Solid Hydrolysis Research Articles

Potential of ozonolysis as a pretreatment for energy grasses

This study investigated the effect of ozonolysis on Miscanthus × giganteus, Miscanthus sinensis 'Gracillimus', Saccharum arundinaceum and Saccharum ravennae, collectively referred to as 'energy grasses'. Studies were conducted at three different ozone concentrations (40, 50 and 58 mg/l) using two ozone flow configurations - uni-directional and reversed flow. Pretreatment conditions for each variety were optimized based on lignin content and glucan recovery in ozonated solids. Results showed that ozonolysis was effective in removing up to 59.9% lignin without cellulose degradation. However, subsequent hydrolysis of pretreated solids with Cellic® CTec2 at 0.06 g/g raw biomass provided glucan conversion lower than untreated samples suggesting enzyme inhibition by lignin degradation products formed during ozonolysis. Future studies investigating hydrolysis efficiency of washed pretreated solids with higher enzyme loadings are therefore warranted to optimize the hydrolysis process and make it functionally feasible.

The Formation of Plasma Acid at Atmospheric Pressure and its Application in Hydrolysis of Microcrystalline Cellulose

In this paper, plasma acid was obtained by treating distilled water with dielectric barrier discharge at atmospheric pressure in order to hydrolyze cellulose. The acidity of plasma acid was studied through a single factor experiment. A plasma acid with pH value of 1.42 was obtained and used to hydrolyze microcrystalline cellulose at 80°C for 60min. Under this condition, the integrated optical density (IOD) of the hydrolysis sample was 0.589. Based on standard glucose curve, the total reducing sugar (TRS) was calculated to be 53.75mg and the TRS yield was 53.75%. The filtrate was evaporated to get the solid hydrolysis sample to be analyzed by High-performance liquid chromatography (HPLC). The results showed that the sample mainly consisted of glucose, which proved that microcrystalline cellulose could be hydrolyzed by plasma acid. Therefore, it could be concluded that it was an environmentally friendly and economical method to hydrolyze the microcrystalline cellulose by plasma acid.

Performance of plastic- and sponge-based trickling filters treating effluents from an UASB reactor

The paper compares the performance of two trickling filters (TFs) filled with plastic- or sponge-based packing media treating the effluent from an upflow anaerobic sludge blanket (UASB) reactor. The UASB reactor was operated with an organic loading rate (OLR) of 1.2 kgCOD m(-3) d(-1), and the OLR applied to the TFs was 0.30-0.65 kgCOD m(-3) d(-1) (COD: chemical oxygen demand). The sponge-based packing medium (Rotosponge) gave substantially better performance for ammonia, total-N, and organic matter removal. The superior TF-Rotosponge performance for NH(4)(+)-N removal (80-95%) can be attributed to its longer biomass and hydraulic retention times (SRT and HRT), as well as enhancements in oxygen mass transfer by dispersion and advection inside the sponges. Nitrogen removals were significant (15 mgN L(-1)) in TF-Rotosponge when the OLRs were close to 0.75 kgCOD m(-3) d(-1), due to denitrification that was related to solids hydrolysis in the sponge interstices. For biochemical oxygen demand removal, higher HRT and SRT were especially important because the UASB removed most of the readily biodegradable organic matter. The new configuration of the sponge-based packing medium called Rotosponge can enhance the feasibility of scaling-up the UASB/TF treatment, including when retrofitting is necessary.

