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Palm oil mill industry generates a large amount of palm oil mill effluent (POME) and empty fruit bunches (EFB) as byproducts. Biogas production from anaerobic co-digestion of POME with EFB was investigated under mesophilic condition. The amount of POME and EFB was varied from 2 to 10 gVS and size of EFB was varied from 0.5-6 centimeter. High methane yield and high biodegradability were achieved at the size of 0.2 mm with 63-70% biodegradability with a methane yield of 320 mL CH4/gVS. The POME:EFB ratio of 4.5-7.5 and size EFB of 3.3-6 centimeters shown acceptable biodegradability value of 40-50% with a methane yield of 282 mL CH4/gVS. The POME:EFB ratio of 4.5-7.5 and size EFB of 3.3-6 centimeters was more practical for biogas production due to reducing the cost of size reduction

The sulfate-rich wastewater from rubber smoked sheet industry could generate hydrogen sulfide (H2S) under anaerobic condition, which created bad smell to the community and might cause toxicity and damage to the environment. The H2S can be removed from the biogas by sulfur-oxidizing bacteria (SOB) with the ability to converted H2S to sulfate. Sulfate-reducing bacteria (SRB) could remove sulfate in wastewater before anaerobic treatment for biogas production. The microbial sludge from wastewater and anaerobic digestion system was collected and test for sulfate and H2S removal efficiency. Anaerobic microbial sludge has a high ability to produced methane from gelatin with a specific methane production rate of 92.4 ml CH4 gVSS-1 day-1. Anaerobic microbial sludge has lower methane production when gelatin and sulfate used as a substrate with a specific methane production rate of 81.4 ml CH4 gVSS-1 day-1. The biomethane potential, hydrogen sulfide removal and sulfate removal in anaerobic digestion system by addition of enriched cultures of SOB and SRB were investigated. The methane yield of SRB consortium was 60.1 ml CH4/gCOD with 20% sulfate reduction from wastewater and no sulfide reduction. The methane yield of SOB consortium was 41.9 ml CH4/gCOD with no sulfate and sulfide reduction from wastewater. The addition of SRB consortium could increase methane production by reducing sulfate concentration in wastewater consequently to a reduced concentration of H2S in biogas.

Hydrogen sulfide (H2S) is one of the most problematic contaminants in biogas. The removal of H2S from biogas is necessary in order to clean biogas and prevent gas engine. The efficiency evaluation on H2S removal from palm oil mill biogas by biofilter was investigated. Eight sludge samples from biofilter systems of palm oil mill biogas were tested for H2S removal by grown in thiosulfate mineral medium under an anaerobic condition at atmospheric pressure. Analytical data demonstrated that average amounts of CH4, CO2, and H2S in inlet biogas were 62%, 35%, and 0.95%, respectively. The highest H2S removal rate of 0.35 g/L/d was found sludge A (Asian palm oil company). It also found that the major product for sludge A was elemental sulfur of 13,650 mg/L and could produce the highest sulfate concentration of 300 mg/L. In contrast, sludge I (Thai Indo palm oil factory) has the lowest H2S removal with rate (0.09 g/L/d.) Microbial activity for H2S removal was increased with the decrease in pH from 7.12 to 6.40 due to H2S dissolved medium. The suitable condition for the growth of sulfur oxidizing bacteria affected on H2S removal efficiency from palm oil mill biogas by biofilter systems.

The cultivation of Chlorella sp. TISTR 8411 on biogas effluent of seafood processing wastewater was investigated. Chlorella sp. biomass was used for biogas production by anaerobic co-digestion with seafood processing. Chlorella sp. biomass cultivated on 50, 60, 70, 80, 90, and 100% of biogas effluent was 0.184, 0.121, 0.061, 0.048, 0.039, and 0.032 g/L, respectively. The highest growth of Chlorella sp. biomass was 0.184 g/L from 50% biogas effluent. Methane yield from anaerobic co-digestion of seafood processing wastewater with 10, 20, 30, 40, and 50% v/v Chlorella sp. biomass was 131, 152, 173, 188 and 193 ml CH4/gVS, respectively. Methane yield from Chlorella sp. biomass was 44 ml CH4/gVS. Methane yield from seafood processing wastewater was 18 ml CH4/gVS. 10 times of methane yield was improve in anaerobic co-digestion seafood processing wastewater with Chlorella sp. biomass at 40 and 50 % v/v. Anaerobic co-digestion seafood processing wastewater with Chlorella sp. biomass has great potential for biogas production.

