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T E C H N O L O G Y G U I D A N C E
A N A L Y S I S O F B I O D I G E S T E R SA N D D E H Y D R A T
O R ST O M A N A G E O R G A N I C S O N S I T E
Food waste is pulped and dewateredexample above) prior to
dehydrationby thermal means. Units can includepulping or be paired
with stand-aloneequipment. A Somat dehydrator isshov/n below.
ending organicsdisposalbansand/orcomm itments to divert food
waste fromlandfills has led to fairlyaggressivemarketing hyvendorso
f^ on site food wasteprocessingsystems.PartiZoNeale
C URRENT interest in and/orgovernment mandates to di-vert source
separated organ-ics (SSO) frequently outpacesdevelopment of locally
avail-able composting and anaero-bic digestion capacity. Foodwaste,
the predominant S S O in the com-mercial organics stream, is wet
andheavy leading to financial and logisticalchallenges when
trucking it from thegenerator to an often distant
processingfacility. This reality has led to opportu-nities for
on-site processing systemsthat either: 1) Substantially reduce
theweight an d volume of the organics priorto hauling; or2
Biologically break downand liquefy the organics to the pointthat
they can be disposed through theexisting sanitary sewer system,
elimi-nating hau ling for this waste stream al-together. This
dynamic has led to manyorganics generators being solicited
withincreasingfirequencyby on-site systemvendors, particularly in
sta tes like Mas-sachusetts, Connecticut, Vermont andCalifornia,
which a re a t the forefront of
implementing organics diversion poli-cies.For ge nerators
subject to upcomingorganics dispo sal ban s (see Mas-sachu setts
Sets the Table for an O rgan-ics Ban, December 2012) and who arenot
already separating their organicsfor composting, on-site solutions
app earto be a veritable silver bullet.As SSO generators and
facility man-agers attempt to obtain informationabout on-site
systems independent ofthe sales calls and marketing claims,they can
encounter difficulty findin g ob-jective comparative studies tha t
discussthe range of available options applica-ble to their
site-specific considerations.The goal of this two-part article
seriesis to provide an objective analysis for in-stitutional,
commercial and industrial(ICI) generators of food waste. Part
1describes and discusses two categoriesof on-site processing
technologies forthe ICI sector: biodigesters (otherwiseknown as wet
systems) and dehydra-tors ( dry systems). Part 2 includescase
studies of users of various on-sitesystem s. Not all commercially
availab le
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In gen eral, on-site system s may effec-
ng to the sales literatu re, un its be-3 000lbs or more of
or-
t to most ICI kitchens is the per-e sepa rating and hauling
of
use, perm itting requirem ents and com-ty of the purchase r to
independently
lts across solutions.
Photocourtesy on nsite Waste Solutions
The EcoVim 250 dehydrator installed tthe La Quinta Resort Spa
processes250 lbs/day of food waste, yielding 25lbs of processed
organics.Throughout the process of conductingresearc h for this a
rticle, one of the mostchallenging aspects was to identify
andsuccessfully contact distributors andvendors of the various
technologies. Ofthe approximately nine biodigestercompanies
contacted, only half returnedcalls despite repeated attempts.
Thisnarrowed the universe of companiesprofiled. Also precluded from
the re-search set were companies that did not
have contact information in the U.S.and/or lacked reference
facilities in theU.S. In the dehydration m arketplace,we found that
changes in distributionagreements are quite common, leadingto
confusion as to who is selling what,what party is responsible for
mainte-nance, and difficulty reconciling differ-ing product claims.
Unfortunately thisever-changing landscape m akes it verydifficult
for potential customers to con-duct independent due diligence.
