Butanol production in a sugarcane biorefinery using ethanol as feedstock. Part II: Integration to a second generation sugarcane distillery

Life cycle assessment on calcium zincate production methods for rechargeable batteries

The world's energy transition from fossil to renewable energy is unthinkable without further research in energy storage. Decreasing the environmental impacts from the production of energy storage technologies is essential for achieving a green energy transition. Calcium Zincate (CAZN) is used as active material in rechargeable zinc-based batteries (and other products, such as heterogeneous catalysts for biodiesel or antifungal products). They present a low-cost, safer, alternative to Lithium based batteries and are targeted as replacement solutions for lead-acid batteries. We propose a novelty in the synthesis of CAZN, the hydro-micro-mechanical process (HMMS). The residence time of this new route is about 20 times lower than the traditional processes, so its production needs less infrastructure and can deliver quicker at an industrial scale. In addition, laboratory tests indicate that HMMS CAZN has more reaction surface area and the activation of the battery is 1.77 times faster. Using the life cycle assessment (LCA) method, we compare this new process with the current best option, hydro-thermal synthesis (HTS). The cradle-to-gate results per kg of CAZN already indicates that HMMS is an environmentally better alternative for all indicators; especially when considering the normalization of the results with the residence time and the surface area, HMMS delivers better results, with improvements of 97 % in global warming, for instance. With this, we demonstrate that, outside of the cradle-to-gate, variables that make the final products better service units or give more function should be considered as valuable additional information when deciding among alternatives. This also highlights the importance of life cycle thinking when working with chemical processes and substances. In the sensitivity analysis, we developed 7 scenarios related to the energy demand of the processes, and we incorporated the projection in the European electricity mix for 2030 and 2050.

Potentials of bio-butanol conversion to valuable products

In the last decade, there was observed a growing demand for both n-butanol as a potential fuel or fuel additive, and propylene as the only raw material for production of alcohol and other more bulky propylene chemical derivatives with faster growing outputs (polymers, propylene oxide, and acrylic acid). The predictable oilfield depletion and the European Green Deal adoption stimulated interest in alternative processes for n-butanol production, especially those involving bio-based materials. Their commercialization will promote additional market penetration of n-butanol for its application as a basic chemical. We analyze briefly the current status of two most advanced bio-based processes, i.e. ethanol–to-n-butanol and acetone–butanol–ethanol (ABE) fermentation. In the second part of the review, studies of n-butanol and ABE conversion to valuable products are considered with an emphasis on the most perspective catalytic systems and variants of the future processes realization.

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.

Investigation of uncertainties associated with the production of n-butanol through ethanol catalysis in sugarcane biorefineries

This study evaluated the viability of n-butanol production integrated within a first and second generation sugarcane biorefinery. The evaluation included a deterministic analysis as well as a stochastic approach, the latter using Monte Carlo simulation. Results were promising for n-butanol production in terms of revenues per tonne of processed sugarcane, but discouraging with respect to internal rate of return (IRR). The uncertainty analysis determined there was high risk involved in producing n-butanol and co-products from ethanol catalysis. It is unlikely that these products and associated production route will be financially attractive in the short term without lower investment costs, supportive public policies and tax incentives coupled with biofuels' production strategies.

Review of catalytic systems and thermodynamics for the Guerbet condensation reaction and challenges for biomass valorization

This review deals with homogeneous and heterogeneous catalytic processes for the Guerbet condensation, as well as discusses biomass sources, thermodynamics and technological considerations.