Biochar production technology

Biochar production system introduction

Biochar can be produced using several thermal conversion technologies, depending on the feedstock type, desired biochar characteristics, and production scale. Below is an overview of the main biochar production technologies, their principles, and typical outputs.

Pyrolysis (Most Common Method)

Definition: Thermal decomposition of biomass in the absence or near-absence of oxygen.
Temperature: 300–700 °C
Main products: Biochar, bio-oil, and syngas (ratios depend on conditions).

Type	Conditions	Key Features	Biochar Yield
Slow Pyrolysis	350–550 °C, long residence time (minutes–hours)	Maximizes biochar yield; used in most biochar plants	30–50%
Fast Pyrolysis	450–650 °C, short residence time (seconds)	Maximizes bio-oil; less biochar	10–20%
Intermediate Pyrolysis	400–600 °C, moderate residence time	Balanced production of char, oil, and gas	20–35%
Flash Pyrolysis	>700 °C, very short time (milliseconds)	Focus on bio-oil production	<10%

Fixed-bed reactors
Rotary kilns
Fluidized-bed reactors
Auger (screw-type) reactors

Technology	Temperature (°C)	Atmosphere	Feedstock Moisture	Main Products	Biochar Yield	Typical Use
Slow Pyrolysis	350–550	Anaerobic	Dry	Char, oil, gas	30–50%	Biochar production
Fast Pyrolysis	450–650	Anaerobic	Dry	Bio-oil	10–20%	Bio-oil, R&D
Gasification	700–1000	Partial oxidation	Dry	Syngas	5–10%	Energy
HTC	180–250	Subcritical water	Wet	Hydrochar	50–70%	Wet biomass
Torrefaction	200–300	Anaerobic	Dry	Solid bio-coal	70–80%	Fuel
Microwave Pyrolysis	300–700	Anaerobic	Dry	Char, gas	20–40%	Lab-scale, specialty char
Traditional Kilns	300–500	Limited air	Dry	Char	25–50%	Small-scale, low-cost

In CPMTP the technology we adapt, and supply is slow pyrolysis – auger reactor. The unique feature of our technology is that the pyrolysis gas is combusted in the reactor, so the system does not produce bio-oil and wood vinegar. The high temperature flue gas is heat exchanged and applied to meet customers’ specific needs. Please refer to the A Few Design Examples.

CPMTP Pyrolysis technology

Expertise in converting thermal energy into practical use, aiming to supply fully integrated system solutions.
Customized design to meet customers’ specific needs for:
- The use of Pyrolysis heat to be converted to
  - ✅ Hot air, or
  - ✅ Hot water, or
  - ✅ Hot oil, or
  - ✅ Steam, or
  - ✅ Electricity
- Adding value to biochar, – producing biochar-based fertilizers (BBF)
  - ✅ Ultra-fine powdered biochar & minerals
  - ✅ Liquid BBF or liquid biochar
  - ✅ Pelletized / granulated BBF

Pyrolysis heat is to generate steam through a waste heat boiler

Data Summary
(Example assumptions & estimates)
Assuming work 7,200 hours / year

Total coffee husk input (12% MC)	6,480T
Total coffee husk biochar output (0% MC)	1,880T
Approx. selling of steam to garment factory	8,000T
Rated power	70kw
Actual power consumption	50kwh

Pyrolysis heat is heat exchanged to hot air used for drying in the processing season, or generate electricity in the non-processing season, through an ORC system (Organic Rankine Cycle)

Data Summary
(Example assumptions & estimates)
Assuming work 7,200 hours / year

Total CGT pellets input (8% MC)	7,200T
Total CGT biochar output (0% MC)	2,000 - 3,000T
Approximate electricity generation	648 MWh
Rated power	83kw
Actual power consumption	65kwh

Making waste wood biochar while drying wet wood feedstock (hot air):

Feedstock initial moisture content 15% - 50%
Hot air temperature: 150 - 220°C (heat-exchanged from pyrolysis heat)
Duration of drying: 5 - 30 minutes
Target moisture content after drying: 12%

Making biochar while drying Nuts in Shell (hot water or hot air):

Temperature: 40°C to 45°C
Duration for drying: 3–10 days
Target moisture content: 10% or slightly lower
Avoid temperatures above 50°C, as high heat can affect the product quality.
Can supply 45M³ hot water at 60ºC for drying).

Longer useful life is built into the design, material selection, and the manufacturing of this production system.
The refractory materials are used in the inner layer of the reactor chamber, high temperature tolerance up to 1,500°C, that gives longer durability of the equipment.
The material for the reactor trough auger where the pyrolysis takes place using 310S stainless steel, which is specifically for applications at temperatures up to 1,150°C in continuous service (the pyrolysis area usually 500-700°C).
The reactor has 5 layers, for ultimately effective retaining of the heat.
Stainless steel 304 or 316L are used in the majority parts of the material handling equipment, pipes and connecting parts, etc.
System Automation Control: with stable moisture content and particle size of the raw biomass material input, the pyrolysis operation can be developed into highly automated with sound efficiency.
Biochar cooling & humidifying system for safe-handle of hot biochar. The wet scrubber for emission control.

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Equipment reliability and durability

Need to operate 7000-8000 hours per year
Continuously operating in high temperature 700-950ºC
The harsh operating condition and long hours continuous running impose highly demanding requirements on the design & material used

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Through-put capacity & carbon content

Customers & investors all want good through-put and higher carbon content, for carbon credits and biochar product

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Meeting regulatory & standard requirements

Tough biochar industry’s standards on the biochar and emissions (e.g. PAHs, CH4)
Local authorities’ emission standards

The considerations of users’ experience is built into the design & manufacture of the equipment
The consideration of equipment’s reliability & durability are built into the detailed design and material selection process
The consideration of the optimization, which has the effect to enhance equipment handling capacity, and to minimize emissions, are also built into the detailed design.

Biochar value-adding equipment

Horizontal ribbon mixer is usually used for mixing powders with powders, powders with liquids, also good in mixing paste-like, viscous or heavy materials.

The grinding machine is continuous process to produce uniform particle size. The powder size can be controlled & ranged from 425 Micron to ultrafine 4.5 Micron or 4,500 Nm.