Confir-mation of' product promises is compli-cated by the fact that
many of thesesystems are distributed by resellers,equipment leas
ing companies andwaste con sultants (separate from
directdistribution), who often change th e sys-tem that they
sell/lease for a myriad ofreasons. This distribution opacity
hascreated confusion and uncertainty inthe marketplace.BASIC
DESCRIPTIONSDehydrators and biodigesters em-ploy varying levels and
different typesof technology. Dehydrators use a me-chanical/thermal
approach that effec-tively sep arate s liquids from the
solids.Dehydration sy stems can include pulp-ing within the
dehydratoritself or canbe coupled with stand-alone pulpingand
dewatering units to achieve maxi-
For Precision Screening-J Composted Yard WasteJ Top Soil
OperationsWaste Treatment ScreeningReclaiming Landfill Projects
INDUSTRIES dditional Equipment SystemsCustomized to Your
Specifications Bagging. Palletizing.v ' Soil Blending Systems
Plusv^ Flow Feeders. Hammermills.v ^ D i s c S t > p . i r a U i
i > k C'l ' , i-''. / i -
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Photo cour tesy of BioGreen
D E H Y D R T O R V E N D O R S ystem desc r ipt ions excerpted
fromsaies iiterature, interviews andven-dor ciaims are
summarized:Ecovim: Decomposing c i iamber is capabie of produc ing
180F durin gprocessing to ensu re end product isessen t ia iiy odor
free ; End produc t can be used as a sou amendmentsuitable for use
in landsc aping; Sys-t e m c a p a b le o f r e d u c i n g c o m
-postable waste weight and volume by83 % to 93% depend ing on waste
in-put; No negative environ men t dam-age from TSS or B OD.Somat:
Decomposing chamber willheatthewaste,kiiianybacteriaandre -duce the
waste matter by up to 93% ;Temperatures up to 180F ens ure end
mum volume and weight reduction.With both approaches, the liquid
por-tion is disposed of through the sewerand th e greatly reduced
solid portion isdisposed of or diverted for recycling. Atlocations
with higher volumes such ascollege cafeterias, preprocessing
sepa-rately and then dehyd rating in the unitPhoto cour tesyo
fGaia
The Gaia dehydrator has an 8 to 11hour processing cycle and can
beequipped with a tote lifter to emptyfood was te into the
machine.
product is odor free; End product is ideal for use as soil
amendment.Gaia: Accelerates reduction pro-ce ss based on drying,
steril izing andgr inding mixed food scraps and or-ganic waste; .
During 8 to 11 hoursprocessing cycle, food waste weightand volume
are reduced by up to 90perce nt; Pro prietary blower chambertechn
ology that enables addit ion ofnew food scraps without loss of
pro-cessing eff ic iency whi le uni t is oper-a t ing; Dou ble he
lix shre dder andblade design prevents jamming andlowers
maintenance co sts; Output is s te r i l i zed , d eh y d r a ted m
a te r ia l .(Gaia recommends analysis of outputto determin e its
best application. )
is recommended for best results. Thethree companies most
established inselling d ehyd rators are Somat, Eco Vimand Gaia
although other machines areavailable. There are also hybrid
sys-tems available such as the BioGreen.This system combines
elements ofbiodigesters with dehydrators result-ing in a pelletized
organicresidual by-product. Over-all, composters interviewedwho
receive the output fromdehydrators expressed sat-isfaction with
this feedstockas it contains valuable ni-trogen and carbon.
Biodigesters rely upon ad-dition of proprietary biolog-ical
agents and water toachieve their promised re-sults of accelerated
decom-position. The systems ap-pear to break down theorganics
enough to get them down thedrain (after adding water), which
dis-tinguishes them from garbage dispos-
BioGreen s hybrid system (shown at aninstallation in Boston)
combineselements of biodigesters anddehydrators, resulting in a
pelletizedorganic residual by-product.
als (which directly macerate the mate-rials).Biodigesters all
utilize additives,which in most cases are a proprietarymix of
enzymes and microbes. (An ex-ception is EnviroPu re, which claims
its BioMix does not con tain any m icrobes,bacteria or enzymes but
instead iscompr ised of mine ra l s , n u t r i e n t s ,amino
acids and vitamins.) The addi-tives in these systems essentially
ac-celerate the decomposition processand, with the addition of
incrementalam oun ts of wa ter, transform the or-ganic solids into
a liquid within a 24-hour period. Many of the companies de-scribe
the techno logy as wa ste towater although it should be noted th
atthe water is gray wate r, which maycontain relatively high levels
of bio-chemical oxygen demand (BOD) thatcan be corrosive to
plumbing, detri-mental to wastewater treatment sys-tems and may
contain high levels ofnonbeneficial bacteria.
Many of these machines originated inSouth Korea and have been
licensed tovarious entities to sell in the U.S. The
Table 1. iodigesters ai idisciiargeto sewer)
VendorCapacity/24 hours lbs)
BioHitech America 800-3,000Green KeyEnv i roPure
ow8rKno t
300-2,000120-3,000
110-2,000
/Installs100+
1550+-
Footprint*Lx W inches)70x4476x48
110x12069x48
Weight*lbs)2 000
1.6353 700
1,500
Power equirements208v - 30 amp
3 phase220v - 60kz
3 phase220v - 40 amp
3 phase208v - 60hz
3 phase
WaterHot & coldHot & cold
Cold
Hot & cold
Water Usagemax. ga l24/hrs)
30033 4452320
EffluentDischarged*gal/day)
400-500415
-_
FrequencyO fSeeding month)
23-_
BiologicMicrobes
& enzymesMicrobes
& enzymesM i c ronu t r i en t s
Microbes& enzymes
'Dimen s ion s and specs for la rges t u n i t
22 B I O C Y C L E O C T O B E R 2 0 1 3
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ly the systems process and convert 1 gallon/4 lbs of
Tables 1 and 2 summarize details onsed in th is article.Due to
the relatively small installed
systems. After interviewing mu l-district levels, regulato ry
offi-
d o it. Biodigester com-
he install as replacingxture such as a slop sink,no permitting.
