热过氧化氢预处理对花生秸秆酶解的影响

以花生秸秆为原料,通过单因素试验探究热H_2O_2预处理对花生秸秆酶解的影响,结果表明所有试验组均显著(p0.05)可提高酶解还原糖产量,进一步设计正交试验对预处理条件进行优化,结果表明:100℃,2 h,6%H_2O_2可作为最优预处理条件,在该预处理条件下酶解还原糖产率相比于未处理秸秆,提高154.56%。分别对预处理前后花生秸秆成分、化学特性以及物理结构进行测定,并分析热H_2O_2能有效提高花生秸秆酶解效率的原因。     

碱性双氧水预处理玉米秸秆性质研究

使用碱性双氧水对玉米秸秆进行预处理,可以有效提高秸秆的酶解效果。实验表明,最优预处理参数为使用分别占秸秆质量16%的 H₂O₂和25.6% 的NaOH,于40℃下预处理秸秆24 h。对经不同预处理剂处理后的秸秆进行酶解,发现NaOH及碱性双氧水预处理秸秆的酶解还原糖产量为7.48 g/L和8.26 g/L,而经H₂O及H₂O₂预处理秸秆的还原糖产量仅为1.35 g/L和1.59 g/L。通过木质纤维素含量及SEM分析发现,氢氧化钠主要作用为溶解秸秆中的木质素及半纤维素,而双氧水的存在则会破坏秸秆表面结构。计算秸秆预处理前后质量损失发现,双氧水的存在不能显著提高秸秆预处理后的质量损失,但会氧化分解被氢氧化钠溶解的大分子物质,对此过程机理及产物还需进行深入的研究。     

NaOH预处理对油菜秸秆厌氧消化产气性能的影响

研究了不同浓度NaOH(质量分数为2%,4%和6%)预处理对油菜秸秆厌氧消化产气性能的影响。结果表明:6%NaOH预处理组累积产甲烷量达到了12 337 m L,单位VS产甲烷量为264.3 m L/g,较未处理组、2%NaOH预处理组和4%NaOH预处理组分别提高了38.0%,10.2%和7.00%;T90为23 d,较未处理组、2%NaOH预处理组和4%NaOH预处理组分别提高了19,12,5 d;氨氮为742 mg/L,碱度为7 400 mg/L,p H为7.42,三者均在适宜范围内。综合考虑,6%NaOH预处理组的油菜秸秆厌氧消化产气效率较高。     

超声波辅助离子液体预处理的纤维素酶解糖化

利用超声波辅助离子液体1-烯丙基-3-甲基咪唑甲酸盐([Amim][COOH])对纤维素进行预处理,并测定聚合度变化和酶解速率。试验表明,再生纤维素的聚合度有明显下降;酶解速率随预处理温度的增加呈现先增加后下降的趋势,在90℃出现最大值;在外加超声波条件下,经离子液体预处理的纤维素酶解初速度可达11.10g/(L·h),相比未处理的纤维素,酶解速度提高33%。通过电子显微镜和红外光谱分析,再生纤维素出现了解聚现象,结晶度也明显下降。     

NaOH/H2O2预处理促进玉米秸秆酶解产糖工艺条件的研究

采用正交实验初步探讨了NaOH/HO2O2对经白腐菌Hyrophous sp.254处理15 d的玉米秸秆进行预处理的最佳条件.在NaOH/H2O2预处理过程中,NaOH浓度、H2O2体积分数、底物浓度及预处理时间均对秸秆的纤维素酶酶解效率存在一定影响.试验表明,NaOH/H2O2的最佳预处理条件:NaOH浓度为7g/L,H2O2体积分数为0.7%,底物浓度为50g/L,处理时间为24h.在优化的工艺条件下,玉米秸秆的还原糖产量达到了0.417 g/g,H2O2用量减少了30%,废水排放量减少了60%.     

不同预处理方法对麦草纤维素酶解效果的影响

以麦草纤维素为研究对象,将其进行机械粉碎后,分别采用碱浸泡/蒸汽、蒸汽/碱浸泡、蒸汽、冷冻/蒸汽、碱浸泡/冷冻等方法进行预处理,然后加入纤维素酶进行酶解,通过检测酶解液中葡萄糖含量来评价麦草纤维素预处理的效果。研究结果表明,预处理后的麦草纤维素经NaOH溶液浸泡后,再用蒸汽处理40 min,酶解24 h后葡萄糖产率较预处理前的葡萄糖产率有明显增加(提高15%);经NaOH溶液浸泡后再进行超低温(-80℃)冷冻处理,酶解12 h后葡萄糖产率有所增加,酶解48 h后葡萄糖产率比预处理前提高23%。     

