Type of CHP system: Anaerobic digestion

Plant owner:

Nahwärme Atzbach is a limited company owned by 5 shareholders as managing directors with equal rights (4 farmers and one representative of the municipality).

Commissioned: 2003

Status of plant: Commercial

Contractor details:

CHP: Cerveny / Perkins TESI 3008 200 kWel, 34% efficiency;
Generator: Stanford HCI 434 E2;
Fermenter: continuous fermenter (concrete)
SO2 removal by means of an air compressor combined with a gas measurement unit.

Power generation: Gas engine

Plant enlargement to 500 kW is planned for spring 2003

Main fuel:

Biogas
6000 m3 pig and cattle manure (50:50), 1750 m3 grass, and 1750 m3 maize silage

Nominal capacities & efficiencies:
Gross electrical output: 0,2 MWe
Net electrical output: 0,13 MWe
Heat output: 0,29 MJ/s
Electrical efficiency, gross: 34 %
Overall efficiency, gross: 84 %
Power to heat ratio: 0,7

How is plant controlled:

The plant operation is controlled by the biogas yield.

Heat backup:

Dual fuel burner of 600 kW able to use also biogas.

Heat usage: Heating only

Energy usage:

The annual electricity production amounts to 1,400 MWh (2002) , of which 7-8 % are for own consumption, and 82 – 83% are feed into the gread. Heat production amounts to 2,000 MWh/a, of which max. 0,5% are used for heating the boiler house, 20% for the heating of the fermentation unit, and the rest approx. 1500 kWh is fed into the public heating grid (3.5 km, heating and warm water in summer and winter)

DH inlet temperature: 90 °C

DH return temperature: 50°C

Fuel storage:

The fuel storage has a size of 2500 m3 for silage and 380 m3 for animal manure. 40 days of operation are full load are possible.

Plant description:

The plant is operated as “bio-company”, that means most of the biomass used derives from biological agriculture, just a small amount of additionally bought maize and liquid manure is from conventional farming.
Authorisation: ElWOG 2001
Prior purpose of the biogas plant is to provide heat for completion of the existing wood chips heating plant Atzbach.

Digester capacity: 2000

Residence time: 40

Process temperature: mesophilic process, temperature: 38,5 °C

Annual gas production: 800000

Gas quality: 52 – 54% methan, heating value: 5,2 – 5,4 kWh/m3

wet fermentation, dry matter 15% (silage 30%, manure 7-10%), two-level process

Electricity sale info:

The feed in rate in Austria is regulated by law and depends on the type of biomass used and on the size of the plant.

Data collected and quality assured by: Austrian Energy Agency.

Contact person: Elvira Lutter