• Energy Research

Use of waste cooking oil derived biodiesel (WCOB) as an alternative fuel in diesel engines has increased significantly in recent years. The impact of WCOB on particulate emissions from diesel engines needs to be investigated thoroughly. This study was conducted to make a comparative evaluation and size-differentiated speciation of the particulate bound elements from ultra low sulfur diesel (ULSD) and WCOB and a blend of both of the fuels (B50). Particle mass and their elemental size distributions ranging from 0.01-5.6 μm were measured. It was observed that more ultrafine particles (UFPs, 70%) of the total estimated health risk.

A novel thermochemical conversion route has been developed that yields 5-hydroxymethylfurfural (HMF) from food waste biomass (FWB) in the presence of a heterogeneous catalysts (zirconium phosphate (ZrP)). The ZrP catalyst was prepared by precipitation followed by calcination at 400 (ZrP-400) and 600 °C (ZrP-600) and was characterized by SEM, XRD, XPS, N2 sorption and NH3-TPD. The optimized reaction conditions were identified to maximize HMF yield by varying the type of catalyst, the catalyst loading and the reaction time. The highest HMF yield achieved was 4.3%. On average 33% higher yield for ZrP-600 was obtained compared to that for ZrP-400, which might be due to higher number of acid sites on ZrP-600. The ZrP catalyst was easily regenerated by thermal treatment and showed stable activity upon its reuse. Preliminary calculations of the "minimum selling price" of HMF suggest that it is economically attractive to make this industrially-relevant chemical from FWB.

Co-combustion of hydrochar with lignite was investigated by means of thermogravimetric analysis. Hydrochars were produced from coconut fibers and eucalyptus leaves under hydrothermal conditions at 250°C. The hydrochar was added in varying amounts to lignite for combustion. The results indicated that hydrothermal treatment decreased the volatile matter content and increased the fixed carbon content of the biomaterials. The elevated energy density and decreased ash content of the hydrochar improved its combustion behavior when co-fired with lignite for energy production. The hydrochars derived from coconut fiber and eucalyptus leaves had similar chemical compositions and showed similar influences on lignite combustion. Hydrochar addition increased the burnout and shortened the combustion range of the hydrochar-lignite blends. High combustion efficiency was observed due to the synergistic interactions between hydrochar and lignite during the co-combustion process. A kinetic study showed that the combustion process of hydrochar-lignite blends followed first-order reaction rates.

A carbon-rich solid product, denoted as hydrochar, was synthesized by hydrothermal carbonization (HTC) of palm oil empty fruit bunch (EFB), at different pre-treatment temperatures of 150, 250 and 350 °C. The conversion of the raw biomass to its hydrochar occurred via dehydration and decarboxylation processes. The hydrochar produced at 350 °C had the maximum energy-density (>27 MJ kg(-1)) with 68.52% of raw EFB energy retained in the char. To gain a detailed insight into the chemical and structural properties, carbonaceous hydrochar materials were characterized by FE-SEM, FT-IR, XRD and Brunauer-Emmett-Teller (BET) analyses. This work also investigated the influence of hydrothermally treated hydrochars on the co-combustion characteristics of low rank Indonesian coal. Conventional thermal gravimetric analysis (TGA) parameters, kinetics and activation energy of different hydrochar and coal blends were estimated. Our results show that solid hydrochars improve the combustion of low rank coals for energy generation.

There has been an increasing concern about the emissions of airborne particulate matter (PM) from diesel engines because of their close association with adverse health and environmental impacts. Among the alternative fuels being considered, biodiesel made by the transesterification of waste cooking oil has received wide attention in recent years because of its low cost and the added advantage of reducing waste oil disposal. This study was conducted to make a comparative evaluation of the particulate-bound elements emitted from ultra low sulphur diesel (ULSD) and waste cooking oil-derived biodiesel (B100) and a blend of both the fuels (B50). It was observed that the PM mass concentrations were reduced by about 36% when B100 was used. Crustal elements such as Mg, K and Al were found to be in higher concentrations compared to other elements emitted from both B100 and ULSD. Zn, Cr, Cu, Fe, Ni, Mg, Ba, K were found to be higher in the biodiesel exhaust while Co, Pb, Mn, Cd, Sr, and As were found to be higher in the ULSD exhaust. To evaluate the potential health risk due to inhalation of PM emitted from diesel engines running on ULSD and B100, health risk estimates based on exposure and dose–response assessments of particulate-bound elements were calculated assuming exposure for 24 h. The findings indicate that the exposure to PM of the B100 exhaust is relatively more hazardous and may pose adverse health effects compared to ULSD.

