Innovation provider

Eggersmann Anlagenbau GmbH & Co. KG

Contact

Max-Planck-Straße 15, 33428 Marienfeld, Germany Tel.: + 49 (0) 05247 / 9808 - 0 Fax: + 49 (0) 05247 / 9808 - 40 E-Mail: info(at)f-e.de Web: www.f-e.de

Description

Input:                        Biowaste (including contaminents)
Process:                   mesophil batch dry fermentation
Key features:          concrete-garage-like fermenters, percolate tank, CHP generator
Output:                     Biogas (electric power, heat), compost, separated contaminents
 
PRE-TREATMENT
Biowastes can be pre-treated through initial screening (80 – 100 mm) or directly processed if it seems to be adequate. Intensive comminution and addition of liquid is not necessary as the substrate does not need to be transformed into a pumpable status.
 
START-UP OPERATION
The filling of the fermenter tunnel is carried out with a wheel loader. The gas tightness of the fermenter gates is guaranteed by a circular compressed air sealing with a special profile. Within the first hours the material is aerobically pre-treated via the aerated floor. The required mesophile process temperature is quickly achieved by self-heating and the hydrolytic degradation of the biomass is already initiated.


FERMENTATION
The actual digestion phase is initiated by the termination of the aeration and a simultaneous inoculation with anaerobic biology through irrigation with pre-heated percolate. The organic acids are effectively dissolved in the drainage liquid, discharged into the percolate fermenter and there immediately transformed through the permanently available methanogenous biology.
Thus any acidification is successfully prevented. After a few days the methane forming biology is established in the fermenter tunnel, and the main gas formation occurs here. To support the process, percolate is evenly spread at a high rate over the substrate by means of a sprinkler system. The gas mixture generated during the early fermentation phase can already be delivered to the gas storage, as all of the dry fermenters are operated in a temporarily staggered batch mode. The large-scale biogas storage fully balances the discontinuous biogas production of the individual fermenter. The anaerobic process is bound to high moisture contents in the substrate and an intensive exchange of the metabolic products within the plant components. The effective discharge of the percolate is guaranteed by means of the floor gradient, drainage channels and hole-grid segments which are installed at the inner walls of the fermenter. Accumulation zones in the substrate are prevented through the additional horizontal drainage while a current flow-through of the pile with a high amount of percolate is assured. The closed loop operation by means of the heated percolate fermenter also guarantees that the necessary process temperature is maintained. A problematic sedimentation of mineral fines in the percolate fermenter is impossible, as the self filtering function of the substrate is used and an additional sand trap is installed.
 
PROCESS TERMINATION
After three weeks of retention time the gas production eases in the dry fermenter tunnel. At this time the digestion process is directly stopped through the termination of percolation and intensive aeration (oxygen supply). An efficient rotary piston blower is used for necessary high-pressure aeration. Hence any biogas contained in the pore volume of the substrate is reliably expelled. The exhaust air is lead to the gas storage until the methane content falls below a certain threshold level, then switched versus the biofilter. After that the digestate will be discharged by means of a wheel loader from the fermenter tunnel. In order to adhere to the worker’s protection rules and protection from emissions the fermenters are de-aerated with a three-fold air exchange rate during the filling and discharging processes. The final product of the treatment is a kind of digestate compost which can suitably be conditioned in a further process according to the intended application.

Advantages

-        none to low pre-treatment of input
-        maximum of 10% digestate is required for inoculation
-        aerobic start up phase for quicker start of the process
-        special drainage system allows high percolate exchange rates
-        aerobic shut down operation

Innovative aspects (ecologic, social and economic)

-        robust process technology also with high impurity content (sand, plastics, textiles, fibers)
-        low pump wear due to few solid content in percolate
-        biological stabile process, simple process control
-        high plant availability, less failure, short revision/inspection times
-        small amounts of waste water (no mechanical solid-fluid separation)
-        low electrical and thermal energy consumption for the process
-        easy further treatment/ processing of digestate in the composting process
-        a maximum of 10% digestate is required for inoculation (reduces working effort)
-        aerobic start-up phase for accelerated start of the process (use of aerobic self-heating)
-        special drainage system allows high percolate exchange rates ( dynamic mass exchange)
-        fully equipped and big dimensioned percolate fermenter (high process stability)
-        aerobic shut down operation (safe degassing, dewatering/ pre-drying of the residues

Application examples


EXAMPLE OF A KOMPOFERM PLANT FOR BIOWASTE
Annual capacity                           20.000 t/a
Reinjection of inoculation material    max. 15%
Process period                            21 days
Dry fermenter                            8 pieces (22 m x 4.5 m)
Percolate fermenter                     1 piece (Ø 16 m)
Gas storage volume                     550 m³
Biogas yield                                1,8 Mio. m³/a
Electricity yield, gross                    3,75 Mio. kWh/a
Heat yield, gross                         4,2 Mio. kWh/a
Digestate for further processing      17.500 t/a
Waste water amount                    max. 800 m³/a

Cost

Investment 15.000 Mg/a : 3.180.000 EUR net

Investment 30.000 Mg/a : 6.350.000 EUR net

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Country of origin

Germany

Country of application

Year

2005

National Contact Point

Daniel de Graaf
Umweltbundesamt
Wörlitzer Platz 1
06844 Dessau-Roßlau

Tel. +49 (0)340 21033407
Fax. +49 (0)340 21043407

» daniel.degraaf@uba.de
» www.uba.de