Local communities in southern Africa derive many benefits from marula [Sclerocarya birrea（A.Rich.） Hochst.subsp.caffra（Sond.） Kokwaro].These include the contribution of this species towards health,nutrition,food s...Local communities in southern Africa derive many benefits from marula [Sclerocarya birrea（A.Rich.） Hochst.subsp.caffra（Sond.） Kokwaro].These include the contribution of this species towards health,nutrition,food security and conservation by sharing local skills and knowledge related to it.Marula fruits can be eaten fresh,squeezed to make juice,brewed in traditional beer or used to make jam and jelly.The kernels are also edible and can be pressed to extract oil for cooking and cosmetics,i.e.,for skin and hair application.The bark,roots,seeds and leaves are exploited for traditional medicinal purposes.Marula has acquired significant commercial value since its fruits and other products have entered local,regional and international trade in southern Africa.To diver-sify fruit production and satisfy the increasing demands for this resource,several domestication initiatives have been carried out at regional and international levels.The accumulated knowledge and skills relevant to the establishment and commercialization of marula therefore provide an effective guide in areas where marula remains undomesticated or underutilized.We discuss the great importance of marula in southern Africa to reveal its great potential to regions where it remains unexploited.展开更多
To identify and develop alternative and renewable sources of fuel for the transport sector is a present challenge for engineers and researchers. This work was carried out to assess yield of marula (Sclero carrya/birre...To identify and develop alternative and renewable sources of fuel for the transport sector is a present challenge for engineers and researchers. This work was carried out to assess yield of marula (Sclero carrya/birrea) nut and chemical properties of crude marula nut oil for biodiesel production in Botswana. Chemical extraction of marula oil was done to establish actual oil content by use of hexane / iso-propyl alcohol solvent in a soxhlet set up. Distillation was carried out on a Rotavapor system prior to oil purging using nitrogen gas. The results indicated that marula nuts have about 58.6% oil content. Characterisation of the extracted crude oil was carried out to determine its chemical composition using the Waters GCT Premier Time of Flight (TOF) Mass Spectrometer (MS) coupled to the Agilent 6890N Gas Chromatography (GC) system. Ethyl oleate (ethyl ester) was found to be the dominant fatty acid. Trans-Oleic acid was also abundant but could not be quantified because it was not found in the standard mixture. Crude marula oil was also found to have an ester content of 93.7%, acid value of 1.4mgKOH/g, and free fatty acid content of 0.7%. These results are marginally out of specifications for biodiesel by international standards, implying that crude marula oil is a potential substrate for biodiesel production.展开更多
The quest for biofuel production and use in Botswana is driven by factors including volatile oil prices, need for fuel security, potential for job creation, potential reduction in greenhouse gas emissions, and economi...The quest for biofuel production and use in Botswana is driven by factors including volatile oil prices, need for fuel security, potential for job creation, potential reduction in greenhouse gas emissions, and economic diversification. In line with national efforts to come up with energy sources that are both environmentally friendly and sustainable, this work was carried out to compare performance properties of native crude marula (Sclerocarya birrea) seed oil and petrodiesel fuel on a variable compression engine test rig with automatic data acquisition set up. Parameters such as engine torque, brake power and specific fuel consumption were measured at different loads for the two fuels. The results indicate that engine performance when powered with crude marula oil compares favourable with those for petrodiesel. Optimum numerical values for engine torque, brake power and specific fuel consumption were 28.2 Nm, 6.27 W and 0.34 g/kWh respectively for petrodiesel, and 22.7 Nm, 6.6 W, 0.33 g/kWh respectively for crude marula oil. The engine performance was also analysed for same parameters, namely, engine torque, brake power and specific fuel consumption when powered