The above-ground biomass yield of willow (Salix spp.) clones selected in the previous study was evaluated after two-growing seasons in Tohoku and Kinki regions, which had annual mean temperatures of 11°C and 15°C, respectively. In both regions, the S. pet-susu Kimura clone KKD exhibited more vigorous growth than the other three clones (S. pet-susu Kimura clone HB471, S. sachalinensis Fr. Schm. clone SEN and S. psuedolinearis Nasarov clone FXM), and its above-ground biomass yield per unit area was largest among four clones tested. In the Kinki region, KKD had an above-ground biomass yield of 26.8 tDM ha-1 two years after planting, suggesting that KKD could attain an acceptable yield even in two years. The root distribution pattern of KKD was an inverted-cone shape, whereas that of SEN and FXM a disk-like shape. Moreover, KKD had more sinker roots. We estimate that such a characteristic root morphology of KKD is closely related to its high biomass productivity.
Microwave-induced pyrolysis of palm kernel shell was carried out to investigate the effects of microwave power and bed temperature on the mass and energy yields of bio-oil. The conditions were 573 K and 1 kW, 623 K and 1 kW, 573 K and 2 kW, and 623 K and 2 kW. The biomass conversion was enhanced by higher pyrolysis temperature. The target product, i. e. the liquid or so-called bio-oil, consisted of two layers; upper watery and lower oily layers. Higher microwave irradiation power favored higher selectivity towards the lower layer bio-oil. This result implies that higher irradiation enhanced faster heating, thus a higher selectivity towards the lower layer bio-oil. The calorific value and carbon content of bio-oil obtained showed considerable dependency on the bed temperature and microwave power. On the other hand, char properties showed little dependency on the bed temperature and microwave power. The highest overall bio-oil energy yield of 32 % was obtained at 2 kW and 573 K.
In response to the importance of assessing both positive and negative impacts caused by biomass utilization for energy, number of initiatives in the world are currently working on development of criteria and indicators for sustainable biomass utilization. Although there is abundant biomass to be utilized in East Asia, it is difficult to say that countries in this region are at forefront of those initiatives. In this context, in order to provide a decision-making methodology to evaluate sustainability of biomass energy utilization in East Asia, the authors were formed as an expert working group in 2007 and since then has been conducting researches to assess its sustainability with the concept of triple bottom line; namely, environmental, economic and social aspects of sustainability. In addition to the development of a methodology and indicators for sustainability assessment for biomass energy utilization, we have field-tested the applicability of the methodology in selected four East Asian countries. This paper firstly explain the methodology the working group developed, secondly the results and lessons learned from the field-tests of the methodology, and thirdly the latest works based on those lessons, aiming at comprehensive assessment of the sustainability of biomass energy initiatives at small to large scale in East Asian countries.
Native lignin in woody biomass was selectively converted to lignophenol with p-cresol and concentrated sulfuric acid through the phase separation system. The lignophenol was treated in 0.5 N NaOH solution at 170 °C for 30 min to give phenylcoumaran type aromatic dimers by the selective cleavage of Cβ-O-4 linkages assisted with intramolecular nucleophilic attack to Cβ position. Thorough washing of the acidinsoluble fraction with NaOH under ultrasonic irradiation enabled to isolate the aromatic dimers in acidsoluble fraction quantitatively. The yield of the dimers reached around 40 and 60% for Hinoki and Eucalyptus lignophenol, suggesting that the dimers could be obtained in high yields of 13 and 17% based on Hinoki and Eucalyptus, respectively. The resulting dimers demonstrated a potential for a plasticizing agent of lignin-based polymers.
In this study, thermal conduction and gas generation during pyrolysis of biomass in a packed bed were investigated experimentally and numerically. The setting temperature of the furnace, TS, was varied between 673 K and 1073 K, while the diameter of the biomass particles, DP, was varied between 0.34 mm and 1.13 mm. The heating rate of the furnace was 400 K/h. Experimental results for thermal conduction showed that the average gas temperature, TG, in the packed bed increased steeply from 500 K to 800 K with time. This sudden increase in gas temperature was steeper when the particle diameter was increased. The time course of the average gas temperature could be partially reproduced by numerical simulation which takes into account the change in porosity during pyrolysis. However, the sudden increase in gas temperature observed experimentally did not agree with that obtained by the simulation. The sudden increase in gas temperature was considered to be due to larger heat transfer of the radiation at the surface of the packed bed than that of the thermal conduction from the heated wall caused by volume reduction during pyrolysis. Experimental results for gas generation indicated that the mass flow rate of the generated gas had a maximum at a certain time, tmax, for TS 〉 773 K due to secondary decomposition of tar. tmax became longer as the diameter of the biomass decreased. The reasons are as follows. In the packed bed, not only heat transfer due to volume reduction, but also an endothermic reaction would simultaneously occur. The sudden increase in gas temperature for smaller particles could be less steep than that for larger particles due to this endothermic reaction. Therefore, the time required for decomposition of tar is longer for smaller particles. It was found that the calculated gas flow rate, taking into account the effect of the temperature distribution in the packed bed, agreed with the experimental results except for the gas flow rate due to tar decomposition.
