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Bioenergy > Technologies > Thermochemical technologies > Pyrolysis

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Pyrolysis is a thermochemical conversion technology used to produce energy from biomass. It involves the heating of organic materials in the absence of reagents, especially oxygen, to achieve decomposition. When pyrolysis takes place in the presence of water, it is called hydrous pyrolysis.

Flowchart of pyrolysis (Source: DOE).


Types of Pyrolysis Technologies

Pyrolysis technologies can be categorized as being of two types:

  • Fast Pyrolysis, and
  • Slow Pyrolysis.

Fast Pyrolysis

Fast pyrolysis (Flash pyrolysis) takes place in less than two seconds with temperatures between 300 and 550 degrees Celsius. Char accumulates quickly in fast pyrolysis and must be removed frequently.

Fast Pyrolsis can be further categorized into the following:

  • Ablative Fast Pyrolysis - pressure is applied to biomass to increase speed of decomposition through use of centrifugal or mechanical force. Larger particles of biomass can be used in this process.
  • Cyclonic Fast Pyrolysis - also called vortex fast pyrolysis, separates the solids from the non-condensible gases and returns them to the mixer.
  • Rotating Cone Fast Pyrolysis - uses a compact high intensity reactor in which biomass of ambient temperature is mixed with hot sand. Upon mixing with the hot sand, the biomass decomposes into 70% condensible gases with 15% non-condensible gases and 15% char.

Feedstocks for Fast Pyrolysis

  • Any Organic Material
    • Pretreatment: sorting
    • Qualifications: none

Slow Pyrolysis

Feedstocks for Slow Pyrolysis

  • Any Organic Material
    • Pretreatment: sorting
    • Qualifications: Waste must be pre-sorted and processed to <6 mm (1 to 2 mm. preferred) and <10% moisture content to assure high heat transfer rate.


Products of pyrolysis include:

Advantages of Pyrolysis

  • Generally a simple, low-cost technology capable of processing a wide variety of feedstocks producing gases, a bio-oil, bio-chemicals, and charcoal. A promising approach is the production of a bio-oil that can be used to power ethanol, biodiesel or other local industries facilities, and a charcoal. The charcoal is incorporated into the soil to promote its fertility and organic matter through synergistic processes between the soil, soil organisms, the roots fo the plants, water and the CO2 and nitrogen in the atmosphere.

Commercialization Status

  • Pilot project:
    • Cashton Greens Energy Park, Cashton WI.
  • Limited commercialization:
    • Dynamotive, Canada.

Sustainability and Environmental Concerns

  • By using waste streams and fully sustainable biomass, there are many environmental benefits including greenhouse gas stabilization.

Societal Impacts

  • Properly structured, this technology provides waste collecting jobs for low-income people and opportunities for skilled technicians. This benefits communities through waste clean up (public health benefits), the use of local feedstocks and by providing decentralized power and fuels as well as charcoal to increase soil fertility and organic matter levels.



  • Seaweed could have important biofuel role, say scientists, 6 July 2011 by "Researchers at Aberystwyth University say kelp seaweed could provide an important alternative to land-based biofuels, but the suitability of its chemical composition varies with the seasons."
    • "They say harvesting the kelp in July, when carbohydrate levels are at their highest, would ensure optimal sugar release for the production of biofuel."
    • "Kelp can be converted to biofuels through fermentation or anaerobic digestion – to produce ethanol and methane – or pyrolysis, to produce bio-oil through a method of heating the fuel without oxygen. But the chemical composition of the seaweed is important for these processes to be effective."
    • "Land-based plants have been the focus of most biofuel research. But biofuels have a disadvantage as they create conflict between using land to grow either food or fuel. Marine ecosystems are considered an untapped resource that could address this conflict, and provide for over half of global biomass energy."[1]


Sketch of an apparatus for testing biofuel potential of various agricultural wastes, created by the RPI spring 2010 biomass capstone group. Image from The New York Times blog article A New Approach to Biofuel in Africa
  • A New Approach to Biofuel in Africa, 12 July 2010 by Ron Eglash: "The biofuel concept: If you just burn plant materials, you put out a lot of bad pollutants. But if you heat the materials in a container without oxygen (“pyrolysis”), you leave most of the carbon as “biochar,” which makes an excellent soil additive (in fact Amazon Indians built up rich soils over hundreds of years using biochar). The gas that is given off by pyrolysis can be processed into clean-burning fuel."
    • "All of which sounds great, but skeptics point out that Africa is a prime target for biofuel land grabs, which destroy small farms and forest preserves. Hence the importance of using agricultural residues like corn cobs, and researching the impact."[2]
  • DOE Announces up to $11 Million for Biofuels Technology Development, 28 May 2010 by US Department of Energy: "The U.S. Department of Energy (DOE) today announced up to $11 million in funding over three years for research and development in the area of thermochemical conversion of biomass into advanced biofuels that are compatible with existing fueling infrastructure. The objective of this funding is to improve the conversion of non-food biomass to liquid transportation hydrocarbon fuels via pyrolysis, a process that decomposes biomass using heat in the absence of oxygen to produce a bio-oil that can be upgraded to renewable diesel, gasoline, or jet fuel."
    • "DOE anticipates selecting three to four projects under this announcement and will require a minimum of 20% cost share from applicants. Selected projects will also be required to include an analysis of greenhouse gas reductions as compared with petroleum fuels."[3]


  • Dead Forests to Fuel Vehicles, 15 September 2009 by CleanTechnica: "The University of Georgia Research Foundation has developed an innovative way to turn dead trees into a liquid fuel and has licensed it to Tolero Energy in California. We could be driving on our dead forests as soon as 2010."
    • "The technology represents a leap forward for the biofuels industry. Not only does the resulting biofuel need no additional refinement before blending with diesel fuel, but it is a naturally very low-sulphur biofuel."
    • "Tolero will use this low-cost, on-site process to turn waste biomass into sustainable and renewable forms of energy and industrial products. The biomass is heated at carefully controlled high temperatures in the absence of oxygen, a process known as fast pyrolysis. The vapors produced during pyrolysis rapidly condense into a bio-oil that can be added to biodiesel or petroleum diesel. Other pyrolysis by-products are gas and bio-char, which can be used as a soil amendment."[4]









This information was developed by the United States Environmental Protection Agency, Office of Research and Development, in cooperation with the Biomass Coordinating Council of the American Council on Renewable Energy (ACORE).

Pyrolysis edit

Fast pyrolysis | Slow pyrolysis
Pyrolysis feedstocks: Wood residues, Gynerium sagittatum
Pyrolysis oil
Low temperature pyrolysis

Bioenergy conversion technologies edit
Technologies categorized by bioenergy processes:

Biochemical: Aerobic, Anaerobic, Landfill gas collection (LFG), Biodiesel production, Ethanol production
Thermochemical: Combustion, Gasification, Pyrolysis, Depolymerization

Technologies categorized by feedstock:
Algae | Cellulosic technology

Technologies by commercialization status:

Analysis of technologies: Life-cycle analysis


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