稻草秸秆辐照酶解工艺优化

通过采用60Co-γ辐照处理稻草秸秆,提高稻草秸秆的酶解效果。采用离子色谱仪测定稻草秸秆酶解液中可发酵性糖的含量,对水解温度、加酶量、液固比、水解时间4个因素进行单因素试验分析,对稻草秸秆酶解条件进行优化,建立稻草秸秆辐照酶解新工艺。研究结果表明,稻草秸秆辐照剂量在0～2 000 kGy内,辐照预处理最佳剂量为1 200 kGy;得到稻草秸秆最优辐照酶解条件:预处理辐照剂量为1 200 kGy、水解温度为45℃、水解时间为36 h、液固比为60、加酶量为120 U/g。在此最佳条件下,稻草秸秆纤维素、半纤维素总转化率达71%。     

氨化预处理对稻秆和鸡粪干式厌氧发酵的影响

针对秸秆类废弃物厌氧发酵的速度慢以及常规的氨化预处理后物料氨氮含量高影响后续厌氧发酵的问题,提出鸡粪和稻秆混合物氨化预处理工艺,并在35℃条件下,研究经此氨化预处理工艺处理后物料的干式厌氧发酵效果及降解情况。结果表明:以鸡粪为氮源和营养源可取得较好的秸秆预处理效果,预处理后物料的挥发性脂肪酸总量及成分均优于未处理组;经氨化预处理后物料的干式厌氧发酵产气效果优于未处理组,总固体(TS)和挥发性固体(VS)去除率较高,发酵后剩余物的挥发性脂肪酸总量及成分均优于未处理组,产气潜力更大。     

微波辅助MgO/SBA-15预处理对玉米秸秆厌氧消化的影响

为探索微波辅助MgO/SBA-15预处理玉米秸秆对其厌氧消化产气的影响,采用Mg O/SBA-15对玉米秸秆进行预处理,并在中温条件下进行厌氧消化产气试验。试验结果表明:微波辅助Mg O/SBA-15预处理玉米秸秆能有效破坏其原始构态,提高纤维素回收率和底物的可生物降解性,为厌氧发酵产沼气奠定良好的基础。在MgO/SBA-15与干基质的质量比分别为0%、10%、20%的条件下,预处理后的玉米秸秆厌氧消化产气能力较未预处理组有较大提高,厌氧消化启动时间有所提前。与对照组相比,经10%和20%MgO/SBA-15预处理的玉米秸秆单位挥发性固体(volatile solid,VS)产气量分别可提高55.28%和41.00%;90%最大产气量厌氧消化时间分别缩短1d和0 d;VS减少率分别提高7.3%和4.1%。综合考察预处理效果、日产气量、累积产气量和厌氧消化启动时间,相比于质量比20%的MgO/SBA-15组,质量比为10%的Mg O/SBA-15预处理效果更好。     

四氢糠醇-稀酸体系预处理杂交狼尾草的试验研究

以杂交狼尾草为研究对象,采用四氢糠醇-硫酸体系在常压较低温度下进行预处理研究,优化该预处理体系得到最佳预处理条件为0.1 mol/L硫酸、反应温度120℃、反应时间2 h、固液比为1∶12,在此条件下残渣中纤维素、半纤维素的保留率分别为86.17%、9.01%,木质素脱除率为98.16%;对预处理残渣进行酶解,72 h时酶解率可达99.01%,比未处理原料的酶解率高2.6倍。通过使用扫描电镜、X射线衍射、红外光谱、热重分析等方法对预处理后残渣及原料的组成及结构进行分析测试,表明四氢糠醇-硫酸预处理能有效脱除木质素及半纤维素,破坏平整的原料表面结构,提高原料的酶解率。     

Enhancement of paddy straw digestibility and biogas production by sodium hydroxide-microwave pretreatment

Biogas has become a promising energy substitute to fossil fuels. Lignocellulosics, being cheap and renewable resource, could be very well used as a feedstock for biogas generation. Paddy straw is an abundant lignocellulose which is rich in organic matter like cellulose, hemi-cellulose and lignin. It is generally disposed off by burning causing environmental pollution whilst it can be used for biofuel generation. The digestibility of paddy straw is low due to high lignin and silica content. The present study was carried out to enhance paddy straw digestibility and biogas production through sodium hydroxide (NaOH) pretreatment. The paddy straw was pretreated with NaOH by soaking (24 h) in different concentrations of NaOH (2, 4, 6, 8 and 10%) and supplementing with microwave irradiations (30 min, 720 W, 180 °C). 4% NaOH-30 min microwave was found to be the best pretreatment which resulted in 65.0% decrease in lignin content and 88.7% reduction in silica content. This increased digestibility due to reduced lignin and silica content resulted in 54.7% increase in biogas production. Scanning Electron Microscopy of pretreated paddy straw revealed breakdown of lignocellulose structure resulted from the tearing of different layers of cell wall of paddy straw.     

