轻工业纤维素生物质过程残渣能源化技术

以农产品为原料的轻工业大都是典型的流程工业,在通过转化过程将原料转化为食品、饮料、添加剂、调味料、纸和中成药等产品的同时产生被称为过程残渣的固体废物与废料,如白酒糟、酒精糟、醋糟、甘蔗渣、中药渣、油粕、酱渣、菌渣和造纸黑液可熔渣等.这些残渣产生于特定的生产过程,富含纤维素、蛋白质或木质素,因此代表一种已经被集中的生物质资源.它们同时含水50%-80%、易腐烂变质、甚至呈弱酸碱性,因此是重要的环境污染源.本文着眼于轻工生物质过程残渣的高值化利用,分析指出富含纤维素的白酒糟、醋糟、甘蔗渣、中药渣、茶渣和造纸边角料等适合作为生物质能源而被转化利用,并根据资源特征提出了可能的技术路线.通过分别对热化学路线涉及的脱水干燥、燃烧发电与气化发电技术和集成乙醇发酵、沼气发酵的复合转化技术进行技术综述,最后针对不同规模的富含纤维素轻工生物质过程残渣能源化提供了技术选择建议.     

Production and energetic use of biogas from energy crops and wastes in Germany

The production of biogas for reducing fossil CO₂ emissions is one of the key strategic issues of the German government and has resulted in the development of new process techniques and new technologies for the energetic use of biogas. Progress has been made in cultivating energy crops for biogas production, in using new reactor systems for anaerobic digestion, and in applying more efficient technologies for combined heat and power production. Recently, integration of fuel cells within the anaerobic digestion process was started, and new technologies for biogas upgrading and conversion to hydrogen were tested. This article describes the trends in Germany for achieving more efficient energy production.     

Siloxanes in Biogas: Approaches of Sampling Procedure and GC-MS Method Determination

A new approach of siloxane sampling based on impinger, micro-impinger, adsorption on active carbon, and direct TedlarBag methods followed by gas chromatography-mass spectrometry (GC-MS) was developed for the analysis of three linear (L2–L4) and four cyclic (D3–D5) volatile methyl siloxanes (VMSs). Three kinds of organic liquid-medium characterized by different polarities, namely acetone, methanol, and d-decane as siloxanes trap were arranged in the experiment which is widely discussed below. Thus, the GC-MS equipped with SUPELCOWAX-10 capillary column was employed to perform monitoring of VMS content in the analyzed biogas samples originating from landfill, wastewater treatment plants, and agriculture biogas plants. In all samples that have undergone the analysis, cyclic and linear VMSs were found in quantities exceeding 107.9 and 3.8 mg/m³, respectively. Significant differences between siloxanes concentrations depending on biogas origin were observed. Moreover, the high range of linearity (0.1 to 70.06 mg/m³), low LoD (0.01 mg/m³), low LoQ (0.04 mg/m³), and high recovery (244.1%) indicate that the procedure and can be applied in sensitive analyses of silica biogas contaminants. In addition to the above, the impinger method of sampling performed better than active-carbon Tube and TedlarBag, particularly for quantifying low concentrations of siloxanes. Overall, the evaluation of sampling methods for biogas collection simplified the analytical procedure by reducing the procedural steps, avoiding the use of solvents, as well as demonstrated its applicability for the testing of biogas quality.     

轻工业纤维素生物质过程残渣能源化技术

以农产品为原料的轻工业大都是典型的流程工业,在通过转化过程将原料转化为食品、饮料、添加剂、调味料、纸和中成药等产品的同时产生被称为过程残渣的固体废物与废料,如白酒糟、酒精糟、醋糟、甘蔗渣、中药渣、油粕、酱渣、菌渣和造纸黑液可熔渣等。这些残渣产生于特定的生产过程,富含纤维素、蛋白质或木质素,因此代表一种已经被集中的生物质资源。它们同时含水50%—80%、易腐烂变质、甚至呈弱酸碱性,因此是重要的环境污染源。本文着眼于轻工生物质过程残渣的高值化利用,分析指出富含纤维素的白酒糟、醋糟、甘蔗渣、中药渣、茶渣和造纸边角料等适合作为生物质能源而被转化利用,并根据资源特征提出了可能的技术路线。通过分别对热化学路线涉及的脱水干燥、燃烧发电与气化发电技术和集成乙醇发酵、沼气发酵的复合转化技术进行技术综述,最后针对不同规模的富含纤维素轻工生物质过程残渣能源化提供了技术选择建议。     

Thermochemical pretreatment of water hyacinth for improved biomethanation

Water hyacinth was subjected to various thermochemical pretreatments and used as a substrate in anaerobic digestion for biomethanation. Results indicate that the pretreatment increased the solubility of biomass and improved gas production. Best results were obtained when water hyacinth was treated at pH 11.00 and temperature 121‡C. Severe treatment conditions showed a negative effect, especially on methanogenic bacteria caused by toxic compounds produced during treatment.     

Temperature and Inoculum Origin Influence the Performance of Ex-Situ Biological Hydrogen Methanation

The conversion of H₂ into methane can be carried out by microorganisms in a process so-called biomethanation. In ex-situ biomethanation H₂ and CO₂ gas are exogenous to the system. One of the main limitations of the biomethanation process is the low gas-liquid transfer rate and solubility of H₂ which are strongly influenced by the temperature. Hydrogenotrophic methanogens that are responsible for the biomethanation reaction are also very sensitive to temperature variations. The aim of this work was to evaluate the impact of temperature on batch biomethanation process in mixed culture. The performances of mesophilic and thermophilic inocula were assessed at 4 temperatures (24, 35, 55 and 65 °C). A negative impact of the low temperature (24 °C) was observed on microbial kinetics. Although methane production rate was higher at 55 and 65 °C (respectively 290 ± 55 and 309 ± 109 mL CH₄/L.day for the mesophilic inoculum) than at 24 and 35 °C (respectively 156 ± 41 and 253 ± 51 mL CH₄/L.day), the instability of the system substantially increased, likely because of a strong dominance of only Methanothermobacter species. Considering the maximal methane production rates and their stability all along the experiments, an optimal temperature range of 35 °C or 55 °C is recommended to operate ex-situ biomethanation process.     

