20121103 - Biology of composting - eau.eeastover/compost_course/20121103... · Biology of composting 07.11.2012, Tartu (Estonia) jf, FiBL, CH-Frick 1 Research Institute of Organic

Biology of composting 07.11.2012, Tartu (Estonia)

jf, FiBL, CH-Frick 1

Research Institute of Organic AgricultureForschungsinstitut für biologischen Landbau

Biology of composting

Jacques Fuchs ([email protected])

Institut de recherche de l’agriculture biologique

www.fibl.org Introduction to composting and anaerobic digestion, Tartu, Nov. 2012, jf

Introduction to composting and anaerobic digestion

› Introduction

› How does composting work?

› Composting: process management

› Conclusions


Introduction ?


Introduction

› What means composting ?

The term „composting“ describes a natural process,

in which microorganisms transform organic residues

in stabilized products.

Products resulted from composting:

- “heat”

- compost (more or less mature)


Introduction

› Composting. Compost ?

Composting shall not only be a cheap waste

treatment. It shall be a way to improve soil fertility,

the plant growth and the plant health in long terms.

These improvements shall be approved by the

process control.


Introduction

› Compost ?

Compost is the solid, crumble, brownish to black

brown product of an aerobic degradation of biogenic

waste or organic material. There are huge numbers of

microorganisms working under constant access of

air (oxygen) and with enough moisture in the material

mix. There is not only degradation, but also new

formation.




Introduction

› What is suitable for composting ?

Green waste


Introduction


Egg shells


Introduction


manure


Introduction


› Theoretically all organic residues can be composted or digestated.

› However, not each one is easy to handle, biodegradable, and free from toxics and pathogenic germs.

› Depending of the system used, some residues are more or less easy to be treated

› Depending of the system, some input materials have to be treated before processing (e.g. pasteurization of kitchen waste before mesophilic anaerobic digestion)

› The start mixture is important for the success of the process


Introduction

› Ways of degradation for organic material:

Anaerobic(anaerobicdigestion)

Aerobic(composting)


Introduction

› Differences between

composting and anaerobic digestion?

› Oxygen

› Energy balance

› Degradation products

› Phases

› Utilization field

› Lignin (wood) can not be decomposed anaerobe!




How does composting work ?



› The natural cycle of life

Energie

CO2O2

Watermicroorganisms

Energy(heat)

Humus(compost)

Mineral nutrients

O2 CO2

livingorganisms

Organic residues



› Two elements are especially important in the cycle of life:

› Carbon (source of energy)

› Nitrogen (protein formation)

1 www.fibl.org Introduction to composting and anaerobic digestion, Tartu, Nov. 2012, jf


› The cycle of carbon:



› The cycle of nitrogen:



› The microorganisms of composting

Bacteria Mushrooms Actinomycetes






› Bacteria

› aerobic / anaerobic

› very active at the beginning

of the process

› responsible for the hot phase

› can not abolish wood efficiently




› Mushrooms

› aerobic

› abolish wood

› creation of stabilized crumbs

› important during maturity stage




› Actinomycetes (ray fungus)

› can abolish substances, which can

not be abolish with bacteria or

mashrooms, for example chitin

› responsible for decomposition of difficult decomposable materials



› Composting: two steps system

› Step 1: Process of decomposition (mostly bacteria at work)

› intensive microbiological activity

› increasing in temperature

› extreme loss in volume

› naturally hygienisation

› Step 2: Maturity stage (mostly mushrooms at work)

› creation of stable humus

› development of positive characteristics of compost



› Degradation of cellulose during hot step

CO2 + H2O + energie

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› Degradation of proteins during hot step

NH3 + CO2 + H2O + (H2S) + energie

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› Dissolution of ammonia in water

liquid ammonia

&

+&

-

ammonia

ammonium

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› Nitrification to nitrate

nitric acid

oxygen

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-

& -&+&

& & +&

ammonium

nitrate

liquid ammonia



› Maturity stage protein

(ammoniac) NH3

NH 4+ (ammonia) & OH -

(basic)

(oxygen from air) O2

NO 3-

(nitrate) & H+ (acide) & 22 H O (Wasser)

nitric acid

gaseouslosses

Nitrit NO 2-laughing gas N O2

air nitrogen N2

(water) 2OH

gaseouslosses

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› Maturity stage› Decomposition of lignin and building of humus

