BIOMASS AND BIOENERGY 38 (2012)68-94 Available at www.sciencedirect.com BIOMASS BIOENERGY ScienceDirect ELSEVIER http://www.elsevier.com/locate/biombioe Review of fast pyrolysis of biomass and product upgrading A.V.Bridgwater* Aston University Bioenergy Research Group,Aston Triangle,Birmingham B4 7ET,UK ARTICLE INFO ABSTRACT Article history: This paper provides an updated review on fast pyrolysis of biomass for production of Received 27 August 2010 a liquid usually referred to as bio-oil.The technology of fast pyrolysis is described including Received in revised form the major reaction systems.The primary liquid product is characterised by reference to the 27 January 2011 many properties that impact on its use.These properties have caused increasingly Accepted 28 January 2011 extensive research to be undertaken to address properties that need modification and this Available online 3 March 2011 area is reviewed in terms of physical,catalytic and chemical upgrading.Of particular note is the increasing diversity of methods and catalysts and particularly the complexity and Keywords: sophistication of multi-functional catalyst systems.It is also important to see more Fast pyrolysis companies involved in this technology area and increased take-up of evolving upgrading Biomass processes. Bio-oil 2011 Elsevier Ltd.All rights reserved. Catalyst 1. Introduction technology with applications in most industrialised and developing countries and development is concentrated on Biomass fuels and residues can be converted to more valuable resolving environmental problems [2].Gasification has been energy forms via a number of processes including thermal, practiced for many years and while there are many examples biological,and mechanical or physical processes.While bio- of demonstration and pre-commercial activities [3,4]there are logical processing is usually very selective and produces a small still surprisingly few successful operational units.This review number of discrete products in high yield using biological focuses on the emerging advanced technology of fast pyrol- catalysts,thermal conversion often gives multiple and often ysis both as an integrated process for production of a liquid complex products,in very short reaction times with inorganic fuel that can be used directly and as an intermediate pre- catalysts often used to improve the product quality or spec- treatment step to convert solid biomass into a higher energy trum.Pyrolysis has been applied for thousands of years for content transportable liquid for subsequent processing for charcoal production but it is only on the last 30 years that fast heat,power,biofuels,and chemicals.This technology is pyrolysis at moderate temperatures of around 500C and very widely expected to offer a considerable contribution in the short reaction times of up to 2 s has become of considerable short term in terms of versatility,improved efficiency and interest.This is because the process directly gives high yields of environmental acceptability. liquids of up to 75 wt%which can be used directly in a variety of applications [1]or used as an efficient energy carrier. Fig.1 summarises the markets for the products from the Fast pyrolysis three main thermal processes available for converting bio- mass to a more useful energy form-pyrolysis,gasification and Pyrolysis is thermal decomposition occurring in the absence combustion.Combustion is a well-established commercial of oxygen.Lower process temperatures and longer vapour ·Tel.:+441212043381;fax:+441212043680 E-mail address:a.v.bridgwater@aston.ac.uk. 0961-9534/$-see front matter@2011 Elsevier Ltd.All rights reserved. doi10.1016/j.biombioe.2011.01.048Review of fast pyrolysis of biomass and product upgrading A.V. Bridgwater* Aston University Bioenergy Research Group, Aston Triangle, Birmingham B4 7ET, UK article info Article history: Received 27 August 2010 Received in revised form 27 January 2011 Accepted 28 January 2011 Available online 3 March 2011 Keywords: Fast pyrolysis Biomass Bio-oil Catalyst abstract This paper provides an updated review on fast pyrolysis of biomass for production of a liquid usually referred to as bio-oil. The technology of fast pyrolysis is described including the major reaction systems. The primary liquid product is characterised by reference to the many properties that impact on its use. These properties have caused increasingly extensive research to be undertaken to address properties that need modification and this area is reviewed in terms of physical, catalytic and chemical upgrading. Of particular note is the increasing diversity of methods and catalysts and particularly the complexity and sophistication of multi-functional catalyst systems. It is also important to see more companies involved in this technology area and increased take-up of evolving upgrading processes. ª 2011 Elsevier Ltd. All rights reserved. 1. Introduction Biomass fuels and residues can be converted to more valuable energy forms via a number of processes including thermal, biological, and mechanical or physical processes. While bio￾logical processing is usually very selective and produces a small number of discrete products in high yield using biological catalysts, thermal conversion often gives multiple and often complex products, in very short reaction times with inorganic catalysts often used to improve the product quality or spec￾trum. Pyrolysis has been applied for thousands of years for charcoal production but it is only on the last 30 years that fast pyrolysis at moderate temperatures of around 500
C and very short reaction times of up to 2 s has become of considerable interest. This is because the process directly gives high yields of liquids of up to 75 wt.% which can be used directly in a variety of applications [1] or used as an efficient energy carrier. Fig. 1 summarises the markets for the products from the three main thermal processes available for converting bio￾mass to a more useful energy form - pyrolysis, gasification and combustion. Combustion is a well-established commercial technology with applications in most industrialised and developing countries and development is concentrated on resolving environmental problems [2]. Gasification has been practiced for many years and while there are many examples of demonstration and pre-commercial activities [3,4] there are still surprisingly few successful operational units. This review focuses on the emerging advanced technology of fast pyrol￾ysis both as an integrated process for production of a liquid fuel that can be used directly and as an intermediate pre￾treatment step to convert solid biomass into a higher energy content transportable liquid for subsequent processing for heat, power, biofuels, and chemicals. This technology is widely expected to offer a considerable contribution in the short term in terms of versatility, improved efficiency and environmental acceptability. 2. Fast pyrolysis Pyrolysis is thermal decomposition occurring in the absence of oxygen. Lower process temperatures and longer vapour * Tel.: þ44 121 204 3381; fax: þ44 121 204 3680. E-mail address: a.v.bridgwater@aston.ac.uk. Available at www.sciencedirect.com http://www.elsevier.com/locate/biombioe biomass and bioenergy 38 (2012) 68 e9 4 0961-9534/$ e see front matter ª 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.biombioe.2011.01.048