Reduction of irreversibility generation in sugar and ethanol production from sugarcane

Sugarcane is one of the most important industries of the Brazilian economy, and its main products are sugar and ethanol. Most of the industrial plants produce both products in an integrated process, in which the sugarcane bagasse is a by-product that can be used as a fuel in the cogeneration system. The bagasse is used as the only fuel of the plant, supplying all energy required for the process, and also producing electricity surplus that may be sold to the grid. In this paper, exergy analysis is used to assess an integrated sugar and ethanol plant with its cogeneration system. The plant was divided into eight sub-systems to evaluate the irreversibility generation in each separately. Data from typical sugarcane factories in Brazil, which produce sugar and ethanol, were used in the process simulation. The analysis has shown that the sub-systems with the highest contribution for the total irreversibility generation of the plant were co-generation, juice extraction and fermentation. Some improvements are proposed, including process thermal integration and the introduction of more efficient equipments for prime mover and steam and electricity generation. The analysis indicated that the total irreversibility could be reduced by 10% should those changes be implemented.     

Catalytic fast pyrolysis of sugarcane bagasse pith with HZSM-5 catalyst using tandem micro-reactor-GC-MS

Fast pyrolysis of biomass is praised as an efficient and feasible process to selectively convert lignocellulosic biomass into bio-fuels and bio-chemicals. Pith of sugarcane bagasse could be an attractive lignocellulosic waste from depithing process from pulp and paper mill, which can utilize for production of biofuel and added value products. In this study, we employed a tandem micro-reactor coupled with gas chromatography-mass spectroscopy to investigate the products distribution from pith of sugarcane bagasse via catalytic fast pyrolysis. In the operating conditions, pyrolysis temperature and HZSM-5 catalyst had significant effect on products and distributions. An increase in the pyrolysis temperature from 400°C to 550°C led to an increase in the yield of phenolic compounds (6.3%, w/w%), followed decrease at higher temperature. The maximum carboxylic acids (10.6%) and furfural (3.5%) were obtained at lower temperature. At presence of HZSM-5 catalyst, the selectivity of aromatics such as benzene, toluene, indene, and naphthalene were improved.     

Dilute mixed-acid pretreatment of sugarcane bagasse for ethanol production

Integral utilisation of bagasse is a high priority for the diversification of the sugarcane industry. The application of a biorefinery philosophy to bagasse utilisation requires its fractionation into its main components: cellulose, hemicelluloses and lignin. The first stage in that process is the pretreatment, in which a considerable part of hemicelluloses is solubilised, and cellulose is activated towards enzymatic hydrolysis. In this work, a pretreatment method using a mixture of sulfuric and acetic acid is investigated. Two different solid-to-liquid ratios (1.5:10 and 1:10) were used in the pretreatment. Both conditions efficiently hydrolysed the hemicelluloses giving removals above 90%. The extractive components were also effectively solubilised, and lignin was only slightly affected. Cellulose degradation was below 15%, which corresponded to the low crystallinity fraction. The analysis of the morphology of pretreated bagasse confirmed the results obtained in the chemical characterization.     

Improving bioethanol production from sugarcane: evaluation of distillation, thermal integration and cogeneration systems

Demand for bioethanol has grown considerably over the last years. Even though Brazil has been producing ethanol from sugarcane on a large scale for decades, this industry is characterized by low energy efficiency, using a large fraction of the bagasse produced as fuel in the cogeneration system to supply the process energy requirements. The possibility of selling surplus electricity to the grid or using surplus bagasse as raw material of other processes has motivated investments on more efficient cogeneration systems and process thermal integration. In this work simulations of an autonomous distillery were carried out, along with utilities demand optimization using Pinch Analysis concepts. Different cogeneration systems were analyzed: a traditional Rankine Cycle, with steam of high temperature and pressure (80 bar, 510 °C) and back pressure and condensing steam turbines configuration, and a BIGCC (Biomass Integrated Gasification Combined Cycle), comprised by a gas turbine set operating with biomass gas produced in a gasifier that uses sugarcane bagasse as raw material. Thermoeconomic analyses determining exergy-based costs of electricity and ethanol for both cases were carried out. The main objective is to show the impact that these process improvements can produce in industrial systems, compared to the current situation.     

