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At least 91 records · Page 5
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DOE OSTI2023

Mild organosolv pretreatment of sugarcane bagasse with acetone/phenoxyethanol/water for enhanced sugar production

This study conducted mild organosolv pretreatment of sugarcane bagasse with acetone/phenoxyethanol/water (APW) solutions to improve sugar production in the subsequent enzymatic hydrolysis step. Here, the Box–Behnken design was used to optimize pretreatment conditions based on lignin removal. Further examination of the data revealed that lignin removal was positively correlated (R 2 > 0.95) with the combined severity factor (CSF). Pretreatment under the optimal conditions (125 °C–120 min, 0.17 M H 2 SO 4 , liquid–solid ratio of 15) led to 98.1% lignin removal and 74.5% cellulose digestibility compared to a low digestibility of 9.3% with raw sugarcane bagasse (SCB). Moreover, the APW process showed effective fractionation of pine, corn stalk and bamboo, and lignin removal was over 90%. The recovered lignin was characterized by 2D-HSQC NMR and 31P NMR, suggesting that the pretreatment resulted in breakage of β-O-4, total phenolic OH and H-units increased. However, the enzymatic hydrolysis efficiency (EHE) of samples with a lower lignin content (<4%) varied significantly. Correlations between various substrate-related factors of the pretreated SCB and EHE were analyzed to understand this observation. The results showed that the surface area of cellulose, lateral order index, CrI, and specific surface area were the predominant factors for enzymatic hydrolysis rather than lignin properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

A high-solid DES pretreatment using never-dried biomass as the starting material: towards high-quality lignin fractionation

This study investigated a high-solid diol deep eutectic solvent (DES) pretreatment using a wet substrate as the starting material. This pretreatment led to a remarkable glucan saccharification of 94.8% with efficient lignin and xylan removal (as high as 63.1% and 73.0%, respectively). Here the chemical structures of the substrates were analyzed comprehensively to reveal the impact of the pretreatment. In addition, over 90% of the removed lignin was recovered from the pretreated liquid, which exhibited a well-preserved β-O-4 structure (46–56/100Ar). The protection mechanism of our DES was investigated by 2D HSQC NMR, GPC, and 31 P NMR analysis. This study emphasized that diol-based DES pretreatment of undried lignocellulosic biomass at a high-solid loading can significantly utilize both carbohydrates and lignin fractions with high saccharification yields and high-quality lignin as a co-product.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

The importance of ester cleavage in the butylamine pretreatment of hybrid poplar

Butylamine is an effective in-and-out pretreatment solvent for hybrid poplar. It penetrates the cell walls and breaks ester cross-linkages, facilitating lignin release and improving enzymatic digestion. This work explores the “in-and-out” pretreatment of hybrid poplar with butylamine as a distillable protic solvent and reagent. The butylamine solvent can be removed by vacuum distillation with >95% solvent removal in all cases, providing a valuable scheme for efficient solvent recovery and recycling. Running the reaction with neat butylamine at 140 °C for 3 hours results in high yields of monosaccharides (90% glucose and 71% xylose) after enzymatic digestion, and a good tolerance to water content with no significant reduction in glucose yield up to an 8 : 1 water : butylamine ratio. We investigate the mechanisms of this pretreatment using powder X-ray diffraction, thermogravimetric analysis, fluorescence microscopy, elemental analysis, solid state and solution state nuclear magnetic spectroscopy to observe chemical and material markers of the pretreatment chemistry. The results suggest that the butylamine leaves the macro and microstructural properties of the lignocellulose relatively unaltered, but conducts targeted ester cleavage chemistry to remove cross-links between the various biopolymers and partially solubilize the lignin component of the biomass. These findings should act to guide future development of pretreatment chemistry for the development of biorefinery processes, and assist in the utilization of biomass as a starting point for chemical syntheses.