Oil palm trunk (OPT) an abundant agriculture waste was evaluated as an alternative lignocellulosic biomass resource for bioethanol production. Sulfite-based SPORL pretreatment (Sulfite Pretreatment to Overcome Recalcitrance of Lignocellulose) was applied to the OPT to enhance its enzymatic saccharification. The pretreatment conditions were optimized through a designed experiment within the ranges of temperature 170–190oC, time for 30 min, 2–6% sulfite, and initial H2SO4 concentrations 3–7% (w/w). The overall saccharides (hexoses and pentoses) recovery of SPORL pretreated was 62.5%. SPORL pretreatment removed 38.8% lignin from the OPT as lignosulfonate in the liquor with great potential for co-product development, and 93.9% xylose was dissolved, which were the main reasons why the SPORL pretreatment could enhance the enzymatic hydrolysis of the OPT. The results indicated that over 92% of the cellulose in the pretreated OPT with 7% H2SO4 and 6% Na2SO3 at 190oC was enzymatically hydrolyzed to glucose within 48 h with a cellulase loading of 15 FPU/g cellulose, and overall glucose yield was 66%.

A two-stage thermophilic fermentation for hydrogen and methane production from wastewater of cassava rice and corn starch at different concentration (5,10 and 15 g/L) was studied. The hydrogen production from cassava starch at concentrations of 5 g/L gave the highest hydrogen yield and followed by cassava starch at a concentration 10 g/L, rice starch at concentrations of 15 g/L. The hydrogen and methane yields from cassava starch processing wastewater by two-stage was 81.5 L H2 kgCOD-1 and 310.5 L CH4 kgCOD-1, respectively with total energy yield of 13363 kJ kgCOD-1. Mixed hydrogen and methane (biohythane) production was 9.51 L biogas l-1 with containing of 55% CH4, 11% H2 and 34% CO2.

Ethanol was produced from oil palm frond juice (OPFJ) by using Saccharomyces cerevisiae yeast cells. Experiments were operated in a batch mode by varying the oil palm age between 3-4, 4-7, 7-10, 10-20 and 20-25 years. Experimental results showed that OPFJ at 3-4 years gave the highest concentrations of glucose and ethanol as 31.26 and 11.50 g/l. Ethanol yield was 0.39 g-ethanol/g-glucose, which estimated as 76.47% of the theoretical yield (0.51 g-ethanol/g-glucose). Additionally, the Monod and modified Gompertz equations were used to describe the kinetics of substrate utilizationand product formation. The values of the kinetic parameters in Monod and modified Gompertz equations of OPFJ extracted from oil palm aged 3-4 years were evaluated: maximum specific growth rate ( μ max ) was 0.29 g/g-VSS.hr, saturation concentration ( K s ) 47.05 g/l, maximum ethanol concentration ( P m ) 11.50 g/l, maximum ethanol production rate ( r p,m ) 0.24 g./l.hr and lag phase 0.12 hr. Both models fitted well to the experimental data, which had the high regression coefficient values (R 2 >0.95).

Old oil palm trunk (OPT) is available in large quantity in Southeast Asia and a potential lignocellulosic biomass resource for bioethanol production. Dilute acid (DA) pretreatment was applied to the old oil palm trunk for enzymatic saccharification. The pretreatment conditions were investigated through a fractional factorial experiment design. The pretreated substrates were analyzed for chemical composition, and their enzymatic digestibility was investigated and compared. The results indicated that the DA pretreatment was able to improve enzymatic hydrolysis by removing hemicelluloses from OPT. Mild pretreatment preserved more hemicellulose and cellulose in pretreated OPT, but severe pretreatment was necessary to achieve satisfactory enzymatic hydrolysis of OPT. For example, the DA pretreatment with 3% H 2 SO 4 at 180 °C for 40 min could achieve an 80% enzymatic hydrolysis.

Solid state anaerobic digestion is a safe and environmental friendly technology to dispose solid wastes, could produce methane and reduce the volume of wastes. Three biomass residues from palm oil mill plant including empty fruit bunches (EFB), palm press fiber (PPF) and decanter cake (DC) were evaluated for methane production by solid state anaerobic digestion. Oil palm biomass was mixed with inoculum at F/I ratio of 2:1, 3:1, 4:1, 5:1 and 6:1 based on the volatile solid (VS). Results show that among the five F/I ratios tested, the F/I ratio of 2:1 gave the highest methane yield and methane production for all biomass residues. The highest cumulative methane production of 2180 mLCH 4 was obtained from EFB followed by PPF (1964 mL CH 4 ) and DC (1827 mL CH 4 ) at F:I ratio of 2:1. The highest methane yield of 144 mL CH 4 /gVS was obtained from EFB followed by PPB (140 mL CH 4 /gVS) and DC (130 mL CH 4 /gVS) at F/I ratios of 2:1. Methane production from EFB, PPF and DC by SS-AD was 55, 47 and 41 m 3 CH 4 /ton, respectively. These results collectively suggested that EFB could be a promising substrate for methane production by SS-AD