Scenedesmus dimorphus (Turpin) Kützing growth with digestate from biogas plant in outdoor bag photobioreactors

Digestate coming from an Anaerobic Digestion unit in a Biogas Plant, feeded on cow manure and vegetable waste from markets, has been used. About 8–35 L polyethylene transparent bags have been employed as cultivation container, outdoor. Different aliquots of digestate, alone or mixed with commercial liquid fertiliser, were employed to cultivate in batch Scenedesus dimorphus, a freshwater green microalga, in the ENEA facilities of Casaccia Research Center, near Rome, Italy. The cultivation period was June–July 2013. The average daily yields of dry microalgae biomass varied from 20 mg/L/d to 60 mg/L/d, mean 38.2 mg/L/d. Final dry biomass concentration varied from 0.18 to 1.29 g/L, mean 0.55 g/L. S. dimorphus proved to be very efficient in removing N and P from the culture medium. Another fact emerged from these trials is that S. dimorphus inner composition resulted to be variable in response to the tested different culture conditions.     

Efficiency of Fe3O4 Nanoparticles with Different Pretreatments for Enhancing Biogas Yield of Macroalgae Ulva intestinalis Linnaeus

In this work, different pretreatment methods for algae proved to be very effective in improving cell wall dissociation for biogas production. In this study, the Ulva intestinalis Linnaeus (U. intestinalis) has been exposed to individual pretreatments of (ultrasonic, ozone, microwave, and green synthesized Fe₃O₄) and in a combination of the first three mentioned pretreatments methods with magnetite (Fe₃O₄) NPs, (ultrasonic-Fe₃O₄, ozone-Fe₃O₄ and microwave-Fe₃O₄) in different treatment times. Moreover, the green synthesized Fe₃O₄ NPs has been confirmed by FTIR, TEM, XRD, SEM, EDEX, PSA and BET. The maximum biogas production of 179 and 206 mL/g VS have been attained when U. intestinalis has been treated with ultrasonic only and when combined microwave with Fe₃O₄ respectively, where sediment were used as inoculum in all pretreatments. From the obtained results, green Fe₃O₄ NPs enhanced the microwave (MW) treatment to produce a higher biogas yield (206 mL/g VS) when compared with individual MW (84 mL/g VS). The modified Gompertz model (R² = 0.996 was appropriate model to match the calculated biogas production and could be used more practically to distinguish the kinetics of the anaerobic digestion (AD) period. The assessment of XRD, SEM and FTIR discovered the influence of different treatment techniques on the cell wall structure of U. intestinalis.     

Evaluating the biochemical potential for Irbid’s food waste as a source for energy

Solid waste generated from the city of Irbid is all directed to a local unlined landfill with no gas collection system. More than half of the waste stream is made of food waste which turns the landfill to a concentrated point source of greenhouse gases. To assess the impact that the landfill has at the moment on global warming and to evaluate the future value of the city’s waste as a source of biogas, 20 trucks of municipal solid waste were sampled. In addition, food waste samples from Irbid were collected from five different sources for 12 weeks to quantify their generation rates and to measure their components and chemical composition. Irbid’s solid waste was found to have a distinctively high biodegradable content 68%, which is typical of developing countries’ solid waste. Physical assessment showed that 38%, 6%, 33% and 23% of the food waste was rice, meat, fruits and vegetables, and bread, respectively. Measured methane yields for the volatile solids (VS) in rice, meat, fruits and vegetables, and bread were 362, 499, 352 and 375 mL/g VS, respectively. A representative food waste sample was created to test the actual methane yield and compare it to calculated one. Actual methane yield (414 mL/g VS) was greater than the calculated value (370 mL/g VS) based on food type proportions and their specific methane yield. To assess the anaerobic biodegradability of food waste, a stoichiometric calculation of the methane production was made based on the elemental analysis of all food waste elements. Food waste was found to have the chemical formula C₇H₁₆O₅N and calculated methane potential of 447 mL/g VS; indicating 85% anaerobic biodegradability of food waste, which makes Irbid’s waste perceived as a valuable source of energy.     

Effect of O2 and H2O on the tri-reforming of the simulated biogas to syngas over Ni-based SBA-15 catalysts

A series of Ni/SBA-15 catalysts with Ni contents from 7.5 wt% to 15 wt% were prepared by impregnation method. The effect of O2 and H2O on the combined reforming of the simulated biogas to syngas was investigated in a continuous flow fixed-bed micro-reactor. The stability of the catalyst was tested at 800 ℃. The results indicated that 10 wt%Ni/SBA-15 catalyst exhibited the highest catalytic activities for the combined reforming of the simulated biogas to syngas. Under the reaction conditions of the feed gas molar ratios CH4/CO2/O2/H2O = 2/1/0.6/0.6, GHSV = 24000 ml•g{cat}-1\cdoth-1 and the reaction temperatureT = 800 ℃, the conversions of CH4 and CO2 were 92.8% and 76.3%, respectively, and the yields of CO and H2 were 99.0% and 82.0%, respectively. The catalytic activities of the catalyst did not decrease obviously after 100 h reaction time on stream.