Synthesis and characterization of hazelnut oil-based biodiesel

The demand for diesel fuel far exceeds the current and future biodiesel production capabilities of the vegetable oil and animal fat industries. New oilseed crops that do not compete with traditional food crop are needed to meet existing energy demands. Hybrid hazelnut oil is just such an attractive raw material for production of biodiesel. Hazelnut oil was extracted from hybrid hazelnuts and the crude oil was refined. Hazelnut oil-based biodiesel was prepared via the transesterification of the refined hazelnut oil with excess methanol using an alkaline catalyst. The effects of reaction temperature, time and catalyst concentration on the yield of diesel were examined, and selected physical and chemical properties of the biodiesel were evaluated. The biodiesel yield increased with increasing temperature from 25 to 65 °C and with increasing catalyst concentration from 0.1 to 0.7 wt%. The increase in yield with reaction time was nonlinear and characterized by an initial faster rate, followed by a slow rate. Hazelnut oil-based biodiesel had an average viscosity of 8.82 cP at 25 °C, which was slightly higher than that of the commercial soy-based diesel (7.92 cP at 25 °C). An approximate 12 °C higher onset oxidative temperature and a 10 °C lower cloud point of hazelnut oil biodiesel than those of its commercial soy counterpart indicated a better oxidative stability and flowability at low temperature. The average heat of combustion of hazelnut oil biodiesel was 40.23 kJ/g, and accounted for approximately 88% of energy content of diesel fuel. The fatty acid composition of hazelnut oil-based biodiesel was the same as the nature oil.     

Transesterification of epoxidized soybean oil to prepare epoxy methyl esters

Epoxidized methyl esters were prepared by the transesterification of epoxidized soybean oil (ESBO). The transesterification was complete in 10 min at 50 °C without loss of the epoxide function. Epoxidized methyl esters represent a renewable substrate that is readily converted into surfactants, fuel additives, and other industrial products. The implementation of this reaction will increase the availability of epoxidized methyl esters and promote the development of new biobased products.     

Essential oil variation among and within six Achillea species transferred from different ecological regions in Iran to the field conditions

The compositions of essential oils of 19 accessions belonging to six different Achillea species, transferred from the natural habitats in 10 provinces of Iran to the field conditions, were assessed. The relationship between the leaf areas of selected accessions with their essential oil content was also investigated. Essential oil yield of dried plants obtained by hydro-distillation ranged from 0.1 to 2.7% in leaves. Results indicated a significant variation in oil composition among and within species. Total of 94 compounds were identified in 19 accessions belonging to the six species of A. millefolium, A. filipendulina, A. tenuifolia, A. santolina, A. biebersteinii and A. eriophora. The major constituents of the leaves in the tested genotypes were determined as germacrene-D, bicyclogermacrene, camphor, borneol, 1,8-cineole, spathulenol and bornyl acetate. According to the major compounds, four chemotypes were defined as: (I) spathulenol (1.64–34.31%) + camphor (0.2–15.61%) (7 accessions); (II₁) germacrene-D (18.78–23.93%) + borneol (7.93–8.26%) + bornyl acetate (11.56–14.66%) (5 accessions); (II₂) germacrene-D (13.28–36.28%) + bicyclogermacrene (5.93–8.4%) + 1,8-cineole (15.26–19.41%) + camphor (14.95–23.32%) (2 accessions); (III) borneol + camphor (52.04–63.27) (2 accessions); (IV) germacrene-D (45.86–69.64%) (3 accessions). The relationships of chemotypes with soil type and climatic conditions of collected regions were assessed, as probable reasons of high variations in essential oil components, and discussed.     

Methyl ester of Sal oil (Shorea robusta) as a substitute to diesel fuel—A study on its preparation, performance and emissions in direct injection diesel engine

Many research reported vegetable oil as a potential substitute for diesel engines with its ester form known as biodiesel. The biodiesel can be prepared by different process using vegetable oil and alcohol. The common process used for biodiesel preparation is known as transesterification. This paper presents the transesterification of Sal oil (Shorea robusta) into Sal oil methyl ester (SOME) and its performance in direct injection diesel engine. Several process parameters such as catalyst quantity, molar ratio of alcohol, reaction temperature and reaction time were studied and the optimized process conditions are amount of catalyst (NaOH) - 0.25 wt%, alcohol (methanol) - 150% excess, reaction temperature - 65 °C and reaction time - 1.5 h. The studies with SOME as fuel in the direct injection diesel engine shows that the exhaust emissions such as CO, HC and NO_x are reduced by 25%, 45% and 12%, respectively compared to diesel without significant difference in thermal efficiency. Based on this study it is concluded that the SOME can be used as fuel without any modifications in the engine and hence this biodiesel can be a potential substitute to standard diesel fuel.     

