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

2 days………………………………...4weeks

2 days old 2 weeks old 4 weeks old

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

Pathogen count for 9 day residence

Pathogens in the heap

Pathogen count during Ht experiment

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.

Thank you "

!! David Gordon (Research School of biology, ANU)

!! Barry Hughes ( ANU Green)

!! Peter Agnew (Facilities and Services, ANU)

!! Alan Muir (RSB workshop)

!! Robert Philips (RSB workshop)

!! James Forge (RSB workshop)