Thesis (MSc Food Sc )--Stellenbosch University, 2002. / ENGLISH ABSTRACT: South Africa is a developing country that relies heavily on its agricultural sector for
economical welfare especially in the Western Cape Province. However,
development gives rise to new technologies, new products, economical stability
and unfortunately also to the production of larger volumes of liquid and solid
waste.
Anaerobic composting is becoming a very attractive treatment option for
solid waste disposal because of its unique operational advantages and two valueadded
by-products, compost and biogas. Over the last decade progress has been
made in anaerobic digestion of solid wastes, but no literature could be found on
the anaerobic composting of apple and peach pomace.
The main objective of this study was to develop a method to anaerobically
compost apple and peach pomace. In the first phase important operational
parameters were identified and a method was developed to optimise the
parameters. In the second phase of the study, the scaling-up and optimisation of
the process were the major objectives.
During the first phase of this research 2 L modified glass containers were
used as composting units. The most important operational parameters (leachate
pH, inoculum source and size, and initial moisture levels) were identified.
Anaerobic compost from previous tests, brewery granules and anaerobic sludge
were also used as inocula and evaluated for the best source of microbes. After
optimising all the identified parameters, good results were obtained, which
included higher biogas production, good volume reductions, less bad aromas and
a compost product with a neutral pH.
After developing the 2 L laboratory-scale method to compost the apple
pomace anaerobically, the next step was to ascertain if the method would work if
larger volumes of solid fruit waste were composted. A special 20 L composting
unit made of PVC was designed to suit the operational requirements of the
anaerobic composting process. It was also decided to mix apple pomace and
peach pulp together and to use this solid waste source as part of the composting
substrate.
Different inocula, including cattle manure, anaerobic sludge, brewery
granules and anaerobic compost produced in the previous tests, were used. Although good results were obtained with the anaerobic compost and cattle
manure as inoculum, the aim was also to decrease the composting period by
shortening the pH stabilisation period. To achieve this, it was decided to add
NaHC03 to the substrate to be composted to facilitate a faster pH stabilisation.
The composting period was subsequently shortened to 25 days with satisfactory
results, which included a volume reduction, biogas production and faster pH
stabilisation.
An upflow anaerobic sludge blanket (UASB) bioreactor was also used to
assist the composting process by facilitating the removal of the VFA's present in
the composting leachate. This proved to be a valuable addition to the composting
process as the UASB bioreactor also provided the composting units with a
'moisturising liquid', which was 'enriched' with a consortium of active anaerobic
bacteria when the effluent from the bioreactor was re-added to the composting
units.
With all the operational parameters in place, good results were obtained
and these included a volume reduction of 60% (m/m), a good biogas production, a
composting period of only 25 days, a compost that was free of bad aromas, a final
compost pH of > 6.5, final leachate COD values of less than 3 000 rnq.l", and a
final leachate VFA's concentration of between 0 and 250 rnq.l".
If in future research further scaling-up is to be considered, it is
recommended that the composting unit be coupled directly to the UASB
bioreactor, thus making the process continuous and more practical to operate. If
the operational period of the anaerobic composting set-up could be further
shortened and the inoculum adapted so that the process could be used for the
treatment of other difficult types of solid wastes, it would probably be
advantageous for the fruit processing industry to use this method as an
environmental control technology. / AFRIKAANSE OPSOMMING: Suid-Afrika is 'n ontwikkelende land wat baie afhanklik is van die sukses van die
landbousektor vir ekonomiese welstand, veral in die Wes Kaap Provinsie.
Ontwikkeling gaan gepaard met nuwe tegnologie, nuwe produkte, ekonomiese
stabiliteit en daarmee saam gaan die produksie van groter volumes vlooiebare en
soliede afvalprodukte.
Anaërobiese kompostering is tans besig om opgang te maak as en
doeltreffende behandelingstegnologie vir vaste afvalstowwe. Tydens die laaste
dekade is baie vooruitgang gemaak in die veld van anaërobiese vertering asook
kompostering van afvalmateriaal met en hoë vaste stof inhoud. Anaërobiese
kompostering van appel- en perskepulp, afkomstig van die versappingsindustrie,
het tot dusver min aandag geniet.
