Date of Award

Fall 12-15-2023

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

Advisor

Adriaan R. P. van Heiningen

Second Committee Member

Valdeir Arantes

Third Committee Member

Douglas W. Bousfield

Additional Committee Members

M. Clayton Wheeler

Mehdi Tajvidi

Abstract

Market trends show growing interest in cellulose nanomaterials due to their low environmental impact. However, current nanocellulose isolation technologies face technoeconomic and life cycle limitations. Previous research has shown that enzymatic treatments effectively reduce the energy input for mechanical nanocellulose isolation. Simultaneously, there is potential to improve the viability of cellulosic ethanol facilities by coproducing nanocelluloses as high-value product obtained from agricultural feedstock. Here, our goal was to study the mass balance of enzymatic-mechanical processes that coproduces cellulosic sugars and nanocelluloses, evaluating the technical feasibility of converting lignified and non-lignified materials.

First, we have determined a feasible 50:50 mass ratio to obtain nanocelluloses and sugars using efficient-saccharification enzyme cocktails. This ratio, derived from breakeven point in the enzyme cost equation, was set as target for converting carbohydrates.

We investigated the coproduction of nanocelluloses (CNC and CNF) and high-titer sugars from hardwood bleached kraft pulp (HBKP), varying cellulose conversion. The integration was technically feasible and required low energy consumption. Total sugars concentration was 61–165 g.L-1. Optimizing CNC yield via response surface yielded in 4.4–8.7 g/100g of HBKP. CTec2 treatment significantly reduced the energy input for CNF isolation with energy savings up to 80% when compared to ultra-refining HBPK without pretreatment (25 kWh.kg-1).

A new process method was studied to pretretreat sugarcane bagasse (SCB) and sugarcane straw (SCS), obtain sodium acetate and sugars, and isolate lignin-containing nanocelluloses (LCNC and LCNF). The pretreatment involved a modified version of the Deacetylation and Mechanical Refining (DMR) process, that was considered versatile and promoted full valorization of the biomasses. The pretreated materials had high fines level (83.6 – 87.9%) after Cellic CTec3/HTec3 treatment, hence significantly low energy input was required during ultra-refining. Total sugars concentration was 37–48 g.L-1 for SCB and 31.3 g.L-1 for SCS. LCNC yield was 5–7 g/100g of SCB and 6 g/100g of SCS. LCNF yield was 67–72 g/100g of SCB and 72 g/100g of SCS.

The isolated lignin-containing nanocelluloses showed promising surface chemistry both as suspensions and films. LCNFs had high hydrophobicity (94o to 102º), low wettability (up to 810s), and good thermostability (Tmax 334–337 oC).

Comments

This work was produced under a Cotutelle agreement to obtain a joint doctorade degree, being Doctor in Science degree in Industrial Biotechnology (Biomass conversion concentration) from University of São Paulo (Brazil) and Doctor of Philosophy degree in Chemical Engineering from the University of Maine.

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