educompost, ks & jf energy from bio wastes energy from bio wastes: fundamental considerations,...

Educompost, ks & jf

Energy from bio wastes

Energy from bio wastes: Fundamental considerations,

data, comparison from products

Dr. Konrad Schleiss, UMWEKO

Dr. Jacques FuchsBiophyt SA

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Fondamentals The energy potential from wastes is considerable

Depending of their treatment, it cost or produce more or less energy

More dry the wastes are, more easy is the energy use by combustion

More wet the wastes are, more easy is the energy use by anaerobic digestion

Important for its energy efficiency is the use of the energy, not its global production

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Treatment by burning Burning use the complete energy capital of the

products; waste will be completely mineralized

Products are only mineral (ashes)

The energy content is describe by the highest calorific value (Gross Calorific Value GCV, without water) and the

lower calorific value (Net Calorific Value - NCV)

Wastes have a middle calorific value from NCV=3 kWh/kg

Bio wastes with a DM from 35 - 40% have a NCV = 0,1-0,5 kWh/kg

So the bio wastes bring not so much energy in the incineration plants

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Calorific value of wood and of bio wastes

Calorific value of bio waste is

similare to the calorific value of

wood if we consider only the

organic matter content

Valeur calorifique [kWh/kg]

Teneur en eau [%]

Relation entre la valeur calorifique et la teneur en eau (Jonas & Görtler, 1997)

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Treatment by composting

Generally, about 50% of the organic matter will be degradated by composting

In average, 0,03 kWh/kg of bio wastes are needed

According to Heller, compost contain still 2,6 kWh/kg MS = 1,3/kg MF = 0,78/lt MF = approx. 50% from input GCV

GCV from biowaste = 1,3 - 1,7 kWh/kg

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Treatment by anaerobic digestion

An average of 100 m3 biogas per ton of bio waste is produce

It correspond to approx. 600 kWh

If we produce fuel wit it, approx. 400 kWh can be used

If we produce electricity (without use of heat), we obtain approx. 140 kWh/t or 0,14 kWh/kg

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Comparison of the energey balances

CompostingAnaerobic

fermentation (solid material)

Incineration chips

Energy used 30140

25(40 electr. + 100 heat)

Production of usable energy

0 600 2000

Balance -30460

1975 (heat)(140 electr. + 280 heat)

Energy usual used

0 140 1975

Source: Kompost und Energie aus biogenen Siedlungsabfällen ATAL (Amt für technische Anlagen und Lufthygiene) und AGW (Amt für Gewässerschutz und Wasserbau, Kz ZH) Nov 1997

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Comparison (canton Zurich)

-0.5

0

0.5

1

1.5

2

2.5

incineration (6)

Anaerob. Dig.(6)

Composting(20)

En

erg

y u

sable

[kW

h/k

g Moyenne

Maximum

Minimum

Médiane

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Comparison

Incinerators burn normally waste with high energy content

New incinerators utilized very efficiently the energy

Also if the energy content of bio wastes is twice less important as the household wastes, the energy usable

by incineration is twice higher as by anaerobic digestion

The energy content in compost and digestate is here not consider

If we consider the organic matter, the comparison could be different...

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What are the products of the different treatments ?

Energie

Digestate solid

Digestate liquide

Anaerobic digestion:

Composts

(different qualities)

Composting:

Energie

Ashes

Incineration:

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Remark:

With an appropriate composting process, it is

possible to produce compost out of digestate.

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Which differences have the products out a agricultural

point of view.

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Chemical properties from composts, digestates and wood ashes

Source de données pour le compost, digestat et eau de pressage: Konrad Schleiss, Analysen des Kanton Zürich, 2004

Source de données cendres: Risikoanalyse zur Abfalldüngerverwertung in der Landwirtschaft, FAL, 2001

Compost Digestat Eau de pressage Cendres de boisMédiane (max./ min.) Médiane (max./ min.) Médiane (max./ min.) Médiane (max./ min.)

MS [% MF] 47,9 (30,7 / 75,8) 51,1 (41,8 / 68,5) 11,1 (2,5 / 19,6) 95MO [% MS] 44,7 (17,0 / 72,2) 44,9 (35,6 / 61,1) 49,0 (38,9 / 64,5) 0 Valeur pH 7,9 (7,0 / 8,6) 7,8 (7,5 / 8,6) 7,7 (7,5 / 8,1) Salinité [mS] 2,5 (0,9 / 6,6) 2,7 (1,7 / 5,3) 16,0 (7,3 / 22,9)NO3-N [g N/t TS] 284 (0 / 1506) 455 (0 / 968) 2554 (995 / 5458) 0NH4-N [g N/t TS] 28 (0 / 482) 913 (515 / 2001) 13057 (1288 / 38710) 0 NO3-N/NH4-N 6,6 (0,0 / 427,1) 0,4 (0,0 / 1,2) 0,25 (0,06 / 2,87) Ntot [kg N/t TS] 13,0 (6,9 / 26,1) 12,6 (8,8 / 26,0) 35,3 (19,1 / 69,7) 0 P2O5 [kg/t TS] 6,2 (3,7 / 12,9) 7,2 (5,8 / 10,1) 14,3 (9,9 / 24,3) 24K2O [kg/t TS] 10,5 (5,6 / 25,5) 10,3 (7,4 / 24,9) 35,1 (18,1 / 90,8) 70 Ca [kg/t TS] 53,9 (23,8 / 148,6) 62,9 (42,2 / 154,9) 36,5 (19,1 / 71,4) 300 Mg [kg/t TS] 6,5 ( 3,5 / 15,2) 6,3 ( 4,6 / 9,0) 9,5 ( 7,5 / 11,6) 25 SO4 [kg/t TS] 4,5 (2,0 / 7,5) 4,7 (3,3 / 7,0) 8,0 (5,0 / 10,2)