As such,
IO D IG E S T E R V E N D O R S
chute is pictured o ne s biodigester. Units ran ge inty from 120
to 3 000 lbs/24-
S YSTEM descriptions excerptedfrom saies literature,
interviewsand vendor ciaims are summa-rized:BioHitech
America:Eco-Safe Di-gester saves up to 50 percen t/month from
reduced hauiing costs;iVlonitors pH and can introduce eitheracidic
or alkaiine solution to restoreeffluents to near neutral levels;
BOD,C O D , TSS levels typically under ac-ceptable limits; Can
digest up to2,500 lbs/day, including
vegetables,fruits,meat,fish,poultry, grains, cof-fee grinds, egg
shells and dairyprod-ucts, with decomposition occurringwithin 24
hours; Approximately 100gallons of effluent are produced byevery
1,200 pounds of food diges ted.EnviroPure(wet): EPW
oodWasteDisposal is self-contained, continualfeed system;
By-products include nu-trient depleted gray water effluentsafe for
disposal into municipal wastewater sewer systems (see Table 1
inmain article); Effluent can be reusedfor irrigation and
agricultural applica-tions; Processes in batch or continual
vendors often do not proactively con-tact the local wastewater
agency re-gardin g acceptable discharge levels forB O D FOG (fats,
oils, grease) and totalsolids levels unless requested to do soby
the customer.Permitting authorities are cognizantof potential
wastewater system issuestha t may stem from traditional
garbagegrinding or macerating of food wasteprior to direct disposal
into a treatm entplant's sanitary sewer system, e.g., po-ten t ial
to cause s lugs, otherw iseknown as clogs. As such, many
munici-palities explicitly prohibit this grindingwith direct
disposal. As autho rities be-come more aware of the potential
forproblematic new effiuent dischargesinto their sewer systems, a
serious con-cern arises regarding potential damageto the plumbing
systems over t ime.
feed modes with complete decompo-sition offoodwas te typically
within 24hours and available in operational pro -cessing capacit
ies ranging from150lbs to 6,000lbs perd a y ; Utilizes allnatural
EP-BioMix formulation thatprovidest h e natural bacteria present
inthe food w ith critical nutrients requiredfor rapid breakdown
offood.Green Key: Add food and in 24hoursa ll organic material
breaks downinto a n odor-free, reusable waterefflu-ent; Permitting
process is generallysimilar to installing a dishwasher, butmay vary
as different municipalitieshavedifferent code requirements; Wa-ter
effluent can be treated and col-lected for grey water e . g .
toilet flush-ing or irrigation purposes).Power Knot: Unit, named
LiquidFood Composter, decomposes foodwithin 24 hours; Discharge is
safe toenter sewage syste m; Payback is typically 18 to 36 months;
Wastefood is not being chopped but it is de-composed to such a
degree that it be-comes a liquid and can exit the ma-chineonly
through a fine meshscreen.
W astewater from indu stries tha t gener-ate large amounts of
food waste tend tocarry high levels of chemical and biolog-ical
pollutants, especially BOD. Whenmixed in a sanitary sewer system
withsulfates, norm ally prese nt in the humandigestive track , hyd
rogen sulfide (H2S),can be formed. H2S is a corrosive andacidic gas
that can corrode pipes no ta desirable outcome for those responsi-b
le for main ta in ing p lumbing andwastewater systems. Municipalit
iesand districts with smaller wastewatertreatment facilities and/or
older build-ings with narrower drains are particu-larly vulnerable
to these effects due tosmaller volumes and pipe sizes.