Die hoofdoel van hierdie navorsing was om 'n anaërobiese komposterings
metode te ontwikkel vir die beheer van vrugte afval om sodoende die basis neer te
lê vir en nuwe tegnologie wat baie voordele (biogas en kompos) inhou. In die
eerste fase is die belangrikste operationele parameters geïdentifiseer om
sodoende beter beheer oor die anaërobiese proses uit te oefen. In die tweede
fase is die anaërobiese proses wat gedurende die eerste fase ontwikkel is,
opgeskaal om optimum resultate te verkry.
Gedurende die eerste fase van hierdie verhandeling was 2 L
gemodifiseerde glas houers gebruik as komposteringseenhede. Die belangrikste
operasionele parameters (pH beheer, inokulasie grootte, vloeistofvlakke en
hoeveelheid vog asook vlugtige vetsuur produksie en verwydering) vir die beheer
van die anaërobiese komposteringsproses was geïdentifiseer en gebruik as
uitgangspunt om 'n anaërobiese komposteringsmetode te ontwikkel. Anaërobiese
slyk, brouery granules en anaërobiese kompos van vorige eksperimente was as
inokula gebruik. Gedurende hierdie studies was goeie resultate verkry en het 'n
hoë biogas produksie, goeie volume reduksies, vermindering van slegte aromas
en kompos met 'n neutrale pH ingesluit. .
Nadat hierdie goeie resultate met die 2 L laboratorium-skaal metode verkry
was, was groter volumes vaste vrugte afval gebruik om te bepaal of dieselfde
metode toegepas kan word op en groter skaal. Spesiale 20 L
komposteringseenhede was ontwerp om aan die operasionele vereistes van 'n anaërobiese proses te voldoen. Dit was ook besluit om appel pulp met perske
pulp te meng en te gebruik as deel van die komposteringssubstraat.
Verskeie inokula was weereens gebruik en het die volgende ingesluit: vars
beesmis, anaërobiese slyk, brouery granules en anaërobiese kompos van vorige
eksperimente. Hoewel baie goeie resultate met vars beesmis en anaërobiese
kompos as inokula verkry was, was 'n volgende doel gewees om die kompoterings
tydperk te verkort deur die pH vinniger te stabiliseer. Daar was besluit om
NaHC03 by die komposteringssubstraat te voeg en so 'n vinniger pH stabilisasie
te fasiliteer.
'n UASB ('upflow anaerobic sludge blanket') bioreaktor was ook gebruik om
die komposteringsproses aan te help deur die vlugtige vetsure wat in die
kompostloog teenwoordig was, te verwyder. Die insluiting van die bioreaktor in die
anaërobiese komposteringsproses het bygedra tot die sukses van die proses
deurdat die uitvloeisel as 'n vogmiddel vir die komposteringseenhede gebruik was
en 'n konsortium van aktiewe anaërobiese bakterieë bevat het.
Nadat al die operationele parameters in plek was, was goeie resultate
bereik en het die volgende ingesluit: 'n volume reduksie van 60% (m/m), goeie
biogas produksie, 'n komposteringstyd van 25 dae, 'n kompos wat vry was van
slegste aromas, 'n finale kompos pH van >6.5, finale loog CSB van <3 000 rnq.l'
en 'n finale vetsuur konsentrasie van tussen 0 en 250 mq.l'.
lndien verdere navorsing onderneem word, word dit aanbeveel dat die
UASB bioreaktor direk aan die komposteringseenheid gekoppel word om
sodoende die proses meer aaneenlopend en die proses prakties makliker
uitvoerbaar te maak. Indien die operationele tydperk nog korter gemaak kan word
en die inokulum aanpasbaar kan wees om moeilik verteerbare afvalprodukte te
akkomodeer, sal hierdie tegnologie baie voordelig wees as 'n metode om
omgewingsbesoedeling te beheer
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52651 |
| Date | 12 1900 |
| Creators | Griessel, Wilmare |
| Contributors | Britz, T. J., Fourie, P. C., Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 100 p. |
| Rights | Stellenbosch University |
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