Cd [g/t TS] (GW: 1) 0,32 (0,12 / 0,49) 0,20 (0,12 / 0,62) 0,52 (0,14 / 0,66) 0,3-2,7Cu [g/t TS] (GW: 100) 40,7 (19,1 / 724,3) 38,7 (24,2 / 1504,0) 75,3 (38,0 / 106,8) 86-376 Ni [g/t TS] (GW: 30) 14,7 (5,9 / 29,7) 10,9 (4,3 / 19,1) 25,5 (9,8 / 38,5) 36-140 Pb [g/t TS] (GW: 120) 32,1 (8,2 / 66,9) 27,3 (17,4 / 55,2) 41,9 (15,1 / 90,4) 3,4-39,9 Zn [g/t TS] (GW: 400) 123,5 (71,9 / 316,9) 90,5 (42,4 / 189,6) 231,7 (153,6 / 355,4) 81-522 Zn [g/t TS] (GW: 400) 123,5 (71,9 / 316,9) 90,5 (42,4 / 189,6) 231,7 (153,6 / 355,4) 81-522

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Hygienic quality of the products:

Ashes: OK

Compost: OK

Digestates ?

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Hygienic quality of digestates:Influence of anaerobic digestion on survival from of clubroot

1 55 14

2 55 14

3 55 14

100

100

99

1

0

0

4 55 7

5 55 7

6 55 7

92

100

98

0

22

1

7 35 14

8 35 14

9 35 14

93

98

99

96

98

98

withoutanaerobic digestion

with

% diseased plantsTest

No.

Temp.

[ °C ]

Duration of anaerobic digestion

[days]anaerobic digestion

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Hygienic quality of digestates:

thermophile (55°C)

mesophile (35°C)

Temperatur assume not a hygienisation of the digestate. Other actions have to be done.

OK

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Hygienic quality of digestates:

thermophile (55°C)

mesophile (35°C)

Post-composting of solid digestate: OK

Post-treatement liquide digestate ?

Prée-treatement of input materials?

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Biological quality of the products

Ashes

● Biologically dead

● Availability of nitrogen: neutral (bring no nitrogen in soil, but immobilized also no nitrogen)

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Liquid digestate ● Relatively similar to liquid manure

● Can be spread only when the plants can assimilate nitrogen (to be consider by the

calculation of the needed storage capacity)

● Concentrated N-fertilizer for the plants

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Solid digestate● Qualitatively similar to manure

● Phytotoxic

● Problematic of nitrogen: depending of its storage and its post-treatment, the digestate can bring relatively important quantity of mineral nitrogen to the soil, but

can also immobilized the soil nitrogen.

● Biologically not stable

● Low disease suppressivity potential

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Compost● Depending of its maturity stage: stabilized product,

good compatible with plants

● Influence positively the plant health(disease suppression)

● Problematic of nitrogen: depending of its maturity stage and of the process management, can blocked nitrogen in the soil, or give some nitrogen free in the

soil

● Influence positively the soil biology

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And the organic matter ?

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Importance of organic matter for the soil fertility

Influence the soil structure

Influence the water management

Protection against erosion

Amélioration of the soil biological activity

Influence the climat

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Quality of the organic matter of the different products

Every organic matter bring to the soil has not the same effect. Easy degradable

organic matter can also influence negatively the organic balance of a soil,

because it promote too much the microorganisms responsible for the mineralization of the organic matter.

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Quality of the organic matter of the different products

Ashes: no organic matter

Liquid digestate: organic matter very quickly degradable

Solid digestate: organic matter easily degradable

Compost: depending of its maturity stage, organic matter middle to high stable

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Middle or long term influence of the different products on the humus level

in soil

Ashes: neutral

Liquid digestate: neutral or negativ

Solid digestate: neutral or slightly positive

Compost: slightly to strong positive

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Conclusions:

There is more than only energy in bio wastes. These other aspects have to be consider when we choose a concept of

treatment for these products.

What do you mean ? How many kilowatts do we have in a

fertile soil ?

educompost, ks & jf energy from bio wastes energy from bio wastes: fundamental considerations,...

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