A.E. Atabani

A review of thermochemical conversion of microalgal biomass for biofuels: chemistry and processes

Renewable biomass sources are organic materials, in which solar energy is stored in bio-chemical bonds, and which commonly contain carbon, hydrogen, oxygen, and nitrogen constituents, along with traces of sulfur. Renewable biomass is now considered as a crucial energy resource, which is able to meet a range of energy requirements, including generating electricity and fueling vehicles. Among all the renewable energy sources, microalgal biomass is unique, since it profitably stores solar energy. It is one of the renewable sources of carbon that can be effectively converted into expedient solid, liquid, and gaseous biofuels through different conversion techniques. In this review, thermochemical conversion technologies involving microalgal biomass are highlighted, with emphasis on the background chemistry and chemical processes. Thermochemical conversion of microalgal biomass via pyrolysis, hydrothermal liquefaction, gasification, torrefaction, and direct combustion for bioenergy production from microalgal species is discussed, though there are limited literature sources available on these technologies. The unique features of hydrothermal gasification and supercritical gasification technologies are described, with the chemical reactions involved in these processes. The decomposition pathways of the main chemical components present in the microalgal biomass, such as carbohydrates and proteins, are well elucidated with the chemical pathways. The pros and cons of direct combustion are also spotlighted.

A study of production and characterization of Manketti (Ricinodendron rautonemii) methyl ester and its blends as a potential biodiesel feedstock

Globally, more than 350 oil-bearing crops are known as potential biodiesel feedstocks. This study reports on production and characterization of Manketti (Ricinodendron rautonemii) methyl ester and its blends with diesel. The effect of Manketti biodiesel (B5) on engine and emissions performance was also investigated. The cloud, pour and cold filter plugging points of the produced biodiesel were measured at 1, 3 and 5 °C, respectively. However, the kinematic viscosity of the biodiesel generated was found to be 8.34 mm2/s which was higher than the limit described by ASTM D6751 and EN 14214. This can be attributed to the high kinematic viscosity of the parent oil (132.75 mm2/s). Nevertheless, blending with diesel improved this attribute. Moreover, it is observed that at all engine speeds, B5 produced lower brake power (1.18%) and higher brake specific fuel consumption (2.26%) compared to B0 (neat diesel). B5 increased the CO and HC emissions by 32.27% and 37.5%, respectively, compared to B0. However, B0 produced 5.26% higher NO emissions than B5.

Production, characterization, engine performance and emission characteristics of Croton megalocarpus and Ceiba pentandra complementary blends in a single-cylinder diesel engine

Compounding energy demand and environmental issues necessitate suitable alternative or partial replacement of fossil fuels. Among the possible sources, biodiesel from non-edible vegetable oil sources is more economically feasible and possesses characteristics close to those of petroleum diesel. Two potential non-edible biodiesel feedstocks “Croton megalocarpus” and “Ceiba pentandra” were used for biodiesel production through esterification and transesterification process on a laboratory scale. Biodiesel characterization, engine performance and emission characteristics were investigated in an unmodified direct injection, naturally aspirated, single-cylinder diesel engine. 20% (v/v) of each of C. megalocarpus (CM), C. pentandra (CP) and their combined blends (CMB20, CPB20, CMB15CPB05, CMB10CPB10, and CMB05CPB15) were tested under varying engine speeds ranging from 1000 rpm to 2400 rpm at full load conditions. CMB20 and CPB20 reduced the brake power (BP) by 2.63% and 3.70%, brake thermal efficiency (BTE) by 5.97% and 3.72%, carbon monoxide (CO) emission by 1.09% and 2.39%, hydrocarbon (HC) emission by 1.48% and 4.62% and smoke emission by 12.35% and 17.13%, respectively compared to petroleum diesel. On the other hand, CMB20 and CPB20 increased the brake specific fuel consumption (BSFC) by 9.74% and 7.63%, NOX emission by 13.19% and 15.45%, respectively. A mixture of 10% of both biodiesels with diesels (CMB10CPB10) provides better performance and emission characteristics. CMB10CPB10 reduced BP, BTE, CO, HC and smoke by 0.53%, 0.50%, 5.21%, 8.38% and 20.71%, respectively and increased BSFC and NOX by 3.90% and 18.66%, respectively compared to conventional diesel. A combined blend of CM and CP could be a sustainable substitute for fossil diesel in the context of performance and emission.

Perspective of safflower (Carthamus tinctorius) as a potential biodiesel feedstock in Turkey: characterization, engine performance and emissions analyses of butanol–biodiesel–diesel blends

ABSTRACT Safflower (Carthamus tinctorius) is widely farmed in Turkey. This study investigates the physicochemical properties of safflower biodiesel and its blends with Euro diesel and butanol. A polynomial curve-fitting method was used to predict kinematic viscosity and density of the ternary blends. Furthermore, characteristics such as DSC, FT-IR, UV-Vis and TGA were adopted to evaluate the influence of butanol addition on biodiesel–diesel blends. Engine performance parameters such as BP, torque and BSFC and emissions such as CO, HC, NOx and EGT were studied. Safflower methyl ester satisfied both EN 14214 and ASTM D 6751 standards regarding viscosity, flash point and density. However, iodine value was quite high. Oxidation stability fails to satisfy either standard. This is due to the high level of unsaturated fatty acids (91.05%). A reduction in BP, torque, HC and CO coupled with an increase in BSFC, NOx emissions and EGT was observed for all blends compared to Euro diesel. Overall, all blends appear to be good alternatives to biodiesel–diesel blends. This work supports that biodiesel can be blended with diesel and butanol as ternary blends (up to 20%) for use as a fuel in compression ignition (CI) engines. Therefore, combustion characteristics of blends shall be further investigated.