Enzymes pose another potentiallyproblematic element to many of
the bio-logical systems. In one interview with awastewater
enforcement officer, con-
2 ehydrators
apacity24 hours(lbs)125-3,300U p to 22066-4,400
VentingNoNoNo
processing
WaterNoNoNo
DrainYesYesYes
Temp.CF )180180200
Weight/Vol.Reduction( )83-93
93U p to 90
AcceptsUncoatedCardboard& PaperY e s ; u p to 15%
YesYes
Electric(volt)220
208-480
ContinuousOrBatchBatchBatch
Continuous*
ElectricityUs e(largest unit)16-20 kw3 k w400-1,400 kwh/day
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BioHitech America utilizes microbes andenzymes to break down
food waste inits biodigesters (two units shown side-by-side at a
food bank installation inNe w Jersey).
cern was expressed tha t using enzymesto liquefy organics only
serves to breakdown the waste temporarily, with muchof the FOG
congealing again furtherdownstream. Similar issues have beenraised
about bacteria as a FOG man-agement tool. The fact that many
ofthese chemical and hiological solutionsare new to the market
means th at theseagents and the vendors who sell themare
essentially self-regulated, whichcan lead to overly liberal
interpretationof sewer regulations.
RECONCILING PRODUCT CLAIMSWITH REALITYWaste ToWater The scope
ofresearch for this article includedinterviewing vendors, users,
con-sultants and wastewater offi-cials. Throughout this process,the
most challenging aspect hasheen suhstantiation of the ven-dors'
marketing claims. (In addi-tion, a number of companies, es-pecia l
ly in the hiodiges termarket, appear to he activelymarketing
systems hut are notaccessible via telephone or email.)Biodigester
vendors use the claim, waste to water. All of the h
iodigestersystems included in this study claim sig-nificant B O D
and total suspended solids(TSS) reduct ion al though thisclaim is
clearly the most difficultto independently confirm hecause:1)
Levels vary depending on thetype of initial waste fed into
themachine (some organics such asdough and dairy have
inherentlyhigher BOD levels); 2) Levels aredepen dent on seed count
of themicroorganisms (the amount ofbacteria present at any
giventime); and 3) Very few indepen-dent studies of effluent
character-ization are puhlicly availahle.Table 3 provides an
example of a
Organics RecyclingAuthority
u J i v r S i G l l B / l / B L E B \ l f f l G Y S U S T A IN A
B IL W e a r e the experts.. .
with over 5 4 ye rsof articlesand reports on comp
osting,anaerobic digestion,greeninfrastructure, com mu
nitysustainability initiatives,national and global trends.
I O Y L ESUBSCRIBE N OW www.BioCycle.netJust 4 9 = 12
printissues A l l online content(or call 510.967.4135 ext.21
vendor's effluent claims. Bear in mindthat substantial amounts
of water areadded to a substrate (organic waste)tha t already h as
a liquid content of ap-proximately 85 percent w ater.Food Waste In
Com post Out. Twoclaims found in the marketing materi-als of deh
ydra tor systems are FoodW aste In, Compost Out and FoodWaste In,
Potable Water O u t . First, theclaim th at th e residual is stable
enoughto be directly utilized like compost isproblematic as the
solid residual, if notadequately cured, can lead to large fun-gal
colonies, odors and associated is-sues. Studies have shown tha t
using d e -hydrated food waste as a soi lamend ment, e ither alone
or mixed withcompost, creates an environment con-
Green Key's literature notes that wa tereffluent from its
biodigester (unit sho>vninstalled at a university dining hall)
canbe treat ed and collected for greywater uses.ducive to fungus
and attractive to a va-riety of unwelcome vectors (see FoodW aste
Diversion At U rban University,December 2011). Interviewees have
in-dicated the key variable influencingfungus growth is the
moisture contentpresent in the residu al after a full treat-men t
cycle, which appears to vary fi-omsystem to system. The o ther
componentof all dehydration systems is the liquidportion that has
heen captured in a va-por form, reconstituted in a vessel andthen
disposed via a drain. omevendorsclaim that this water is potahle
(onesalesperson isreported to actually drinkthe water at sales
calls to prove it).Bearing in mind that that the liquidportion has
m easurable B O D levels, it isadvisable that hoth the liquid and
thesolid fractions are tested to ensure nodeleterious impacts.C O S
T S V S B E N E F I T S
A s with any add itional piece ofequip-ment in most commercial
and institu-tional kitchen settings, space considera-tions are
always a significant hurdle toovercome. Also, depending on
whichmachine and/or technology a g eneratoris considering
(biodigesters and dehy-
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Table3 xampleo fbiodigestereffluent claimsWastewater
DischargeCriteriaBiochemical oxygen demand (BOD)Fats,oiis grease
FOGs)Total suspended solids (TSS)
Limits mg/L)300-500100-150300-500
Effluent mg/L)25-30G-10
25-35Source: nviroPure
dration systems alike), access to a drainand/or plumbing (hot
and cold or justcold) are considerations. The relativelyhigh amount
of water required for hiodi-gesters is cited by users as both cost
andsustainab ility considerations.Akey ben-efit cited by vendors of
dehydration sys-tems is that they effectively split thewaste into
its two basic components,solids and liquids, and process them
sep-arately. As an example, a typical dehy-drator will convert 250
pounds of foodwaste into 25 pounds of sterile organicbiomass and 25
gallons of water.Dehydrators are engineered to maxi-mize energy
efficiency although theamount of electricity required is
higherrelative to a biodigestion system. Anoth-er aspect of dehyd
rators th at has been cit-ed as a implementation challenge is
thatmost units are batch systems, which canlead to large amounts of
organic wasteneed ing to be stored while waiting for
theuninterruptible process to finish. Biodi-gesters, on the other
hand, are continu-ous feed systems; waste may be added atany time
as long as there is sufficientroom in the vessel.