using the same fuels over a range of compression ratios while the load was fixed at 80%. Optimum numerical values for engine torque, brake power and specific fuel consumption were 27.2 Nm, 3.67 W and 0.59 g/kWh respectively for petrodiesel, and 26.3 Nm, 3.6 W, 0.34 g/kWh respectively for crude marula oil. The results indicate that compression ratio of 16:1 yields optimum engine performance in terms of engine torque and brake power for both fuels under review. However, marula oil fuel recorded smooth steady increase in performance profile across all compression ratios which out-performs petrodiesel on lower compression ratios for engine torque and brake power, and is largely better than petrodiesel on fuel consumption.展开更多
Sclerocarya birrea(Marula)seed oil was extracted and characterized for its physico-chemical properties and fatty acid compositions,respectively,by using standardized laboratory methods of the Association of Official a...Sclerocarya birrea(Marula)seed oil was extracted and characterized for its physico-chemical properties and fatty acid compositions,respectively,by using standardized laboratory methods of the Association of Official and Analytical Chemist(AOAC).The fuel and lubrication properties of marula oil were also determined by using the ASTM methods,and the oil was evaluated in terms of its antiwear,viscometrics,volatility,stability,environmental compatibility properties and energy content.It was found that the high percentage of mono-unsaturated oleic acid(73.6%)provided the oiliness that makes marula oil a natural alternative to genetically modify high oleic acid sunflower oil used in biodiesel production.The aggregate properties of seed oiliness as exemplified by the high oleic acid content,high saponification value(178.6 mg/KOH)and viscosity(41 mm2/s)makes marula oil to be prospective based oil for engine crank case biolubricants with antiwear and friction reduction properties.However,the higher oil viscosity exhibited by marula seed oil in comparison to diesel could pose some durability problems to compression ignition engines,when used directly as fuel.Nonetheless,the reduction of oil viscosity would be required by heating,blending with diesel fuel,or by transesterification to forestall the risk of engine failure resulting from the use of unmodified marula oil.The flash point of marula oil(235℃)is somewhat close to that of monograde SAE 40 mineral oil(240℃),and appreciably higher than that of diesel fuel(52℃).The high flash point makes the seed oil less flammable and ensures safer handling and transportation.While,the low pour point(-13.7℃)ensures the oil usability for engines at cold start and under low load conditions.The oxidation stability of marula oil is ascribed to the traces of natural antioxidants presented in the oil and improves the oil’s shelf life,notwithstanding the high peroxide value(4.58 mequiv/kg),and linolenic acid content(0.3%),which ought to have been the culprit for lipolytic hydrolysi展开更多
基金supported by the "948" Project of State Forestry Administration of China (Grant No. 2011-4-43) the National Science and Technology Major Project of China (Grant No. 2009ZX09308-002)
文摘Local communities in southern Africa derive many benefits from marula [Sclerocarya birrea（A.Rich.） Hochst.subsp.caffra（Sond.） Kokwaro].These include the contribution of this species towards health,nutrition,food security and conservation by sharing local skills and knowledge related to it.Marula fruits can be eaten fresh,squeezed to make juice,brewed in traditional beer or used to make jam and jelly.The kernels are also edible and can be pressed to extract oil for cooking and cosmetics,i.e.,for skin and hair application.The bark,roots,seeds and leaves are exploited for traditional medicinal purposes.Marula has acquired significant commercial value since its fruits and other products have entered local,regional and international trade in southern Africa.To diver-sify fruit production and satisfy the increasing demands for this resource,several domestication initiatives have been carried out at regional and international levels.The accumulated knowledge and skills relevant to the establishment and commercialization of marula therefore provide an effective guide in areas where marula remains undomesticated or underutilized.We discuss the great importance of marula in southern Africa to reveal its great potential to regions where it remains unexploited.