Valorization of spent coffee grounds recycling as a potential alternative fuel resource in Turkey: An experimental study

ABSTRACT In this study, recycling of spent coffee grounds (SCG) as a potential feedstock for alternative fuel production and compounds of added value in Turkey was assessed. The average oil content was found (≈ 13% w/w). All samples (before and after extraction) were tested for scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), calorific value, surface analysis and porosity, Fourier transform infrared (FT-IR), and elemental analysis to assess their potential towards fuel properties. Elemental analysis indicated that carbon represents the highest percentages (49.59% and 46.42%, respectively), followed by nitrogen (16.7% and 15.5%), hydrogen (6.74% and 6.04%), and sulfur (0.851% and 0.561%). These results indicate that SCG can be utilized as compost, as it is rich in nitrogen. Properties of the extracted oil were examined, followed by biodiesel production. The quality of biodiesel was compared with American Society for Testing and Materials (ASTM) D6751 standards, and all the properties complied with standard specifications. The fatty acid compositions were analyzed by gas chromatography. It was observed that coffee waste methyl ester (CWME) is mainly composed of palmitic (35.8%) and arachidic (44.6%) acids, which are saturated fatty acids. The low degree of unsaturation provides an excellent oxidation stability (10.4 hr). CWME has also excellent cetane number, higher heating value, and iodine value with poor cold flow properties. The studies also investigated blending of biodiesel with Euro diesel and butanol. Following this, a remarkable improvement in cloud and pour points of biodiesel was obtained. Spent coffee grounds after oil extraction is an ideal material for garden fertilizer, feedstock for ethanol, biogas production, and as fuel pellets. The outcome of such research work produces valuable insights on the recycling importance of SCG in Turkey. Implications: Coffee is a huge industry, and coffee has been widely used due to its refreshing properties. This industry generates large quantities of waste. Therefore, recycling of spent coffee grounds for producing alternative fuels and compounds of added value is crucial. Elemental analysis indicated that coffee waste can be utilized as compost, as it is rich in nitrogen. Coffee waste after oil extraction is an ideal feedstock for ethanol and biogas production, garden fertilizer, and as fuel pellets. The low degree of unsaturation provides excellent oxidation stability. Its biodiesel has also excellent cetane number, higher heating value, and lower iodine value.

Optimization of the esterification process of crude jatropha oil (CJO) containing high levels of free fatty acids: a Malaysian case study

ABSTRACT Biodiesel as an alternative fuel is one of the best choices among other sources due to its immense potential to reduce pollutant emissions when used in compression ignition engines. Malaysia is considered one of the top biodiesel-producing countries. The main crop for biodiesel production is currently palm oil. However, Jatropha curcas has recently drawn the attention of the Malaysian government as an alternate species for producing high yields of oil. While an evaluation of biodiesel production, blending, engine performance and emissions characteristics of Malaysian-produced jatropha methyl ester has been made recently, few studies have optimized the esterification of the crude oil. This paper is the study of an optimization process for Malaysian CJO using an acid-catalyst pretreatment process to reduce the relatively high free fatty acid (FFA) percentages of crude jatropha oil to below 1% using design of experiments and response surface methodology, with the help of Minitab software. The main findings of the current investigation are that using the acid catalyst H2SO4 at 0.225% (v/v), an MeOH-to-oil ratio of 12.29% (w/w) and a reaction time of 149.76 min are the optimum process parameters for the esterification reaction.

Extraction and Utilization of Sudanese Acacia Senegale Seeds (Gum Arabic) Oil for Biodiesel Production in Sudan

Abstract This study aims to figure out secondary uses of Acacia senegal var. senegal (family Leguminosae). The seeds were collected from El Obayed in Kordofan state, Sudan, during the season 2015–16. Solvent extraction technique was utilized to extract the oil from the A. senegal seeds. The oil content of these seeds was found to reach 20% w/w. The extracted oil was subjected to physicochemical evaluation; the results showed that its free fatty acid content was 3.8 g/L, its saponification value was 848.4 mL/g, iodine value was 89.144 mL/g, peroxide value was 6.0 mL/g, its moisture content was 0.8%, density was 0.915 g/cm3, refractive index was 1.4628, and color was 1.5/29.04 (red/yellow). The extracted oil was converted into biodiesel through a transesterification reaction, and its physicochemical properties were investigated. The produced biodiesel density at 15°C and 20°C, cloud point, and cold filter plugging point (CFPP) were found to be 0.8834 and 0.8808 g/cm3; 18°C, 14°C, and 11°C; and 198oC, respectively. Also, its IR and gas chromatography–mass spectrometry (GC–MS) were recorded. All results showed that it is of acceptable qualities as a biodiesel.

Energy Economical and Environmental Analysis of Industrial Boilers Using VSD

As a result of the successful implementation of the industrialization plan in 1985; Malaysia has changed from an agricultural economy into industrial based economy. The industrial sector represents the highest consuming sector across all other sectors and accounts for about 48% of all total energy demand. This paper is concerned with an energy saving, economic and environmental analysis of industrial boilers in Malaysia when using variable speed drives (VSD). The results obtained when reducing the speed of water pumps by 60% show that 4 GWh, 93.6% of energy, RM 863,375 and 2,160 ton of CO2 could be saved annually. These results represent high energy saving, environmental and economic benefits associated with this energy saving technology. ABBREVIATIONS