FAQ

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Q&A on the Subcritical Water Treatment System

What is the basic principle?
The system decomposes materials using only saturated steam at 230°C and a pressure of 23 atmospheres. A household pressure cooker operates at around 7 atmospheres and can break down bones completely. By increasing the pressure to around 20 atmospheres, it enters what's generally known as a subcritical state.
What is the processing time and flow?
There are four main steps: loading and sealing, pressurization, depressurization, drying, and discharge. Each batch takes approximately 3 hours, depending on the required level of dryness. Therefore, in 24-hour operation, up to 8 batches can be processed per day.
What can be processed?
One example is a designated industrial waste intermediate treatment facility in Kumiyama, Kyoto, which processes infectious medical waste from hospitals.
Other materials that can be processed include:
  • Food waste
  • Sewage sludge
  • Bagasse
  • Agricultural and fishery residues
  • Plastics
  • Disposable diapers
In general, any organic matter can be processed.
Are there any recyclable materials with value?
Yes.
Mixed waste can be processed as-is. After processing, inorganic substances can be separated and recycled.
Residual materials from industrial waste can be used as auxiliary fuel, but usage must be approved by the relevant government agency (prefectural authority).
Examples:
  • Mixed waste→ auxiliary fuel
  • Diapers and plastics→ fuel
  • Food waste→ fermented methane for power generation
  • Feces, animal residue, bagasse, distillery waste, vegetables→ compost and liquid fertilizer
  • Seaweed and algae→ bioethanol
However, legal regulations, necessary equipment, and proper planning must be in place for each usage.
How safe is the system? What are the required standards?
When handling waste, the system must comply with waste management laws and local ordinances regarding environmental standards.
  • Buildings and boilers require inspection under the Building Standards Act and Fire Service Act.
  • Pressure vessels (main unit) are classified as Class 1 pressure vessels, inspected and approved by the Labor Standards Inspection Office through the manufacturer. Official documentation is available for verification.
No combustion is involved, so no dioxins are generated.
What is the ideal location for the facility?
While larger areas are preferable, a minimum of about 1,000 m² (approx. 300 tsubo) is ideal.
Facilities require:
  • Electricity.
  • Sewage system
Caution: Urbanization control zones may prohibit construction. Usage regulations also vary by project.
What is the plant's processing capacity?
Each batch processes approximately 7.5 m³.
Multiply this by the number of batches per day to determine total capacity.
When converting to weight, refer to the Ministry of the Environment’s bulk density tables.
Each batch takes approximately 3 hours.
What kind of energy does the plant use?
The system requires:
  • Electricity (100V and 200V industrial power).
  • Water supply
  • Sewage system.
  • Boiler fuel: kerosene or heavy oil (Type A)
    A cubicle transformer is also needed for power.
Note: CO₂ emissions are less than 1/16th of incineration using the same amount of fossil fuel.
What are the environmental impacts?
Compared to traditional incineration:
  • CO₂ emissions are about 1/16 (even for plastics).
  • No direct fire is used.
  • No dioxins are produced..
All discharged materials are fully sterilized, making them safer.
Exhaust and wastewater are released from a single exit, through equipment that complies with laws and environmental standards.
What permits and regulations apply?
The basic environmental standards follow Japanese law.
However, there are various use cases:
  • Industrial waste treatment
  • On-site treatment
  • As a pre-treatment system.
Therefore, detailed consultation is required during the planning stage to confirm necessary procedures and compliance.
What is the delivery time?
If land and buildings are already available, and the system is a secondary (plant) facility, it typically takes about 1 year from contract signing to trial operation.
If the project involves:
  • Purchasing land
  • Constructing buildings
  • Obtaining permits.
… then additional time is required depending on those conditions.
Subject to change depending on global and economic conditions.
What are the costs?
The initial cost for a basic system is approximately 500 million yen (subject to change based on location, usage, and timing).
Exact pricing can only be provided after the design phase.
The running costs and labor expenses are relatively low.
However, due to variability in chemicals and peripheral equipment, precise estimates cannot be given without further information.