Techno-economic analysis of 1,3-propanediol, sorbitol, itaconic acid, and xylooligosaccharides production from sugarcane-based feedstocks

Date
2023-03
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Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: In an effort to reduce the human impact on the environment and reduce our reliance on finite fossilbased resources, the need for cost-competitive bioproducts is increasing. One of the potential feedstocks for the establishment of a successful green economy is sugarcane. The South African sugar industry is facing several economic challenges that can be lessened by adding an annexed biorefinery producing high-value bio-products to existing sugarcane mills, to diversify their revenue streams. Both first generation (1G) (molasses) and second generation (2G) (bagasse and trash) feedstock can be used in a biorefinery. This project aimed to evaluate the feasibility of a biorefinery annexed to a South African sugar mill, based on a selection of potential products. Four different bio-products were considered for production from sugarcane-based feedstocks. 1,3- Propanediol (PDO) is a useful building block used in producing the popular textile iiolytrimethylene terephthalate. It can be used as a precursor in polyurethane production among several other uses. Xylooligosaccharides (XOS) is an emerging prebiotic with the outlook of giving value to the hemicellulose portion of lignocellulose. Sorbitol is a well-known sugar alcohol predominantly used in the food industry and for vitamin-C production with the potential of replacing several fossil-based chemical products. Itaconic acid (IA) can become an important commodity biochemical with applications in several polymers, detergent builders, and surfactants if the market price of this product can become competitive with its fossil-based equivalents. These selected 4 products were assessed for economic and environmental feasibility in their own right, together with comparison to alternative products reported elsewhere. Following the development of the process scenarios from literature, the economic feasibility of the scenarios was evaluated using discounted cash flow sheets. PDO production from 1G, 1G2G, and crude glycerol was compared. It was found that a direct fermentation strategy utilising 1G feedstock had the lowest energy and capital investment costs. Consequently, it was the most profitable PDO scenario with an internal rate of return (IRR) of 75.36%. XOS production was found to have the highest IRR of all the investigated scenarios at 87.94%. However, despite having a lower IRR of 77.73%, PDO and XOS co-production better utilized the available 1G and 2G feedstock and would likely be a safer investment. Sorbitol production with green hydrogen resulted in one feasible scenario for the 1G sorbitol and mannitol co-production, while two other scenarios were found to have an IRR within 2% of the preferred IRR of 20%. The low market price and energy-intensive fermentation process for IA production led to unfeasible IA scenarios. The environmental performance of investigated scenarios has been compared by determining their greenhouse gas (GHG) emissions with a GHG calculator tool. Sorbitol production, direct PDO production, PDO and XOS co-production, and 1G IA production were found to have low GHG emissions while indirect PDO production, XOS production, and 1G2G IA production had high GHG emissions. Two scenarios, direct PDO production and PDO and XOS co-production from 1G2G feedstock were consequently identified as biorefinery scenarios that will both have economic and environmental benefits and are therefore recommended as possibly feasible biorefinery scenarios.
AFRIKAANS OPSOMMING: In ‘n poging om die menslike impak op die omgewing te verminder en ons afhanklikheid van beperkte fossielgebaseerde hulpbronne te verminder, neem die behoefte aan koste-mededingende bioprodukte toe. Een van die potensiële voerstowwe vir die stiging van ‘n suksesvolle groen ekonomie is suikerriet. Die Suid-Afrikaanse suikerbedryf ondervind verskeie ekonomiese uitdagings wat verminder kan word deur die ‘n aangehegte bioraffindery wat hoëwaarde bioprodukte produseer aan ‘n bestaande suikerrietmeul aan te heg, om hul inkomste strome te diversifiseer. Beide eerste generasie (1G) (molasse) en tweede generasie (2G) (bagasse en bruin blare) voerstowwe kan gebruik word in ‘n bioraffindery. Hierdie projek het die doel gehad om die lewensvatbaarheid van ‘n bioraffindery wat aan ‘n Suid-Afrikaanse suikermeul aangeheg is, te evalueer, gebaseer op ‘n seleksie van potensiële produkte. Vier verskillende bio-produkte is oorweeg vir produksie uit suikerriet-gebaseerde voerstowwe. 1,3- Propanediol (PDO) is ‘n nuttige bousteen wat gebruik word in die produksie van die gewilde tekstiel politrimiëleenterftalaat. Dit kan gebruik word as ‘n voerstof in poliuretaan produksie en het verskeie ander toepassings. Xylooligosakkariede (XOS) is ‘n opkomende prebiotikum met die vooruitsig om waarde aan die hemisellulose gedeelte van lignosellulose te gee. Sorbitol is ‘n bekende suikeralkohol wat hoofsaaklik in die voedselbedryf en vir vitamien-C produksie gebruik word, met die potensiaal om verskeie fossielgebaseerde produkte te vervang. Itakoniese suur (IA) kan ‘n belangrike kommoditeitsbiochemikalie word met toepassings in verskeie polimere, wasmiddelbouers en oppervlakaktiewe stowwe as die markprys van hierdie produk mededingend word met sy fossielgebaseerde ekwivalente. Hierdie vier geselekteerde produkte is geassesseer vir ekonomiese en omgewingslewensvatbaarheid in eie reg en is vergelyk met ander bioprodukte elders gerapporteer. Na die ontwikkeling van die proses scenario’s uit literatuur, is die ekonomiese lewensvatbaarheid van die scenario’s geëvalueer deur gebruik te maak van afgeskaalde kontantvloei-lêers. PDO-produksie vanaf 1G, 1G2G, en ru-gliserole was vergelyk. Dit is bevind dat ‘n direkte fermenteringsstrategie met 1G voerstowwe, die laagste energie- en kapitaalbeleggingskoste gehad het. Dit was dus die mees winsgewende PDO-scenario met ‘n interne opbrengskoers (IRR) van 75.36%. XOS-produksie het die hoogste IRR van al die ondersoekte scenario’s getoon met 87.94%. Nietemin het PDO en XOS koproduksie, ondanks ‘n laer IRR van 77.73%, die beskikbare 1G en 2G voerstowwe beter benut en sal waarskynlik ‘n veiliger belegging wees. Sorbitol produksie met groen waterstof het gelei tot een winsgewende scenario vir die 1G sorbitol en mannitol ko-produksie, terwyl twee ander scenario’s binne 2% van die verkose IRR van 20% was. Die lae markprys en energie-intensiewe fermenteringsproses vir IA-produksie het gelei tot onwinsgewende IA-scenario’s. Die omgewingsprestasie van ondersoekte scenario’s is vergelyk deur hul uitstoot van kweekhuisgasse (GHG) te bepaal met ‘n GHG-rekenaar-hulpmiddel. Sorbitol-produksie, direkte PDO-produksie, PDO en XOS ko-produksie, en 1G IA-produksie het lae GHG-uitlatings getoon, terwyl indirekte PDOproduksie, XOS-produksie, en 1G2G IA-produksie hoë GHG-uitlatings gehad het. Twee scenario’s, direkte PDO-produksie en PDO en XOS ko-produksie vanaf 1G2G voerstowwe, is gevolglik geïdentifiseer as bioraffindery scenario’s wat beide ekonomiese en omgewingsvoordele sal hê en daarom aanbeveel word as moontlike lewensvatbare bioraffindery scenario’s.
Description
Thesis (MEng)--Stellenbosch University, 2023.
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