The pulp industry in Taiwan discharges tons of wood waste and pulp sludge (i.e., wastewater-derived secondary sludge) per year. The mixture of these two bio-wastes, denoted as wood waste with pulp sludge (WPS), has been commonly converted to organic fertilizers for agriculture application or to soil conditioners. However, due to energy demand, the WPS can be utilized in a beneficial way to mitigate an energy shortage. This study elucidated the performance of applying torrefaction, a bio-waste to energy method, to transform the WPS into solid bio-fuel. Two batches of the tested WPS (i.e., WPS1 and WPS2) were generated from a virgin pulp factory in eastern Taiwan. The WPS1 and WPS2 samples contained a large amount of organics and had high heating values (HHV) on a dry-basis (H_HD) of 18.30 and 15.72 MJ/kg, respectively, exhibiting a potential for their use as a solid bio-fuel. However, the wet WPS as received bears high water and volatile matter content and required de-watering, drying, and upgrading. After a 20 min torrefaction time (t_T), the H_HD of torrefied WPS1 (WPST1) can be enhanced to 27.49 MJ/kg at a torrefaction temperature (T_T) of 573 K, while that of torrefied WPS2 (WPST2) increased to 19.74 MJ/kg at a T_T of 593 K. The corresponding values of the energy densification ratio of torrefied solid bio-fuels of WPST1 and WPST2 can respectively rise to 1.50 and 1.25 times that of the raw bio-waste. The H_HD of WPST1 of 27.49 MJ/kg is within the range of 24–35 MJ/kg for bituminous coal. In addition, the wet-basis HHV of WPST1 with an equilibrium moisture content of 5.91 wt % is 25.87 MJ/kg, which satisfies the Quality D coal specification of the Taiwan Power Co. requiring a value of above 20.92 MJ/kg.

Combined heat and power production from biogas is now playing an important role in energy and resource utilization as well as pollution control in waste water treatment. This research used biogas from the Bali Sewage Treatment Plant in New Taipei City, Taiwan, as a major source of fuel for the electricity generation. A micro gas turbine electricity generator, Capstone CR-30, which possesses a maximum rated power load (P_WL) of 30 kW, was equipped to convert biogas into electricity. The biogas is mainly composed of CH₄ (56.1 ± 8.0 vol.%), CO₂ (25.5 ± 9.8 vol.%), H₂ (0.5 vol.%), and H₂S (0.99 ± 0.07 ppmv). During the test operation period of the generator, it was found that the thermal efficiency increases from 19.8% to 23.4% kWh_e/kWh_th, while the electricity generation efficiency (η_EB) also rises from 0.93 to 1.09 kWh_e/m³ biogas as the P_WL increases from 10 kW to 30 kW. The results indicated that the generator has a better performance with higher P_WL. At P_WL = 30 kW, the average adjusted concentrations of CO and NOx (adjusted to 15 vol.% O₂) emitted from the generator are 86 ppmv and 17 ppmv, respectively. Both are much lower than the emission standards of stationary sources in Taiwan of 2000 ppmv and 150 ppmv, respectively. Thus, P_WL of 30 kW was selected in cooperation with biogas inflow = 0.412 m³/min and air/fuel ratio (i.e., air/biogas ratio) = 76.0 vol./vol. for the long-term regular operation. At the above setting conditions for long-term operation, the generator continuously consumed the biogas and provided stable electricity generation at a rate of 19.64 kWh_e/h for a 2-year running period. Moreover, the greenhouse gas can be cut off with a rate of 10.78 kg CO₂e/h when using biogas as fuel for electricity generation. Overall, this research proves that the application of a micro gas turbine electricity generator not only has promising performance for using biogas but also gives a significant reduction of greenhouse gas emission, which fits the concepts of the circular economy and environmental protection.

In this study, biomass of rice straw (RS) and wood (WD) and their torrefied biomass (RS_T and WD_T) were used as solid bio-fuel (SBF) for co-firing individually with coal in a commercial continuous chain-grate steam boiler system, which was conducted at fixed input rate of heating value of mixture of SBF and coal and at fixed air flow rate. The effects of key system parameters on the gaseous and particulate pollutions and ash were examined. These include SBF type and blending ratio (R_BL) of biomass (i.e., SBF) in the mixture of coal and biomass based on heating values for co-firing. The results indicated that wood, which possesses high heating value while less amount of ash, is more suitable for co-firing with coal than rice straw. Torrefaction can increase the heating value of biomass and homogenize its property, being beneficial to co-firing. Also, torrefaction can decompose the hydroxyl group of biomass, which makes biomass tending to possess hydrophobicity. This, in turn, helps the storage and transportation of biomass. Generally, adding the RS (with R_BL = 5-10%), WD (2-15%), RS_T (2-10%), and WD_T (2-20%), respectively with coal decreases the emissions of NO_x and SO₂, but increases that of CO (except RS_T). The emission of HCl is little. The addition of biomass also increases the emission of fine particulate matters (PM) especially PM_2.5 in the flue gases, raising PM_2.5/PM₁₀₀ from 34.87 to 78.35 wt.% (Case 50%WD_T). These emissions for the Cases tested satisfy with Taiwanese emission standards of stationary sources which set limitations of NOx, SO₂, CO, and HCl < 350, 300, 2000, and 80 ppmv, while PM < 50 mg/m³, respectively. The results support the use of RS, WD, RS_T, and WD_T for co-firing with coal.

