• Energy Research

Abstract Combustion of fossil fuels has a significant share in producing harmful emissions in the global emission context. With a threat of fossil fuel crisis and the necessity of reducing emission from diesel engine combustion system, biodiesel is considered as one of the key environmentally-friendly diesel fuel alternatives. In this study, sunflower biodiesel has been considered as a key ingredient to infuse waste plastic (polystyrene, PS) as another cleaner source of hydrocarbon fuel in the diesel engines. Polystyrene was infused (5% w/v) into sunflower biodiesel to produce a blend of diesel-biodiesel-polymer (DBP) fuel. The emission characteristics of the diesel, diesel–biodiesel (binary blend) and diesel-biodiesel-polymer (ternary blend) were compared in an unmodified diesel engine. The results showed that the emission compositions of the DBP were comparable to those of diesel which effectively reduced the NOx emission, as compared to diesel-biodiesel blend. In addition, the brake specific fuel consumption (BSFC) and CO emission were reduced in DBP, as compared to biodiesel and diesel fuels. Based on these results, it can be concluded that the polymer blended fuels could be potentially used as another emission reducing fuel source in an unmodified diesel engine. The utilisation of waste polymers in biodiesel production could help find an alternative use for non-recyclable plastics, while also contributing to cleaner emission.

An alternative landfill capping technique known as ‘Phytocapping’ (establishment of perennial plants on a layer of soil placed over the waste) was trailed in Rockhampton, Australia. In this technique, trees were used as ‘bio-pumps’ and ‘rainfall interceptors’ and soil cover as ‘storage’ of water. The environmental performance of the phytocapping system was measured based on its ability to minimise water percolation into the waste. The percolation rate was modelled using HYDRUS 1D for two different scenarios (with and without vegetation) for the thick and thin caps, respectively. Results from the modelling showed percolation rates of 16.7 mm year−1 in thick cover and 23.8 mm year−1 in thin cover, both of which are markedly lower than those expected from a clay cap. Results from monitoring and observations showed that 19 trees out of 21 tree species grew well in the harsh landfill environment. Top ten performing species have been identified and are recommended to be grown on phytocaps in the Central Queensland region.

This paper investigates the interactive relationship between three operating parameters (papaya seed oil (PSO) biodiesel blends, engine load, and engine speed) and four responses (brake power, BP; torque; brake specific fuel consumption, BSFC; and, brake thermal efficiency, BTE) for engine testing. A fully instrumented four cylinder four-stroke, naturally aspirated agricultural diesel engine was used for all experiments. Three different blends: B5 (5% PSO biodiesel + 95% diesel), B10 (10% PSO biodiesel + 90% diesel), and B20 (20% PSO biodiesel + 80% diesel) were tested. Physicochemical properties of these blends and pure PSO biodiesel were characterised, and the engine’s performance characteristics were analysed. The results of the engine performance experiments showed that, in comparison with diesel, the three PSO biodiesel blends caused a slight reduction in BP, torque, and BTE, and an increase in BSFC. The analysis of variance and quadratic regression modelling showed that both load and speed were the most important parameters that affect engine performance, while PSO biodiesel blends had a significant effect on BSFC.

Abstract Energy conversion efficiencies of three pyrolysis reactors (bench-scale auger, batch, and fluidized bed) were investigated using rice straw as the feedstock at a temperature of 500 °C. The highest bio-oil yield of 43% was obtained from the fluidized bed reactor, while the maximum bio-char yield of 48% was obtained from the batch reactor. Similar bio-oil yields were obtained from the auger and batch type reactors. The GCMS and FTIR were used to evaluate the liquid products from all reactors. The best quality bio-oil and bio-char from the batch reactor was determined to have a heating value of 31 MJ/kg and 19 MJ/kg, respectively. The highest alkali mineral was found in the bio-char produced from the auger reactor. The energy conversion efficiencies of the three reactors indicated that the majority of the energy (50–64%) was in the bio-char products from the auger and batch reactors, while the bio-oil from the fluidized bed reactor contained the highest energy (47%). A Sankey diagram has been produced to show the flows of product energy from each pyrolysis process. The result will help determine which conversion process would be optimal for producing specific products of bio-char, bio-oil, and gas depending on the needs.

