The continuous transesterification of mixed fat was done on the plug flow reactor packed with the static mixers. The transesterification using 0.5 wt% KOH, 0.8 wt% TMAH and mixed catalyst[40 v/v% KOH(0.5 wt%)+60 v/v% TMAH(0.8 wt%)] was conducted with the changes of molar ratios, weight percentage of beef, flow rates and number of static mixer's elements at 65℃. The overall conversion of mixed fat at 1:8 molar ratio, 50 wt% of beef and 24 of static mixer's elements increased until 0.7mL/min of flow rate. The overall conversion of mixed fat showed 96% at those conditions. So, the optimum operating conditions on tublar reactor were 1:8 molar ratio, 50 wt% of beef, 0.7 mL/min of flow rate and 24 of static mixer' s elements.

A simple in-situ biomethane system to upgrade biogas was developed by using differential solubility of biogas which normally contains 35-45% carbon dioxide (CO2) and 55-65% methane (CH4) by volume. The biomethane system consists of mesophilic plug-flow sorghum digester coupled with a leachate recycle loop to an external CO2 stripper. The leachate produced in the mesophilic plug-flow digester flows to the stripper where dissolved CO2 is removed. Then the leachate that CO2 was completely stripped out is recycled back to the plug-flow reactor, resulting in absorbing CO2 and enriched CH4 contents in digester offgas from the mesophilic plug-flow digester. Offgas CH4 contents was correlated well with leachate recycle rates and alkalinity. To maintain a biogas methane content over 95%, 3 volume of leachate recycle per volume of reactor per day(3 v/v-d) and at the reactor alkalinity of 4 g/L as CaCO3 was required. Even at an intermittent stripping ratio up to 3 hours stripping(N2 sweep gas 700 ml/min) and 1 hour no-stripping, the offgas methane content over 95% was achieved. It thus resulted in a 25% reduction in the total energy and sweep gas consumption. The TVS removal efficiency of the biomethane system was 80 percent which corresponded to 96% of the control reactor. The leachate recycle rates directly affected methane productivity that appeared to be 0.71 v/v-d at 3 volume of leachate recycle per volume of reactor per day(3v/v-d) and at the reactor alkalinity of 4 g/L as CaCO3.

Graphene oxide (GO)-titania composites have emerged as an attractive heterogeneous photocatalyst that can enhance the photocatalytic activity of TiO2 nanoparticles owing to their potential interaction of electronic and adsorption natures. Accordingly, TiO2-GO mixtures were synthesized in this study using a simple chemical mixing process, and their heterogeneous photocatalytic activities were investigated to determine the degradation of airborne organic pollutants (benzene, ethyl benzene, and o-xylene (BEX)) under different operational conditions. The Fourier transform infrared spectroscopy results demonstrated the presence of GO for the TiO2-GO composites. The average efficiencies of the TiO2-GO mixtures for the decomposition of each component of BEX determined during the 3-h photocatalytic processes were 26%, 92%, and 96%, respectively, whereas the average efficiencies of the unmodified TiO2 powder were 3%, 8%, and 10%, respectively. Furthermore, the degradation efficiency of the unmodified TiO2 powder for all target compounds decreased during the 3-h photocatalytic processes, suggesting a potential deactivation even during such a short time period. Two operational conditions (air flow entering into the air-cleaning devices and the indoor pollution levels) were found to be important factors for the photocatalytic decomposition of BEX molecules. Taken together, these results show that a TiO2-GO mixture can be applied effectively for the purification of airborne organic pollutants when the operating conditions are optimized.

Methane production from grain dust was studied using a 3 L laboratory-scale anaerobic plug flow digester. The digester was operated at; temperature of 35, 45, and 55℃ hydraulic retention time(HRT) of 6 and 12 days; and influent concentration(S_0) of 7.8 and 9.0 % total solids(%TS). With ten different operation conditions, this study showed the significant effects of temperature, hydraulic retention time, and influent concentration on methane production, The highest methane-production rate achieved was 1.903 (L methane) /(L digester)(day) at 55℃, 6 days HRT, and S_0 of 7.8 %TS. A total of 3.767 L of biogas per day with a methane content of 50.57% was obtained from this condition. The ultimate methane yield(B_0 was found to be a function of temperature and influent concentration, and was described as : B_0= 0.02907T-0.1263-0.00297(T-10)(%TS), where TS is the total solids in the liquid effluent, and T is temperature(℃). Our results showed that thermophilic condition is better than mesophilic for grain dust stabilization in an anaerobic plug flow digester.