Saccharification of recalcitrant biomass and integration options for lignocellulosic sugars from Catchlight Energy’s sugar process (CLE Sugar)

BackgroundWoody biomass is one of the most abundant biomass feedstocks, besides agriculture residuals in the United States. The sustainable harvest residuals and thinnings alone are estimated at about 75 million tons/year. These forest residuals and thinnings could produce the equivalent of 5 billion gallons of lignocellulosic ethanol annually. Softwood biomass is the most recalcitrant biomass in pretreatment before an enzymatic hydrolysis. To utilize the most recalcitrant lignocellulosic materials, an efficient, industrially scalable and cost effective pretreatment method is needed.ResultsObtaining a high yield of sugar from recalcitrant biomass generally requires a high severity of pretreatment with aggressive chemistry, followed by extensive conditioning, and large doses of enzymes. Catchlight Energy’s Sugar process, CLE Sugar, uses a low intensity, high throughput variation of bisulfite pulping to pretreat recalcitrant biomass, such as softwood forest residuals. By leveraging well-proven bisulfite technology and the rapid progress of enzyme suppliers, CLE Sugar can achieve a high yield of total biomass carbohydrate conversion to monomeric lignocellulosic sugars. For example, 85.8% of biomass carbohydrates are saccharified for un-debarked Loblolly pine chips (softwood), and 94.0% for debarked maple chips (hardwood). Furan compound formation was 1.29% of biomass feedstock for Loblolly pine and 1.10% for maple. At 17% solids hydrolysis of pretreated softwood, an enzyme dose of 0.075 g Sigma enzyme mixture/g dry pretreated (unwashed) biomass was needed to achieve 8.1% total sugar titer in the hydrolysate and an overall prehydrolysate liquor plus enzymatic hydrolysis conversion yield of 76.6%. At a much lower enzyme dosage of 0.044 g CTec2 enzyme product/g dry (unwashed) pretreated softwood, hydrolysis at 17% solids achieved 9.2% total sugar titer in the hydrolysate with an overall sugar yield of 85.0% in the combined prehydrolysate liquor and enzymatic hydrolysate. CLE Sugar has been demonstrated to be effective on hardwood and herbaceous biomass, making it truly feedstock flexible.ConclusionsDifferent options exist for integrating lignocellulosic sugar into sugar-using operations. A sugar conversion plant may be adjacent to a CLE Sugar plant, and the CLE Sugar can be concentrated from the initial 10% sugar as needed. Concentrated sugars, however, can be shipped to remote sites such as ethanol plants or other sugar users. In such cases, options for shipping a dense form of sugars include (1) pretreated biomass with enzyme addition, (2) lignocellulosic sugar syrup, and (3) lignocellulosic sugar solid. These could provide the advantage of maximizing the use of existing assets.

Anaerobic co-digestion of solid waste: Effect of increasing organic loading rates and characterization of the solubilised organic matter

The impact of stepwise increase in OLR (up to 7.5kgVS/m3d) on methane production, reactor performance and solubilised organic matter production in a high-loading reactor were investigated. A reference reactor operated at low OLR (<2.0kgVS/m3d) was used solely to observe the methane potential of the feed substrate. Specific methane yield was 0.33lCH4/gVS at the lowest OLR and dropped by about 20% at the maximum OLR, while volumetric methane production increased from 0.35 to 1.38m3CH4/m3d. At higher loadings, solids hydrolysis was affected, with consequent transfer of poorly-degraded organic material into the drain solids. Biodegradability and size-fractionation of the solubilised COD were characterized to evaluate the possibility of a second stage liquid reactor. Only 18% of the organics were truly soluble (<1kD). The rest were in colloidal and very fine particulate form which originated from grass and cow manure and were non-biodegradable.

The role of anaerobic sludge recycle in improving anaerobic digester performance

Solids retention time (SRT) is a critical parameter for the performance of anaerobic digesters (AD) in wastewater treatment plants. AD SRT should increase when active biomass is input to the AD by recycling anaerobic sludge via the wastewater-treatment tanks, creating a hybrid aerobic/anaerobic system. When 85% of the flow through the AD was recycled in pilot-scale hybrid systems, the AD SRT increased by as much as 9-fold, compared to a parallel system without anaerobic-sludge recycle. Longer AD SRTs resulted in increased hydrolysis and methanogenesis in the AD: net solids yield decreased by 39–96% for overall and 23–94% in the AD alone, and AD methane yield increased 1.5- to 5.5-fold. Microbial community assays demonstrated higher, more consistent Archaea concentrations in all tanks in the wastewater-treatment system with anaerobic-sludge recycle. Thus, multiple lines of evidence support that AD-sludge recycle increased AD SRT, solids hydrolysis, and methane generation.