Herb and oil composition of dill (Anethum graveolens L.): Effects of crop maturity and plant density

Steam-distilled dill (Anethum graveolens L.) oil yield and composition varies with the relative amount of vegetative and reproductive tissue and the maturity of the plant material distilled. The characteristics of the dill plant at harvest may be manipulated through production practices. A study was conducted in western Montana to determine the effects of crop maturity and plant density on dill plant growth and on oil production and quality. The crop was harvested at intervals from early fruit formation through fruit pigmentation. Oil yield declined with fruit maturity over the sampling period, particularly after the completion of fruit ripening and “seed” shatter. The carvone content of the oil increased and α-phellandrene decreased as the plant progressed from flowering to fruit ripeness. The highest oil yields with maximum carvone levels were obtained when most of the fruits on primary umbels were pigmented but had not become dry and fully mature. The balance between carvone and phellandrene in the oil was a function of the proportion of mature umbel tissue to vegetative and immature umbel tissue. Seeding rates of 2.2–17.9 kg ha⁻¹ resulted in average plant densities of 100–474 plants m⁻². Total biomass production and oil yield were generally unaffected by plant density, but plant population influenced plant architecture and oil composition. Plants grown at low density had a more extensive development of umbellate fruiting structures and a lower proportion of leaf and stem tissue than did plants at high density. Carvone was higher in oil from widely spaced plants, while phellandrene, α-pinene, and dill ether (3,9-epoxy-1-p-menthene) were lower. Harvest date and plant density affected oil composition in a complementary manner. An early harvest or high plant density is preferable if herbaceous oil characteristics are desired, while a late harvest or low plant density is suitable when growing dill for seed or for a high-carvone oil.     

Fuel properties of oil from genetically altered Cuphea viscosissima

A genetically altered plant strain (Cuphea viscosissima VS-320) was identified which produces an oil with elevated levels of medium- and short-chain triglycerides. Previous studies have suggested that such an oil may be appropriate for use as a substitute for diesel fuel without chemical conversion of component triglycerides to methyl esters. This oil is also of interest for other industrial applications. This paper discusses the oil composition of C. viscosissima VS-320 and presents the analysis of several important alternative fuel screening properties of this oil: dynamic viscosity for shear rates of 1.617–64.69 s⁻¹ at temperatures of 25–80°C, boiling point at atmospheric pressure, temperature dependence of vapor pressure (from 40 to 760 mmHg for the 300–400°C temperature range), and heat of vaporization (ΔH_v). These properties have been established as indicators of fuel performance and can be used for initial screening of possible diesel fuel substitutes. These properties are compared to those of diesel, biodiesel, and vegetable oils. Analysis of these properties suggests that further genetic development of this plant as a source of diesel fuel is warranted.     

Synthesis and physical properties of mono-estolides with varying chain lengths

Saturated mono-estolide methyl esters and enriched saturated mono-estolide 2-EH esters were synthesized from oleic and different saturated fatty acids under three different synthetic routes. Estolide numbers (EN), the average number of fatty acid units added to a base fatty acid, varied with synthetic conditions. The attempts at obtaining saturated mono-estolide 2-EH esters, EN = 1, via distillation proved to be challenging, which lead to estolide samples with EN > 1 and the pour point values followed the same trend as the high EN estolides. The other synthetic routes provided saturated mono-estolide methyl esters with EN = 1. The resulting pour point values showed a linear relationship between the saturated capping chain length and pour point. As the saturated capping chain length increased the pour points also increased (higher temperatures): C-2 capped ?30 °C, C-10 capped ?12 °C, and C-18 capped 3 °C.The saturated mono-estolide methyl ester viscosities also showed an increase in viscosity at 40 and 100 °C as the saturated chain lengths increased. The viscosities for the C-4 saturated mono-estolide methyl ester was 9.5 cSt at 40 °C and 2.6 cSt at 100 °C, while medium chain length derivations (C-10 saturated mono-estolide methyl ester) were 19.7 cSt at 40 °C and 4.2 cSt at 100 °C, and at the longer chain length derivations (C-18 mono-estolide methyl esters) were 27.6 cSt at 40 °C and 10.7 cSt at 100 °C. In general, a new series of saturated oleic mono-estolide methyl esters were synthesized and physical properties were collected. The physical property data indicated that both chain length and EN affect low temperature properties.     

