Multi-product biorefineries from lignocelluloses: a pathway to revitalisation of the sugar industry?

Abstract

BackgroundDriven by a range of sustainability challenges, e.g. climate change, resource depletion and expanding populations, a circular bioeconomy is emerging and expected to evolve progressively in the coming decades. South Africa along with other BRICS countries (Brazil, Russia, India and China) represents the emerging bioeconomy and contributes significantly to global sugar market. In our research, South Africa is used as a case study to demonstrate the sustainable design for the future biorefineries annexed to existing sugar industry. Detailed techno-economic evaluation and Life Cycle Assessment (LCA) were applied to model alternative routes for converting sugarcane residues (bagasse and trash) to selected biofuel and/or biochemicals (ethanol, ethanol and lactic acid, ethanol and furfural, butanol, methanol and Fischer–Tropsch synthesis, with co-production of surplus electricity) in an energy self-sufficient biorefinery system.ResultsEconomic assessment indicated that methanol synthesis with an internal rate of return (IRR) of 16.7% and ethanol–lactic acid co-production (20.5%) met the minimum investment criteria of 15%, while the latter had the lowest sensitivity to market price amongst all the scenarios. LCA results demonstrated that sugarcane cultivation was the most significant contributor to environmental impacts in all of the scenarios, other than the furfural production scenario in which a key step, a biphasic process with tetrahydrofuran solvent, had the most significant contribution.ConclusionOverall, the thermochemical routes presented environmental advantages over biochemical pathways on most of the impact categories, except for acidification and eutrophication. Of the investigated scenarios, furfural production delivered the inferior environmental performance, while methanol production performed best due to its low reagent consumption. The combined techno-economic and environmental assessments identified the performance-limiting steps in the 2G biorefinery design for sugarcane industry and highlighted the technology development opportunities under circular bioeconomy context.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-017-0761-9) contains supplementary material, which is available to authorised users.

Simulation and comparison of processes for biobutanol production from lignocellulose via ABE fermentation

“…Simultaneous saccharification and fermentation combined with GS is a promising approach for butanol production as the slow release of sugars in conjunction with product removal minimizes inhibition of substrate on microbial activity and thus increases the butanol yield and productivity . Wheat straw was pretreated using sulfuric acid at 1% (w/w) with a solids loading of 8.6% (w/w), at 121°C and 2 atm for 60 min, followed by neutralization with ammonia.…”

“…The process flow diagram for a separation train based on LLE and distillation is shown in Fig. and, again, can be used to recover and purify the ABE solvents from either the fermentation broth or the in situ separation (gas stripping) condensate . The product stream from fermentation was contacted with oleyl alcohol in an extraction column using a mass ratio of solvent to extractant of 0.983 with a contact time of 1 h. After contacting, an extractant recovery column was used to recover 99.99% of the oleyl alcohol for recycling and the raffinate was sent for anaerobic digestion.…”

A carbon footprint assessment of multi‐output biorefineries with international biomass supply: a case study for the Netherlands

“…The differences in scope, system design, and functional unit limit the scope for comparison with other multi‐output biorefinery studies such as Mandegari et al . and Farzad et al . Nevertheless, the GHG footprint of the individual outputs of the biorefinery to lactide and ethanol are compared with single‐output processes as shown in Table .…”

Process design and economic evaluation of integrated, multi‐product biorefineries for the co‐production of bio‐energy, succinic acid, and polyhydroxybutyrate (PHB) from sugarcane bagasse and trash lignocelluloses

“…Multiproduct plant biorefineries have been investigated for the production of furfural, xylitol, medium‐density fiberboard (MDF), and electricity from sugarcane lignocelluloses, of which the production of xylose syrup and furfural combined with MDF was profitable, with reported internal rates of return (IRR) of 16% and 19%, respectively . Other examples include the co‐production of ethanol, lactic acid, furfural, butanol, methanol, and electricity from sugarcane bagasse and trash in various scenarios, of which ethanol and lactic acid co‐production was the most profitable, with a reported IRR of 25.4% . More recently, succinic acid and the polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), have been identified as suitable to include in the range of multi‐product biorefineries .…”