Pretreatment of olive tree biomass with FeCl3 prior enzymatic hydrolysis

Olive tree biomass (OTB) is an agricultural residue which can be used as raw material for bioethanol production. OTB was pretreated with 0.05–0.275M FeCl3 solutions at 120–180°C for 0–30min. Enzymatic hydrolysis yields were used for assessing pretreatment performance. Optimum FeCl3 pretreatment conditions were found to be 152.6°C, 0.26M FeCl3 for 30min. Under such conditions, 100% of hemicellulose was removed, and enzymatic hydrolysis of pretreated solids resulted in a yield of 36.6g glucose/100g of glucose in the raw material. Hemicellulosic sugar recovery in the prehydrolysate was 63.2%. Results compare well with those obtained by other pretreatment strategies on the same raw material, confirming FeCl3 solutions as a new, feasible approach for bioethanol production.

Thermal and thermo-chemical pre-treatment of four waste residues and the effect on acetic acid production and methane synthesis

In this study four diverse solid waste substrates (coal, Kraft pulp solids, chicken feathers and chicken processing waste) were thermally pre-treated (70, 140 and 200°C), under an inert (nitrogen) or oxidative (oxygen) atmosphere, and then anaerobically digested.Membrane inlet mass spectrometry during the thermal and thermo-chemical reactions was successfully used to establish oxygen and carbon dioxide gas fluxes and product formation (acetic acid). There was significant solids hydrolysis pre-treatment at 200°C under an oxidative atmosphere, as indicated by a decrease in the volatile suspended solids and an increase in dissolved organic carbon. Greater concentrations of volatile fatty acids were produced under oxidative conditions at higher temperatures.The methane yield more than tripled for feathers after pre-treatment at 140°C (under both atmospheres), but decreased after oxidative pre-treatment at 200°C, due to the destruction of available carbon by the thermo-chemical reaction. Methane yield more than doubled for the Kraft pulp solids with the 200°C pre-treatment under oxidative conditions. This study illustrated the power of wet oxidation for solids destruction and its potential to improve methane yields generated during anaerobic digestion.

Anaerobic digestion of Organic Fraction of Municipal Solid Waste (OFMSW) in two-phase system

In view of recovering energy resource from the treatment of Organic Fraction of Municipal Solid Waste (OFMSW), anaerobic digestion of OFMSW prior to aerobic composting as post-treatment was considered. This study aimed to determine the operational characteristics and efficiency of a two-phase system composed of a fed-batch hydrolysis reactor (phase I) and a methanogenic Upflow Anaerobic Sludge Blanket (UASB) reactor (phase II). The effluent of the UASB reactor was recycled to the phase I reactor to avoid high levels of Volatile Fatty Acids (VFAs), which may inhibit methanogenesis and hydrolysis of solids.

Characterisation of the products from pyrolysis of residues after acid hydrolysis of Miscanthus

Platform chemicals such as furfural and hydroxymethylfurfural are major products formed during the acid hydrolysis of lignocellulosic biomass in second generation biorefining processes. Solid hydrolysis residues (HR) can amount to 50wt.% of the starting biomass materials. Pyrolysis of the HRs gives rise to biochar, bio-liquids, and gases. Time and temperature were variables during the pyrolysis of HRs in a fixed bed tubular reactor, and both parameters have major influences on the amounts and properties of the products. Biochar, with potential for carbon sequestration and soil conditioning, composed about half of the HR pyrolysis product. The amounts (11–20wt.%) and compositions (up to 77% of phenols in organic fraction) of the bio-liquids formed suggest that these have little value as fuels, but could be sources of phenols, and the gas can have application as a fuel.