Palasz, Joseph M↗
DOE OSTI2023

Production of carotenoids from aromatics and pretreated lignocellulosic biomass by Novosphingobium aromaticivorans

ABSTRACT Carotenoids are lipophilic compounds found in the membranes of various organisms. Individual carotenoids are also commodity chemicals, produced industrially for use as food additives, nutritional supplements, cosmetics, and pharmaceuticals. The alphaproteobacterium Novosphingobium aromaticivorans has previously been established as a potential platform microbe for converting aromatic compounds derived from lignocellulosic plant biomass into valuable extracellular products. Here, we show that N. aromaticivorans DSM 12444 cells naturally produce the carotenoid nostoxanthin, and we construct a set of gene deletion mutants that accumulate β-carotene, lycopene, or zeaxanthin, which are predicted intermediates in nostoxanthin biosynthesis as well as commodity chemicals. We also show that a mutant strain heterologously expressing a CrtW protein accumulates the carotenoid astaxanthin. When grown on vanillate as the carbon source, we find that the levels of carotenoids are not significantly affected by O 2 concentration in the tested range of 5% to 21% O 2 . We also show that these carotenoids are produced at comparable levels when strains are grown in liquor from alkaline pretreated sorghum biomass [sorghum alkaline pretreatment liquor (APL)], which contains a mixture of aromatics. Finally, we construct strains that produce zeaxanthin, β-carotene, or astaxanthin concurrently with 2-pyrone-4,6-dicarboxylic acid, a potential building block for biodegradable polymers, when grown in sorghum APL. Combined, our results show that N. aromaticivorans can simultaneously produce valuable intracellular and extracellular commodities when grown in the presence of either pure aromatics or pretreated lignocellulosic biomass. IMPORTANCE There is economic and environmental interest in generating commodity chemicals from renewable resources, such as lignocellulosic biomass, that can substitute for chemicals derived from fossil fuels. The bacterium Novosphingobium aromaticivorans is a promising microbial platform for producing commodity chemicals from lignocellulosic biomass because it can produce these from compounds in pretreated lignocellulosic biomass, which many industrial microbial catalysts cannot metabolize. Here, we show that N. aromaticivorans can be engineered to produce several valuable carotenoids. We also show that engineered N. aromaticivorans strains can produce these lipophilic chemicals concurrently with the extracellular commodity chemical 2-pyrone-4,6-dicarboxylic acid when grown in a complex liquor obtained from alkaline pretreated lignocellulosic biomass. Concurrent microbial production of valuable intra- and extracellular products can increase the economic value generated from the conversion of lignocellulosic biomass-derived compounds into commodity chemicals and facilitate the separation of water- and membrane-soluble products.

09 BIOMASS FUELS↗
DOE OSTI2020

Editors’ Choice—Uncovering the Role of Alkaline Pretreatment for Hydroxide Exchange Membrane Fuel Cells

Alkaline pretreatment is perceived as an essential step for high-performance hydroxide exchange membrane fuel cells (HEMFCs), but its exact function is not fully understood. Here we show that alkaline pretreatment is only necessary when carboxylates are generated from platinum- or palladium-catalyzed oxidation of primary alcohol solvents during membrane electrode assembly (MEA) fabrication. When alkaline pretreatment is needed, bicarbonates are a better choice than the most commonly used hydroxide bases. We further demonstrate that MEAs with Pt/Pd-free catalysts, which can be used in HEMFCs, exhibit a better performance without the alkaline pretreatment: a voltage of 0.64 V at 1.0 A cm −2 and a peak power density of 0.69 W cm −2 in H 2 /O 2 . The optimization or elimination of the alkaline pretreatment will simplify the fabrication process for fuel cells and thus reduces their manufacturing costs.

Shi, Lin↗
DOE OSTI2024

Two-dimensional heteronuclear single quantum coherence (HSQC) NMR spectra of lignin isolated from Populus trichocarpa residues after CELF pretreatment and CBP fermentation