文摘To identify and develop alternative and renewable sources of fuel for the transport sector is a present challenge for engineers and researchers. This work was carried out to assess yield of marula (Sclero carrya/birrea) nut and chemical properties of crude marula nut oil for biodiesel production in Botswana. Chemical extraction of marula oil was done to establish actual oil content by use of hexane / iso-propyl alcohol solvent in a soxhlet set up. Distillation was carried out on a Rotavapor system prior to oil purging using nitrogen gas. The results indicated that marula nuts have about 58.6% oil content. Characterisation of the extracted crude oil was carried out to determine its chemical composition using the Waters GCT Premier Time of Flight (TOF) Mass Spectrometer (MS) coupled to the Agilent 6890N Gas Chromatography (GC) system. Ethyl oleate (ethyl ester) was found to be the dominant fatty acid. Trans-Oleic acid was also abundant but could not be quantified because it was not found in the standard mixture. Crude marula oil was also found to have an ester content of 93.7%, acid value of 1.4mgKOH/g, and free fatty acid content of 0.7%. These results are marginally out of specifications for biodiesel by international standards, implying that crude marula oil is a potential substrate for biodiesel production.
文摘The quest for biofuel production and use in Botswana is driven by factors including volatile oil prices, need for fuel security, potential for job creation, potential reduction in greenhouse gas emissions, and economic diversification. In line with national efforts to come up with energy sources that are both environmentally friendly and sustainable, this work was carried out to compare performance properties of native crude marula (Sclerocarya birrea) seed oil and petrodiesel fuel on a variable compression engine test rig with automatic data acquisition set up. Parameters such as engine torque, brake power and specific fuel consumption were measured at different loads for the two fuels. The results indicate that engine performance when powered with crude marula oil compares favourable with those for petrodiesel. Optimum numerical values for engine torque, brake power and specific fuel consumption were 28.2 Nm, 6.27 W and 0.34 g/kWh respectively for petrodiesel, and 22.7 Nm, 6.6 W, 0.33 g/kWh respectively for crude marula oil. The engine performance was also analysed for same parameters, namely, engine torque, brake power and specific fuel consumption when powered using the same fuels over a range of compression ratios while the load was fixed at 80%. Optimum numerical values for engine torque, brake power and specific fuel consumption were 27.2 Nm, 3.67 W and 0.59 g/kWh respectively for petrodiesel, and 26.3 Nm, 3.6 W, 0.34 g/kWh respectively for crude marula oil. The results indicate that compression ratio of 16:1 yields optimum engine performance in terms of engine torque and brake power for both fuels under review. However, marula oil fuel recorded smooth steady increase in performance profile across all compression ratios which out-performs petrodiesel on lower compression ratios for engine torque and brake power, and is largely better than petrodiesel on fuel consumption.
文摘Sclerocarya birrea(Marula)seed oil was extracted and characterized for its physico-chemical properties and fatty acid compositions,respectively,by using standardized laboratory methods of the Association of Official and Analytical Chemist(AOAC).The fuel and lubrication properties of marula oil were also determined by using the ASTM methods,and the oil was evaluated in terms of its antiwear,viscometrics,volatility,stability,environmental compatibility properties and energy content.It was found that the high percentage of mono-unsaturated oleic acid(73.6%)provided the oiliness that makes marula oil a natural alternative to genetically modify high oleic acid sunflower oil used in biodiesel production.The aggregate properties of seed oiliness as exemplified by the high oleic acid content,high saponification value(178.6 mg/KOH)and viscosity(41 mm2/s)makes marula oil to be prospective based oil for engine crank case biolubricants with antiwear and friction reduction properties.However,the higher oil viscosity exhibited by marula seed oil in comparison to diesel could pose some durability problems to compression ignition engines,when used directly as fuel.Nonetheless,the reduction of oil viscosity would be required by heating,blending with diesel fuel,or by transesterification to forestall the risk of engine failure resulting from the use of unmodified marula oil.The flash point of marula oil(235℃)is somewhat close to that of monograde SAE 40 mineral oil(240℃),and appreciably higher than that of diesel fuel(52℃).The high flash point makes the seed oil less flammable and ensures safer handling and transportation.While,the low pour point(-13.7℃)ensures the oil usability for engines at cold start and under low load conditions.The oxidation stability of marula oil is ascribed to the traces of natural antioxidants presented in the oil and improves the oil’s shelf life,notwithstanding the high peroxide value(4.58 mequiv/kg),and linolenic acid content(0.3%),which ought to have been the culprit for lipolytic hydrolysi