Process Evaluation of Enzymatic Hydrolysis with Filtrate Recycle for the Production of High Concentration Sugars

Process simulation and lab trials were carried out to demonstrate and confirm the efficiency of the concept that recycling hydrolysate at low total solid enzymatic hydrolysis is one of the options to increase the sugar concentration without mixing problems. Higher sugar concentration can reduce the capital cost for fermentation and distillation because of smaller retention volume. Meanwhile, operation cost will also decrease for less operating volume and less energy required for distillation. With the computer simulation, time and efforts can be saved to achieve the steady state of recycling process, which is the scenario for industrial production. This paper, to the best of our knowledge, is the first paper discussing steady-state saccharification with recycling of the filtrate form enzymatic hydrolysis to increase sugar concentration. Recycled enzymes in the filtrate (15-30% of the original enzyme loading) resulted in 5-10% higher carbohydrate conversion compared to the case in which recycled enzymes were denatured. The recycled hydrolysate yielded 10% higher carbohydrate conversion compared to pure sugar simulated hydrolysate at the same enzyme loading, which indicated hydrolysis by-products could boost enzymatic hydrolysis. The high sugar concentration (pure sugar simulated) showed inhibition effect, since about 15% decrease in carbohydrate conversion was observed compared with the case with no sugar added. The overall effect of hydrolysate recycling at WinGEMS simulated steady-state conditions with 5% total solids was increasing the sugar concentration from 35 to 141g/l, while the carbohydrate conversion was 2% higher for recycling at steady state (87%) compared with no recycling strategy (85%). Ten percent and 15% total solid processes were also evaluated in this study.

Calorimetric and Microscopic Studies on the Noncatalytic Hydrothermolysis of Ammonia Borane

The hydrothermolysis of ammonia borane (AB) can release more hydrogen than AB thermolysis itself at mild temperatures. To obtain more insight into the noncatalytic hydrothermolysis, we investigated this process using a high-pressure differential scanning calorimeter and characterized the condensed residue by thermal analysis and infrared spectroscopy. For mass ratios of AB to water of 3.6, 1.44, and 0.72, the first pyrolysis step is not completed in 1 h at 85 °C. As the temperature increases from 25 to 115 at 1 °C min–1, there exist two exothermic peaks for the mass ratio of 3.6, centered around 82 and 103 °C on the heat flow curve, attributed to the hydrolysis and the first step of AB pyrolysis, respectively. For the mass ratio of 1.44, the top temperatures of these two exothermic peaks are 90 and 100 °C, respectively. However, for the mass ratio of 0.72, only the exothermic peak related to hydrolysis is observed, and its top temperature is ca. 106 °C. At temperatures up to 115 °C, the structural features associated with the product of the second pyrolysis step are absent for the mass ratios of 1.44 and 3.6. In the noncatalytic hydrothermolysis, the hydrolysis occurs much faster than the pyrolysis, and the latter is accelerated by both the heat desorbed from the hydrolysis and its product. Our findings suggest that water prefers reacting with AB rather than binding to the hydrolysis product to form hydrates and the hydrolysis itself can generate about 9 wt % of hydrogen with respect to the total mass of AB and water if sufficient AB is present. In this case, the heat of hydrolysis is 131 kJ (mol of AB)−1, and the solid hydrolysis product decomposes at temperatures about 350 °C.