Hot water treatment of biomass has been extensively studied for autohydrolysis. The process is frequently used for fractionation of biomass components or pretreatment of enzymatic saccharification. Understanding the reaction mechanism of lignin degradation under hydrothermal conditions at lower temperatures is important for improving such fractionation or pretreatment processes. In this study, a lignin-based material: lignocresol was synthesized from native lignin and p-cresol with concentrated sulfuric acid through the phase separation system. Since the benzylic positions are partly occupied by p-cresol, lignocresol should rather be an advantageous model lignin to examine the reactions at the reactive benzylic position while avoiding drastic polymerization and insolubilization. Lignocresol was hydrothermally treated from 110 to 300 °C and then analyzed by GPC, TG and FT-IR in order to estimate the structural change of lignin during the hot water treatments. To around 200 °C, the weight-average molecular weight of lignocresol was firstly increased and then decreased probably due to the formation of benzylic aryl ether (α-O-4) linkages followed by the hydrolysis. At 250 °C, lignocresol significantly increased the thermal stability, suggesting that the active benzyl positions were consumed by self-condensation reaction. In the range from 250 to 300 °C, prompt depolymerization was observed probably due to the cleavage of β-aryl ether (β-O-4) linkages.
Saccharification of cellulosic biomass is essential for the production of bioethanol and other industrial chemicals. The development of an immobilized cellulase is one important alternative to save the cost of cellulase. Until now, various inorganic and organic materials have been tested for the carrier of immobilized cellulases. A lignin-based polymer: lignophenol is also a candidate due to the high protein adsorption capacity via hydrophobic interaction. In this study, two kinds of lignocresols were synthesized from a softwood (Hinoki) and a hardwood (Eucalyptus) with p-cresol and 72% sulfuric acid through the phase separation system. The immobilized cellulases were prepared by simple mixing of Trichoderma cellulase and the lignocresols. The adsorption capacity of Eucalyptus lignocresol for cellulase was lower than Hinoki. It is probably because Eucalyptus lignocresol is rather hydrophilic due to the lower molecular weight and the linear structure with more phenolic hydroxyl groups. The dependences of temperature on the enzymatic activities of the Hinoki and Eucalyptus lignocresol-immobilized cellulases were similar to the native cellulase. While, Hinoki and Eucalyptus lignocresols demonstrated the wider distinct optimum pH range than native cellulase, respectively. Lignocresol-immobilized cellulase successfully hydrolyzed CMC-Na with a small gradual decrease of the enzymatic activity as it was reused repeatedly. The reduction of the enzymatic activity was more pronounced in Eucalyptus than in Hinoki.
Waste mixture of food and plastics is one of the most refractory wastes, because conventional recycling techniques require the separation of the waste into each group before treatment. In this work, new recycling technique was developed to produce an excellent composite fuel using subcritical water. The waste mixture was agitated with sawdust as a plastic dispersed material in subcritical water at 200 °C and 1.6 MPa for 30 min, and the composite fuel particles with less than 20 mm in size were produced. The fuel had a high heating value close to that of coal and the fixed carbon ratio was 93 %. The fuel was dried in a short time of one third of conventional drying period. This was because a part of the surface tissue and cell wall of the biomass was decomposed by subcritical water and water inside the biomass was evaporated easily. The roles of subcritical water were the stabilization of the dispersed melting plastic particles, the removal of toxic elements such as chlorine and sulfur, and the saving of drying energy and the realization of high energy efficiency more than 4.When the composite fuel was pressed into pellet, the pellet fuel ignited easily and burned in a biomass stove stably for long time. The concentrations of the toxic compounds in the combustion gas were far below the emission standard of small boiler. The composite fuel was demonstrated to be safe and clean.
Biomass energy systems are expected to be useful for making low carbon society. For the wide spread of biomass energy systems, acceptance by the consumers is important, but recognition for them by the public is obscure at present. It has remarkable feature of supplying liquid fuel which can be used traffic energy without thoroughgoing modifications of transportation systems. We launched a social survey to investigate the perception of biomass fuels in Kingdom of Thailand and the responses were analyzed with conjoint analysis. Subjects were asked to choose their favorite petrol for their car from four alternatives of fuels with attribute of percentage of alcohol, material crops, unit costs and CO2 reduction rate. The analysis proved that sugar canes and cassavas are favored than rice straws for raw materials. Alternatives with larger amount of CO2 reduction were preferred and high cost alternatives were avoided. Effects of respondent characteristics on choice behavior were also analyzed.
This paper showed the abatement cost and the amount of GHG emission reduction if charcoal cookstove is used instead of fossil fuel-based cookstove such as kerosene and LPG cookstoves. The abatement cost per tonne emission reduction is calculated as the net present value (NPV) of the incremental cost between the fossil-based and the charcoal cookstoves divided by the total emissions reduction. The incremental cost refers to the difference between the generation costs per GJ from the different energy systems. The abatement costs of using charcoal cookstove instead of LPG stove and charcoal cookstove instead of kerosene cookstove amount to PhP10,725.64/t-CO2e and PhP5,149.9085/t-CO2e reduction, respectively. However, the use of charcoal cookstove instead of kerosene cookstove and LPG cookstove will result to displacement of 4.9485 t-CO2e and 2.6676 t-CO2e for a period of five years, respectively. The shift from the use of kerosene and LPG cookstoves to charcoal cookstove would result to large reduction of GHG emission to the atmosphere knowing that cooking particularly in the residential sector consumes large amount of energy.Having obtained abatement cost values provides a concrete measure for assessing the potentials of biomass energy technologies in reducing hazardous emissions. Such information is useful for comparing different technologies and will help guide policy makers to decide on which technologies should be promoted for further development and deployment.