A packed bed reactor was evaluated for hydrogen sulfide (H 2 S) removal by sulfur-oxidizing bacteria attached as a biofilm on salak fruit seeds (SFS). The bacteria were isolated from the sludge of the wastewater of a biogas plant. The promising isolate from the previous work was used in a biofilter, and its capacity to remove H 2 S was evaluated at effects of time of operation, effects of biogas flow rate, effects of axial distance, and packing material. Obtained results showed that isolate attached to SFS in an 80 cm height and 8 cm inside diameter biofilter column could decrease H 2 S in biogas from 142.48 ppm to 4.06 ppm (97.15% removal efficiency) for a biogas flow rate of 8550 g m À3 h À1 corresponding to a residence time of 4 h. Simple kinetic models of sulfide removal and bacterial growth was proposed to describe the operation of the biofilter. The radial H 2 S concentration gradient in the flowing gas is to be neglected so is the H 2 S concentration in the biofilm at certain axial distance. Meanwhile, the rate of H 2 S degradation was approximated by Monod type equation. The obtained simultaneous ordinary differential equations solved by Runge-Kutta method. Comparing the calculated results and the experimental data, it can be concluded that model proposed can sufficiently describe the performance of the H 2 S removal. The suitable values of the parameters are as follows: m max = 0.0000007 (s À1), K S = 0.0000039 (g cm À3), k G = 0.0086 (cm s À1), H S = 0.9 ((g cm À3)/ (g cm À3)), and Y x/s = 10.

This study tried to explore characterization of biodegradable plastic from jackfruit seeds and rice waste. Jackfruit seeds and rice waste contain starch, so it can be used for plastic material with addition of several additives such as polyvinyl alcohol (PVA), glycerol, chitosan and sorbitol. Starch is one of polysaccharides that be used as raw material for biofilms. Polyvinyl alcohol is the most important plastic in making water-soluble films. It was ability to form films, emulsifiers, and its adhesive properties. Polyvinyl alcohol has high tensile strength, good flexibility, and good oxygen barrier. Sorbitol and glycerol are also an additive in the manufacture of biodegradable plastics from starch, which is a plasticizer that increase elasticity. Chitosan have effects to bioplastic, such as biodegradable, hydrophilicity, and anti bacterial. This research aims to determine the effect of addition of PVA, glycerol, chitosan and sorbitol to optimum characteristics of bioplastic. The parameters to be examined bioplastic include thickness, moisture content, tensile strength, and % elongation. Increasing of glycerol added to the plastic material effect to decrease of tensile strength of bioplastic and elongation, lower water resistance and more easily degraded. Increasing of chitosan added to the plastic material effect to higher tensile strength, lower elongation, higher resistance to water and lower degradation. Increasing of PVA added to the plastic material effect to increasing of the tensile strength of the bioplastic and decreasing of elongation of bioplastic, but the increasing of sorbitol effect to decreasing of tensile strength and increasing of elongation of bioplastic.

The utilization of biomass as a source of new and renewable energy is being carried out. One of the technologies to convert biomass as an energy source is pyrolysis which is converting biomass into more valuable products, such as bio–oil. Bio–oil is a liquid which produced by steam condensation process from the pyrolysis of coconut shell. The composition of biomass such as hemicellulose, cellulose and lignin will be oxidized to phenol as the main content of the bio–oil. Production of bio–oil from coconut shell was investigated via fast pyrolysis reactor. Fast pyrolysis was carried out at 500 °C with a heating rate of 10 °C and 1 hour holding time at pyrolysis temperature. The Bio-oil chemical composition was investigated using GC–MS. Percentage value of phenol, 2–methoxy phenol, 3–methoxy 1,2–benzenediol, and 2,6–dimethoxy phenol was 45.42%, 13.37%, 10.09%, and 11.72% respectively.

Abstract. Elimination of H2S in biogas was performed by bio-filtration, in which H2S degrading bacteria immobilized on the packing material inside a column. Bacteria was taken from the local area, while salak fruit seed was used as packing material because it has a quite large carbon content, porous and has a high water absorption capability. To obtain a quantitative description of the process, which is useful in the design of large-scale bio-filters, two kinetics models were proposed. Model 1 assumes intra-film gradient does not exist and the gas phase is quasi-steady-state. Model 2 assumes intra-film gradient exists and the gas phase is quasisteady-state. Comparison of the calculation results using the two models to the experimental data suggested the use of model 2. This conclusion is based on both the trend and the accuracy. The trend of model 1 is more conceivable. However, for rough calculation, model 1 could be used for the reason that it is simpler than model 2. The average absolute errors of model 1 and 2 are comparable, approximately 6 ppm. It can also be concluded that intra-film gradient significantly affects the overall rate processes, while the gas phase can be assumed to be quasi-steady-state.