Influence of storage conditions on the production of hydrocarbons from herbaceous biomass

An agricultural residue, sugarcane bagasse (Saccharum spp., hybrid), was used in this study and was stored in piles for 3–26 weeks. Analytical pyrolysis of fresh bagasse samples and samples taken from the center of the bagasse piles after 3.25, 6.5, 13 and 26 weeks of storage showed only small changes in their chemical compositions (pentosans, hexosans and lignin). However, samples taken from the outer surface layer (pile crust) had significantly lower contents of pentosans and hexosans and higher contents of lignin compared to the fresh samples. Samples taken from microbially degraded portions of the pile (composting fraction) showed preferential degradation of the pentosans relative to the hexosans and lignin. The pentosan content of the composting fraction was significantly lower than that from the fresh samples and samples from the centers of the piles. Because of the preferential degradation of the pentosans, the hexosans and lignin contents were relatively higher for the composting fraction compared to the fresh samples. These results clearly indicate that most of the deterioration observed in the bagasse piles occurred on the outer surface layers.

Catalytic upgrading of the bagasse pyrolysis vapors also showed that the yield of hydrocarbons from the pile crust was 23% lower than that for the fresh material. However, there were no significant differences between the yields of hydrocarbons from the fresh samples and samples taken from the center of the pile after 3.25, 6.5, 13 and 26 weeks of storage.     

Differences in the chemical structure of the lignins from sugarcane bagasse and straw

Two major residues are produced by the sugarcane industry, the fibrous fraction following juice extraction (bagasse), and the harvest residue (straw). The structures of the lignins from these residues were studied by pyrolysis coupled to gas chromatography-mass spectrometry (Py-GC/MS), nuclear magnetic resonance (NMR), and derivatization followed by reductive cleavage (DFRC). Whereas the lignin from bagasse has a syringyl-rich p-hydroxyphenyl:guaiacyl:syringyl (H:G:S) molar composition of 2:38:60, the lignin from straw is guaiacyl-rich (H:G:S of 4:68:28). The compositional differences were also reflected in the relative abundances of the different interunit linkages. Bagasse lignin was primarily β–O–4′ alkyl-aryl ether substructures (representing 83% of NMR-measurable linkages), followed by minor amounts of β–5′ (phenylcoumarans, 6%) and other condensed substructures. The lignin from straw has lower levels of β-ethers (75%) but higher relative levels of phenylcoumarans (β–5′, 15%) and dibenzodioxocins (5–5/4–O–β, 3%), consistent with a lignin enriched in G-units. Both lignins are extensively acylated at the γ-hydroxyl of the lignin side-chain (42% and 36% acylation in bagasse and straw), predominantly with p-coumarates (preferentially on S-units) but also with acetates (preferentially on G-units) to a minor extent. Tetrahydrofuran structures diagnostically arising from β–β-coupling (dehydrodimerization) of sinapyl p-coumarate or its cross-coupling with sinapyl alcohol were found in both lignins, indicating that sinapyl p-coumarate acts as a monomer participating in lignification. The flavone tricin was also found in the lignins from sugarcane, as also occurs in other grasses.     

Efficient sugar production from sugarcane bagasse by microwave assisted acid and alkali pretreatment

Sugarcane bagasse represents one of the best potential feedstocks for the production of second generation bioethanol. The most efficient method to produce fermentable sugars is by enzymatic hydrolysis, assisted by thermochemical pretreatments. Previous research was focused on conventional heating pretreatment and the pretreated biomass residue characteristics. In this work, microwave energy is applied to facilitate sodium hydroxide (NaOH) and sulphuric acid (H₂SO₄) pretreatments on sugarcane bagasse and the efficiency of sugar production was evaluated on the soluble sugars released during pretreatment. The results show that microwave assisted pretreatment was more efficient than conventional heating pretreatment and it gave rise to 4 times higher reducing sugar release by using 5.7 times less pretreatment time. It is highlighted that enrichment of xylose and glucose can be tuned by changing pretreatment media (NaOH/H₂SO₄) and holding time. SEM study shows significant delignification effect of NaOH pretreatment, suggesting a possible improved enzymatic hydrolysis process. However, severe acid conditions should be avoided (long holding time or high acid concentration) under microwave heating conditions. It led to biomass carbonization, reducing sugar production and forming ‘humins’. Overall, in comparison with conventional pretreatment, microwave assisted pretreatment removed significant amount of hemicellulose and lignin and led to high amount of sugar production during pretreatment process, suggesting microwave heating pretreatment is an effective and efficient pretreatment method.     