Potential bioethanol and biogas production using lignocellulosic biomass from winter rye, oilseed rape and faba bean

To meet the increasing need for bioenergy several raw materials have to be considered for the production of e.g. bioethanol and biogas. In this study, three lignocellulosic raw materials were studied, i.e. (1) winter rye straw (Secale cereale L), (2) oilseed rape straw (Brassica napus L.) and (3) faba bean straw (Viciafaba L.). Their composition with regard to cellulose, hemicellulose, lignin, extractives and ash was evaluated, as well as their potential as raw materials for ethanol and biogas production. The materials were pretreated by wet oxidation using parameters previously found to be optimal for pretreatment of corn stover (195 °C, 15 min, 2 g l⁻¹ Na₂CO₃ and 12 bar oxygen). It was shown that pretreatment was necessary for ethanol production from all raw materials and gave increased biogas yield from winter rye straw. Neither biogas productivity nor yield from oilseed rape straw or faba bean straw was significantly affected by pretreatment. Ethanol was produced by the yeast Saccharomyces cerevisiae during simultaneous enzymatic hydrolysis of the solid material after wet oxidation with yields of 66%, 70% and 52% of theoretical for winter rye, oilseed rape and faba bean straw, respectively. Methane was produced with yields of 0.36, 0.42 and 0.44 l g⁻¹ volatile solids for winter rye, oilseed rape and faba bean straw, respectively, without pretreatment of the materials. However, biogas productivity was low and it took over 50 days to reach the final yield. It could be concluded that all three materials are possible raw materials for either biogas or ethanol production; however, improvement of biogas productivity or ethanol yield is necessary before an economical process can be achieved.     

Evaluation of pretreatment potential and hydrogen recovery from lignocellulosic biomass in an anoxic double-staged bioelectrochemical system

The possible impact of bio and electrochemical reactions during pretreatment of rice straw using solvents, sulphuric acid (SA), ammonia (AM), sodium hydroxide (NA), and distilled water (W) was investigated. The total volatile fatty acids (tVFAs) of 163.48 ± 10.49 mM in the electrochemical pre-treatment in the presence of sodium hydroxide (ENA) followed by sulfate-reducing bacteria (EBA) (140.88 ± 0.07 mM) indicating the involvement of electrolytic breakdown of lignocellulosic biomass. The hydrogen production of 0.224 ± 0.05 and 0.218 ± 0.10 mM/g of the substrate was found in the ENA and anoxic sodium hydroxide pre-treatment (CNA) respectively. There was no detectable gasification in SA and AM electrochemical pre-treatments. The major advantage of the electrochemical process is the formation of acetic acid at a lower temperature, whereas processes like autohydrolysis form it at high temperatures during stream explosion pretreatment. The hydrogen production of 1.26 mM/g was found from anoxic hydrolysate pretreated (ECP) rice straw. The SEM and FTIR analysis show distortion of outer layers of biomass in the electrochemical pretreatment (ECP) system, which improved its accessibility towards enzymes for value-added product recovery.     

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.     

秸秆发酵产氢的碱性预处理方法研究

以麦秆、稻草和滤纸为发酵底料,以厌氧活性污泥为接种物,采用不同的预处理方法去除木质素并提高纤维素的降解率,从而提高其发酵产氢能力。试验表明对于相同的底料,经过NaOH预处理和纤维素酶解后的还原糖含量、总产气量、总产氢量和氢气浓度都要高于经过氨水预处理的底料,而未经过预处理的底料发酵产氢能力最差。利用10g经过NaOH预处理的麦秆和稻草,经纤维素酶解后在发酵产氢过程中的降解率分别为23.2%和12.5%,总产氢量分别为363.3mL和254.9mL,发酵产气中氢气浓度分别为23.8%和29.1%。发酵液相中主要产物为乙醇、乙酸和丁酸。     

不同预处理对玉米芯酶解特性和形态结构的影响研究

研究了硫酸、氢氧化钠、双氧水和碱性双氧水预处理玉米芯对其纤维素酶解率的影响,并利用扫描电镜、红外光谱仪和X射线衍射仪分析处理前后的玉米芯显微结构、官能团和结晶性。结果表明,4种预处理方法对玉米芯结构都有不同程度的破坏,能够有效提高玉米芯的酶解产糖率;其中含有1.5%氢氧化钠的碱性双氧水预处理玉米芯,酶解率最高为46.08%,玉米芯质量损失率为29.84%;预处理后木质素特征峰基本消失,玉米芯的结晶指数和结晶度显著提高,分别为1.527和49.35%。     