Here we present a curated dataset of a series of two-dimensional heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectra of lignin isolated from a woody energy crop (Populus trichocarpa) residues after co-solvent enhanced lignocellulosic fractionation (CELF) pretreatment and consolidated bioprocessing (CBP) process. The natural poplar variant GW-9947 from the Center for Bioenergy Innovation (CBI) was used. The poplar was knife milled and passed through a 1 mm sieve. The CELF pretreatment was performed in a Parr autoclave reactor with 7.5 wt % solids loading, 0.5 wt% H2SO4 as catalyst at 150°C with 15, 25 and 30 minutes, respectively. Tetrahydrofuran was added in a 1:1 mass ratio with water as the pretreatment solvent. The residues from CELF pretreatment were then subjected to CBP using the bacterium C. thermocellum DSM 1313. CBP fermentations were performed at 60 °C in a shaker at 50 grams/L solids loadings. Lignin was isolated from the pretreated samples after ball-milling in a porcelain jar with ceramic balls via Retsch PM 200 at 580 rpm for 2.5 h followed by enzymatic hydrolysis in acetate buffer (pH 4.8, 50 °C) for 48 h. The lignin samples were characterized using 13C–1H HSQC experiments which were performed in a Bruker Avance III HD 500 MHz NMR spectrometer operating at a frequency of 125.12 MHz for the 13C nucleus. A standard Bruker pulse sequence was used on a Prodigy platform cryoprobe. The dry lignin samples were dissolved in deuterated dimethylsulfoxide for HSQC experiments. The spectra were acquired under the following acquisition conditions: 210 ppm spectral width in F1 (13C) dimension with 256 data points and 11 ppm spectral width in F2 (1H) dimension with 1024 data points, a 90° pulse, a one bond C–H coupling constant of 145 Hz, a 1.0 s pulse delay, and 64 scans. All the data was processed using the TopSpin 3.6 software (Bruker BioSpin). The NMR spectra provides structural characteristics information about lignin remaining in solids after CELF (150 °C with 15, 25 and 30 minutes) process and C. thermocellum CBP.

Lignin structure, HSQC, poplar, CELF, CBP, CBI↗
DOE OSTI2024

Lignin molecular weights of Populus trichocarpa residues after CELF pretreatment

Here we present a dataset of molecular weights of lignin from a woody energy crop (Populus trichocarpa) residues after a series of co-solvent enhanced lignocellulosic fractionation (CELF) pretreatment. The natural poplar variant GW-9947 from the Center for Bioenergy Innovation (CBI) was used. The poplar was knife milled and passed through a 1 mm sieve and CELF pretreatment was performed in a Parr autoclave reactor with 7.5 wt % solids loading, 0.5 wt% H2SO4 as catalyst at 150°C with various time. Tetrahydrofuran was added in a 1:1 mass ratio with water as the pretreatment solvent. Lignin was isolated from the pretreated samples after ball-milling in a porcelain jar with ceramic balls via Retsch PM 200 at 580 rpm for 2.5 h followed by enzymatic hydrolysis in acetate buffer (pH 4.8, 50 °C) for 48 h. The solid residue was isolated by centrifugation and hydrolyzed again with freshly added buffer and enzymes for another 48 h. After filtration, the solid residue was extracted twice with 96% (v/v) 1,4-dioxane/water mixture at room temperature overnight. The extracts were combined, rotary evaporated, and freeze-dried to recover lignin. The lignin samples were then derivatized in an acetic anhydride/pyridine (1:1, v/v) mixture and stirred at room temperature for 24 h. Ethanol was added to the reaction mixture, left for 30 min and then removed with a rotary evaporator. The addition and removal of ethanol was repeated at least 3 times until all traces of acetic acid were removed. Acetylated lignin samples were then dissolved in tetrahydrofuran (THF) at a concentration of 1.0 mg/mL. The molecular weight of acetylated lignin was measured by a gel permeation chromatography (GPC) on a PSS-Polymer Standards Service (Warwick, RI, USA) GPC SECurity 1200 system featuring Agilent HPLC 1200 components equipped with four Waters Styragel columns (HR1, HR2, HR4 and HR6) and an UV detector (270 nm). Tetrahydrofuran was used as the mobile phase and flow rate was 0.3 mL/min. The Polymer Standards Service WinGPC Unity software (Build 6807) was used for data processing for all the samples. The data provides information about the effects of CELF pretreatment time at 150 ºC on lignin molecular weights.

09 BIOMASS FUELS↗
DOE OSTI2024

Economical methods for performing oxidative catalytic pretreatment of plant biomass using a single-stage two oxidant process

An improved alkaline pretreatment of biomass is provided that is a single-stage, two oxidant alkaline oxidative pretreatment process. The process uses a homogenous catalyst with at least two oxidants (Hydrogen peroxide and enhanced levels of oxygen) in an alkaline environment to catalytically pretreat lignocellulosic biomass in a single-stage oxidation reaction. The provided single-stage alkaline-oxidative pretreatment improves biomass pretreatment and increase enzymatic digestibility to improve the economic feasibility of production of lignocellulose derived sugars.