Optimization of dilute acid and hot water pretreatment of different lignocellulosic biomass: A comparative study

Pretreatment of biomass to alter their recalcitrant structures is an essential step to obtain high yield of products via bioconversion processes. In this study, main emphasis was to compare the results evaluated in terms of total reducing sugars (TRS) yield after acid and hot water pre-treatment process performed with laboratory scale equipment using different lignocellulosic biomass. The biomass chosen for this purpose i.e. sugarcane bagasse and bamboo were collected from Guwahati, Assam and their physico-chemical characteristics were examined using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermo gravimetric analysis (TGA) including proximate and ultimate analysis. Crystalinity of the biomass used was observed to be 33.15% and 31.29% for sugarcane bagasse and bamboo respectively. Hot water and dilute acid pretreatment allows selective solubility of hemicellulose which improves the accessibility of enzymes for cellulose hydrolysis. The highest yield of TRS was observed at run order 8 for both acid and hot water pretreatment (23.49 and 26.50 gL⁻¹) with respect to sugarcane bagasse. But, the pretreatment results obtained for bamboo was slightly different to that of sugarcane bagasse. The highest yield of TRS was obtained at run order 8 for acid (15.6 gL⁻¹) and run order 10 for hot water (17.98 gL⁻¹) pretreatment respectively. Irrespective of biomass type, hot water pretreatment process produced more TRS than acid pretreatment process.     

Ethanol production from enzymatic hydrolysis of sugarcane bagasse pretreated with lime and alkaline hydrogen peroxide

In this work we evaluated ethanol production from enzymatic hydrolysis of sugarcane bagasse. Two pretreatments agents, lime and alkaline hydrogen peroxide, were compared in their performance to improve the susceptibility of bagasse to enzymatic action. Mild conditions of temperature, pressure and absence of acids were chosen to diminish costs and to avoid sugars degradation and consequent inhibitors formation. The bagasse was used as it comes from the sugar/ethanol industries, without grinding or sieving, and hydrolysis was performed with low enzymes loading (3.50 FPU g⁻¹ dry pretreated biomass of cellulase and 1.00 CBU g⁻¹ dry pretreated biomass of ??-glucosidase). The pretreatment with alkaline hydrogen peroxide led to the higher glucose yield: 691 mg g⁻¹ of glucose for pretreated bagasse after hydrolysis of bagasse pretreated for 1 h at 25 °C with 7.35% (v/v) of peroxide. Fermentation of the hydrolyzates from the two pretreatments were carried out and compared with fermentation of a glucose solution. Ethanol yields from the hydrolyzates were similar to that obtained by fermentation of the glucose solution. Although the preliminary results obtained in this work are promising for both pretreatments considered, reflecting their potential for application, further studies, considering higher biomass concentrations and economic aspects should be performed before extending the conclusions to an industrial process.     

Waste biomass to liquids: Low temperature conversion of sugarcane bagasse to bio-oil. The effect of combined hydrolysis treatments

This article describes the influence of different sugarcane bagasse hydrolysis pretreatments on modifications to biomass feedstock and the characteristics of the resultant pyrolysis products. Sugarcane bagasse was pretreated with acid, alkaline or sequential acid/alkaline solutions and pretreated samples were then subjected to a low temperature conversion (LTC) process under He or O₂/He atmospheres at 350-450 °C. Both pretreated samples and sugarcane bagasse in natura were analyzed by determination of their chemical composition and by thermogravimetric, FTIR and SEM analyses. The gases yielded during LTC were monitored on-line by quadrupole mass spectrometry, and the liquid fractions obtained were characterized by FTIR and ¹H and ¹³C NMR. Irrespective of the sugarcane bagasse pretreatment applied, the main bio-oil component obtained was levoglucosan. However, the LTC yield of bio-oil depended on the hydrolysis treatment of the biomass and decreased in the presence of O₂. The acid hydrolysis pretreatment increased the LTC bio-oil yield notably.     