Enhancement of the conventional anaerobic digestion of sludge: comparison of four different strategies

Anaerobic digestion (AD) is the preferred option to stabilize sludge. However, the rate limiting step of solids hydrolysis makes it worth modifing the conventional mesophilic AD in order to increase the performance of the digester. The main strategies are to introduce a hydrolysis pre-treatment, or to modify the digestion temperature. Among the different pre-treatment alternatives, the thermal hydrolysis (TH) at 170 degrees C for 30 min, and the ultrasounds pre-treatment (US) at 30 kJ/kg TS were selected for the research, while for the non-conventional anaerobic digestion, the thermophilic (TAD) and the two-stage temperature phased AD (TPAD) were considered. Four pilot plants were operated, with the same configuration and size of anaerobic digester (200 L, continuously fed). The biogas results show a general increase compared to the conventional digestion, being the highest production per unit of digester for the process combining the thermal pre-treatment and AD (1.4 L biogas/L digester day compared to the value of 0.26 obtained in conventional digesters). The dewaterability of the digestate became enhanced for processes TH + AD and TPAD when compared with the conventional digestate, while it became worse for processes US + AD and TAD. In all the research lines, the viscosity in the digester was smaller compared to the conventional (which is a key factor for process performance and economics), and both thermal pre-treatment and thermophilic digestion (TAD and TPAD) assure a pathogen free digestate.

Application of cellulase and hemicellulase to pure xylan, pure cellulose, and switchgrass solids from leading pretreatments

Accellerase 1000 cellulase, Spezyme CP cellulase, β-glucosidase, Multifect xylanase, and beta-xylosidase were evaluated for hydrolysis of pure cellulose, pure xylan, and switchgrass solids from leading pretreatments of dilute sulfuric acid, sulfur dioxide, liquid hot water, lime, soaking in aqueous ammonia, and ammonia fiber expansion. Distinctive sugar release patterns were observed from Avicel, phosphoric acid swollen cellulose (PASC), xylan, and pretreated switchgrass solids, with accumulation of significant amounts of xylooligomers during xylan hydrolysis. The strong inhibition of cellulose hydrolysis by xylooligomers could be partially attributed to the negative impact of xylooligomers on cellulase adsorption. The digestibility of pretreated switchgrass varied with pretreatment but could not be consistently correlated to xylan, lignin, or acetyl removal. Initial hydrolysis rates did correlate well with cellulase adsorption capacities for all pretreatments except lime, but more investigation is needed to relate this behavior to physical and compositional properties of pretreated switchgrass.

The preparation of Mg-based hydro-reactive materials and their reactive properties in seawater

Mg-based lamellar materials were prepared by high-energy milling. The XRD, SEM, TG and BET techniques were used to characterize the materials. Their hydrolysis properties in seawater were studied by measuring the hydrogen volume produced and by calculating the rate of hydrogen evolution. The solid hydrolysis products were analyzed by SEM and XRD. The experimental results showed that the milled samples were substantially more reactive than the unmilled Mg powder in air according to initial oxidization temperature. In the hydrolysis process, the unmilled Mg powder barely reacted with seawater. However, the milled Mg powder showed noticeable reactivity in seawater, generating 906 mL/g of hydrogen in 10 min, an evolution of 97.1% of the theoretical yield. The Mg-based hydro-reactive materials including Co or Ni were more reactive in seawater than milled Mg powder due to the creation of a micro-galvanic cell. The Mg/Co sample produced 575 mL/g of hydrogen in the first minute. Mg(OH) 2 was the main reaction product of magnesium with seawater. It accumulated in a three-dimensional form composed of nanosized Mg(OH) 2 chip.

Annual performance analysis and comparison of pellet production integrated with an existing combined heat and power plant

Three optional pellet production processes integrated with an existing biomass-based CHP plant using different raw materials (wood chips and solid hydrolysis residues) are studied. The year is divided into 12 periods, and the integrated biorefinery systems are modeled and simulated for each period. The annual economic performance of three integrated biorefinery systems is analyzed based on the simulation results. The option of pellet production integrated with the existing CHP plant with the exhaust flue gas and superheated steam as drying mediums has the lowest specific pellet production cost of 105 €/t pellet, the shortest payback time of less than 2 years and the greatest CO 2 reduction of the three options. An advantage in common among the three options is a dramatic increase of the total annual power production and significant CO 2 reduction in spite of a small decrease of power efficiency.