Changes in fatty acid composition of coriander (Coriandrum sativum L.) fruit during maturation

Changes in fatty acids were studied during maturation of coriander (Coriandrum sativum L.) fruits cultivated in the North-East of Tunisia (Charfine). The fruits matured in 55 days after flowering (DAF). Oil and petroselinic acid synthesis proceeded at a steady rate up to 32 DAF. The first results showed a rapid oil accumulation started at newly formed fruits (9.6 ± 0.2%) and continued until their full maturity (26.4 ± 0.5%). During fruit maturation, fatty acid profiles varied significantly among the nine stages of maturity. At the 32th DAF, palmitoleic, gadoleic, erucic and docosahexenoic acids were not detected and petroselinic acid had a highest amount (84.8 ± 4.5%). Fruits development resulted mainly in an increase of petroselinic acid and a decrease of palmitic acid (C16:0). At full maturity, the main fatty acids were petroselinic acid (80.9 ± 5.7%), followed by linoleic (13.6 ± 2.9%), palmitic (3.6 ± 0.1%) and stearic (0.7 ± 0.1%) acids. Saturated and polyunsaturated fatty acids decreased significantly and monounsaturated fatty acids increased during maturation of coriander fruit. Coriander fruits at the first four stages of maturity have a healthy nutritional value and the last five stages were with important economic and industrial applications. Results of this study indicate that the variation in the fatty acid composition of coriander fruit during maturation may be useful in understanding the source of nutritionally and industrially important fatty acids in this fruit. Coriander fruit is potentially an important source of petroselinic acid which has numerous industrial applications.     

Large applications of fertilizer N at planting affects seed protein and oil concentration and yield in the Early Soybean Production System

An inverse relationship between soybean [Glycine max (L.) Merr.] seed protein and oil concentration is well documented in the literature. A negative correlation between protein and yield is also often reported. The objective of this study was to determine the effect of high rates of N applied at planting on seed protein and oil. Nitrogen was surface-applied at soybean emergence at rates of 290 kg ha⁻¹ in 2002, 310 kg ha⁻¹ in 2003, and 360 kg ha⁻¹ in 2004. Eight cultivars ranging from Maturity Group II–IV were evaluated under the Early Soybean Production System (ESPS). However, not all cultivars were evaluated in all 3 years. Glyphosate herbicide was used in all 3 years and a non-glyphosate herbicide treatment was applied in 2002. Cultivars grown in 2003 were also evaluated under an application of 21.3 kg ha⁻¹ of Mn. All cultivar, herbicide, and Mn treatments were evaluated in irrigated and non-irrigated environments with fertilizer N (PlusN treatment) or without fertilizer N (ZeroN treatment). When analyzed over all management practices (years, cultivars, herbicide, and Mn treatments), the PlusN treatment resulted in a significant decrease in protein concentration (2.7 and 1.9%), an increase in oil concentration (2.2 and 2.7%), and a decrease in the protein/oil ratio (4.7 and 4.6%) for the irrigated and non-irrigated environments, respectively. However, the overall protein and oil yield increased with the application of fertilizer N at planting (protein: 5.0% irrigated, 12.7% non-irrigated and oil: 9.9% irrigated and 18.9% non-irrigated). These increases were due to the increase in seed yield with the application of large amounts of fertilizer at planting. Additionally, a significant correlation (r = 0.45, P = 0.0001) was found between seed protein concentration and seed yield. No significant correlation was found between seed oil concentration and seed yield. The data demonstrate the inverse relationship between protein and oil and indicate that large amounts of N applied at planting do not change this relationship.     

