To supply the market with technology for the small-scale, local production of biogas. Organic waste is collected on site and converted into a resource in the form of e.g. electric or thermal energy.
Plug flow technology
The MR biogas reactor is based on plug flow technology whereby the material flows slowly from the inlet through the reactor to the outlet. This ensures there is no accidental mixing of undigested and digested material.
Plug flow technology has three principal advantages:
- The chemical steps in the digestion process take place in a given order without interfering with each other, which results in a stable process with a high level of digestion.
- Agitator energy consumption can be reduced to negligible amounts. Only a single screw feeder to slowly move the material through the reactor and prevent sedimentation is necessary. The 200 m³ screw feeder is powered by a small 130 W electric motor.
- Thermophilic digestion requires no additional hygienization of the substrate. Because digested materials never mix with undigested materials, reactor dwell time is sufficient to hygienize the substrate, which may thus be directly used as a fertilizer or disposed of in landfill.
High DS levels
Because the MR can cope with high levels of dry material (DS above 10% of sewage sludge), there are a number of advantages. Because the amount of water that must be heated is considerably lower, energy consumption for heating substrates with high DS levels is greatly reduced.
Higher DS levels also enhance reactor efficiency as a larger proportion of the volume is used for organic material instead of unnecessary amounts of water. This means an MR takes up less space compared to conventional digesters.
The substrate is heated to the correct temperature before it is introduced into the reactor in order not to disturb the digestion process by being at too low a temperature. Because the reactor is kept warm via a heating coil in the jacket, there is no need for immersion heaters or recirculating flows through an external heat exchanger, which are common heating solutions in conventional digesters. And because no recirculation flow is necessary for heating, the plug flow upon which the MR is based is not disrupted.
Because digestion takes place at a higher temperature (≈ 55°C) more gas is extracted than with mesophilic digestion (≈ 30 – 40°C).