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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 (PWL) 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% kWhe/kWhth, while the electricity generation efficiency (ηEB) also rises from 0.93 to 1.09 kWhe/m3 biogas as the PWL increases from 10 kW to 30 kW. The results indicated that the generator has a better performance with higher PWL. At PWL = 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, PWL 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 kWhe/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.

This study used the subcritical hydrothermal liquefaction technique (SHLT) in the co- liquefaction of process rejects at a wastepaper-based paper mill (PRWPM) and waste soybean oil (WSO) for the production of biofuels and bio-char material. PRWPM emits complicated waste composed of cellulose, hemicellulose, lignin, and plastic from sealing film. The waste is produced from the recycled paper process of a mill plant located in central Taiwan. The source of WSO is the rejected organic waste from a cooking oil factory located in north Taiwan. PRWPM and WSO are suitable for use as fuels, but due to their high oxygen content, their use as commercial liquid fuels is not frequent, thus making deoxygenation and hydrogenation necessary. The temperature and pressure of SHLT were set at 523–643 K and 40–250 bar, respectively. The experimental conditions included solvent ratios of oil–water, temperature, reaction time, and ratios of solvent to PRWPM. The analysis results contained approximated components, heating values, elements, surface features, simulated distillations, product compositions, and recovery yields. The HHV of the product occurred at an oil–water ratio of 75:25, with a value of 38.04 MJ kg−1. At an oil–water ratio of 25:75, the liquid oil-phase product of SHTL has the highest heating value 42.02 MJ kg−1. Higher WSO content implies a lower heating value of the oil-phase product. The simulated distillation result of the oil-phase product with higher content of alcohol and alkanes obtained at the oil–water ratio of 25:75 is better than the other ratios. Here, the carbon number of the oil product is between C8–C36. The product conversion rate rises with an increase of the WSO ratio. It is proved that blending soybean oil with water can significantly enhance the quality of liquefied oil and the conversion rate of PRWPM. Therefore, the solid and liquid biomass wastes co-liquefaction to produce gas and liquid biofuels under SHLT are quite feasible.

This study used thermal cracking with hydrogen (HTC) to produce bio-fuel oil (BFO) from jatropha oil (JO) and to improve its quality. We conducted HTC with different hydrogen pressures (PH2; 0–2.07 MPa or 0–300 psig), retention times (tr; 40–780 min), and set temperatures (TC; 623–683 K). By applying HTC, the oil molecules can be hydrogenated and broken down into smaller molecules. The acid value (AV), iodine value, kinematic viscosity (KV), density, and heating value (HV) of the BFO produced were measured and compared with the prevailing standards for oil to assess its suitability as a substitute for fossil fuels or biofuels. The results indicate that an increase in PH2 tends to increase the AV and KV while decreasing the HV of the BFO. The BFO yield (YBFO) increases with PH2 and tr. The above properties decrease with increasing TC. Upon HTC at 0.69 MPa (100 psig) H2 pressure, 60 min time, and 683 K temperature, the YBFO was found to be 86 wt%. The resulting BFO possesses simulated distillation characteristics superior to those of boat oil and heavy oil while being similar to those of diesel oil. The BFO contains 15.48% light naphtha, 35.73% heavy naphtha, 21.79% light gas oil, and 27% heavy gas oil and vacuum residue. These constituents can be further refined to produce gasoline, diesel, lubricants, and other fuel products.

Effects of reaction conditions on the production of alcohols (AOHs) 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 (XCO) and specific production rates of alcohol (SPRAOH) and alkane (SPRAlk) are highly depended on temperature (T). In T = 423–573 K, maximum yield of alcohols (YAOH) and SPRAOH occur at T = 523 K. In the meantime, well performance gives the selectivity of ethanol (SEtOH) of 52.0 C%. For the studies on varying H2/CO mole ratio (MH/C) from 1 to 4 at 523 K, the appropriate MH/C to produce EtOH is 2, giving higher ratios of SPRAOH/SPRAlk and YAOH/YAlk than those with other MH/C. As for varying the total gas flow rates (QG) of 300, 450, 600 to 900 cm3 min−1 tested at T = 523 K and MH/C = 2, the lower QG provides longer reaction time (or gaseous retention time, tR) thus offering higher XCO, however lower productivity. For setting pressure (PST) = 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 PST should give both higher XCO 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.

Autoclaving of food wastes (FW) for the resource recovery and reutilization was studied using the pilot plant scale. Experiments were conducted at various temperatures of 408, 428, and 438 K and times of 15 and 60 min. The in-filled steam to the autoclave was supplied by the incineration plant with a gauge pressure of 7 kg/cm2 and a temperature of 443 K or above. The results obtained from the experiments show that the less energy- and time-consuming autoclaving conditions (408 K and 15 min, denoted as Case A408-15) are effective. Comparisons of the properties and characteristics of autoclaved FW (FWA) of Case A408-15 with those of FW are made. The wet bulk volume and wet bulk density of FW A are dramatically reduced to 15.64% and increased to 313.37% relative to those of FW, respectively. This makes the subsequent processing and reuse for FWA more convenient than FW. The autoclaving results in an increase of carbon content and a decrease of nitrogen content, and thus an increase of the C/N ratio of FWA. The contents of sulfur, hemi-cellulose, and cellulose of FWA are also reduced. All these fluctuations are beneficial for making compost or other usages from FWA than FW. The autoclaved liquid product (LA) separated from FWA and liquid condensate (LC) from the released gas possess high COD and TOC. These two liquids can be mixed for use as liquid fertilizers with proper conditioning. Alternatively, further anaerobic digestion of the mixture of FWA, LA, and LC can offer enhanced biogas production for power generation. All these thus match the appeal of sustainable materials management and circular economy. The emitted gas from autoclaving contains no CO and some hydrocarbons. Suitable air pollution control is needed. The results and information obtained are useful for the proper recovery and reuse of abundant food wastes from domestic households and food industries.