Chemical composition and profile characteristics of Osage orange Maclura pomifera (Rafin.) Schneider seed and seed oil

Studies were conducted on the properties of seeds and oil extracted from Maclura pomifera seeds. The following values (on a dry-weight basis) were obtained for M. pomifera seed, respectively: moisture 5.88%, ash 6.72%, oil 32.75% and the high protein content 33.89%. The carbohydrate content (20.76%) can be regarded as a source of energy for animals if included in their diets. The major nutrients (mg/100 g oil) were: potassium (421.65), calcium (218.56) and magnesium (185.00). The physicochemical properties of the oil include: the saponification number 174.57; the iodine value 141.43; the p-anisidine value 1.86; the peroxide value 2.33 meq O₂/kg; the acid value 0.66; the carotenoid content 0.59 mg/100 g oil; the chlorophyll content 0.02 (mg/100 g oil) and the refractive index 1.45. Polymorphic changes were observed in thermal properties of M. pomifera seed oil. This showed absorbency in the UV-B and UV-C ranges with a potential for use as a broad spectrum UV protectant. The main fatty acids of the crude oil were linoleic (76.19%), oleic (13.87%), stearic (6.76%) and palmitic acid (2.40%). The polyunsaturated triacylglycerols (TAGs) LLL, PLL, POL + SLL, OLL, OOL (L: linoleic acid, O: oleic, P: palmitic acid and S: stearic acid) acids were the major TAGs found in M. pomifera seed oil. A relatively high level of sterols making up 852.93 mg/100 g seed oil was present. The sterol marker, β-sitosterol, accounted for 81% of the total sterol content in the seed oil and is followed by campesterol (7.4%), stigmasterol (4.2%), lupeol (4.1%) and Δ⁵-avenesterol (3.2%). The seed oil was rich in tocopherols with the following composition (mg/100 g): α-tocopherol 18.92; γ-tocopherol 10.80; β-tocopherol 6.02 and δ-tocopherol 6.29. The results showed that M. pomifera seed oil could be used in cosmetic, pharmaceutical and food products.     

Evapotranspiration,yield, and water-use efficiency responses of Lesquerella fendleri at different growth stages

Lesquerella fendleri (Gray) Wats. is a potential new oilseed crop for the arid southwestern United States. Lesquerella seed oil with similar properties as castor oil is being considered as a domestic replacement for the imported castor oil. Development of new crops with low irrigation needs is of high priority. Because the most critical stage of sensitivity to moisture deficits has not been determined in Lesquerella species, the objectives of this study were: (i) to identify the most critical stage or stages for moisture deficit and, (ii) to determine the effect of moisture deficit on yield, yield components, oil and fatty acid composition. Two-year field studies were conducted at the New Mexico State University, Leyendecker Plant Science Research Center. The experimental design was a randomized complete block. The treatments consisted of (a) T1: Continuous favorable soil moisture [irrigated at 50% soil water depletion (SWD)]. (b) T2: Moisture stress (75% SWD) from establishment to initial flowering with no stress from flowering to final harvest (50% SWD). (c) T3: No stress imposed from establishment to initial flowering (50% SWD) followed by stress to final harvest (75% SWD). (d) T4: Moisture stress (75% SWD) from establishment to final harvest. The amount of water applied ranged from 810 to 729 mm for the first year, and 810 to 625 mm for the second year. Seed weight per plant and number of pods per plant were generally higher when water availability was maintained at or above 50% SWD throughout the growing season. Neither seed number per pod nor seed size was influenced by irrigation treatments. Lesquerella was more sensitive to water availability during flowering and seed development as a greater loss in seed yield occurred when irrigation was delayed to 75% SWD during that stage of development. Seed yield and dry matter production from the 2 year field studies were closely related to the seasonal cumulative evapotranspiration. For each millimeter of evapotranspiration, seed yield increased from 1.8 kg ha⁻¹ mm in 1994–1995 to 1.3 kg ha⁻¹ mm for 1995–1996. The dry matter production increased 13.4 kg ha⁻¹ for each mm increase in seasonal evapotranspiration during 1994–1995. This relationship was a second order polynomial with an R² of 0.86 during 1995–1996. The WUE_gr and WUE_dm were highest under the most favorable water availability conditions for growth and seed development. Delaying irrigation to 75% SWD throughout the crop growth period resulted in the lowest oil content. Lesquerolic acid content was not affected by irrigation during both the growing seasons.     