This research investigated the application of palm shell char as a catalyst for the catalytic steam reforming of tar after the sorption enhanced gasification (SEG) process. The catalytic activities of palm shell char and metal-supported palm shell char were tested in a simulated SEG derived syngas with tar model compounds (i.e., toluene and naphthalene) at a concentration of 10 g m⁻³ _NTP. The results indicated that palm shell char had an experimentally excellent catalytic activity for tar reforming with toluene and naphthalene conversions of 0.8 in a short residence time of 0.17 s at 900 °C. A theoretical residence time to reach the complete naphthalene conversion was 1.2 s at 900 °C for palm shell char, demonstrating a promising activity similar to wood char and straw char, but better than CaO. It was also found that potassium and iron-loaded palm shell chars exhibited much better catalytic activity than palm shell char, while the parallel reaction of gasification of K-loaded palm shell char influenced the conversion with its drastic mass loss. Moreover, contrary to CaO, palm shell char presented relatively low selectivity to benzene, and its spontaneous gasification generated extra syngas. In summary, the present study demonstrated that the low-cost material, palm shell char, can successfully be used as the tar-reforming catalyst after SEG process.

The effects of ultrasonic and ozonation pretreatments on organic solubilization, anaerobic biodegradability, and biogas production were elucidated in this study. Two pretreatment methods for batch anaerobic digestion for biogas recovery with the same material and experimental conditions were the focus for comparison. Anaerobic digestion experiments were conducted at ambient temperature with the solid retention time set to 25 days. The obtained results indicated that the soluble chemical oxygen demand increased from 0.344 without pretreatment to 1.023 and 1.228 g/L with ultrasound and ozone pretreatments, respectively, whereas the yields of biogas production in the 25 days increased by 32.3 and 52.9% via ultrasonic irradiation and ozonation relative to the control case, respectively. The biodegradability of the organic compounds of the samples for the cases of ultrasound, ozone pretreatments, and control achieved 55.9, 64.31, and 39.18%, respectively, in terms of chemical oxygen demand (COD) removal efficiencies. The physicochemical characteristics of sludge flocs were investigated via scanning with particle sizes, which were obviously affected by pretreatments of sonication and ozonation, resulting in finer particles than in the control case.

Effects of reaction conditions on the production of alcohols (AOH_s) and alkanes (Alk) from CO and H₂, which can be obtained from the gasification of biomass, using a molybdenum sulfide (MoS₂)-based catalyst of MoS₂/γ-Al₂O₃ were studied. A high-pressure fixed packed bed (HPFPB) was employed to carry out the reaction. The results indicate that the conversion of CO (X_CO) and specific production rates of alcohol (SPR_AOH) and alkane (SPR_Alk) are highly depended on temperature (T). In T = 423–573 K, maximum yield of alcohols (Y_AOH) and SPR_AOH occur at T = 523 K. In the meantime, well performance gives the selectivity of ethanol (S_EtOH) of 52.0 C%. For the studies on varying H₂/CO mole ratio (M_H/C) from 1 to 4 at 523 K, the appropriate M_H/C to produce EtOH is 2, giving higher ratios of SPR_AOH/SPR_Alk and Y_AOH/Y_Alk than those with other M_H/C. As for varying the total gas flow rates (Q_G) of 300, 450, 600 to 900 cm³ min⁻¹ tested at T = 523 K and M_H/C = 2, the lower QG provides longer reaction time (or gaseous retention time, t_R) thus offering higher X_CO, however lower productivity. For setting pressure (P_ST) = 225–540 psi, a supply of higher pressure is equivalent to providing a larger amount of reactants into the reaction system, this thus suggests the use of higher P_ST should give both higher X_CO and productivity. The assessment of the above results indicates that the MoS₂/γ-Al₂O₃ catalyst favors the production of alcohols over alkanes, especially for ethanol. The information obtained is useful for the proper utilization of biomass derived gases of CO and H2.