Tomoko Ogi

Cellulose decomposition in hot-compressed water with alkali or nickel catalyst

Abstract Cellulose, a major component of woody biomass, was reacted in hot-compressed water using a sodium carbonate catalyst, a reduced nickel catalyst or no catalyst at different reaction temperatures from 200 to 350°C. The reaction mixture was separated into oil, gases, residue and aqueous phase to discuss the reaction mechanism based on the product distribution. Hydrolysis can play an important role in forming glucose/oligomer, and the obtained glucose/oligomer can decompose quickly to non-glucose aqueous products, oil, char and gases. Under the catalyst-free condition, the interpretation of the observation led to a simplified reaction scheme, which produced finally char and gases through oil as intermediates. With regard to the alkali catalyst, the observation suggested a role of the alkali catalyst in inhibiting the formation of char from oil (stabilization of oil); resulting in oil production. On the other hand, the nickel catalyst could catalyze the steam reforming reaction of aqueous products as intermediates and the methanation reaction.

Liquid fuel production from sewage sludge by catalytic conversion using sodium carbonate

Abstract For the production of liquid fuels and as a means of pollution control, sewage sludge was directly converted into heavy oils. The sewage sludge, having a moisture content of 75 wt %, was heated under pressurized nitrogen over the temperature range 250–340 °C in the presence of sodium carbonate. The yields and properties of the heavy oil produced depended strongly on the catalyst loading and reaction temperature. Liquid fuels having heating values of ≈ 33 MJ kg − 1 were obtained in 50 wt % yields on an organic basis. The energy balance of this liquefaction process is briefly discussed.

Oil production from garbage by thermochemical liquefaction

Abstract Garbage was converted directly into oil by thermochemical liquefaction for the recovery of energy in the form of liquid fuel. The garbage with a moisture content of about 90 wt% was prepared by mixing cabbage, boiled rice, boiled and dried sardine, butter, and the shell of short-necked clam. The mixture was heated under pressurized nitrogen at 250°, 300°, or 340°C for 0.1, 0.5, or 2 h, with or without sodium carbonate as a catalyst (0 or 4% on a dry solid basis). Oil yield and its properties strongly depended on catalyst addition and reaction temperature, while holding time showed no marked effect. Oil was obtained in the highest yield of 27.6% on an organic basis under the following conditions: catalyst addition, 4 wt%; temperature, 340°C; pressure, 18 MPa; and holding time, 0.5 h. The oil had a calorific value of 36 MJ kg−1 and a viscosity of 53,000 mPas at 50°C. Its carbon content, hydrogen content, nitrogen content and oxygen content were 73.6, 9.1, 4.6 and 12.7%, respectively.

Analysis of oil derived from liquefaction of Botryococcus Braunii

Abstract Botryococcus braunii is a colonial green microalga that produces and accumulates oily hydrocarbons called botryococcenes (36% based on organics). It was reported that more oil was obtained than hydrocarbons in B. braunii when thermochemical liquefaction was applied to B. braunii for recovery of botryococcenes. In this paper, the properties of oil obtained by thermochemical liquefaction are clarified. The liquefied oil of B. braunii was fractionated into three fractions by silica gel column chromatography and analyzed to determine its composition. The yields of the three fractions based on organics were 5% of lower molecular weight hydrocarbons (MW, 197–281), 27.2% of botryococcenes (MW, 438–572) and 22.2% of polar substances (MW, 867–2209). The maximum recovery (78%) of botryococcenes in the liquefied oil was achieved at 200°C with the use of a catalyst.

Studies on the direct liquefaction of protein-contained biomass: The distribution of nitrogen in the products

In studies of the direct aqueous liquefaction of protein-contained biomass such as sewage sludge, nitrogen derived from proteins is distributed in both the oil and aqueous phases. The nitrogen in the oil is very difficult to remove by hydrotreatment over nickel/molybdenum catalysts. Egg albumin was used as a model protein in direct liquefaction studies of the nitrogen distribution in the products. The oil yield from albumin (10%) was much less than that obtained from actual feedstocks (typically in the range 30–40%). The nitrogen content of the oil (9%) represented less than 5% of the total nitrogen, while in the liquefaction of actual feedstocks, 30–50% of the nitrogen in the feedstock was found in the oil. No distribution of nitrogen to oil under 150°C occurred because of no oil yield. The majority of the nitrogen in albumin (80%) was distributed to the aqueous phase above 200°C. The distribution of nitrogen to oil was completed by 250°C. Sodium carbonate, used as a catalyst, prevented the distribution of nitrogen to oil. Albumin was decomposed to ammonia, not to amino acids.

Biomass energy potential in Thailand.