Evaluation of Camelina sativa oil as a feedstock for biodiesel production

The oilseed crop Camelina sativa (camelina) has lower production costs than oilseed rape in some climates. For this reason, the production of biodiesel-grade methyl ester from camelina oil was evaluated. The evaluation included quality assessment of esters produced in laboratory and pilot plant, an examination of methods of improving ester low-temperature properties, and vehicle trials. Laboratory esterifications gave ester yields similar to rape-seed oil. Six 350 kg batches of unrefined camelina oil with acid values from 3 to 6 were esterified in a pilot plant. Ester-specific properties were satisfactory with one exception; the iodine number of 155 far exceeded the value of 120 required by the relevant EU standard. Fuel-specific properties of the camelina methyl esters were largely within specification, though low-temperature behaviour could be a problem in some climates. This problem could be overcome by the use of suitable pour-point depressants or by blending with diesel oil. In vehicle tests, the reduction in fuel economy with camelina ester was similar to that with biodiesel from other feedstocks. The high iodine number of camelina methyl ester did not lead to a more rapid deterioration of the lubricating oil. However, it was concluded that further engine trials would be needed before the use of camelina ester as an undiluted vehicle fuel could be recommended.     

Bio-oil production from soybean (Glycine max L.); fuel properties of Bio-oil

Soybean oil cake (SOC) has been studied to produce bio-oil in a fixed-bed pyrolysis unit. The effect of pyrolysis parameters on the product yields and compositions were investigated. The highest bio-oil yield of a ca 25.8 wt.% was obtained at 400 °C pyrolysis temperature with a heating rate of 50 °C/min for particles of 0.425–0.600 mm in size. The various characteristics of bio-oil acquired under these conditions were identified. The empirical formula of bio-oil with a calorific value of 33.6 MJ/kg was established as CH_1.37O_0.15N_0.14. The chemical characterization studies showed that the bio-oil obtained from SOC might be a potentially valuable source as renewable fuel and chemical feedstocks.     

Characterization and degradation of lignin from steam explosion of pine and corn stalk of lignin: The role of superoxide ion and ozone

Steam explosion of corn stalk in the presence of 3% sulphuric acid at 200 °C for 5 min gave the highest recovery of lignin. Lignin has M_w = 2640 and M_z = 93,994. In the UV spectrum absorptions at λ = 231 and 280 nm were recorded. ¹H NMR spectrum of lignin showed signals attributable to cinnamaldehyde units, guaiacyl units, and syringyl units. Syringyl and guaiacyl units are in 1:1 ratio. ¹³C NMR spectrum showed signals for guaiacyl, syringyl, and p-hydroxyphenyl units. The spectrum showed a prevalence of guaiacyl units. The ¹³C NMR spectrum is in agreement with the presence of cinnamic units. The same characterization was performed on lignin from pine. The irradiation of lignin from pine from steam explosion process in the presence of oxygen, in conditions described for the formation of superoxide ion, for different irradiation time was followed isolating the lignin and determining the average molecular weight. The experiments showed that, until 8 h irradiation, M_n decreases, while M_w and M_z increases. After 8 h irradiation an inverse behaviour was observed, with an increase of M_n and a decrease of M_w and M_z. These results are in agreement with an initial polymerization process followed by a photoinduced degradation. Ozonization was carried out in acetonitrile–methanol solution. The reaction showed a zero-order kinetics. After 50 min the average molecular weight of lignin is the half. The reaction mixture was analyzed by using GC–MS. Oxalic acid was determined.     

Polyphenolic extract and essential oil quality of Thymus zygis ssp. gracilis shrubs cultivated under different watering levels

