Effects of thermo-chemical pre-treatment on anaerobic biodegradability and hydrolysis of lignocellulosic biomass (original) (raw)
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Pretreatment Impact on Biomethanation of Lignocellulosic Waste
Single Cell Biology, 2016
Lignocelluloses are often a major or sometimes the sole components of different waste streams from various industries, forestry, agriculture and municipalities. Hydrolysis of these materials is the first step for either digestion to biogas (methane) or fermentation to ethanol. However, enzymatic hydrolysis of lignocelluloses with no pre-treatment is usually not so effective because of high stability of the materials to enzymatic or bacterial attacks. Pre-treatment helps to improve the process of hydrolysis. In this work different methods of pre-treatment were studied. The present work illustrates the effect of acid, alkaline pre-treatment on different sizes of wheat straw and anaerobic digestion of treated biomass for the production of biogas in batch stirred tank bioreactor under particular parameters. The quality and quantity of biogas produced was analysed by gas chromatography and water displacement methods respectively. The Untreated wheat straw gave a biogas yield of 104 ml/g and methane content of 64%. Acid treated wheat straw gave biogas yield of 130, 140 and 134 ml/g and methane content of 68%, 72%, 75% for 1%, 2%, 5% acid concentration respectively. Similarly, for alkali treatment gave biogas yield of 124, 128, 126ml/g and methane content of 66%, 69%, 71% for 1%, 2%, 5% NaOH concentration respectively.
Biomass & Bioenergy, 2015
Biochemical composition and reactivity are key factors controlling the biodegradability of lignocellulosic residues. In the present study, 14 lignocellulosic substrates including 6 agricultural and 8 forest residues were analyzed for 9 biochemical characteristics, including BioMethane Potential (BMP), Biological Oxygen Demand (BOD), Enzymatic Cellulose Degradation tests (ECD), Van Soest and NREL fractionation methods. The data obtained were exploited by principal component analysis (PCA) and other statistical methods to investigate the possible correlations between the parameters. The study showed that the contents in particular lignin or in non-extractible residues (RES) were the characteristics which influenced most the anaerobic biodegradability (BMP), while the influence of the soluble fraction was quite low. BMP was well correlated with the ratio of the contents in non-lignin over lignin fractions and the cellulose to lignin ratio. Regarding agricultural residues, BMP was better correlated with lignin content than with RES content. Agricultural and forest residues exhibited distinct characteristics of aerobic and anaerobic biodegradability. Good correlation was observed between ECD and lignin content. Finally, it was also observed that Van Soest's and NREL methods did not provide the same results in terms of biochemical composition.
Pretreatment methods of lignocellulosic biomass for anaerobic digestion
AMB Express, 2017
Agricultural residues, such as lignocellulosic materials (LM), are the most attractive renewable bioenergy sources and are abundantly found in nature. Anaerobic digestion has been extensively studied for the effective utilization of LM for biogas production. Experimental investigation of physiochemical changes that occur during pretreatment is needed for developing mechanistic and effective models that can be employed for the rational design of pretreatment processes. Various-cutting edge pretreatment technologies (physical, chemical and biological) are being tested on the pilot scale. These different pretreatment methods are widely described in this paper, among them, microaerobic pretreatment (MP) has gained attention as a potential pretreatment method for the degradation of LM, which just requires a limited amount of oxygen (or air) supplied directly during the pretreatment step. MP involves microbial communities under mild conditions (temperature and pressure), uses fewer enzyme...
Anaerobic Digestion of Lignocellulosic Substrates: Benefits of Pre-Treatments
Current sustainable/renewable energy reports, 2019
Purpose of Review This paper offers a review of the most actual pre-treatment technologies applied to lignocellulosic biomasses to produce methane. By reviewing the recent literature findings, we aim to explain the rationale behind the pre-treatment selection, how the substrate composition influences the choice, and the effect of each treatment on the lignocellulose fraction. Recent Findings The well-known anaerobic digestion is still a hot topic as proved by the number of scientific published papers. To increase competitiveness in the energy production market, the methane production has to be maximized; lignocellulosic biomass feedstock needs a pre-treatment step to be better exploited. The increased biomass conversion efficiency will positively influence the cost-benefit ratio. Lignocellulosic biomass duly pre-processed has proven to be a valid feedstock option in modern anaerobic digestion plants. Summary The strengths of the biogas as an energy carrier are explained outlining the current role of anaerobic digestion among the available processes to recover energy from biomasses. The pre-treatments presented here are grouped in three traditional main categories (physical, chemical, and biological), even if the most recent and successful applications are a combination of more processes, and a sharp separation is not always applicable. There is no one best treatment technology, but the choice is dependent on biomass characteristics, process parameters, and plant size. Therefore, the trend is toward the application of combined technologies to maximize biogas production while reducing inhibition effects.
Springer Science Reviews, 2014
A successful biogas production process depends upon adequate hydrolysis of macromolecules in the substrate and stable further conversion. The complex and rigid structure of cellulosic, hemicellulosic and lignin chain is preventing lignocellulosic biomass to reach efficient hydrolysis, therefore pretreatment of a substrate is needed for higher biogas and methane yields. There are several different physical and chemical methods of pretreatments available which include the usage of acids, alkalis, organic solvents, ionic detergents, steam, high pressure, grinding, ultrasound, and microwave irradiation. Physico-chemical pretreatments act rapidly on lignocellulose but their upscaling is very expensive in industry. Many studies have been made in finding the best combination of different pretreatment methods and also new biological techniques which could make lignocellulose pretreatment cheaper and environmentally more friendly. Using natural abilities of different fungi, bacteria or yeast to degrade lignocellulose simplifies the whole process. Also cocktails of biotechnologically produced enzymes are effective in degrading lignocellulose. Keywords Lignocellulose Á Physico-chemical pretreatments Á Biological pretreatments Á Enzymatic hydrolysis Á Biogas Biogas Production Process Anaerobic digestion of lignocellulosic materials is too slow in nature to be applicable in biogas production at industry level. Poor lignin degradation, production of toxic digested Endorsed by Prof. Romana Marinšek Logar.
