Composting - Rowan University
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Transcript Composting - Rowan University
Composts
What is compost and why use it?
What organisms are involved in the composting
process?
What chemical changes occur during composting?
What are the optimal conditions for composting
Does composting kill harmful pathogens (plant
and human), nematodes and weed seeds?
Temperature
Moisture
Oxygen
Safety regulations
Compost production systems
Small scale
Commercial
What is compost – why use it?
Composting is the
decomposition of plant
remains and other onceliving materials to make an
earthy, dark, crumbly
substance that is excellent
for adding to houseplants or
enriching garden soil.
•compost improves soil structure, texture, aeration - increases
the soil's water-holding capacity.
•Compost loosens clay soils and helps sandy soils retain water.
•improves soil fertility and stimulates healthy root development
•Organic matter provides food for microorganisms - nitrogen,
potassium, and phosphorus mineralized
Top 10 Reasons to Compost
10.Be environmentally responsible.
9. Reduce need for chemical fertilizers, mulch.
8. Create a healthy landscape.
7. Improve the quality of your soil.
6. Reduce amount of yard waste going to landfill.
5. Protect the Chesapeake Bay and watershed.
4. Decrease water use in your landscape.
3. Protect privacy. Use shredded personal papers!
2. It's easy. Good exercise.
1. Free bin for Howard County residents!
The Science of Composting
Composting is the natural process in which living
organisms decompose organic matter into
inorganic matter in the soil.
The organisms feed on the organic material and
through respiration generate the energy that they
use for movement, growth, reproduction or
stored energy.
The organism excrete inorganic material that
enriches the soil.
When the organisms die, their bodies add to the
organic matter in the compost pile.
Fresh Organic
Materials
+
Oxygen
Microbes,
Moisture,
and Time
Compost
+
Carbon
Dioxide
+
Energy
Slide credit: Tom Richard, Penn State University
Organisms use carbon as a source of
energy and nitrogen to grow and
reproduce.
•Too little N:
•there will be few
microorganisms,
and decomposition
will be slow.
•Too much N:
•some will turn to
ammonia that will
volatilize, creating
an odor.
Factors affecting the compost process
C:N
ratio
Aeration
Size and
texture
NB. Moisture level also critical
Moisture level is also critical
•Optimum moisture content
40-60%
•Feels moist to touch, but
when squeezed only
produces few drops
Ideal conditions for composting
Parameter
Moisture
C:N ratio
Oxygen
Temperature
Bulk density
pH
OK
40-65%
20-40:1
>5%
43-66 C
1000 lbs/yd
5.5-9.0
Ideal
45-60%
25-35:1
>10%
54-60 C
1000 lbs/yd
6.5-8.0
The Science of Composting:
Chemistry
Important factors in compost chemistry
Oxygen
Needed to oxidize carbon for energy
Without oxygen will produce rotten egg smell
pH Level
Acids form as organisms digest organic material and
lowers pH
Lower pH encourages fungi and the break down of
“tough” matter
If pH too low (<4.5) limits microorganisms’ activity
The Science of Composting:
Physics
Important factors for compost physics:
Temperature
3 Phases
Want to maintain temperature between 55-600C
Temperature impacted
Heat generated by organism
Heat lost to environment through conduction, convection
and radiation shape and size of pile
Moisture content (specific heat and heat capacity of
water)
The Science of Composting:
Physics
Important factors for compost physics:
Particle size
Microorganism activity occurs on surface of
organic material
The more surface area for organisms to attack,
the quicker the decomposition want smaller
particles
Flip-side: The smaller the particles, the more
dense and compact the material resulting in poor
oxygen circulation
The main players
1. Bacteria:
major decomposers, breakdown
simpler forms of organic material
2. Actinomycetes:
degrade complex organics such as
cellulose, lignin, chitin, and proteins –
earthy” smell, long “spider webs”
filaments
3. Fungi:
Break down tough debris, too dry, too
acidic or too low in nitrogen for
bacteria to eat
What do microbes in compost do?
Consume organic matter to grow
Mineralize nutrients
Organic to inorganic forms (protein to NH4)
Transform nutrients
Stabilize organic matter
Aerobic oxidation produces CO2
Anaerobic produces reduced compounds
organic acids, alcohols
Nitrification – pH and temperature sensitive
NOTE: invertebrates not important in high temperature
composting, only in cold
Starting your Compost Pile
- Ideal size is 3 ft. x 3 ft. x 3 ft. (27 cubic
ft.)
Easier to turn, aerobic action
- No larger than 5 x 5 x 5
- Can become anaerobic
Compost production systems
Small scale
Compost piles
need to be at
least one cubic
to hold the
heat from
decomposition
Passive composting
Commercial composting
Large scale
Passive aeration with turning or actively
aerated systems
Vermicomposting
Vermicomposting is the process of using worms and micro-organisms
to turn kitchen waste into a black, earthy-smelling, nutrient-rich
humus.
The worms used in vermicomposting are called redworms (Eisenia
foetida), also know as red wigglers, manure worms, red hybrid or
tiger worms.
http://lancaster.unl.edu/pest/resources/vermicompost107.shtml
Feedstock conditioning - grinding
Moisture management - most important factor to
stabilize biological and chemical properties
Processing – turned windrows
Compost blankets to moderate moisture
www.vanierselcompost.com/. ../productie.htm
Composting - windrow
Turning helps
aeration and
to move
material from
edge into hot
center region
CO2
Hot
Cool
O2
Graphic credit: Tom Richard, Penn State University
Composting – Static forced air
CO2
Hot
O2
Cool
Graphic credit: Tom Richard, Penn State University
•Air forces heat
outwards
•Some systems
can switch
direction to
keep base core
at high enough
temperature
•Also helps
control odor
Processing - forced aeration
Contain, treat leachate
Compost blankets – beware moving from fresh to curing
www.vanierselcompost.com/. ../productie.htm
Cure compost with 40-50% moisture
to promote competitive microorganisms and
avoid salmonella regrowth