Thymus zygis ssp. gracilis shrubs were cultivated as an experimental crop under different watering level, in order to achieve 81, 63, 44 and 30% of the local potential evapotranspiration (ETo). After 4 years of cultivation, thyme leaves were analyzed on the basis of their essential oil (yield and quality), total phenolic content, free radical-scavenging activity and polyphenolic profile.Essential oil yield values ranged between (2.3 ± 0.7) and (3.6 ± 0.7)% for 81 and 30% ETo equivalent, respectively. The comparison of essential oil production at the 2nd and 4th years of cultivation showed that using watering levels higher than 30% ETo equivalents reduced significantly (P < 0.05) the essential oil yielded by these shrubs with time.Analysis of total phenolic content, polyphenolic profile, and radical scavenging activity were performed using post-distillation dry leaves. Total phenolic content values ranged from (122.2 ± 19.3) to (108.5 ± 19.2) mg of gallic acid equivalents (GAEs)/g of dry plant for the highest and lowest watering level treatment, respectively. Regarding the polyphenolic profile, rosmarinic acid, followed by apigenin, ferulic, carnosic and caffeic acids, was the phenolic component quantified at the highest concentrations. Radical-scavenging activities (IC₅₀) concentrations varied from (3.7 ± 1.6) mg/mL for 81% ETo to (7.4 ± 2.3) mg/mL 30% ETo.In spite of the intra-specific variability detected, the individual analysis of shrubs has allowed the selection of plants which are characterised by having adequate levels of essential oil and polyphenolic extract (yield and quality), almost all of them being cultivated under a 60% ETo watering level. These selected shrubs will allow us to make further vegetative propagations in order to obtain homogeneous field crops with plants of contrasted quality cultivated under a 60% ETo watering level.     

Determination of selection criteria for seed yield and seed oil content in Vernonia (Vernonia galamensis variety ethiopica)

The magnitude of relationships among different traits is important in plant breeding programs to identify the best selection criteria and improve the efficiency of selection. This study was conducted to determine relationships between seed yield and seed oil content with other important agronomic traits among 36 diverse accessions of Vernonia (Vernonia galamensis variety ethiopica), a potentially novel industrial oilseed crop. Field evaluations were conducted during 2005, 2006 and 2007 at the Limpopo Province in South Africa using a partially balanced lattice design. Simple correlation and path analysis were performed to identify the best selection criteria for increased seed yield and seed oil content. Simple correlation and path analyses revealed that the formation of productive primary heads strongly associated with increased seed yield (r_g = 0.81, p < 0.001). Furthermore, path analysis indicated selection for increased number of primary heads would bring about simultaneous and favorable change towards reduced days to maturity and shorter plant height. Further associational study of traits with seed oil content showed a significant (p < 0.05) correlation between oil content with 1000 seed weight (r_g = 0.4). The path analysis, however, exposed seed yield followed by 1000 seed weight with significant direct effect on seed oil content. The study demonstrated that selection for increased number of productive primary heads is the principal selection criterion to improve seed yield. Whereas selection for 1000 seed weight and increased seed yield serve as major selection criteria to achieve increased oil content in V. galemanesis.     

Castor yield in response to planting date at four locations in the south-central United States

Oilseed crops have potential use in the production of biodiesel. Currently, most oil going into the production of biodiesel is derived from soybean (Gylcine max L.) grown in the central U.S. Inability of the southeastern states to compete with central U.S. soybean production has lead to the search for alternative oilseeds. The high oil content and unique properties of castor (Ricinus communis L.) give it potential for use as biodiesel. However, there is limited information on potential yields, adaptation, and planting dates of adaptation of modern castor cultivars. This study was designed to determine potential yields and ideal planting dates of castor at various locations in Mississippi and Tennessee. A single castor cultivar was sequentially planted at 14 day intervals, at four locations, ranging from Memphis, TN south to Poplarville, MS. Annual planting occurred from 1 April to 1 July at all locations, except the 1 April planting date was excluded from the two northern locations. Mean yield ranged from 89 to 1954 kg ha^?1. Northern most locations and earliest plantings resulted in the greatest yields. Precocious flowering of castor immediately after 1 April planting at Shubuta, MS was associated with a lower yield. This flowering event was also observed at Poplarville, but did not significantly affect yield. The yield reductions due to southern planting coupled with precocious flowering at the southern locations seem to indicate a limited zone of adaptation for castor.     

