Post on 12-Sep-2021
In-Vessel composting systems
Microbial and compost dynamics
Amardeep Wander
Evolution Ecology and Genetics,
Australian National University Canberra, Australia
The Challenge
!! From 2010 to 2050, Global Urban Population is
estimated to increase from 3b to 6b (World Urban
Prospects, 2011)
!! Positive correlation between Urban population and
waste production (Medina et al, 2011)
!! Organic Waste represents 1/3 to 2/3 of all waste
!! Disrupts nutrient recycling processes
!! Uses 20 %-40 % of landfill space
Why Compost?
!! Reduces volume of organic waste by 40%
!! Recycles a critical resource
-! soil amendment
•! reduces nutrient leaching and erosion
-! ~800 million m3 of compost required
•! agriculture, horticulture, land remediation
!! Reduction in transport costs & greenhouse gase
(Source : Cooperband, 2007, WRAP, 01 Oct 03,)
Pros & Cons of Continuous
Methods
Advantages
!! speed (14-60 days)
!! odour & vermin free
!! low manual handling
!! less land required
!! good control
Disadvantages
!! high capital costs
!! needs monitoring
!! curing required?
!! Product quality?
Aims
!! To manipulate continuous systems to increase
the efficiency of the composting process
-! experience indicates that compost composition
•! pH, salinity, N content, porosity, degree of pasturisation
-! varies with
•! control parameters (temp, moisture, residence time)
•! feed-stock composition (C:N ratio of organic matter)
Methods
!!Chemical composition
-! C:N ratios of the waste being composted
-! chemical composition of the material using NIRS
!! Physical parameters
-!moisture
-! pH
-! temperature
-! electrical conductivity
Compost
pH
EC
moisture Dried and ground
NIR spectra
Principal component
Automated C:N analyser
Microbial Characterization
!! Microbial characterization using 16S gene probe
-! DGGE for initial differentiation
•! separates same sized amplicons based on sequence
-! 454 HTS: define OTU’s, estimate and compare
species richness
•! Titanium GS-FLX amplicon chemistry by 454
•! 1.6 million sequences,~20,000 sequences/sample
Inputs
!! Garden waste: consists of grass clippings,
leaves, and shredded wood collected from
the campus or wood chip.
!! Animal bedding: consists of ‘aspen
sawdust’, faeces and dried urine.
!! Kitchen waste: represents food scraps and
organic waste produced during the
preparation of food by the college
restaurants and residence kitchens.
Compost Maturity Standards
Condition Acceptable Ideal
C:N 15:1 to 35:1 15:1 to 25:1
pH 5.5-9.0 6.5-8.0
EC (dS/m) 1.0 -10 < 4.0
moisture(%) 30 -70 45-60
Temperature of >= 50ºC to be achieved 3 times for heap type composting
Temperature of >= 50ºC to be maintained for 3 days for in vessel composting
Experiments
!! Residence time:
•! Ball bearings as a pulse indicator
•! Residence time of 7,9,12, 26 days was trialed
!! Recycle experiment:
•! Seeding(10%)
-! straight from the output
-! three week old heap
!! Changed inputs:
•! Removed inputs, for example: animal bedding
DGGE fingerprints of the bacterial 16S gene show
little variation in the microbial community as the
material moves through the system
1c
1a
1b
2a
2b
2c
3a
3b
3c
4a
4b
4c
1c
454 data tells a different story
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100% Lactobacillus unclassified gamma protoe streptophyta unclassified bacteriodetes unclassified proteobacteria unclassified bacillales5 pseudomonas leuconostoc unclassified firmicutes7 unclassified bacillaceae5 ureibacillus3 lactobaccilus8 staphylococcus ignatzchineria Unbidentified alpha proteobacteria planifilum rhizobiales Actinomycetales unidentified unidentified bacteroidetes unidentified bacillales4 geobacillus gamma proteobac unidentified5 unclassified bacillaceae4 unclassified firmicutes4 unclassified bacillales3 cerasibacillus pseudomonas lactobacillus7 gamma proteobac unidentified4 pseudonocardiaceae unclassified unclassified proteobacteria3 unclassified bacillales3 sporosarcina pseudochrobactrum unclassified alteromonadales corynebacterium psychrobacter unclassified brucellaceae3 unclassified bacillales2 unclassified bacteria 3 unclassified bacteria 2 bacillus2
Bacterial progression during Ht experiment
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Lactobacillus
unclassified gamma protoe
streptophyta
unclassified bacteriodetes
unclassified proteobacteria
unclassified bacillales5
pseudomonas
leuconostoc
unclassified firmicutes7
unclassified bacillaceae5
ureibacillus3
lactobaccilus8
staphylococcus
ignatzchineria
Unbidentified alpha proteobacteria
planifilum
rhizobiales
Actinomycetales unidentified
unidentified bacteroidetes
unidentified bacillales4
geobacillus
gamma proteobac unidentified5
Conclusion
!!We know very little about the working of
Continuous Systems
!! Need to rethink the standards
!! Further analysis:
-! Establish the relationship between the microbial
communities and the chemical composition of the
material being composted using the 454 data.