Pyrolysis of sugarcane bagasse pretreated with sulfuric acid

Pyrolysis is a promising technique for the recovery of useful gas, tar, and solid products from biomass waste. However, the low tar yields obtained from lignocellulosic biomass are a significant drawback. To enhance tar yields, sugarcane bagasse, which is the most abundant agricultural waste in Fiji, was pretreated at ambient temperature and atmospheric pressure using various sulfuric acid (H₂SO₄) concentrations. Here, the ether bonds of cellulose, hemicellulose, and lignin were partially hydrolyzed. The pretreated samples were then pyrolyzed at 500 °C, and it was confirmed that H₂SO₄-pretreatment disrupted the bagasse cell structure, with the thermogravimetry and differential thermogravimetry results confirming that decomposition occurred at lower temperatures after pretreatment. In addition, tar yields were significantly enhanced from 5.6 wt% to 13.4 wt% for the untreated and 3 M H₂SO₄-pretreated samples respectively. The main components detected in this tar product were levoglucosan, andcellulose-and hemicellulose-derived products, whose proportions were increased following pretreatment. Thus, our work demonstrates that dilute acid pretreatment enhances tar production from sugarcane bagasse due to the production of shorter chain components via the partial hydrolysis of ether bonds.     

Supercritical steam cycles and biomass integrated gasification combined cycles for sugarcane mills

Back in 1970s and 1980s, cogeneration plants in sugarcane mills were primarily designed to consume all bagasse, and produce steam and electricity to the process. The plants used medium pressure steam boilers (21 bar and 300 °C) and backpressure steam turbines. Some plants needed also an additional fuel, as the boilers were very inefficient. In those times, sugarcane bagasse did not have an economic value, and it was considered a problem by most mills. During the 1990s and the beginning of the 2000s, sugarcane industry faced an open market perspective, thus, there was a great necessity to reduce costs in the production processes. In addition, the economic value of by-products (bagasse, molasses, etc.) increased, and there was a possibility of selling electricity to the grid. This new scenario led to a search for more advanced cogeneration systems, based mainly on higher steam parameters (40–80 bar and 400–500 °C). In the future, some authors suggest that biomass integrated gasification combined cycles are the best alternative to cogeneration plants in sugarcane mills. These systems might attain 35–40% efficiency for the power conversion. However, supercritical steam cycles might also attain these efficiency values, what makes them an alternative to gasification-based systems. This paper presents a comparative thermoeconomic study of these systems for sugarcane mills. The configurations studied are based on real systems that could be adapted to biomass use. Different steam consumptions in the process are considered, in order to better integrate these configurations in the mill.     

Comparative study on ethanol production from pretreated sugarcane bagasse using immobilized Saccharomyces cerevisiae on various matrices

Microwave alkali pretreated sugarcane bagasse was used as a substrate for production of cellulolytic enzymes, needed for biomass hydrolysis. The pretreated sugarcane bagasse was enzymatic hydrolyzed by crude unprocessed enzymes cellulase (Filter paper activity 9.4 FPU/g), endoglucanase (carboxymethylcellulase, 148 IU/g), β-glucosidase (116 IU/g) and xylanase (201 IU/g) produced by Aspergillus flavus using pretreated sugarcane bagasse as substrate under solid state fermentation. Concentrated enzymatic hydrolyzate was used for ethanol production using Saccharomyces cerevisiae immobilized on various matrices. The yield of ethanol was 0.44 g_p/g_s in case of yeast immobilized sugarcane bagasse, 0.38 g_p/g_s using Ca-alginate and 0.33 g_p/g_s using agar-agar as immobilization matrices. The immobilized yeast studied up to 10 cycles in case of immobilized sugarcane bagasse and up to 4 cycles in case of agar-agar and calcium alginate for ethanol production under repeated batch fermentation study.     

Life cycle assessment and life cycle costing of bioethanol from sugarcane in Brazil

