This paper discusses the problem of producing biomass fuels using alga expected as future biomass fuels. Based on the result of the basic culture experiment, the culture system using 100 L semicircular shaped water tank was developed in order to examine the culture environment. We examined some of the important elements needed to improve the algae growth: measurement and improvement of the quantity of photon, the measurement of CO₂ dissolution behavior and its dissolution ability, and the flow in the water tank. Finally, the environmental load of the culture system was calculated using Life Cycle Assessment (LCA). We found: 1) by improvement of the reactor setup, the photon quantity more than 140 μmol m^-2 s^-1 was achieved; 2) CO₂ dissolution efficiency was high when the algae were inside the tank. In addition, we found that the bubbling device in the semicircular water tank has the ability for enough stirring in water tank. Finally, it was confirmed from the calculation results that there was still a lot of CO₂ emission even with this improvement.

View full abstract

In Japan, softwood is one of the suitable materials for production of bio-fuels, since forest of softwood accounts approximately 90% in artificial forest in Japan, and it is widely used for constructing the traditional Japanese house. Japanese cypress (Chamaecyparis obtusa), which is known for its high quality lumber has been attracted a lot of interest as a potential feedstock in Japan. The conditions of alkaline peroxide pretreatment were investigated for the enzymatic hydrolysis of Japanese cypress in this study. The suitable condition of the pretreatment was as follows; at 70 °C with 2M sodium hydrate (NaOH) of and 6M hydrogen peroxide (H₂O₂). Almost of hemicellulose and approximately 60% of lignin were disappeared in the AP-pretreated sample. The AP-pretreated sample had the high-crystallinity and the celluolose nano fibers and nano scale "raising" on the surface. The suitable enzyme was Accellease1500 resulted in approximately 60%-glucose yield with 20 mg-protein/g-substrate. These results suggest that the alkaline peroxide hydrogen treatment has the potential as the pretreatment for obtaining glucose from softwood such as Japanese cypress in enzymatic hydrolysis.

View full abstract

Recently, ecological footprint (EF) receives much global attention as a measure to estimate the human impact on the earth. However, the evaluation of EF values is not so easy because of the complexity of its process and the need of numerous data. For that purpose it is required to develop a convenient model for estimating EF values for a variety of countries based on easily available data such as gross domestic product (GDP) and others. A large-scale regression experiment to analyze the comprehensive determinants of EFs across many countries has been carried out. A nonlinear support vector machine (SVM) method was applied to the regression analysis between EFs (dependent variable) of 162 countries and 32 factors (explanatory variables) in various fields. Optimum factors for the modeling were determined by using the sensitivity analysis method as a variable selection technique in SVM. It is demonstrated that 19 factors satisfactorily reproduce the EFs of 162 countries with a coefficient of determination (R²) of 0.930, which is remarkably superior to those of the ordinary least squares (OLS) method. It also is revealed that various factors such as meat consumption and air pollution as well as geographical factors such as population and land area, and economic factors such as GDP and GDP per capita have to be taken into account to construct a model for estimating EFs with high accuracy.

View full abstract

In this study, a solvent extraction technique was investigated for the recovery of hydrocarbons from a concentrated slurry of Botryococcus braunii via thermal pretreatment. Efficient hydrocarbon recovery was achieved by preheating the slurry to temperatures below 100°C to achieve the separation of solids (solid-liquid separation), followed by the solvent extraction of hydrocarbons. This procedure did not require a highly energy consuming drying process. Parameters affecting the energy profit ratio and economy of hydrocarbon recovery, such as heating temperature, water content after solid-liquid separation, extraction time, and solvent-to-algae ratio, were examined with respect to hydrocarbon recovery efficiencies; it was found that heating the mixture to below 100 °C was sufficient for good hydrocarbon recoveries. It was also shown that solvent extraction carried out at room temperature required 2 h to reach saturation. At least 90% of the hydrocarbons could be recovered, even with low solvent-toalgae ratios, by adjusting the algae water content to around 85 wt%.

View full abstract