The economic viability of either of the final product. liquefaction tends to be more economical considering the energy consumption required in the two processes. Pyrolysis requires much higher temperature as compared to liquefaction. this high temperature translates into high energy cost, high tech requirement for maintaining high temperature processes. On the contrary, liquefaction is characterized by high waste water production which is presently generating debate on the economics of this process. 

First of all, all the three products your have mentioned can be produced from a single process. Of course in varying proposition depending on the extent of heating. As such temperature is the main determining factor here. Biocrude is largely produced within the temperature range of 350oC-650oC, which falls within the temperature range suitable for pyrolysis, although other products including syngas and biochar are also produced in small quantities. At higher temperature above this range, Biomass gasification is must dominant [750oC-1100oC]. Liquefaction is similar to pyrolysis but at relatively lower temperature. Water is also used as the delignifying agent unlike in pyrolysis. It could be deduced that Liquefaction tends to be more economical due to low temperature factor, however, the fuel produced have very low quality. In fact, they are mostly reducing sugars with low heating value. The product requires additional processing. In pyrolysis, the high temperature provides additional heating value of the biocrude [not as suitable for direct fuel application].

To answer your question, the nature of the final product you are interested in is the deciding factor as to which process you will follow.

We have recently published 3 papers that, although only dealing with algae, may be of interest

Milledge JJ, Heaven S (2014) Methods of energy extraction from microalgal biomass: a review. Reviews in Environmental Science and Bio/Technology 13 (3):301-320. doi:10.1007/s11157-014-9339-1

Milledge JJ, Smith B, Dyer P, Harvey P (2014) Macroalgae-Derived Biofuel: A Review of Methods of Energy Extraction from Seaweed Biomass. Energies 7 (11):7194-7222

Milledge JJ, Staple A, Harvey P (2015) Slow Pyrolysis as a Method for the Destruction of Japanese Wireweed, Sargassum muticum. Environment and Natural Resources Research 5 (1):28-36. doi:10.5539/enrr.v5n1p28

Liquefaction is a high pressure process and the feeding process could be clompex. Slurries are more suitabale for liquefaction than pyrolysis because the water evaporation energy is reduced at such high pressures and relatively low temperatures. See HTU process. The obtained biocrude is very viscous with tendence to polymerize but with quite good H/C, O/C ratios compared with pyrolysis bio-oil

Biomass Fast Pyrolysis is carried out at atmospheric pressure and moderate temperatures. The feedstock must be dry and milled. The liquid quality is low and must be upgraded, and this upgrading it is not and easy or cheap process.

Jon Makibar John Milledge Y. Alhassan

Thank you all for deep insights towards comparative study on cost effectiveness of Pyrolysis and Liquefaction . Your contributions are highly appreciated.

May I ask, is there anyone working on or know about precise method known to control the cost effectiveness of Pyrolysis and Liquefaction ?

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