Blog · 3 September 2026

Torrefaction vs Pyrolysis vs Gasification: What Actually Differs

In brief

Summary

All three are thermochemical processes that heat material in little or no oxygen. The differences that matter are temperature and what the process is trying to produce. Torrefaction runs coolest (200–350 °C) and aims to keep a solid fuel. Pyrolysis runs hotter and splits the output between solid, liquid and gas. Gasification runs hottest and aims to convert nearly everything to a combustible gas.

The short version

	Torrefaction	Pyrolysis	Gasification
Temperature	200–350 °C	~400–700 °C	Above ~700 °C
Oxygen	Very low	Effectively none	Controlled, sub-stoichiometric
Main output	Solid fuel	Char, bio-oil and gas	Syngas
Output is	Storable, transportable	Mixed; oil needs upgrading	Used immediately, on site
Typical use	Coal replacement, co-firing	Biochar, chemicals, fuels	Power generation

Torrefaction: keep the solid

Torrefaction heats material to 200–350 °C in a low-oxygen environment. It is deliberately gentle. Moisture leaves, the more volatile compounds leave, and what remains is a dry, brittle, carbon-dense solid that has lost mass but kept most of its energy.

The point is the physical change, not just the chemical one. Raw biomass is fibrous and damp; it jams and smears in equipment designed for coal. Torrefied material is brittle and dry, so it grinds and flows like coal. That single property is why torrefaction and not the other two is the process behind biomass co-firing.

Energy content of the output depends on what went in:

Feedstock	Calorific value (Kcal/kg)
Woody biomass	3,700 – 6,000
Rice straw biomass	4,000 – 4,300
Refuse Derived Fuel (RDF)	3,800 – 4,000
Municipal Solid Waste (MSW)	3,700 – 4,000
Undigested STP sludge	3,500 – 3,800

Pyrolysis: split the output

Push the temperature higher and exclude oxygen entirely and the feedstock stops merely drying out and starts decomposing. Pyrolysis produces three streams at once: solid char, a liquid bio-oil, and gas. How the split falls depends on how fast you heat and how long the material stays hot.

This is useful when the char or the oil is the product you want — biochar for soil, or bio-oil as a chemical feedstock. It is less useful when you want the maximum tonnage of storable solid fuel per tonne of input, because a substantial share of the mass leaves as liquid and gas.

Gasification: convert to gas

Gasification goes hotter still and admits a controlled, deliberately insufficient amount of oxygen or steam. The aim is not to burn the material but to convert almost all of its carbon into syngas, a combustible mixture of carbon monoxide and hydrogen, which is then burned to generate power.

The trade-off is storage. Syngas is generally produced and consumed on the same site. A solid fuel can be stockpiled through a monsoon, loaded onto a truck and delivered to a power station two states away.

Keystone Energy operates in both. Its gasification technology was evaluated and approved by an NGT-appointed committee including NEERI, CPCB and MoEF, and the NGT approved a 500 TPD waste-to-electricity plant in Srinagar in 2017.

How to choose

Work backwards from the output you need.

You need a coal substitute a power station can mill. Torrefaction. Nothing else produces the right physical fuel.

You need power at the site where the waste arrives. Gasification. No transport, no storage, no fuel logistics.

You want biochar or a chemical feedstock. Pyrolysis, tuned for the fraction you care about.

KeyTor, Keystone Energy's continuous torrefaction technology · Why co-firing drives torrefaction demand

Questions

What is the difference between torrefaction and pyrolysis?

Temperature and intent. Torrefaction runs at 200 to 350 degrees Celsius and is designed to keep most of the material as a solid fuel, removing moisture and volatiles while retaining energy density. Pyrolysis runs hotter, typically 400 to 700 degrees Celsius, and deliberately splits the feedstock into solid char, liquid bio-oil and gas.

What is the difference between torrefaction and gasification?

Gasification runs at much higher temperatures, typically above 700 degrees Celsius, with a controlled small amount of oxygen or steam, and converts nearly all the carbon into a combustible gas called syngas. Torrefaction keeps the output as a solid fuel. Gasification produces energy you use immediately; torrefaction produces fuel you can store and transport.

Which process suits biomass co-firing?

Torrefaction, because co-firing requires a solid fuel that behaves like coal in existing mills and handling equipment. Gasification produces a gas, which cannot be co-fired in a coal mill. Pyrolysis yields less solid product per tonne of input than torrefaction.

Does Keystone Energy do gasification as well as torrefaction?

Yes. Alongside torrefaction, Keystone Energy's waste-to-energy gasification technology was evaluated and approved by an NGT-appointed committee including NEERI, CPCB and MoEF, and the NGT approved a 500 TPD waste-to-electricity plant in Srinagar in 2017.