01.9 Slurry Processing

Biogas Regions: Train the Trainers Seminar, Wolpertshausen, Germany, 28-29 November 2007

Treatment of DigestateTreatment of Digestate

Michael Köttner


Liquid manure processing and fertilization

Manure storage

After the anaerobic treatment of liquid manure and during the storage nitrogen losses occur in form of ammonia or hydrogen sulfide

Manure land application

During the application nitrogen losses can be presented in gaseous form (ammonia) and in mineral form (nitrate)


Land application techniques

Fertilizer distributor tractor: strong smell and Ammonia emissions, wind-sensitively

Drag hose tractor: precise fertilization, around 41% lower NH 3 emissions


Liquid manure processing and fertilization

No excessive agitation before the application deploy cooled substrate from the final storage, and Spread using emission-reducing techniques (drag hose tractor, etc.) Process the liquid manure

To prevent the nitrate leaching by liquid manure fertilization other measures, besides the type of treatment must be taken into account: Sufficient storage capacity (at least 6 months) Periods of application Quantity of liquid manure (and thus N-quantity) to be applied Spreading technology

Measures during liquid manure application


Treatment technologies for fermenting substrates

Thermal processesPhysical processesChemical procedures

Biological processes


Fermenting substrate

0,92%7,08%

vorher 92,00% Wasser

Gelöste Salze

Partikeltrockenmasse

Water

Dissolved salts

Dry weight particle

before


Thermal processes Drying

Evaporation

IncinerationPyrolysis

Stripping of ammoniaUsing denitrification processes


Drying process

Stable useful product nutrient problem solutions easier to transport

Waste heat utilization

0,52 kWhth Heat energy for drying 1 kg digestate with 3% DM-content

520 kWhth pro t- Digestate


1. Heat coupled microgas turbine in combination with a solar supported digestate drying process at the Farm at Karle, Fuessbach, Germany


Filling of solar thermal drying house


Drying process after 14 days


Physical processesSedimentation

Decantation centrifuge

Sedimentation tankFiltration

Screw press Rotary screen

Osmosis reverse


Screw press - separator (FAN system)

Separation liquid - solid


Decanter separation of the mixture digestate/ fats )

89%26%79%28%75%NH4-n Portion

2,32,62,30,91,2Org. N [kg/t]

3,63,03,60,43,6NH4-n [kg/t]

4,011,74,61,34,8N-total [kg/t]

0,313,41,30,31,2P [kg/t]

2,3%33%4,2%41,4%5,2%DM content

93%7%100%3%97%Weight portion

Liquid fraction Solid fractionDigestate (Fermented

liquid manure) Fat waste Raw liquid

manure

Source: Hengdal fermentation gas/Danish agrarian research Value and efficiency of nutrients and liquid manure

0,60 – 1,20 €80 – 90 %Separated biogas digestate

0,30 – 0,60 €65 – 85 %Digestate (fermented liquid manure)

-60 – 70 %Pig liquid manure

Increase in value per t liquid manure Efficiency nitrogen Fertilizer

Source: Danish agrarian research


Reverse osmosis

Biogas fermentation is ideal pretreatment for membrane processes Fibrous and/or solid material should be separated before this stage The larger the throughput the smaller the DM-content, i.e. the more effective the biogas fermentation was


Chemical procedures

MAPFlocculation

Ammonia stripping

Phosphate precipitation Chemical electroflotation


MAP (Magnesium ammonium phosphate )Struvit reaction by addition of

Phosphoric acid (origin content x 3 - 4),

MgO (Origin content x 6) = Struvit as sediment

Chemical costs of removing1 kg N:

6 Euro

for 1 m³ of pig manure up to 48 euro cost

P addition in improving areas few suitable for the solution of the N-problem


Phosphate precipitation

Using lime-milk - After anaerobic or aerobic organic decomposition, 60 - 70% P can be removed by physical separation

- Remaining phosphoric components are precipitated with lime-milk (30 - 40 kg CaO per m³ of slurry), afterwards under 2ppm P (Weiland 1997)


Ammonia stripping

Stripping of ammonia by steam without Chemical additive CaO additive - unwanted foam formation - sedimentation of solids later washed out by H2SO4

the final product is disappointing


Biological procedures

Composting

WetlandsSoil filter

Straw filter

Nitrification/denitrification


Heap shifting equipment

Composting of solids


Denitrification for removing Nitrogen

Denitrification e.g. the Netherlands

Aim: to deliver N in the form of N2 to the atmosphere

Danger of the laughing gas emission


Treatment costs of animal excrements

Routine 0,5 - 1 €/ animal

productionAdditives with pig liquid manure

Test stage >2,330 (kWh/ m3 H2O)Evaporation and drying process

of chicken dung

> 130.000 Mast animals 18 €/ tproductionIncineration of chicken dung

extensive experience 1,4 - 4,20,5 - 4 (kWh/ m3)Mechanical separation

extensive experience 0,7 - 410-38Ventilation of liquid dung

large farms6,116

(5,6% TM)Biological treatment of pig liquid

manure

limited k.A.low Anaerobic ponds

Test stage 8,1 €/ tk.A.Composting of poultry dung with pine cortex

no delimitation on farm size

12,4 - 37,25 KW/H - 50 KW/H

(for conversion –with

ventilation system)

Composting of solid manure

Application Costs (Eur/ m3)

Energy2)

(kWh/ t)Technologie


The total costs for a decanter separation are about 0,80 € per t. according to data of a Danish biogas manufacturer. This price in Denmark is profitable for

many large cattle farmers.

A further separation in the evaporator has a larger price (approx. 3.40 € per t). This expenditure should be paid back by saved transport costs and by a better

utilization of fertilizer as well as by the improved spreading.

Long distances transportation of manure for the part of manure which cannot be used in direct proximity of the enterprise would be profitable

Economic value of digestate is indicated either as 10 Euros per GV per year or related to the nutrients also

5 5 Euro/ t N, 56 Euro/ t P,28 Euro/ t K.

01.9 Slurry Processing

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