DRANCO-FARM process

DRANCO nv has developed the DRANCO-FARM dry digestion technology to produce renewable energy out of organic substrates such as energy crops, crop residues, agro-industrial by-products etc.
The degradation of organic matter takes place under anaerobic conditions in a vertical digester. The degradable fraction is converted into biogas. The biogas can be used for the production of electricity and/or heat or, after upgrading, as biomethane.

The non-degradable fraction forms a residue, having a total solids content depending on the feedstock. It can be stored and spread back out on the field or it can be treated further (drying/dewatering/…) for the production of high quality soil conditioner.

This dry anaerobic digestion technique is ideal to digest maize, sunflowers, grass, etc. and it is also well-suited to digest pure industrial by-products such as glycerine, rapeseed presscake, dried distiller grains, etc.

Technology

The DRANCO-FARM technology is based on the DRANCO technology and operates at a total solids content of ≥ 15% and is therefore a ‘dry’ digestion technology. DRANCO-FARM is a continuous process (↔ batch digestion).  Continuous dry digestion plants have been used in the municipal solid waste sector for more than 20 years in Europe.  The high concentration of total solids, the thermophilic temperature and the continuous mode allow the digester to reach very high loading rates (> 16 kg of volatile solids per m³ of reactor per day) and biogas productivities (> 10 normalized m³ of biogas per m³ of reactor per day).

DRANCO-FARM process characteristics

• vertical fermenter: feeding at the top and extraction through a conical outlet at the bottom
• single-phase digestion with intensive recycling of the digestate
• thermophilic or mesophilic operation
• compact, well-insulated digesters with minimal heating requirements
• high-rate dry digestion (very high loading rates and biogas productivities can be achieved)
• plug-flow digestion (first-in, first-out)

Advantages

The DRANCO-FARM process has some significant advantages compared to other conventional digestion technologies:

• “dry” anaerobic digestion
  • high solids digestion
  • high loading rate and biogas productivity
  • small digester volumes
  • crust formation or sedimentation is avoided
• vertical digester with conical outlet
  • extraction at the lowest point
  • no accumulation in the digester
  • minimal surface requirement
• one-phase digestion
  • reduced complexity
• no mixing, stirring or gas injection in the digester
  • no maintenance or failures inside the digester
• intensive recirculation
  • well controlled external inoculation
  • optimum mixing of fresh feedstock with digestate
• thermophilic temperature (48-55°C) possible with a minimum of heat
  • higher biogas yield
  • more efficient process
  • kill-off of pathogens and seeds
• automated process control
  • high operational safety
• robust and industrial system
  • high reliability
• no need for water or liquid manure addition

30+ years of waste digestion experience applied to bio-energy production