ChemInform Abstract: Lignocellulosic Biomass Pretreatment Using AFEX

AbstractReview: 11 refs.

Enzymatic Hydrolysis of Switchgrass and Tall Wheatgrass Mixtures Using Dilute Sulfuric Acid and Aqueous Ammonia Pretreatments

Combinations of biomass feedstocks such as perennial grasses or agricultural residues need to be evaluated to ensure maximum flexibility and the long-term viability of the cellulosic ethanol industry. This article reports the enzymatic hydrolysis of solids resulting from dilute sulfuric acid (H2SO4) and aqueous ammonia (NH3OH) pretreatments of switchgrass, tall wheatgrass, and their mixtures. To determine the effectiveness of pretreatment and enzymatic hydrolysis on mixtures of two different feedstocks, switchgrass and tall wheatgrass were used individually and mixed at 1:2 and 2:1 ratios (w/w, dry basis). These four different feedstock combinations were pretreated with either H2SO4 (1.5%, 140°C, 20 min) at a solid loading rate (SLR) of 1:10 (w/v) or soaked in NH3OH (15% w/v, 60°C, 24 h) at SLR of 1:6. The pretreated and untreated (control) samples were subjected to enzymatic hydrolysis by adding cellulase (NS50013, 25 FPU g-1 glucan) and s-glucosidase (Novozyme 188, 50 CBU g-1 glucan) at an initial glucan loading of 1% (w/v). Delignification of 40% and 57% to 60%, respectively, was achieved with all materials during acid and aqueous ammonia pretreatments. Glucose yields of 84% to 98% and 70%, respectively, were achieved from enzymatic hydrolysis of all acid-pretreated and alkali-pretreated samples. Our results suggest that feedstock mixtures can be processed as readily as individual feedstocks, producing glucose yields comparable to those of the individual feedstocks. The results also demonstrate that wheatgrass has a similar composition to switchgrass and has potential as a feedstock for ethanol production.

Combined thermochemical and fermentative destruction of municipal biosolids: A comparison between thermal hydrolysis and wet oxidative pre-treatment

In this study the comparative destruction of municipal biosolids using thermal hydrolysis (140 or 165 °C) and wet oxidation (220 °C) was followed by biological degradation via mesophilic anaerobic digestion (36 °C). Wet oxidation (WO) destroyed more than 93% of the VSS, while thermal hydrolysis (TH) at 140 and 165 °C destroyed 9% and 22%, respectively. Combined TH and anaerobic digestion resulted in approximately 50% VSS destruction. The ultimate methane potential of the combined fractions from the thermal hydrolysis at 140 and 165 °C improved by 12–13% relative to the untreated control sample. Methane production from the WO material was 53% of the control yield and wholly attributable to soluble organic carbon in the liquid fraction, indicating that the WO destroyed all putrescible carbon from the solids fraction. Point sampling during the BMP assay revealed that methanogenic development, not solids hydrolysis, was the kinetic barrier during anaerobic digestion in this study.

Calculating sugar yields in high solids hydrolysis of biomass

Calculation of true sugar yields in high solids enzymatic hydrolysis of biomass is challenging due to the varying liquid density and liquid volume resulting from solid solubilization. Ignoring these changes in yield calculations can lead to significant errors. In this paper, a mathematical method was developed for the estimation of liquid volume change and thereafter the sugar yield. The information needed in the calculations include the compositions of the substrate, initial solids loading, initial liquid density, and sugar concentrations before and after hydrolysis. All of these variables are measurable with conventional laboratory procedures. This method was validated experimentally for enzymatic hydrolysis of dilute sulfuric acid pretreated corn stover at solid loadings up to 23% (w/w). The maximum relative error of predicted glucose yield from the true value was less than 4%. Compared to other methods reported in the literature, this method is relatively easy to use and provides good accuracy.