Abstract Estimation of biomass energy potential including biomass residue and forestry biomass in Thailand was carried out taking into account the amount of biomass residue which has already been used and the possibility of biomass energy plantation in accordance with the National Plan of the Thai Government. According to this estimation, 65 PJ can be derived from agricultural and forestry waste and 770 PJ can be generated if half of the area allocated for cultivation of plantation forests could be used for biomass energy plantations. Today, biomass energy is 810 PJ, which is 30% of the total primary energy.

Thermochemical Liquidization and Anaerobic Treatment of Kitchen Garbage

The pretreatment effect of thermochemical liquidization for anaerobic digestion of kitchen garbage was studied. Model kitchen garbage (dry matter: 11.3%) was thermochemically liquidized at 175°C and 4 MPa with 1 h of holding time. The liquidized garbage was separated into a solid fraction (12.2 wt%) and filtrate (82.9 wt%). The filtrate was anaerobically digested at added volatile solid (VS) concentrations of 1.8–1.9 g/l in a batch system. The biogas yield from the filtrate after 4 d of digestion was 311 ml/g-added VS and the digestion ratio was 67%. The anaerobic treatment of the filtrate indicated fast digestion compared with mechanically disrupted garbage. The diluted supernatant was continuously anaerobically digested by the upflow anaerobic sludge blanket (UASB) method. The range of digestion ratios was 74–75% at an added TOC concentration of 17.0 g/l and an added TOC amount of 1.8–2.8 mg/cm3-granule·d. The solid fraction was suggested to be easily processed to refuse derived fuel, based on its low moisture content. The energy balance of the liquidization and anaerobic digestion treatment process was initially analyzed to be better than direct incineration.

Thermochemical liquidization of anaerobically digested and dewatered sludge and anaerobic retreatment

Abstract The pretreatment effect of thermochemical liquidization for the anaerobic retreatment of anaerobically digested and dewatered sludge was studied. The digested sludge (dry matter; 15.7%) was thermochemically liquidized at 175°C and 4 MPa with a holding time of 1 h. The liquidized sludge was separated by centrifugation to produce a supernatant of 44.7% (w/w) and precipitate of 52.3%. The liquidized sludge and its supernatant were successfully anaerobically digested at the added VS concentrations of 1.6–2.2 g/l. The biogas yield from the supernatant during 8 days of incubation was 339 ml/g-added VS and the digestion ratio was 61% (w/w). The digestion of the supernatant from the liquidized sludge showed a high biogas yield and high digestion ratio. Moreover, the precipitate of the liquidized sludge could be incinerated using a much smaller amount of supplementary fuel than that of the digested sludge.

Microalgal cultivation in a solution recovered from the low-temperature catalytic gasification of the microalga

Microalgal cultivation in a solution recovered from the low-temperature catalytic gasification of the microalga itself was studied. The growth of Chlorella vulgaris in 75-300-fold diluted recovered solution containing phosphate, magnesium ions and micro-elements was comparable to that in the standard culture medium. It was suggested that C. vulgaris could use ammonium in the recovered solution as its nitrogen source and at the same time could provide a source of biomass which was recycled via gasification.

Effects of glucose addition and light on current outputs in photosynthetic electrochemical cells using Synechocystis sp. PCC6714

The effects of glucose addition and light on the current outputs in electrochemical cells using a cyanobacterium Synechocystis sp. PCC6714 were investigated under photo- and chemoheterotrophical conditions. The addition of glucose to the anode solutions of the electrochemical cells resulted in a rapid increase in the current outputs under both light and dark conditions. Although the coulombic outputs were almost the same between under light and dark conditions, the rate of glucose consumption was faster under illumination than in the dark. The total sugar content in the cells of strain PCC6714 increased with the addition of glucose and the total sugar accumulated remained intact during the discharge under illumination, while it decreased gradually in the dark. When the light was switched off after the addition of glucose, the current output markedly increased. The coulombic outputs obtained after darkening were 10 to 80 times larger than that obtained by the addition of glucose under the continuous light or dark conditions. Synechocystis sp. completely incorporated 0.14 mM and 0.42 mM glucose for 1 h and 3 h, respectively, under illumination. There was no difference in the coulombic outputs between 1 h and 12 h illumination times in the electrochemical cells with 0.14 mM glucose. When the light was switched off after 1 h illumination in the electrochemical cells with 0.42 mM glucose, the coulombic output obtained from the electrochemical cell was lower than that in the electrochemical cell with 12 h illumination. This indicates that the current output was produced with higher efficiency with glucose incorporated under illumination than that in the case of glucose incorporated after darkening. The highest coulombic yield of 54% in this experiment was obtained by darkening in the electrochemical cell with 0.14 mM glucose.