Type of CHP system: Anaerobic digestion

Plant owner:

C.V. Biomassa-vergistingsbedrijf De Scharlebelt

Commissioned: 2002

Status of plant: Commercial

Contractor details:

Wolter en Dros Biowatt BV

Power generation: Gas engine

Thermophyl (48°C), 20 days

Main fuel:


The plant consumes per year 22000 ton manure and 3000 ton verge grass.

Manure: 7% dm, 67% organic matter.

Grass: 40% dm, 60% organics

Nominal capacities & efficiencies:

Thermal input, biomass & waste: 1,6 MW

Total thermal input, incl. fossil fuels: 1,6 MW

Gross electrical output: 0,6 MWe

Net electrical output: 0,58 MWe

Heat output: 0,8 MJ/s

Electrical efficiency, gross: 38 %

Electrical efficiency, net: 36 %

Overall efficiency, gross: 87 %

Power to heat ratio: 0,45

Electric efficiency depends on the CH4 content in the biogas and the percentage load on which the engine is set

How is plant controlled:

“Fixed menu” is fed to digesters depending on organic matter (om)

This will be changed soon to increase biogas production and availability

Heat usage: Heating only

Energy usage:

Heat only used in digestion plant. Electricity is fed into the grid

Heat storage size: 10 m3

Hours of full load that the heat storage can meet: 1

Fuel storage:

Net biogas storage capacity: 350 m³ = 2 hour full load

Waste water:

The digestated product is separated in humus and liquid manure, both are manure

Plant description:

Anaerobic digestion plant for verge grass (roadsidegrass) and pig manure.

Environmental license by Province. Gas engine: BEES-B. Other emissions: NH3: 5 mg/m³, SO2: 35 mg/m³, CO: 50 mg/m³, Dust: 10 mg/m³, Emission measurements: Gas engine: Leanox. Ventilation air: acid washer for NH3.

Fuel feeding system:

Manure is pumped into the digester tanks after being heated to 50°C.

Grass is pressed into the tanks by hydraulic press.

The biogas is transported with a blower from storage to gas engine


Manure: 90% pigs, 10% cattle. Verge grass

Digester capacity: 1500 m3

Residence time: 20 days

Process temperature: Thermophilic, 50°C

Annual gas production: Design: 1.000.000 m³. Practice: 500.000 m³. At appr. 25 °C

Specific gas yield: 20 m3 gas/m3 feedstock

Gas quality:

50 – 55 % CH4,

37 – 32 % CO2,

8% N2, 3% O2,

2% others (H2S, H2)


Jenbacher JMS 312 GS-N/B.L

Electric efficiency =  38,7%,

Thermal eff. =  48 %,

Capacity 601 kWel.

Flue gas cleaning:

Biogas is biological cleaned of H2S by mixing up with air unto appr. 3% of O2 in the biogas.

Condensate/water is separated by lowering temperature of the biogas, leaking the water and heating up the gas

The biogas plant was planned to operate for 12 hrs on full load and 12 hours on natural gas.

About 25% of the heat produced is used to heat the feedstock, the other 75% is cooled

The biogas storage capacity of 350 m3 is just sufficient to operate the engine for two hours. Than the engine is switched of for about 3 hours till the storage is filled with biogas. So, there are many starts and stops.


1 employee in daytime, no manning at night

Electricity sale info:

Weekdays, 7:00 – 23:00 high, 23:00 – 7:00 and weekends: low

Total capital cost: 3.500.000 Euro

2002, Existing buildings and ground/site costs.

Plant was build in two steps, by two different contractors

Gas engine and grid connection: 500.000.

Digestion plant and biogas treatment: 1000.000.

Storages and civil: 1.000.000.

Digestate treatment:500,000.

Equipment/vehicles: 500.000

Data collected and quality assured by: Biomass Technology Group BV.

Contact person: Harrie Knoef