Techno-economic analysis of chemically catalysed lignocellulose biorefineries at a typical sugar mill: Sorbitol or glucaric acid and electricity co-production.

Global concerns about depletion of fossil reserves has driven countries towards bio-economies utilising mostly first generation feedstocks. The economic viability of energy self-sufficient biorefineries processing sugarcane lignocelluloses into sorbitol or glucaric acid and electricity was investigated. Aspen Plus® simulations represented glucose conversion processes via SO2-steam explosion or dilute acid pre-treatment, followed by enzymatic hydrolysis. The most economically viable sorbitol scenario using dilute acid pretreatment with a capital investment cost per litre of US$ 3.96/L was marginally profitable having a selling price 5% below the US$ 655/t market price. To secure private investment, the sorbitol selling price should reach US$ 1283/t.

Process design and economic analysis of a biorefinery co-producing itaconic acid and electricity from sugarcane bagasse and trash lignocelluloses.

Itaconic acid has economic potential as a commodity biochemical for the sugar industry, but its production is limited due to high production costs. Using cheaper and alternative lignocellulosic feedstocks together with achieving higher product titres have been identified as potential strategies for viable IA production. Consequently the use of sugarcane bagasse and trash for the production of itaconic acid (IA) and electricity have been investigated for an integrated biorefinery, where the production facility is annexed to an existing sugar mill and new combined heat and power (CHP) plant. Three IA biorefinery scenarios were designed and simulated in Aspen Plus®. Subsequent economic analyses indicated that cheaper feedstocks reduced the IA production cost from 1565.5 US$/t for glucose to 616.5 US$/t, but coal supplementation was required to sufficiently lower the production cost to 604.3 US$/t for a competitive IA selling price of 1740 US$/t, compared to the market price of 1800 US$/t.

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

BACKGROUND: Driven 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. RESULTS: Economic 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. CONCLUSION: Overall, 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.