Hegg, Eric L.↗
DOE OSTI2022

Pretreatment of lignocellulosic feedstocks for cellulose nanofibril production

Cellulose nanofibrils (CNFs) have attracted a great deal of research interest in recent years attributable to the low cost and abundance of lignocellulosic biomass from which they can be extracted. These materials have potential applications in a wide array of areas because of their unique properties such as ultra-high aspect ratios and specific strengths. However, the high energy required to extract CNFs from biomass through fibrillation often makes them prohibitively expensive or negates their inherent sustainability. As such, a variety of biomass treatments prior to fibrillation have been investigated by researchers to reduce the energy requirements of CNF extraction, improve the efficacy of biomass fibrillation and subsequent processes, and/or impart functionality in resulting nanofibrils. In this work, both widely used and emerging mechanical, chemical, and enzymatic pretreatments used prior to fibrillation of lignocellulosic biomass for CNF extraction are reviewed. Attention is given to the effect of these various pretreatments on the properties of the resulting CNFs. Finally, the energy consumption in fibrillation processes with and without the use of pretreatments is compared, and future perspectives on challenges and opportunities in lignocellulosic feedstock pretreatments are discussed.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Chapter 4 - Pretreatment Technologies for Lignocellulosic Biomass Refineries

Pretreatment is a critical step in processing lignocellulosic biomass into biofuel and bioproducts and is considered the energy and cost center of the biomass conversion process. Although a large number of pretreatment technologies have been developed, not all the techniques are viable on a commercial scale at this stage. Moreover, the technology choice and process conditions depend highly on the type of biomass and the overall biorefinery scheme. This chapter provides an overview of different pretreatment methods, including their mechanism, important process parameters, current status, and challenges. The opportunities associated with new technologies and approaches are presented. Emphasis is placed on low-severity thermal pretreatment technologies. The chapter also provides a brief discussion of the challenges to achieving the economic viability of the technologies on a commercial scale.

BIOMASS FUELS↗
DOE OSTI2020

Influence of hydrocracking and ionic liquid pretreatments on composition and properties of Arabidopsis thaliana wild type and CAD mutant lignins

Lignin is the primary contributor to the high cost of biofuel-production from lignocellulosic biomass. Here, in order to study lignin removal and the release of aromatic monomers, we applied hydrocracking and ionic liquid pretreatments on Arabidopsis thaliana biomass from both wild type (WT) and a mutant (CAD cxd) defective in two cinnamyl alcohol dehydrogenase genes involved in the lignin biosynthetic pathway. For Arabidopsis WT, our results highlight that pretreatments reduce average molecular weight of lignin by about 65% and decrease the content of β-O-4 linkages between lignin monomers. For Arabidopsis CAD mutant, an opposite effect is evidenced. Fewer differences were observed on depolymerization and molecular structure of lignin, which indicates that (8-O-4), (8-5), and (8-8) linkages observed in CAD mutant make lignin more resilient to pretreatment than wild-type lignin. Finally, our study shows the potential of hydrocracking pretreatment technology for extracting valuable aldehyde monomers such as vanillin and syringaldehyde from biomass.

09 BIOMASS FUELS↗
DOE OSTI2021

Effective Biomass Fractionation through Oxygen-Enhanced Alkaline-Oxidative Pretreatment

The high recalcitrance of plant cell walls is an obstacle for effective chemical or biological conversion into renewable chemicals and transportation fuels. Here, we investigated the utilization of both oxygen (O 2 ) and hydrogen peroxide (H 2 O 2 ) as co-oxidants during alkalineoxidative pretreatment to improve biomass fractionation and increase enzymatic digestibility. The oxidative pretreatment of hybrid poplar was studied over a variety of conditions. Employing O 2 in addition to H 2 O 2 as a co-oxidant during the two-stage alkaline pre-extraction/coppercatalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment process resulted in a substantial improvement in delignification relative to using H 2 O 2 alone during the second-stage Cu-AHP pretreatment, leading to high overall sugar yields even at H 2 O 2 loadings as low as 2% (w/w of original biomass). The presence of H 2 O 2 , however, was both critical and synergistic. Performing analogous reactions in the absence of H 2 O 2 resulted in approximately 25% less delignification and a 30% decrease in sugar yields. The lignin isolated from this dual oxidant second stage had high aliphatic hydroxyl group content and reactivity to isocyanate, indicating that it is a promising substrate for the production of polyurethanes. To test the suitability of the isolated lignin as a source of aromatic monomers, the lignin was subjected to a sequential Bobbitt’s salt oxidation followed by formic-acid catalyzed depolymerization process. Monomer yields of approximately 17% (w/w) were obtained, and the difference in yields was not significant between lignin isolated from our Cu-AHP process with and without O 2 as a co-oxidant. Thus, the addition of O 2 did not lead to significant lignin crosslinking, a result consistent with the twodimensional heteronuclear single-quantum coherence (2D HSQC) NMR spectra of the isolated lignin.