Abstract Beauty leaf tree (BLT) has been ranked as a valuable 2nd generation feedstock for biodiesel production. This tree is suitable for growing on marginal land to avoid food vs fuel debate. However, at present little is known about its tolerance to marginal soil conditions such as salinity. Thus, a sand culture experiment was conducted, and the seedlings of BLT were exposed to 0, 25, 50, 75 and 100 mM NaCl for up to 245 days. Plant growth and physiological measurements were recorded and the whole leaf and powdered stem were scanned using FTIR-ATR to test if these spectra can be used to delineate differences between the control and the NaCl-treated plants. Results showed that the chlorophyll content and leaf expansion rate were little affected at 25 and 50 mM NaCl, as compared to the control, and they declined at higher NaCl concentrations. The tissue Na and Cl concentrations increased with NaCl increment. The differences between the control and the NaCl-treated plants were distinct at certain FTIR-ATR spectra showing that the plants that were exposed to NaCl had synthesised certain organic compounds to maintain osmotic gradient between the tissues and soil solution. This study found that the biochemical changes that occur in the functional groups of NaCl–treated plants can be detected by the FTIR-ATR spectroscopy, thus showing the potential of this technology to screen large number of genotypes in plant breeding trials. This technology is particularly suited to tree crops that have slow growth rate in the seedling stage.

Abstract This paper explores the impact of non-edible biodiesel blends on emission characteristics under various loading conditions in a naturally aspirated four-strokes multi-cylinder diesel engine. A comparative analysis of the emissions characteristics of four non-edible biodiesel (beauty leaf biodiesel, papaya seed biodiesel, stone fruit biodiesel and tomato seed biodiesel) blends (20% vol. = B20) and diesel was performed by varying engine loads (0, 50 and 100%) and speeds (1200, 1800 and 2400 rpm). The aim was to optimise operating parameters such as biodiesel blends, engine loads and speed on engine emissions such as nitrogen oxide (NOx), carbon dioxide (CO2), hydrocarbon (HC), particulate matter (PM), carbon monoxide (CO) and exhaust gas temperature (EGT). A statistical model and analysis of variance (ANOVA) were used to optimise various parameters. At full load condition and 2400 rpm, the minimum and maximum increase in NOx and CO2 emissions were found to be 4.1% to 23.6% and 1.7% to 19% for papaya seed biodiesel PB20 and beauty leaf biodiesel BTL20 respectively. The results reveal that the engine load and speed were the two most imperative parameters that affected emissions (NOx, HC, PM and CO). Both biodiesel blend and the load were responsible for changing the EGT and NOx emissions. While NOx emissions were unaffected by variations in biodiesel blends, load or speed, the CO2 emissions were not affected by the operating parameters. To conclude, papaya seed oil can be a plausible biodiesel feedstock and its diesel blends with varying engine speeds, and loads can provide optimal engine testing characteristics for negotiating NOx, CO2, HC, PM, CO, and EGT concentration.

AbstractThe extensive use of fossil fuels is depleting its reserve and produces harmful emission causing environmental issues. Hence, considerable attention has been given to alternative sources such as biodiesel. Currently, biodiesel is mainly produced from conventionally grown edible oil plants thus leading to a competition of usage of food versus fuel. The increasing criticism of the sustainability of first generation biodiesels (those derived from edible oils) has raised attention to the use of so-called second and third generation biodiesels. The second generation biodiesel includes non-edible vegetable oils, waste cooking oils as well as animal fats. These are considered as promising substitute for traditional edible food crops as they neither compete with food crops nor lead to land-clearing. This study introduces second generation biodiesel to be used as biodiesel feedstocks. Several aspects of these feedstocks are reviewed and discussed in this paper. These aspects include different sources of biodiesel feedstocks, biodiesel conversion technology and performance and emission characteristics of second generation biodiesel.

Akbar, DH orcid:0000-0002-2269-5056; Ashwath, N orcid:0000-0002-4032-4507; Rolfe, JC orcid:0000-0001-7659-7040 ; Currently, the world is in search of bioethanol feedstock that does not compete with the human food supply and prime agricultural land. A native plant of Mexico, Agave tequilana, is one such feedstock. This plant can grow in arid, semiarid, or marginal lands with minimum rainfall and fertilizer and without competing with the current agricultural feedstocks [13, 14]. To date, only first-generation biofuel, especially bioethanol, is used in commercial production. However the second-generation biofuels may produce cost-effective fuels, but this is yet to be demonstrated as this option is still in precommercial or research and development phase [12]. This chapter aims to review the trends of bioethanol production and to explore the key factors affecting the commercial viability of producing first-generation bioethanol, with a particular focus on Australia. This chapter begins with the categorization of biofuels and bioethanol followed by a description of bioethanol feedstocks, the factors affecting commercial viability of bioethanol production in Australia. The chapter concludes with a review of costs and benefits of bioethanol production in Australia.