Inset photo of the Power Knot illustrateshe types of food w aste
that the unitinstalled adjacent to the range] canprocess.When
compar ing dehydra tors andbiod igeste rs, the significant
differencesare whatgo sin and wh at comes out. De-hydrators
typically do not require addeda ter as they vaporize the liquid via
hightemperature, providing the generatorwith an organic residual
that typicallyshows an 85 to 95 percent reduction inolume and
weight . This res idual ,though, still requires off-site
transport,which represents a discreet cost. Biodi-
gesters, on the other hand, work byadding water to biochemically
slurriedwaste and g etting rid of it via the sewer.Although hauling
is avoided with biodi-gesters, vendors charge for their
propri-etary biological additives, which areadded at intervals
rangingfi omcontinu-ously to once every three to four
months.Another cost component for these sys-tems is the required
regular replacementof the media added to the vessels (woodor
plastic chips) tha t essentially serve asa habitat for the
microorganisms.One of the key sus tainab ility benefits
ofdehydrators vs. biodigesters is that amuch larger fraction of
nutrient value inthe organics is retained. The water th at
isdisposed (condensate)bydehydration sys-tems does contain BODs
although theselevels have not been flagged as a majorconcern.
Effluent from biodigesters, onthe other hand, is raising red flags
in thewastewa ter com munity because if the liq-uid that is being
discharged into thewastewater treatment system does, infact, carry
high levels of BOD and sludge,then the cost of the disposal is
essentiallybeing transferred from the generator tothe municipal
ratepayers.On-site organic waste solutions forlarger organics
generators are appeal-ing on economic, logistical and hy-gienic
levels, but the promise of aproverbial "silver bullet" solution
todealing with large am ounts of organ-ics simply does not exist.
Indeed, w ithevery system reviewed and re-searched there are
tangible benefitsalthough none are without costs andopaque product
claims. Ultimately,wh at is clear is that as a resu lt of thelight
regulatory environm ent govern-ing dehydration and biodigestion
sys-tems coupled with their relatively newappearance on the market,
the customerbear s the responsibility to verify and val-idate
vendor claims. As one individualwho has had experience with these
sys-tems said...buyer be aware
Zo ealehas spent the bulk of hercareerasan equity mutual fund
manager and advo-catefo rsocially responsible investment.
Shecurrently wo rks as a business consultantand is a founder and
director of Save ThatStuff Organ ics an organics solutions
affili-ate of Save That Stuff Inc. Zo is Treasurerof MassR ecycle
and chairs the OrganicsCommittee for that organization.
Thisenvironment lly benefici lbiocatalyst contains acomplex
mixtureofnatural nutrients,vitamins, andtrace elements
specifically designedtodisallowth e formationo f H2S, ammonia
,
merc pt ns an d sk toletoeliminate odorsan d corrosion
problems naturally.
Natural. Biodegradable.Safe.Non-Toxic.Not masking agent
oressential o il.
OC TOB ER 2013 25
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C o p y r i g h t o f B i o C y c l e i s t h e p r o p e r t y
o f J G P r e s s , I n c . a n d i t s c o n t e n t m a y n o t b
e c o p i e d o r
e m a i l e d t o m u l t i p l e s i t e s o r p o s t e d t o
a l i s t s e r v w i t h o u t t h e c o p y r i g h t h o l d e r
' s e x p r e s s w r i t t e n
p e r m i s s i o n . H o w e v e r , u s e r s m a y p r i n t
, d o w n l o a d , o r e m a i l a r t i c l e s f o r i n d i v i
d u a l u s e .
