8/20/2019 Composting Organisms
1/22
Composting OrganismsComposting Organisms
Mary Stromberger Mary Stromberger
Assistant Professor, Soil Microbiology Assistant Professor, Soil Microbiology
Dept. Soil and Crop Sciences, CSUDept. Soil and Crop Sciences, CSU
8/20/2019 Composting Organisms
2/22
Composting of organic wastesComposting of organic wastes
……I have always looked upon decay as being just as wonderful and r I have always looked upon decay as being just as wonderful and r ichich
an expression of life as growth.an expression of life as growth.
---- Henry Miller, The Wisdom of the HeartHenry Miller, The Wisdom of the Heart
• The what and why of composting
• Compost biota and their activities
• Vermicomposting
8/20/2019 Composting Organisms
3/22
The What and Why of CompostingThe What and Why of Composting
• Composting = biological decomposition
and stabilization of organic substrates
– Under biologically-produced thermophilic
temperatures – Produces a final product that is stable, free of
pathogens and plant seeds and can be
beneficially applied to land
8/20/2019 Composting Organisms
4/22
• Reduce waste volume
• Promote plant productivity and soil quality
• Eliminate pathogens, deleterious
organisms, and weed seeds
• Sanitize organic wastes
8/20/2019 Composting Organisms
5/22
Decomposition
processes
Organic residues
Air
Water
Humus-likeOrganic matter
Heat
Gases
(e.g.,CO2, NH3)
Microbial
biomass
8/20/2019 Composting Organisms
6/22
Compost BiotaCompost Biota
• Fauna
• Protozoa
• Decomposer microorganisms
– Bacteria – Actinomycetes
– Fungi
8/20/2019 Composting Organisms
7/22
FaunaFauna
• Important in the
beginning of compost
process• Grind coarse materials
into smaller bits
(communition)• Increases surface
area:volume ratio
• Improves access ofmicrobes to organic
substrates
8/20/2019 Composting Organisms
8/22
ProtozoaProtozoa
• Active in the early
phases of composting• Process smaller bits
of organic matter
• Prey upon microbialpopulations
– Regulates numbers
– Recycles nutrients
http://mtlab.biol.tsukuba.ac.jp/WWW/PDB/Images/Sarcodina/ap/intactcell.jpg
8/20/2019 Composting Organisms
9/22
BacteriaBacteria
• Single-celledprokaryotes
• Smallest livingorganisms
• Most numerous group
in compost• Responsible for most
of the decay and heat
generation in compost• Nutritionally diverse
8/20/2019 Composting Organisms
10/22
Actinomycetes Actinomycetes
• Filamentous bacteria
• Produce geosmin• Degraders of
cellulose,
hemicellulose andlignin
• Important during thethermophilic and
cooling stages
8/20/2019 Composting Organisms
11/22
FungiFungi
• Multicellular eukaryotes
• Include mushrooms,molds and yeasts
• Usually filamentous• Decomposers of
complex plant
polymers – cellulose,
hemicellulose andlignin
8/20/2019 Composting Organisms
12/22
Overview of the compost processOverview of the compost process
Time
T e m p .
MesophilicPhase ThermophilicPhase CuringPhase
20 - 40°C
A few days40 - 65°C, as high as 80°C
A few days to several months
Cooling and maturation
Several months
8/20/2019 Composting Organisms
13/22
Stage 1:Stage 1: MesophilicMesophilic StageStage
• Bacteria and Fungi are key players
– Fauna and protozoa also important
• Decomposition of readily available
substrates
– Sugars, proteins and starch
• Excess energy is released as heat,
causing pile temperature to increase
8/20/2019 Composting Organisms
14/22
Stage 2: Thermophilic StageStage 2: Thermophilic Stage
• Heat-loving bacteria, actinomycetes and
fungi are key players• Heat intolerant organisms go dormant or
are destroyed – Human and plant pathogens
• High temperatures accelerate breakdown
of proteins, fats, and complex polymers
8/20/2019 Composting Organisms
15/22
Microorganisms Associated with Compost PilesMicroorganisms Associated with Compost Piles
Mesophilic Stage Thermophilic Stage
Bacteria 108
cells g-1
Pseudomonas, Bacillus,
Flavobacterium, Clostridium
109
cells g-1
Bacillus, Thermus
Actinomycetes 104 cells g-1
Streptomyces
108 cells g-1
Streptomyces,
Micropolyspora,
Thermoactinomyces,
Thermomonospora
Fungi 106 fungi g-1
Alternaria, Cladosporium,
Aspergillus, Mucor,
Humicola, Penicillium
107 fungi g-1
Aspergillus, Mucor,
Chaetomium, Humicola,
Absidia, Sporotrichum,
Torula (yeast),Thermoascus
8/20/2019 Composting Organisms
16/22
Inner
Thermophilic zone
Cooler temperatures
C o o l e
r t e m p e r a t u
r e s C o
o l e r t e
m
p e r a t u r e s
ZonationZonation of temperaturesof temperatures
• Internal temperatures canbe as high as 70 or 80° C
• Center of pile isdominated by the mostheat-tolerant bacteria
(eg., Bacillus)
• Edges of pile support
diverse populations ofthermophilic bacteria,actinomycetes and fungi
8/20/2019 Composting Organisms
17/22
Importance of turning the pileImportance of turning the pile
Inner
Thermophilic zone
Cooler temperatures
C o o l e
r t e
m p e r a t u
r e s
C o o l e r t e
m
p e r a t u r e s
-Redistributes
microorganisms
-Cools the pile
-Aerates the pile
-Speeds up
decomposition
-Allows microbialsuccession to reoccur
8/20/2019 Composting Organisms
18/22
Stage 3: Curing/Cooling StageStage 3: Curing/Cooling Stage
• Mesophilic bacteria, actinomycetes and fungi
are key players• Further chemical and physical changes in the
compost
– Decomposition of recalcitrant polymers byactinomycetes and fungi
– Degradation of fermentation products, methane, and
other noxious gases which accumulated earlier inanaerobic microsites
– Reduction of odors and toxic intermediates
8/20/2019 Composting Organisms
19/22
VermicompostingVermicomposting
• Composting with
worms and
microorganisms
• Eisenia foetida
– Aka redworms,red wriggler
worms, tiger
worms
– Thrive on rottingvegetation,
compost and
manure
8/20/2019 Composting Organisms
20/22
Physical effects on compostPhysical effects on compost
Burrowing action of
worms help• aerate the compost
• mix substrates
• redistribute
microorganisms
Composting time is faster!
Less need to turn the pile!
Burrowing action of
worms help• aerate the compost
• mix substrates
• redistribute
microorganisms
Burrowing action of
worms help• aerate the compost
• mix substrates
• redistribute
microorganisms
8/20/2019 Composting Organisms
21/22
Biochemical effects on compostBiochemical effects on compost
• Communition of
organic residues – Enhances microbialaccess to substrates
• Production of casts
– Source of readily
available sugars andproteins for microbes
8/20/2019 Composting Organisms
22/22
Final WordsFinal Words
• Composting is a microbial process
• Its rate is controlled by factors which affectmicrobial activities
• Lack of suitable substrates, low moisturecontent, non-optimum temperatures, and
poor oxygen diffusion are the most
common rate-limiting factors in
composting