5 Commercial Aspects of Biomass Deconstruction with Ionic Liquids
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steer research towards solving these weaknesses. In the case of the ionoSolv process, the effective application of [HSO 4 ]-based PILs for biomass fractionation held
high potential for the development of an economical IL-based pretreatment process.
However, it was important to understand the main factors that govern the process economics and resolve any problems. It was also of key importance to build an in-depth
understanding of the process fundamentals and evaluate the process performance at
intensified conditions that might potentially be translated to industry.
5.5.1 Resolving the Key Cost Driver
The first techno-economic assessment of IL-based pretreatment was conducted in
2011 using [C 2 C 1 im][Ace] as a cellulose-dissolving IL [100]. The motivation was
to identify the main operational targets that are needed to be improved for an ILbased pretreatment to be economically competitive with peer technologies. The key
variables driving the process economics were identified to include: (1) IL cost, (2) IL:
solid loading, and (3) IL recovery. The authors emphasized that reducing the IL price
is the sole factor that needs to be targeted to achieve an economically viable process.
This is indeed true as the IL make-up amount (and, thereby, the associated IL makeup cost) is linked to the solid loading and recycle rate. For example, lowering the IL
use in the process by increasing the biomass to ionic liquid ratio from 1:10 to 1:1 will
increase IL make-up cost by an order of magnitude. The study took into consideration
an IL cost range of $2.5–$50 kg
−1 , which were considered reasonable given the scale
of operation, yet they were still 2–50 times higher than organic solvent costs, such
as toluene ($1.03 kg
−1 ) and acetone ($1.30 kg
−1 ). Another techno-economic study
considered more intensified biomass dissolution pretreatment schemes that included
a “one-pot” process and a conventional pretreatment dissolution route [101]. It was
highlighted that even at the most economically optimistic conditions (which might
be very challenging to achieve in reality) of 99.6% IL recovery and 50% biomass,
the process minimum ethanol selling price (MESP) for both schemes was >$6 gal
−1 ,
which is very high compared to a MESP of $2.15 gal
−1 that was estimated for dilute
acid pretreatment [102].
Even though the techno-economic assessments were done based on the IL biomass
dissolution process, it is very likely that the same parameters (IL cost, IL: biomass
loading, and IL recovery) will drive the process economics in IL fractionation processes. As stated earlier, the shift from using an APIL to a PIL for biomass delignification in the ionoSolv process was a key turning point that held so much potential in
resolving the IL high-cost issue. To quantitively assess the anticipated cost reduction,
Chen et al. performed the first economical evaluation that estimated the large-scale
production cost of PILs used in the ionoSolv process [30]. Conducting such an economic evaluation was highly valuable not only to provide the IL production cost
estimate but also to highlight the key aspects that contribute to the IL production
cost, which can serve as a guideline for designing and estimating the cost of other
PILs. In addition, although for the past two decades the cost of ILs has been always
103
steer research towards solving these weaknesses. In the case of the ionoSolv process, the effective application of [HSO 4 ]-based PILs for biomass fractionation held
high potential for the development of an economical IL-based pretreatment process.
However, it was important to understand the main factors that govern the process economics and resolve any problems. It was also of key importance to build an in-depth
understanding of the process fundamentals and evaluate the process performance at
intensified conditions that might potentially be translated to industry.
5.5.1 Resolving the Key Cost Driver
The first techno-economic assessment of IL-based pretreatment was conducted in
2011 using [C 2 C 1 im][Ace] as a cellulose-dissolving IL [100]. The motivation was
to identify the main operational targets that are needed to be improved for an ILbased pretreatment to be economically competitive with peer technologies. The key
variables driving the process economics were identified to include: (1) IL cost, (2) IL:
solid loading, and (3) IL recovery. The authors emphasized that reducing the IL price
is the sole factor that needs to be targeted to achieve an economically viable process.
This is indeed true as the IL make-up amount (and, thereby, the associated IL makeup cost) is linked to the solid loading and recycle rate. For example, lowering the IL
use in the process by increasing the biomass to ionic liquid ratio from 1:10 to 1:1 will
increase IL make-up cost by an order of magnitude. The study took into consideration
an IL cost range of $2.5–$50 kg
−1 , which were considered reasonable given the scale
of operation, yet they were still 2–50 times higher than organic solvent costs, such
as toluene ($1.03 kg
−1 ) and acetone ($1.30 kg
−1 ). Another techno-economic study
considered more intensified biomass dissolution pretreatment schemes that included
a “one-pot” process and a conventional pretreatment dissolution route [101]. It was
highlighted that even at the most economically optimistic conditions (which might
be very challenging to achieve in reality) of 99.6% IL recovery and 50% biomass,
the process minimum ethanol selling price (MESP) for both schemes was >$6 gal
−1 ,
which is very high compared to a MESP of $2.15 gal
−1 that was estimated for dilute
acid pretreatment [102].
Even though the techno-economic assessments were done based on the IL biomass
dissolution process, it is very likely that the same parameters (IL cost, IL: biomass
loading, and IL recovery) will drive the process economics in IL fractionation processes. As stated earlier, the shift from using an APIL to a PIL for biomass delignification in the ionoSolv process was a key turning point that held so much potential in
resolving the IL high-cost issue. To quantitively assess the anticipated cost reduction,
Chen et al. performed the first economical evaluation that estimated the large-scale
production cost of PILs used in the ionoSolv process [30]. Conducting such an economic evaluation was highly valuable not only to provide the IL production cost
estimate but also to highlight the key aspects that contribute to the IL production
cost, which can serve as a guideline for designing and estimating the cost of other
PILs. In addition, although for the past two decades the cost of ILs has been always