09 BIOMASS FUELS↗
DOE OSTI2024

Lignin content of Populus trichocarpa residues after CELF pretreatment and CBP fermentation

Here we present a dataset of lignin content from a woody energy crop (Populus trichocarpa) residues after a series of co-solvent enhanced lignocellulosic fractionation (CELF) pretreatment and consolidated bioprocessing (CBP) process. The natural poplar variant GW-9947 from the Center for Bioenergy Innovation (CBI) was used. The poplar was knife milled and passed through a 1 mm sieve and CELF pretreatment was performed in a Parr autoclave reactor with 7.5 wt % solids loading, 0.5 wt% H2SO4 as catalyst at 150°C with 5, 15, 25 and 30 minutes, respectively. Tetrahydrofuran was added in a 1:1 mass ratio with water as the pretreatment solvent. The residues from CELF pretreatment were then subjected to CBP using the bacterium C. thermocellum DSM 1313. CBP fermentations were performed at 60 °C in a shaker at 50, 75, and 100 grams/L solids loadings. The Klason lignin was measured using a two-step acid hydrolysis process. In brief, the poplar samples were first hydrolyzed by 72 wt% sulfuric acid at 30 oC for an hour. The hydrolysates were then diluted to 4 wt% sulfuric acid using deionized water and subsequently autoclaved at 121 oC for 1 h. Upon the completion of the two-step hydrolysis, the resulting solution was cooled to room temperature and the precipitate was then filtered through a G8 glass fiber filter through a crucible, dried at oven for overnight, and weighed to get the Klason lignin content. The lignin data provides information about lignin content changes after CELF and C. thermocellum CBP process.

Lignin Populus trichocarpa CELF pretreatment CBP f↗
DOE OSTI2022

Effect of Feedstock Variability, Feedstock Blends, and Pretreatment Conditions on Sugar Yield and Production Costs

Mass production of sustainable biofuels replacing fossil fuels will significantly reduce global greenhouse gas emissions. However, biomass feedstock variability, availability, and affordability pose significant risks for the sustainable production of biofuels in biorefinery plants. To derisk the sustainable production of biofuels, this work investigates the sugar yields and production costs of four different feedstocks as well as their blends, using different pretreatment methods: deacetylation and dilute acid pretreatment (DDA) and deacetylation and mechanical refining pretreatment (DMR). We found that not only feedstock species variability, but also feedstock harvesting techniques have large impacts on both sugar yields and production costs. Single-pass harvested corn stover (SPCS) showed higher sugar yields and lower production costs than multipass harvested corn stover, followed by sorghum and switchgrass. The highest glucose yields of 91% and 95.3%, which corresponds to the lowest sugar production costs of $0.2286/lb. and $0.2490/lb., were observed for SPCS using DDA and DMR, respectively. The difference in sugar yields and production costs due to feedstock variability can be largely mitigated by increasing deacetylation severity, especially in DMR. Higher deacetylation severity resulted in decreased sugar production costs in the case of DMR in contrast to increased costs in the case of DDA. Blending switchgrass and sorghum into corn stover, which can significantly increase the feedstock availability and sustainability, resulted in sugar yields and production costs of roughly the weighted average of those derived from constituent individual feedstocks, respectively. Thus, blending feedstocks of different biomass species is a potential successful strategy for sustainable production of biofuels to replace fossil-derived fuels.

09 BIOMASS FUELS↗
DOE OSTI2020

Effects of different pretreatment methods on the drying characteristics and quality of potatoes

Abstract The effects of different pretreatments on the vitamin C content of peeled fresh potato, the drying characteristics, and several quality attributes of dehydrated potatoes were investigated. Citric acid pretreatment (0.1%–0.3%, 10–30 min), steam blanching (100ºC, 1–2 min), and water blanching (95°C, 1–2 min) were found to have no obvious effect on the drying rate of potatoes, whereas temperature was the main influencing factor. In terms of quality of dehydrated diced potato, 20 min of citric acid pretreatment resulted in the highest vitamin C retention and better color. Furthermore, dehydrated potato pretreated with citric acid all showed similar dynamic moisture adsorption curves, namely type II sorption isotherm. The moisture adsorption curves can be well fitted using the Guggenheim–Anderson–deBoer model with R 2 higher than .97.