AbstractThe polyurethane foam (PUF) disk-based passive air samplers (PAS), mounted inside two aluminium bowls to buffer the air flow to the disk and to shield it from precipitation and sunlight, were used for the collection of atmospheric POPs in Singapore during April 2008eJune 2008. Data obtained from PAS measurements are compared to those from active high-volume air sampling (AAS). Single factor ANOVA tests show that there were no significant differences in chemical distribution profiles between actively and passively collected samples(PAHs, F=3.38×10-8) 0.05; OCPs, F=2.71×10-8 0.05). The average air-side mass transfer coefficient (kA) for PAS, determined from the loss of depuration compounds such as 13C6-HCB (1000 ng), 13C12 - 4,4’ DDT (1000 ng) and 13C12-PCB 101 (1000 ng)spiked on the disks prior to deployment, was 0.12 ± 0.04 m s-1. These values are comparable to those reported previously in the literature. The average sampling rate was 3.78 ± 1.83 m3 d- 1 for the 365cm2 PUF disk. Throughout the entire sampling period (∼68 d), most of the PAHs and all OCPs exhibited a linear uptake trend on PAS, while naphthalene, acenaphthylene, acenaphthene and fluorene reached the curvilinear phase after the first ∼30 d exposure. Theoretically estimated times to equilibrium (teq) ranged from around one month for Acy to hundreds of years for DB(ah)A. Sampling rates, based on the time integrated active sampling-derived concentrations and masses collected by PUF disks during the linear uptake phase, were determined for all target compounds with the average values of 2.50 m3 d-1 and 3.43m3 d-1 for PAHs and OCPs, respectively. More variations were observed as compared to those from th depuration study. These variations were most likely due to the difference of physicochemical properties of individual species. The validation and calibration work conducted for PAS in this study clearly indicates that it would be feasible to use such an economic PAS for routine measurements of POPs in the tropical atmosphere at a large network of sampling locations.

In this study, thermal characteristics of raw biomass, corresponding pyrolytic biochars and their blends with lignite were investigated. The results showed that pyrolytic biochars had better fuel qualities than their parent biomass. In comparison to raw biomass, the combustion of the biochars shifted towards higher temperature and occurred at continuous temperature zones. The biochar addition in lignite increased the reactivities of the blends. Obvious interactions were observed between biomass/biochar and lignite and resulted in increased total burnout, shortened combustion time and increased maximum weight loss rate, indicating increased combustion efficiencies than that of lignite combustion alone. Regarding ash-related problems, the tendency to form slagging and fouling increased, when pyrolytic biochars were co-combusted with coal. This present study demonstrated that the pyrolytic biochars were more suitable than raw biomass to be co-combusted with lignite for energy generation in existing coal-fired power plants.

Nitrogen conversion and polycyclic aromatic hydrocarbon (PAH) formation during rapid pyrolysis of hydrochar, lignite and hydrochar–lignite blends have been investigated within a temperature range of 600–900 C. The results showed that in comparison to lignite, a higher percentage of hydrochar nitrogen was retained in the char, and less NH3 and HCN were formed during pyrolysis. During pyrolysis of the individual hydrochar and lignite components, yields of NH3 and HCN reached a maximum at 800 C and then decreased with increasing temperature. Addition of hydrochar to the lignite increased yields of total HCN and NH3 at low pyrolysis temperatures (6700 C), but suppressed their formation at high temperatures (P800 C). Synergistic interactions in hydrochar–lignite blends significantly decreased the total nitrogen percentage in the char, and promoted the conversion into N2 at temperatures P800 C. These synergistic interactions increased with (but were not linearly proportional to) increasing temperatures and hydrochar ratios in the blends. With regard to PAH emissions, relatively less high-ring PAHs were present in tars from pyrolysis of hydrochar–lignite blends than in tars from pyrolysis of lignite alone. These findings suggest that co-processing of hydrochar–lignite blends for energy production may have the additional benefit of reducing emissions of nitrogen pollutants and PAHs.