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› The process parameters

› Temperature

› Composition of gases

› Nmin forms

› Organic substance

› pH-value

› Intensity of extract coloration



› Evolution of temperature during composting

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Duration of process

10

30

50

70





› Evolution of gas composition during composting

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Duration of process0

10

20

O2

CO2



› Evolution of Nmin forms during composting

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200

400

600

NO3--NNH4

+-N NO2--N



› Evolution of pH during composting

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5

6

7

8

9



› Evolution of organic substance during composting

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30

40

50

60

70

80



› Evolution of water extract coloration during composting

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50

100

150



› Evolution of undesirable materials during the rotting process

› heavy metals






before

for example90 kg

degradablematerial

for example10 kg non-degradable

material = 10 %

for example45 kg

degradablematerial

for example10 kg non-degradable

material= 18 %

after




› heavy metals

› other chemical compounds ???

› pathogenic germs and weed seeds



› Final product: compost

› organic fertilization

› amelioration of soil structure

› biological plant protection product

› Compost is not waste material !


Composting: process management



› Process management:

From collecting of green waste

to utilization of the final product



› Factors of process management:

› Concept of green manure collection

› Composting system

› Mixture of raw materials

› Process management

› Storage of end-material





› Concept of waste collection



› Concept of green manure collection

› Can influence the quality of input materials (e.g. quantity of undesirable inputs)

› Organizing the materials needed to become an adequate start mixture


Compost quality management





› Each composting system, has its own specificities

› The different management operation have to be adapted to the system

› Mixture composition

› Coarseness of the start mixture

› Aeration and humidity management

› …



› Composition of the start mixture



› Start mixture

› C:N-ratio („available“)





› C:N-ratio of some materials› Urine: 0.8

› Feathers: 4 – 5

› Chicken manure: 8 – 10

› Grass: 12

› Mature compost: 12 – 15

› Young compost: 15 - 18

› Cows manure: 15 – 20

› Kitchen waste: 23

› Ideal C:N of start mixture: 30 – 35

› Trees leaves 50

› Straw 50 – 150

› Wood (sawdust): 200 - 500



› Start mixture

› C:N-ratio („available“)

› Structure, moisture

› “Ideal mixture”:

› 1/3 rough wood (shredded wood, sieved rest material from compost, snipped bark)

› 1/3 medium-fine, fibrous material(shredded branches, wood fibers, straw, foliage, switch grass , reed, peat from consumed potting compost)

› 1/3 material, nearly without structure(dung, grass, rumen contents, vegetables manure)

› Evtl. utilization of additivespowdered clay, earth, enzymes, microorganisms, fertilizer, etc.



› Process management: humidity



› Process management: humidity

› Enough humidity is necessary to allowed microorganism activities

› Too much humidity prevent a good aeration of the composting material and so a good process development

› At the begin of the process, an important quantity of water is need

› During the maturity phase, the addition of water is to performed very carefully

› Humidity management is one of the most difficult role of the compost manager !



› Process management: aeration



› Process management: aeration

› Mushrooms need oxygen to be active.

› Bacteria can be active without free oxygen. But then they take oxygen from other molecules, what can cause the production of toxic compounds (e.g. nitrite from nitrate)

› The aeration of the compost during the maturation phase is very important. The quality of the products depreciated if not enough oxygen is then available.





› Process management: compost turning



› Process management: compost turning

› Compost turning is not only important to assure an sufficient oxygenation of the compost during the process

› Compost turning is important to become an homogenous product

› Compost turning activate also activate the biological activity of the process



› Process management: storage of the products




› Compost is an living product. If he didn’t be come oxygen, he will died !

› Mature compost didn’t need a lot of oxygen. But a minimum has to be assure. Different factors are important:› Dimensions of the storage pile

› Maturity stage of the products

› Humidity

› Use of additives

› …





Conclusions




Conclusions

› Knowledge of the biology of composting is essential to understand and managed the process

› Process management is the key for a successful production quality compost

› Compost quality is the basic condition to improve the market for the products and so to secure the system.


Thank you very much for your attention …

www.fibl.org www.biophyt.ch

Documents

20121103 - Biology of composting - eau.eeastover/compost_course/20121103... · Biology of composting 07.11.2012, Tartu (Estonia) jf, FiBL, CH-Frick 1 Research Institute of Organic