Biohythane production from co-digestion of palm oil mill effluent (POME) with empty fruit bunches (EFB) and decanter cake (DC) by two-stage solid state anaerobic digestion process was investigated. The first stage, thermophilic hydrogen fermentation of co-digestion of POME with DC at 10, 30, 50 and 70% of DC in POME has hydrogen yield of 16, 14, 3 and 1 ml H 2 /gVS, respectively. Co-digestion of POME with 10% DC gave the best hydrogen yield of 16 ml H 2 /gVS with hydrogen production of 1.4 m 3 /ton mixed waste. Co-digestion of POME with 10% EFB gave the best hydrogen yield of 16 ml H 2 /gVS with hydrogen production of 1.4 m 3 /ton mixed waste. The effluent from the hydrogen production was further converted to methane in the second stage. The methane yield from POME mixed withn10% DC was 391 mlCH 4 /gVS and from POME mixed with 10% EFB was 240 mlCH 4 /gVS. The hydrogen and methane content in biogas was 25.33% and 65.21% respectively. The two-stage solid stage anaerobic digestion process can be removal efficiently of cellulose 57-59%, hemicelluloses 35-40% and lignin 16-27%. Result obtained make practical use for the development of two-stage anaerobic digestion process providing hydrogen and methane co-production from palm oil waste residues.

Anaerobic co-digestion of canned seafood wastewater (CSW) with glycerol waste (GW) and wolffia arrhiza (WA) for methane production was investigated. Methane yields from anaerobic co-digestion of CSW with 1%GW, CSW with 1%GW and 5%WA, CSW with 1%GW and 10%WA and CSW with 1%GW and 15%WA were 577, 789, 545 and 474 mL CH4/g VS-added, respectively. Methane production from CSW with 1%GW and 5%WA increased approximately 4-fold when compared with CSW alone (278 mLCH4/g VS-added). Co-digestion of CSW with 1% GW and 5% WA was the best condition and gave the maximum methane production of 8.8 m3 CH4/m3 mixed wastewater and 96.8% biodegradability. The maximum methane production rate and yield were 3.71 L CH4/L-reactor.day and 858 mL CH4/g VS-added (352 mLCH4/g COD-removed) at OLR of 4 g COD/L. day in UASB reactor. The methane composition in biogas was 62.3%. The Monod, Modified Stover–Kincannon and Grau second-order models were used to explain the performance of UASB reactor. The results showed that the kinetic coefficient of the Modified Stover–Kincannon model could explain the performance of UASB reactor in term of COD removal efficiency and microbial growth by having the regression coefficient (R2) as 0.987.

A two step, included process producing ethanol from oil palm fronts (OPF) by two-stage simultaneous saccharification and Saccharomyces cerevisiae fermentation followed by anaerobic digestion of its effluent to produce methane was investigated. OPF was soaked in dilute sulfuric acid, hydrogen peroxide and water consequently pretreated by microwave for preparing of cellulose and followed by simultaneous saccharification and fermentation. The result indicated OPF soaking in water gave a maximal ethanol yield was 0.32 g-ethanol/g-glucose which was 62.75% of the ethanol theoretical yield (0.51g-ethanol/g-glucose). The effluent from the ethanol production process was used to produce methane with the yield of 514 ml CH4/g VS added. Therefore, soaking in water and microwave co-pretreatment could helpful due to its low toxicity and low corrosion compare to sulfuric acid and hydrogen peroxide which improves the efficiency of enzymatic hydrolysis. The maximum energy output of the process (745 kWh/ ton of OPF) was about 72% of the energy contributed by cellulose fraction, contained in the oil palm frond.

The potentiality in biogas production from anaerobic co-digestion of canned seafood wastewater (CSW) with glycerol waste (GW) was investigated. Methane yields from anaerobic co-digestion of CSW with 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10% (v/v) of GW were 577, 265, 101, 51, 11, 9, 4, 3, 2 and 2 mLCH4/g VS-added, respectively. The anaerobic co-digestion of 99% CSW with 1%GW was the optimal mixture ratio for methane production with a maximum methane yield was 577 mLCH4/g VS-added and 97% biodegradability. Meanwhile, the maximum methane yield of 1%GW and 100%CSW were 211 and 278 mLCH4/g VS-added. Methane yield increased by 108% when compared with digested CSW alone. The maximum methane production from anaerobic co-digestion of 99%CSW with 1%GW was 5.8 m3 CH4/m3 of mixed wastewater and electricity production of 1 m3 mixed wastewater would be 207 MJ or 58 kWh of electricity. Continuous methane production from anaerobic co-digestion of CSW with 1% GW in up-flow anaerobic sludge blanket (UASB) reactors gave methane production rate of 2.33 LCH4/L-reactor.day.

