Revitalizing the sugarcane industry by adding value to A‐molasses in biorefineries

Abstract

The downward trend of global sugar market prices, as well as rising energy prices, threaten the survival of the South African sugar industry. Operating a single‐stage sugar crystallization process, which produces less crystalline sugar along with sucrose‐rich A‐molasses as a by‐product, to which value can be added in an integrated biorefinery, could be a viable solution for the industry. It would offer a diversification option as opposed to the current three‐stage crystallization process designed to achieve maximum sugar recovery. This study presents a rigorous Aspen Plus simulation development and economic assessment of different biorefinery scenarios producing succinic acid (SA) and short‐chain fructooligosaccharides (scFOS) from A‐molasses at target market sizes of 440 kt/year and 160 kt/year, respectively, considering the production capacity and market price interplays. In all, seven scenarios of single‐ or multi‐product(s) biorefinery annexed to an existing sugar mill were developed and assessed. Due to the integration benefits, all scenarios studied delivered an internal rate of return (IRR) between 24.1–61.1%, significantly above the required discount rate of 9.7%. In particular, co‐production of SA and scFOS syrup at production rates 40.5 kt/year and 13.5 kt/year from 70% and 30% of the A‐molasses, respectively resulted in the IRR of 56.1% and was considered the most attractive scenario based on the diverse bio‐production, economic performance and easy market entry of the products determined by low minimum selling prices. The proposed integration can lead to the sustainable operation of existing sugar mills by utilizing resources more efficiently, employment of product diversification and job creation. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd

Techno‐economic assessment of polylactic acid and polybutylene succinate production in an integrated sugarcane biorefinery

“…The final product was purified by evaporation to remove volatile components. The evaporator product was then crystallized and dried at 40 °C to obtain SA with 99.9% w.t purity 17 …”

“…Fermentation of succinic acid was achieved using an engineered strain of Escherichia coli capable of producing free succinic acid with a yield, concentration, and productivity of 0.96 g g -1 , 55.8 g L -1 and 0.77 g L -1 h -1 , respectively for the 1G scenario. 17 The A molasses was diluted with water to obtain the feed concentration of 150 g L -1 . Then 10% v/v of the diluted molasses was used for seed production, while the remaining 90% was fed to the fermenter.…”

“…The evaporator product was then crystallized and dried at 40 °C to obtain SA with 99.9% w.t purity. 17 Recent breakthroughs have been made by Genomaticaʼs researchers (a San Diego-based company) in the direct fermentation of BDO from sugars and a BDO concentration of above 100 g L -1 was achieved using an engineered E. coli strain. 28 The BDO in this study follows the direct fermentation pathway, where A molasses (1G) was fermented to produce BDO.…”

“…The techno‐economics of PBS production, on the other hand, have not been reported extensively. As in the case of PLA, most papers only investigated the techno‐economics of PBS monomer production, i.e., BDO and succinic acid production have been demonstrated to be economically viable in separate reports due to lower feedstock cost and capital investment 2,17–21 . Similar to PLA, the present study will consider PBS production where both monomers are obtained from 1G‐only, 1G2G, or 2G‐only sugarcane materials, producing fully biobased PBS in an energy self‐sufficient biorefinery annexed to an existing sugar mill.…”

“…As in the case of PLA, most papers only investigated the technoeconomics of PBS monomer production, i.e., BDO and succinic acid production have been demonstrated to be economically viable in separate reports due to lower feedstock cost and capital investment. 2,[17][18][19][20][21] Similar to PLA, the present study will consider PBS production where both monomers are obtained from 1G-only, 1G2G, or 2G-only sugarcane materials, producing fully biobased PBS in an energy self-sufficient biorefinery annexed to an existing sugar mill. The preferred production scenarios are identified based on production costs, reflected in the MSPs for an acceptable return on investment in the manufacturing facility of the respective products.…”