The efficiency of nitrogen fertiliser for rice in Bangladeshi farmers’ fields

Bangladesh is currently self sufficient in rice (Oryza sativa L.), which accounts for approximately 80% of the total cropped area, and 70% of the cost of crop production. However, farmers are increasingly concerned about the perceived decline in productivity, expressed as the return on fertiliser inputs. Agronomic efficiency is a measure of the increase in grain yield achieved per unit of fertiliser input that can provide a way to quantify the observation of farmers. This study indicates that the yields achieved where only P and K fertiliser were applied ranged from 3–5 t ha⁻¹, indicating good soil fertility, particular in terms of soil N supply (37–112 kg N ha⁻¹). However, at recommended rates and at rates used by farmers, the yield response to application of fertiliser N was low. Data shows that grain yields were significantly correlated in both years (R² = 0.77 and R² = 0.67) with plant uptake in nitrogen. The internal nitrogen use efficiency seems to confirm that sink formation was limited by factors other than nitrogen. Low agronomic efficiency (5–19 kg grain kg⁻¹ N) was caused by poor internal efficiency (45–73 kg grain kg⁻¹ N), rather than low supply of soil N or loss of fertiliser N. Thus, often the applications of large amounts of N fertiliser (39–175 kg N ha⁻¹) by farmers to increase yields of high yielding variety Boro rice were not justified agronomically and ecologically. A rate of 39 kg N ha⁻¹ is very low, hardly an environmental threat. No one single factor could be identified to explain the low internal efficiency. Therefore, it is concluded that the data presented tend to confirm the indication that yields are limited by a factor other than nitrogen, which could be crop establishment, plant density, water or pest management, micro-nutrients deficiency, poor seed and transplanted seedling quality, varieties and low radiation.     

Synthesis of Jatropha curcas oil-based biodiesel in a pulsed loop reactor

Jatropha curcas oil (JCO) has a high content of free fatty acids and has been used extensively as a feedstock in biodiesel production. In the present study, the transesterification reaction of JCO to Jatropha curcas methyl ester (biodiesel) was performed in a continuous pulsed loop reactor under atmospheric conditions. The JCO was pre-treated prior to the reaction to reduce the free fatty acid content to below 1% (w/w). The operating parameters of the loop reactor were optimised based on the conversion of the JCO to Jatropha curcas biodiesel and included reaction temperature, molar ratio of oil to MeOH, reaction time and oscillation frequency. The findings show that the highest reaction conversion of 99.7% (w/w) was achieved using KOH catalyst and 98.8% conversion was obtained using NaOCH₃ catalyst. The optimal operating conditions were a molar ratio of 6:1, an oscillation frequency of 6 Hz, temperature of 60 °C, feedstock FFA content of 0.5% (w/w) and only 10 min of reaction time. As a commercial commodity, the physical properties of biodiesel were analysed, and they compared well with the characteristics of fossil-based diesel fuel.     

Anti-Rhizoctonia solani activity by Desmos chinensis extracts and its mechanism of action

The objectives of this study were to investigate the mechanisms of action and to evaluate the potential application of Desmos chinensis extracts for controlling rice sheath blight. The dichloromethane extract from D. chinensis demonstrated high antifungal activity against Rhizoctonia solani. The extract was shown to have anti-R. solani activity with minimum inhibitory concentration (MIC) and minimum fungicidal concentration values ranging from 31.2 to 62.5 μg mL⁻¹ and from 62.5 to 500 μg mL⁻¹, respectively. Bioautography on thin-layer chromatography plates demonstrated antifungal activity of the extract with an R_f value of 0.33. A total of 7 compounds, 2 benzoate esters (benzyl benzoate and benzyl 2-hydroxybenzoate), 2 sesquiterpenoids (α-eudesmol and β-eudesmol), 1 aromatic alcohol (benzyl alcohol), 1 aromatic ketone (acetophenone) and 1 diterpenoid (phytol), were detected and identified using gas chromatography–mass spectrometry analysis. Electron micrographs confirmed the effects of the extract on morphological and ultrastructural alterations in the treated fungal cells. The micrographs of the mycelia treated with the extract at 4MIC illustrated aberrant morphology such as shrinkage, partial distortion and globular structures of different sizes along the surface of the mycelia. Damaging membranous structures including disruption of the cell membrane, partial loss of nuclear membranes, and depletion of hyphal cytoplasm and membranous organelles were observed. Foliar application of D. chinensis extract at a concentration of 2 mg mL⁻¹ on rice markedly decreased sheath blight severity. It was concluded that the application of D. chinensis extract can be used as a botanical fungicide to control rice sheath blight.