Brazil has always been the pioneer in the application of bioethanol as a main fuel for automobiles, hence environmental and economic analyses of the Brazilian ethanol industries are of crucial importance. This study presents a comparative life cycle assessment (LCA) on gasoline and ethanol as fuels, and with two types of blends of gasoline with bioethanol, all used in a midsize car. The focus is on a main application in Brazil, sugarcane based ethanol. The results of two cases are presented: base case—bioethanol production from sugarcane and electricity generation from bagasse; future case—bioethanol production from both sugarcane and bagasse and electricity generation from wastes. In both cases sugar is co-produced. The life cycles of fuels include gasoline production, agricultural production of sugarcane, ethanol production, sugar and electricity co-production, blending ethanol with gasoline to produce E10 (10% of ethanol) and E85 (85%), and finally the use of gasoline, E10, E85 and pure ethanol. Furthermore, a life cycle costing (LCC) was conducted to give an indication on fuel economy in both cases. The results show that in the base case less GHG is emitted; while the overall evaluation of these fuel options depends on the importance attached to different impacts. The future case is certainly more economically attractive, which has been the driving force for development in the ethanol industry in Brazil. Nevertheless, the outcomes depend very much on the assumed price for crude oil. In LCC a steady-state cost model was used and only the production cost was taken into account. In the real market the prices of fuels are very much dependent on the taxes and subsidies. Technological development can help in lowering both the environmental impact and the prices of the ethanol fuels.     

A mathematical,economic and energetic appraisal of biomethane and biohydrogen production from Brazilian ethanol plants' waste: Towards a circular and renewable energy development

The high production of sugarcane in Brazil and its application of ethanol and sugar production results in a higher generation of vinasse and bagasse. The treatment of these residues can be carried out using anaerobic co-digestion procedures. Besides promoting waste treatment, it enables energy exploration through biogas and hydrogen generation. Bioenergy use can also generate steam in sugar and alcohol plants by burning, sugarcane milling, fueling vehicles for the transport of products, among others. These energy applications allow total and efficient, energetic exploring of sugarcane. Hence, this study estimated the production of methane, hydrogen, thermal and electrical energy generated from vinasse and bagasse in the autonomous and annexed Brazilian ethanol and sugar plants. Three scenarios present the use of biogas generated: Scenario 1: energy use of all methane from biogas; Scenario 2: hydrogen production from the remaining methane, after considering the energy autonomy of the ethanol plants; Scenario 3: hydrogen production from all the methane generated. All the scenarios which considered the use of methane led to energy self-sufficiency in the sector. However, only annexed plants present economic feasibility for implementing the project. Scenario 2 is highlighted in this study, once beyond the sector's energetic self-sufficiency, the operational conditions enabled the storage of 9.26E+07 Nm³.d^?1 of hydrogen, equal 3.04E+08 ton per year. CH₄ and H₂ production seen in a global scenario of circular economy and energy security have high benefits, contributing to the gradual transformation of an economy dependent on non-renewable resources into a circular and renewable economy.     

Mathematical modeling of thin-layer drying of fermented and non-fermented sugarcane bagasse

This work reports hot-air convective drying of thin-layer fermented and non-fermented sugarcane bagasse. For this purpose, experiments were carried out in a laboratory-scale dryer assessing the effects of solid-state fermentation (SSF) on the drying kinetics of the processing material. The fermented sugarcane bagasse in SSF was obtained with the use of Kluyveromyces marxianus NRRL Y-7571. Drying experiments were carried out at 30, 35, 40 and 45 °C, at volumetric air flow rates of 2 and 3 m³ h^?1. The ability of ten different thin-layer mathematical models was evaluated towards representing the experimental drying profiles obtained. Results showed that the fermented sugarcane bagasse presents a distinct, faster drying, behavior from that verified for the non-fermented material at the same conditions of temperature and volumetric air flow rate. It is shown that the fermented sugarcane bagasse presented effective diffusion coefficient values of about 1.3 times higher than the non-fermented material. A satisfactory agreement between experimental data and model results of the thin-layer drying of fermented and non-fermented sugarcane bagasse was achieved at the evaluated experimental conditions.     

Comparative analysis for power generation and ethanol production from sugarcane residual biomass in Brazil

This work compares the technical, economic and environmental (GHG emissions mitigation) performance of power generation and ethanol production from sugarcane residual biomass, considering conversion plants adjacent to a sugarcane mill in Brazil. Systems performances were simulated for a projected enzymatic saccharification co-fermentation plant (Ethanol option) and for a commercial steam-Rankine power plant (Electricity option). Surplus bagasse from the mill would be used as fuel/raw material for conversion, while cane trash collected from the field would be used as supplementary fuel at the mill. For the Electricity option, the sugarcane biorefinery (mill+adjacent plant) would produce 91 L of ethanol per tonne of cane and export 130 kWh/t of cane, while for the Ethanol option the total ethanol production would be 124 L/t of cane with an electricity surplus of 50 kWh/t cane. The return on investment (ROI) related to the biochemical conversion route was 15.9%, compared with 23.2% for the power plant, for the conditions in Brazil. Considering the GHG emissions mitigation, the environmentally preferred option is the biochemical conversion route: the net avoided emissions associated to the adjacent plants are estimated to be 493 and 781 kgCO₂eq/t of dry bagasse for the Electricity and Ethanol options, respectively.     