Integrated alkali pretreatment and preservation of wet lettuce (Pistia stratiotes) by lactic acid bacteria for fermentable sugar production

An integrated process was proposed by applying NaOH at high solid condition followed by ensilage to pretreat and preserve the biomass of water lettuce for fermentable sugar production. The results showed that the pretreatment with sodium hydroxide prior the inoculation of lactic acid bacteria effectively removed the lignin content from biomass of water lettuce and increased the extractable portion of the biomass. Experimental sets that had received alkali pretreatment had more total organic acids and fewer butyric acids generated than non-pretreated sets. The results also showed that the integrated process can preserve more carbohydrate content of biomass and can give higher fermentable sugar yields than without pretreatment. Overall, the study suggests that treatment with NaOH improves preservation of fresh harvested water lettuce but further investigation of optimal conditions is needed.     

Assessment of the energetic and mechanical properties of pellets produced from agricultural biomass

This paper presents an assessment of the energetic and mechanical properties of pellets produced from agricultural biomass. For the production of pellets the following raw materials were used: wheat straw, rape straw, and maize straw. Additionally, the mixtures of wheat-rape straw, wheat-maize straw, and rape-maize straw (each accounting for 50% of the mass) were applied. The studied resources were ground with the use of a universal shredder driven by a 7.5 kW electric engine. A pelleting machine fitted with a fixed flat matrix with two driven thickening rolls was used to produce the pellets. Analyses of the moisture and calorific value of resources as well as the bulk density and mechanical strength of pellets were performed according to biding standards. The moisture of resources ranged from 16.5% to 18.5% for rape and maize straw, respectively. The average calorific value fluctuated between 15.3 MJ kg⁻¹ for a mixture of wheat and rape straw to 16.2 MJ kg⁻¹ for maize straw. The bulk density and mechanical strength of pellets depended on the type of resources used. The lowest bulk density was recorded for wheat straw pellets (386–420 kg m⁻³), and the highest (561–572 kg m⁻³) for maize straw pellets. The lowest mechanical strength of pellets was noted for rape (95.4–96.8%), whereas the highest was for pellets made from a wheat and maize straw mixture (96.8–98.9%).     

Effect of sodium sulfite on acid pretreatment of wheat straw with respect to its final conversion to ethanol

A pretreatment process that combines dilute acid and sodium sulfite has been applied to wheat straw to study the effect of temperature (120–180 °C) and sodium sulfite concentration (0–3%) on the yield of glucose in subsequent enzymatic hydrolysis and ethanol production by fermentation. The results were compared with both dilute acid pretreatment (without Na₂SO₃ addition) and hot water pretreatment. Formation of furfural and hydroxymethylfurural, which can inhibit ethanol-producing microorganisms, were measured and the ethanol yield in a subsequent fermentation was evaluated. The results indicate that a combination of 180 °C, 30 min, 1% H₂SO₄ and 2.4% Na₂SO₃ during pretreatment produced the highest ethanol yield; 17.3 g/100 g dry weight of initial biomass, which corresponds to 75% of the theoretical yield from glucose. 28 mg of furan inhibitors (sum of furfural and hydroxymethylfurfural) per gram dry weight of initial wheat straw were generated under this condition. Increasing sulfite loading up to 2.4% decreased inhibitor formation, leading to increased delignification and preservation of cellulose from dissolution. On the other hand, an elevated temperature in combination with low pH reduced the amount of solid phase after pretreatment, increased the level of inhibitors and reduced the concentration of ethanol produced by fermentation.     

Pretreatment of straw for power production by pyrolysis and char wash

Co-firing of straw and coal in existing pulverised coal-fired boilers is an option for biomass based power generation. However, the high chlorine and potassium content of straw may cause problems. Experiments with co-combustion of straw and coal in power plants have shown that when a moderate amount of straw is applied (up to 20% on a thermal basis), the most serious problems are deactivation of SCR catalysts applied for NO reduction and deterioration of the fly ash quality caused by potassium. To prevent these problems a pretreatment process is required in which the heating value of the straw is supplied to the boiler without introducing potassium into the furnace chamber. A pretreatment process based on pyrolysis and char wash was investigated. Straw is pyrolysed at moderate temperatures at which the potassium is retained in the char. Potassium and residual chlorine are then extracted from the char by water, and char and pyrolysis gases may be co-fired with coal. Fundamental laboratory studies and technical investigations were conducted to evaluate the pretreatment concept. The investigations indicate, that the low temperature pyrolysis of straw can be performed in a circulating fluid bed reactor applying only straw and straw char as bed material. With a bed temperature of approximately 550°C no significant amount of potassium is released to the gas phase. Applying a counter current moving bed to the char potassium extraction with water will probably be advantageous.