Sun, Xiangfeng↗
DOE OSTI2020

The critical role of lignin in lignocellulosic biomass conversion and recent pretreatment strategies: A comprehensive review

Heterogeneity and rigidity of lignocellulose causing resistance to its deconstruction have provided technical and economic challenges in the current biomass conversion processes. Lignin has been considered as a crucial recalcitrance component in biomass utilization. An in-depth understanding of lignin properties and their influences on biomass conversion can provide clues to improve biomass utilization. Also, utilization of lignin can significantly increase the economic viability of biorefinery. Recent lignin-targeting pretreatments have aimed not only to overcome recalcitrance for biomass conversion but also to selectively fractionate lignin for lignin valorization. Numerous studies have been conducted in biomass characteristics and conversion technologies, and the role of lignin is critical for lignin valorization and biomass pretreatment development. In this review, we provide a comprehensive review of lignin-related biomass characteristics, the impact of lignin on the biological conversion of biomass, and recent lignin-targeting pretreatment strategies. The desired lignin properties in biorefinery and future pretreatment directions are also discussed.

09 BIOMASS FUELS↗
DOE OSTI2025

A chemical-recovery-free ammonium sulfite-based alkali pretreatment of corn stover for low-cost sugar production via fertilizer use of waste liquor

The production of cellulosic sugars is a pivotal strategy for advancing biomass bioconversion. This study evaluated the pretreatment of corn stover using ammonium sulfite and potassium hydroxide to develop comprehensive data on sugar, lignin, chemicals, and overall mass recovery profiles in a batch reactor at 80 °C. The results indicated significant improvements in delignification, deacetylation, enzymatic digestibility, and overall sugar yield. Specifically, pretreating corn stover with a solution of 40 wt% potassium hydroxide and 15 wt% ammonium sulfite at 80 °C for 2 h achieved 78.9 % lignin removal and 82.1 % acetyl removal, resulting in a total sugar yield exceeding 87.5 % with an enzyme loading of 12.5 mg protein/g-glucan plus xylan. The pretreated spent liquor, containing ammonium, potassium, sulfur, biomass-derived organics, and inorganics, demonstrated substantial potential as a fertilizer. The techno-economic analysis projected a minimum sugar selling price of $0.285 per pound, supporting the ongoing development and implementation of chemical-recovery-free pretreatment technology.

09 BIOMASS FUELS↗
DOE OSTI2026

Improving anaerobic digestion of sewage sludge to renewable natural gas by the Advanced Pretreatment & Anaerobic Digestion technology (APAD): Pilot testing

Conventional anaerobic digestion (AD) of sewage sludge in wastewater treatment facilities suffers from low carbon conversion efficiency (CCE = 40%) and requires costly CO2 removal for injection of the produced CH4 into the natural gas grid. To address these limitations, we developed the Advanced Pretreatment and Anaerobic Digestion (APAD) process. This integrates Advanced Wet Oxidation & Steam Explosion (AWOEx) pretreatment of residual sludge after conventional AD, followed by biogas upgradation using a novel methanogenic strain, Methanothermobacter wolfeii BSEL, converting CO2 with H2 into CH4 or RNG (renewable natural gas). Pilot-scale results demonstrated that AWOEx pretreatment achieved a CCE of 62% for the residual sludge, 68% higher than the conventional AD process. The CH4 production was further increased by 79%. Subsequent biogas upgrading in a trickling bed reactor with H2 further enhanced total methane output by 100% and resulted in a final CO2 concentration of =3%. The integrated APAD process achieved a remarkable overall CCE of 83%, resulting in a 200% increase in RNG output when compared to conventional AD. Techno-economic analysis revealed that AWOEx pretreatment alone reduced sludge treatment costs from $494 to $253 per ton of dry solids. The complete APAD process incurred a higher cost of treatment of $530 per ton, driven by prices for bottled H2. The process did, however, show gains in energy recovery and decarbonization. Renewable H2, which may reduce in price in the near future, can positively improve the economics of biogas upgrading for the APAD process.

Life Cycle Assessment (LCA)↗