits
that
a
landfill
will
 destroy
 or
 hinder
 does
 not
 have
 a
 set
 value.
 Note
 also
 that
 land‐filling
 will
 be
 subjected
 to
 higher
 taxes
 in
 the
 upcoming
 years
 and
 that
 the
 Composting
 Bioreactors
bearing
HRS
and
ARS
system
could
be
used
for
thousands
of
composting
 cycles
with
very
little
maintenance
considering
there
are
no
mechanical
parts
and
 that
it
utilizes
no
external
inputs
of
energy.
Overall
the
composting
reactors,
on
the
 short
run,
might
be
more
expensive,
however
the
future
benefits
are
much
higher
 than
 the
 initial
 cost
 considering
 the
 final
 product
 could
 be
 used
 or
 sold
 as
 soil
 fertilizer
and
the
fact
that
land‐filling
is
seen
as
an
outdated
methodology.



Assuming
 that
 a
 composting
 bioreactor
 can
 hold
 90
 kg
 of
 compost
 per
 run
 and
 requires
thirty
days
to
compost
the
latter
with
an
initial
cost
of
90$
and
a
lifecycle
of
 a
thirty
runs
the
total
cost
for
2700
kg
of
organic
matter
is
90$.
The
latter
does
no
 include
the
labor
that
it
requires.
Assume
a
person
is
paid
12$
per
hour
to
fill
the
 barrel
as
a
secondary
task
to
their
main
employment
and
that
it
take
fifteen
minutes
 to
fill/empty
a
barrel
that
is
180$
labor
expense
for
30
runs
summing
up
to
a
total
of



 JAMALEDDINE
&
RAINVILLE
2011
 






 40


270$
for
2700kg
therefore,
about
100$
per
ton.
Now
consider
that
the
land
not
used
 by
 the
 organic
 waste
 is
 kept
 as
 a
 natural
 habitat
 and
 a
 part
 is
 utilized
 for
 the
 building
of
a
housing
project
or
a
park.
The
latter
would
offer
Eco‐System
benefits
 that
the
landfill
would
on
the
other
hand
take
away.
The
bioremediation
capacities
 of
composting
could
also
be
utilized
on
a
small
or
large‐scale
operation.



On
a
larger
scale
assuming
10.8
tones
of
organic
matter,
therefore
10
800kg
needed
 to
be
land
filled
on
a
span
of
1
year
and
that
the
composting
bioreactor
would
cost
 70$
 to
 mass
 produce
 (recycled
 material).
 If
 one
 were
 to
 land‐fill
 the
 10
 tones
 it
 would
cost
a
total
of
920$,
whereas
10
bioreactors
could
have
an
output
of
900
kg
 per
 cycle
 and
 10
 800kg
 output
 per
 year.
 The
 total
 cost
 of
 the
 reactors
 would
 be
 (10*70)+(10*0.25*12*12*2)=
 1420$.
 However,
 cured
 compost
 can
 be
 resold
 at
 a
 price
of
approximately
25$/ton.
Therefore
(10
800kg/
1000)*25=
270$.
That
said,
 the
total
cost
of
composting
the
soil
and
selling
it
would
come
back
to
a
loss
of
230$


including
the
hassle
of
having
someone
fill
and
empty
the
vessels.



From
the
economic
point
of
view,
keeping
in
mind
that
there
is
no
discounting,
the
 overall
cost
of
operating
a
two
hundred
liter
vessel
seems
to
be
higher
than
simply
 sending
 the
 contaminated
 soil
 to
 a
 land
 fill.
 However,
 as
 taxation
 increases
 for
 landfilling
 and
 as
 public
 opinion
 turns
 against
 the
 latter
 practice,
 it
 will
 not
 be
 a
 viable
 option.
 Also,
 the
 reactors
 could
 be
 built
 on
 a
 larger
 scale
 to
 save
 time
 and
 money.

Also,
some
items
like
the
heat
exchanger
within
the
HRS
system
could
be
 recycled
 from
 a
 junkyard.
 A
 more
 in
 debt
 analysis
 utilizing
 discount
 rates,
 Initial
 Cost
analysis
and
exact
item
prices
would
yield
more
concurrent
data
on
whether
 such
a
project
could
have
an
industrial
or
municipal
application.


Conclusion
 


Having
demonstrated
to
a
99.5%
confidence
level
that
the
HRS
system
is
functional
 and
is
distributing
the
heat
uniformly
throughout
our
composting
media
we
can
say
 that
the
initial
objective
of
testing
and
assessing
the
effectiveness
of
the
HRS
system
 has
 been
 attained.
 
 The
 second
 part
 being
 the
 design
 of
 the
 ARS
 system
 was
 also
 completed.
 Although
 the
 feat
 of
 designing
 and
 testing
 the
 HRS
 system
 is
 a
 design
 project
in
itself
the
engineering
process
was
also
utilized
in
the
second
half
of
the
 project,
 as
 the
 ARS
 system
 required
 a
 very
 rugged
 mathematical
 and
 simulation
 intensive
 design
 process.
 One
 should
 note
 that
 the
 Composting
 Bioreactors
 have
 received
a
significant
amount
of
attention
in
the
past
few
months,
investment
and
 funding
 for
 the
 latter
 project,
 including
 an
 application
 for
 a
 patent
 is
 now
 a
 possibility.
 Future
 considerations
 should
 involve
 the
 testing
 of
 the
 ARS
 system
 as
 done
 for
 the
 HRS
 system,
 meaning
 a
 three
 standard
 to
 three
 ARS
 fitted
 200L
 polyethylene
vessels
should
be
run
along
side
to
determine
the
effectiveness
of
the
 latter.
 The
 ARS
 system
 should
 be
 able
 to
 maintain
 higher
 temperatures
 than
 the
 standard
barrels
for
a
prolonged
period
of
time.
Therefore
the
data
analysis
would
 compare
 maximal
 temperatures
 attained
 and
 the
 length
 of
 the
 time
 these
 temperatures
 can
 be
 maintained
 in
 the
 standards
 and
 in
 the
 ARS
 fitted
 systems.


Another
test
could
involve
fitting
three
vessels
with
the
HRS
and
ARS
designs
and
 three
only
with
the
HRS.
Either
of
the
latter
tests
would
require
a
rugged
statistical
 analysis
to
validate
the
data
once
it
is
compiled.






In
conclusion,
one
can
with
great
certainty
declare
that
from
an
academic
point
of
 view
the
Composting
Bioreactors
are
a
success
in
that
the
proof
of
concept
has
been
 attained.
 From
 an
 economical
 or
 industrial
 point
 of
 view
 much
 testing
 and
 manipulations
 should
 be
 done
 to
 better
 the
 reactors
 for
 larger
 scale
 use
 and
 to
 lower
the
cost
of
the
final
product.
In
essence,
the
Composting
Reactors
are
a
work
 in
 progress
 as
 any
 other
 feasible
 engineering
 design;
 there
 is
 much
 room
 for
 improvement.




 JAMALEDDINE
&
RAINVILLE
2011
 






 42



 
 
 
 
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 free
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APPENDIX
D


SKETCHES
OF
THE
C^OMPOSTB^IOREACTORS

 



 
 
 
 
 
 



 


Drawing
1:
HRS
&
ARS
Full‐Size
Representation
 



 
 
 



 
 
 
 



 JAMALEDDINE
&
RAINVILLE
2011
 






 54



 





Drawing
2:
HRS
&
ARS
Full‐Size
Representation



 
 





Drawing
3:
HRS
&
ARS
full‐size
representation
with
inner
contents
visible.