We investigated the feasibility of using Microcystis sp; blue green algae (MB) as a co-substrate to improve the mesophilic anaerobic digestion of cannery seafood wastewater (CSW) supplemented with 1% (v/v) glycerol waste (GW), to maximize bio-methane production. The MB content was set at 5, 10 and 15% (v/v) to find a near optimal methane yield. The maximum 291 mL CH 4 /g VS-added methane yield, corresponding to 4.4 m 3 -CH 4 /m 3 - mixed wastewater, was achieved with a CSW: GW: MB mixture at the volumetric 94:1:5 ratio. The methane yield of CSW digested alone was 278 mL CH 4 /g VS-added (2.2 m 3 CH 4 / m 3 of wastewater). The yields from our other experiments ranged within 81– 150 mLCH 4 /g VS-added. Ratios of MB: CSW exceeding 5% (v/v) gave lower than optimal methane yields. The energy content of methane from 1 m 3 of mixed wastewater, with the near optimal mixture ratio 94:1:5, was 157 MJ or equivalently 44 kWh.

Ethanol production from oil palm frond (OPF) by simultaneous saccharification and Saccharomyces cerevisiae TISTR5048 fermentation was investigated. Solid fraction of OPF (20% TS) was pretreated by 2% H 2 SO 4 , 2% NaOH and 2% NaOH in H 2 O 2 presoaking at room temperature for 24 hours. Pretreated OPF by presoaking in 2% H 2 SO 4 , 2% NaOH and 2% NaOH in H 2 O 2 contained 37%, 42% and 49% of cellulose, respectively. Pretreated OPF was simultaneous saccharification by cellulase enzyme (Cellic CTec2, Novozymes) and sequentially fermentation. Sugar concentration in OPF cellulose hydrolysis of 2% H 2 SO 4 , 2% NaOH and 2% NaOH in H 2 O 2 presoaking was 45.72, 55.73 and 56.94 g/l, respectively. Ethanol concentration of 2% H 2 SO 4 , 2% NaOH and 2% NaOH in H 2 O 2 presoaking was 14.5, 15.0 and 17.2 g/L, respectively. 2% NaOH in H 2 O 2 presoaking was the best pretreatment with 82.11% of total solids recovery and containing 49.9% of cellulose with enzyme digestion ability of 37.6%.

The laboratory-scale UASB reactors were operated at five different hydraulic retention times (HRTs). The various sizes of granules from three different sources: a cassava factory (CS), a seafood factory (SS), and a palm oil mill (PS), having the size range of 1.5-1.7 mm, 0.7-1.0 mm and 0.1-0.2 mm. respectively, were used as inocula for anaerobic digestion of cassava wastewater. For comparison, the first reactor with only granules from its own source (R1, CS) was treated as control. The other two reactors were inoculated with mixed granules from different sources (R2, CS+SS and R3, CS+PS). As HRT decreased from 5 days to 1 day, the organic removal efficiencies decreased from 91.49 to 43.23%, 89.36 to 45.13% and 87.23 to 32.69% for R1, R2 and R3 respectively (or inversely with increasing OLR). In this study selected mathematical models including Monod, Contois, Grau second-order and Modified Stover-Kicannon kinetic models were applied to determine the substrate removal kinetics of UASB reactors. Kinetic parameters were determined through linear regression using experimental data obtained from the steady-state experiments and subsequently used to predict effluent COD. The results showed that Grau second-order and Modified Stover-Kicannon kinetic models were more suitable than the others for predicting the substrate removal for all different sizes of granules. In addition the Upflow Anaerobic Sludge Blanket (UASB) reactor with only granules from a cassava factory gave the best performance.

Effect of organic loading rate (OLR), hydraulic retention time (HRT) and temperature variation on process stability of fermentative hydrogen production from palm oil mill effluent (POME) under thermophilic condition was investigated. High OLR (>70 gCOD/l/d) and low HRT (4 d) has significant affected on hydrogen productivity, process stability and microbial community. Hydrogen production at OLR of 55, 60, 65 and 70 gCOD/l/d was 2.4, 3.4, 4.9 and 3.7 L H 2 /L-POME, respectively. The decreasing in pH and alkalinity and increasing in total VFA could cause the instability of process. The microbial community was changed at OLR >70 gCOD/l/d, HRT 4 d and stop feeding. The dominant microbial community changed from Thermoanaerobacterim sp. to Clostridium sp., Thermoanaerobacterim sp. and Bacillus sp. Hydrogen production at HRT of 2, 4, stop feeding and 2 d was 2.7, 0.8, 0, and 2.6 L H 2 /L-POME, respectively. Hydrogen production, process stability and microbial community was not affected by variation of temperature. Hydrogen production before and after temperature variation was 2.5 and 2.45 L H 2 /L-POME.