Engineering topics

Tucker, Melvin P

Publications and source records attributed to Tucker, Melvin P.

5 records

DOE OSTI2020

Ferrous and Ferric Ion-Facilitated Dilute Acid Pretreatment of Lignocellulosic Biomass under Anaerobic or Aerobic Conditions: Observations of Fe Valence Interchange and the Role of Fenton Reaction

Ferrous ion co-catalyst enhancement of dilute-acid (DA) pretreatment of biomass is a promising technology for increasing the release of sugars from recalcitrant lignocellulosic biomass. However, due to the reductive status of ferrous ion and its susceptibility to oxidation with exposure to atmosphere, its effective application presumably requires anaerobic aqueous conditions created by nitrogen gas-purging, which adds extra costs. The objective of this study was to assess the effectiveness of oxidative iron ion, (i.e., ferric ion) as a co-catalyst in DA pretreatment of biomass, using an anaerobic chamber to strictly control exposure to oxygen during setup and post-pretreatment analyses. Remarkably, the ferric ions were found to be as efficient as ferrous ions in enhancing sugar release during DA pretreatment of biomass, which may be attributed to the observation that a major portion of the initial ferric ions were converted to ferrous during pretreatment. Furthermore, the detection of hydrogen peroxide in the liquors after DA/Fe ion pretreatment suggests that Fenton reaction chemistry was likely involved in DA/Fe ion pretreatments of biomass, contributing to the observed ferric and ferrous interchanges during pretreatment. These results help define the extent and specification requirements for applying iron ions as co-catalysts in DA pretreatments of biomass.

09 BIOMASS FUELS↗

DOE OSTI2019

Improved Biomass Deacetylation and Deconstruction using a Continuous Counter-Current Reactor

Deacetylation and Mechanical Refining (DMR) process is an emerging technology that successfully demonstrated the capability to produce high titer, higher yield, low toxicity sugar and tractable lignin streams at low temperature atmospheric pressure conditions. Previous work has been performed all in batch stirred tank reactors with the scale up to 100kg/day. In this work we have adapted a shaftless inclined screw reactor to perform counter current deacetylation. Continuous counter-current extraction is practiced at the industrial scale in pulping processes to recycle the black liquor at high pressures/temperatures, enabling effective mass and heat transfer to achieve high lignin removal and efficient water/energy usages. Counter-current process steps enable high concentrations of the target compounds to be extracted into the extraction solvent and result in low residual content of the target compound in the extracted residue to increase efficiency and downstream product yields, while keeping the equipment more compact and decreased footprint dimensions compared to batch stirred tank reactors. Preliminary results have shown improved sugar yield in enzymatic hydrolysis at low enzyme loadings for the continuous counter-current deacetylation/mechanical refining process compared to the currently used batch process, while xylan losses into the black liquor are reduced up to 2/3.

09 BIOMASS FUELS↗

DOE OSTI2019

Enhanced Bioconversion in Herbaceous Feedstocks from Impregnation of Co-Catalytic Lewis Acid and Deacetylation and Mechanical Refining

Improvements in conversion processes are needed to further reduce process complexity, biorefinery capital and operating (CAPEX/OPEX) costs, lower enzyme usage. Previous work has demonstrated that deacetylation and mechanical refining (DMR) process effectively deconstructs herbaceous biomass while producing highly digestible lignocellulosic slurries, with high titers of monomeric sugars, at reduced enzyme loadings (Poster 553 Chen at al,). We evaluated a co-catalytic approach using three Lewis acids: Fe+2, Fe+3, and Al+3, in sulfate form, at 1 mM, 5 mM and 10 mM concentrations. Lewis acids were impregnated into corn stover, followed by deacetylation with NaOH, and mechanically refined, prior to enzymatic hydrolysis (EH). Lower concentrations of Lewis acid positively impacted EH yield, increasing concentration lowered EH yield. Likewise Lewis acid treatment was more effective when combined with deacetylation than with deacetylation or Lewis acid treatment, alone. Comparing the effectiveness of the three Lewis acids identified ferrous iron more effective than ferric or aluminum (Fe+2 > Fe+3> Al+3) sulfate. Enzymatic hydrolysis sugar (glucose and xylose) concentration was higher 8% and 13%, respectively, in Fe2+ impregnated corn stover compared to the control. Refining energy required for PFI milling was reduced by ~25% with Fe+2 impregnation. However, treatment with Fenton treatment of the Fe2+ impregnated, deacetylated and PFI milled corn stover resulted in lower yields. for monomeric glucose and xylose due to non-specific degradation of carbohydrates and lignin.

09 BIOMASS FUELS↗

DOE OSTI2017

Biomass Conversion

Biomass constitutes all the plant matter found on our planet, and is produced directly by photosynthesis, the fundamental engine of life on earth. It is the photosynthetic capability of plants to utilize carbon dioxide from the atmosphere that leads to its designation as a 'carbon neutral' fuel, meaning that it does not introduce new carbon into the atmosphere. This article discusses the life cycle assessments of biomass use and the magnitude of energy captured by photosynthesis in the form of biomass on the planet to appraise approaches to tap this energy to meet the ever-growing demand for energy.

09 BIOMASS FUELS↗

DOE OSTI2017

Conversion of Corn Stover Hydrolysates to Acids: Comparison Between Clostridium carboxidivorans P7 and Microbial Communities Developed from Lake Sediment and an Anaerobic Digester

Anaerobic fermentation is an environmentally sustainable technology for converting a variety of feedstocks to biofuels and bioproducts. Considering the complex nature of lignocellulosic hydrolysates, we aimed to investigate product formation from corn stover hydrolysates by using microbial communities under anaerobic conditions. A community developed from lake sediment was able to produce lactic acid from only glucose in the raw or overlimed hydrolysates. Another community from an anaerobic digester, however, was capable of using all hexose and pentose sugars in the raw and undetoxified hydrolysates and released lactic acid at 26.76 g/L. A pure acetogen, Clostridium carboxidivorans P7, was able to grow on the raw and overlimed hydrolysates, too. But the consumption of sugars was minimal and the total released acid concentrations were less than 2 g/L. Next generation sequencing of the enriched community derived from the anaerobic digester revealed the presence of Lactobacillus strains. The predominant species were Lactobacillus parafarraginis (72.6%) and L. buchneri (13.4%). Product titer from using this enriched community can be further enhanced by cultivating at fed-batch or continuous fermentation modes. Results from this study widened the door for producing valuable products from lignocellulosic feedstocks through using mixed cultures.

09 BIOMASS FUELS↗