Comparing biological and thermochemical processing of sugarcane bagasse: An energy balance perspective

The technical performance of lignocellulosic enzymatic hydrolysis and fermentation versus pyrolysis processes for sugarcane bagasse was evaluated, based on currently available technology. Process models were developed for bioethanol production from sugarcane bagasse using three different pretreatment methods, i.e. dilute acid, liquid hot water and steam explosion, at various solid concentrations. Two pyrolysis processes, namely fast pyrolysis and vacuum pyrolysis, were considered as alternatives to biological processing for the production of biofuels from sugarcane bagasse. For bioethanol production, a minimum of 30% solids in the pretreatment reactor was required to render the process energy self-sufficient, which led to a total process energy demand equivalent to roughly 40% of the feedstock higher heating value. Both vacuum pyrolysis and fast pyrolysis could be operated as energy self-sufficient if 45% of the produced char from fast pyrolysis is used to fuel the process. No char energy is required to fuel the vacuum pyrolysis process due to lower process energy demands (17% compared to 28% of the feedstock higher heating value). The process models indicated that effective process heat integration can result in a 10-15% increase in all process energy efficiencies. Process thermal efficiencies between 52 and 56% were obtained for bioethanol production at pretreatment solids at 30% and 50%, respectively, while the efficiencies were 70% for both pyrolysis processes. The liquid fuel energy efficiency of the best bioethanol process is 41%, while that of crude bio-oil production before upgrading is 67% and 56% via fast and vacuum pyrolysis, respectively. Efficiencies for pyrolysis processes are expected to decrease by up to 15% should upgrade to a transportation fuel of equivalent quality to bioethanol be taken into consideration.     

Can Brazil replace 5% of the 2025 gasoline world demand with ethanol?

Increasing use of petroleum, coupled with concern for global warming, demands the development and institution of CO₂ reducing, non-fossil fuel-based alternative energy-generating strategies. Ethanol is a potential alternative, particularly when produced in a sustainable way as is envisioned for sugarcane in Brazil. We consider the expansion of sugarcane-derived ethanol to displace 5% of projected gasoline use worldwide in 2025. With existing technology, 21 million hectares of land will be required to produce the necessary ethanol. This is less than 7% of current Brazilian agricultural land and equivalent to current soybean land use. New production lands come from pasture made available through improving pasture management in the cattle industry. With the continued introduction of new cane varieties (annual yield increases of about 1.6%) and new ethanol production technologies, namely the hydrolysis of bagasse to sugars for ethanol production and sugarcane trash collection providing renewable process energy production, this could reduce these modest land requirements by 29–38%.     

甘蔗渣的不同预处理方法比较及其酶水解的类分形动力学

分别采用NaOH（0.45 mol/L aq.）、HCl（0.034 mol/L aq.）和高温液态水（LHW）三种方法对甘蔗渣进行预处理,并对其组分变化和酶解效果进行了比较。NaOH预处理方法获得最高的木质素去除率,达91.1%,糖损失率达23.5%;HCl和LHW预处理结果类似,木聚糖溶解率分别为85.2%和79.7%,糖损失率均约为15%,木质素去除率均小于16%。三种方法处理的甘蔗渣经纤维素酶水解后得到总单糖（葡萄糖 + 木糖）浓度分别为38.7 g/L（NaOH）、16.1 g/L（HCl）和15.6 g/L（LHW）。综合比较预处理和酶水解工艺,NaOH水溶液预处理法的糖回收率最高,其次为HCl水溶液预处理法,LHW预处理法的糖回收率最低。作为描述纤维素酶反应动力学的有力工具,类分形理论的研究表明,各种预处理后底物的不规则性依次为：HCl＞LHW＞NaOH,其与酶的有效吸附大小依次为：NaOH＞HCl＞LHW。