Bioresources, 2019
Changes in chemical composition and structure of corncob lignocellulosic biomass were investigated relative to pretreatment and anaerobic digestion. The pretreatment involved 1% and 3% sodium hydroxide, 3% and 7% sulphuric acid, as well as medium and high temperature extrusion (in 110 °C and in the range from 140 °C to 160 °C). The chemical components content was studied using a gravimetric method, whereas structure and relations between the carbohydrate and lignin participation were investigated using Fourier transform infrared spectroscopy. It was determined that the chemical treatment, both acidic and alkaline, changed the chemical composition of corncob more significantly than the extrusion. Alkaline pretreatment contributed to significant delignification, while acidic pretreatment reduced the share of hemicelluloses and increased the proportion of lignin, the so-called "pseudolignin". The composition of corncob (control and after pre-treatment) was changed after anaer...
Thermophilic (55°C) anaerobic enrichment cultures were incubated with [14C-lignin]lignocellulose, ['4Cpolysaccharidellignocellulose, and kraft [14C]lignin prepared from slash pine, Pinus elliottii, and 14C-labeled preparations of synthetic lignin and purffied cellulose. Significant but low percentages (2 to 4%) of synthetic and natural pine lignin were recovered as labeled methane and carbon dioxide during 60-day incubations, whereas much greater percentages (13 to 23%) of kraft lignin were recovered as gaseous end products. Percentages of label recovered from lignin-labeled substrates as dissolved degradation products were approximately equal to percentages recovered as gaseous end products. High-pressure liquid chromatographic analyses of CuO oxidation products of sound and degraded pine lignin indicated that no substantial chemical modifications of the remaining lignin polymer, such as demethoxylation and dearomatization, occurred during biodegradation. The polysaccharide components of pine lignocellulose and purified cellulose were relatively rapidly mineralized to methane and carbon dioxide; 31 to 37% of the pine polysaccharides and 56 to 63% of the purified cellulose were recovered as labeled gaseous end products. An additional 10 to 20% of the polysaccharide substrates was recovered as dissolved degradation products. Overall, these results indicate that elevated temperatures can greatly enhance rates of anaerobic degradation of lignin and lignified substrates to methane and low-molecular-weight aromatic compounds.
Industrial Crops and Products, 2018
Anaerobic digestion of lignocellulosic biomass like crop residues have gained attention due to their surplus availability in rural areas. However, anaerobic digestion of such biomass feedstock require pretreatment to increase their digestibility. A combination of chemical (banana peel ash and calcium hydroxide) and thermal treatments (60-90°C for time intervals of 2, 6 and 10 h) is investigated to understand the degradation behavior of two agro-residue biomasses viz. rice straw and corn stalk. Various analytical methods like FTIR, SEM and degradation of fiber (lignin, cellulose and hemicellulose) were employed to assess the efficacy of the pretreatment technique. Post pretreatment, biogas production is also investigated from the pretreated biomass along with the degradation of volatile solids during anaerobic digestion. Longer duration and higher temperature improved biodegradability as compared to short duration and low temperature treatments with differentiated results on both samples. Lignin of corn stalk (∼47%) degrades better than rice straw (∼39%) under identical pretreatments. The biogas production in cubic meter per unit kilogram of volatile solids of rice straw and corn stalk pretreated at 90°C for 6 h was enhanced by 62% and 66%, respectively as compared to untreated rice straw and corn stalk. The know-how generated form the study will be useful to explore the potential benefits of banana peel ash as a pretreatment source for energy recovery via anaerobic digestion from surplus biomasses in rural India.
2014
Lignocellulosic biomass is composed of cellulose, hemicellulose, lignin and extraneous compounds (waxes, fats, gums, starches, alkaloids, resins, tannins, essential oils, silica, carbonates, oxalates, etc). The sugars within the complex carbohydrates (cellulose and hemicellulose) can be accessed for cellulosic bioethanol production through ethanologenic microorganisms. However, the composite nature of lignocellulosic biomass, particularly the lignin portion, presents resistance and recalcitrance to biological and chemical degradation during enzymatic hydrolysis/saccharification and the subsequent fermentation process. This leads to a very low conversion rate, which makes the process uneconomically feasible. Thus, biomass structure requires initial breakdown of the lignocellulosic matrix.
Methods for improving anaerobic lignocellulose substrates degradation
A successful biogas production process depends upon adequate hydrolysis of macromolecules in the substrate and stable further conversion. The complex and rigid structure of cellulosic, hemicellulosic and lignin chain is preventing lignocellulosic biomass to reach efficient hydrolysis, therefore pretreatment of a substrate is needed for higher biogas and methane yields. There are several different physical and chemical methods of pretreatments available which include the usage of acids, alkalis, organic solvents, ionic detergents, steam, high pressure, grinding, ultrasound, and microwave irradiation. Physico-chemical pretreatments act rapidly on lignocellulose but their upscaling is very expensive in industry. Many studies have been made in finding the best combination of different pretreatment methods and also new biological techniques which could make lignocellulose pretreatment cheaper and environmentally more friendly. Using natural abilities of different fungi, bacteria or yeast to degrade lignocellulose simplifies the whole process. Also cocktails of biotechnologically produced enzymes are effective in degrading lignocellulose.