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Abstract Like ester type biodiesel fuel, green diesel is a next generation transportation fuel emerging due to the need for a renewable replacement of internal combustion engine fuel, which is also fully compatible with existing automotive powertrain systems. Besides other limitations, the main obstacle for wider application of such renewable fuels is their relatively high production cost, depending mainly on the raw material cost and the application of more efficient processing technology. Green diesel and ester type biodiesel can be produced from waste vegetable oil by catalytic hydrogenation, homogeneous alkali catalysed transesterification and supercritical non-catalytic transesterification. Techno-economic analysis and the sensitivity analysis reveal that economics of these production technologies strongly depend on the process unit capacity and the cost of feedstock. Green diesel production by catalytic hydroprocessing located in a petroleum refinery appears to be the most cost effective option for unit capacity close to and above 200,000 tonnes/year. Conventional ester biodiesel process and non-catalytic ester biodiesel process under supercritical conditions are less profitable at specified capacity. Unit capacities of the investigated processes which are below 100,000 tonnes/year are likely to result in negative net present values after 10 years of project lifetime.

Abstract Like ester type biodiesel fuel, green diesel is a next generation transportation fuel emerging due to the need for a renewable replacement of internal combustion engine fuel, which is also fully compatible with existing automotive powertrain systems. Besides other limitations, the main obstacle for wider application of such renewable fuels is their relatively high production cost, depending mainly on the raw material cost and the application of more efficient processing technology. Green diesel and ester type biodiesel can be produced from waste vegetable oil by catalytic hydrogenation, homogeneous alkali catalysed transesterification and supercritical non-catalytic transesterification. Techno-economic analysis and the sensitivity analysis reveal that economics of these production technologies strongly depend on the process unit capacity and the cost of feedstock. Green diesel production by catalytic hydroprocessing located in a petroleum refinery appears to be the most cost effective option for unit capacity close to and above 200,000 tonnes/year. Conventional ester biodiesel process and non-catalytic ester biodiesel process under supercritical conditions are less profitable at specified capacity. Unit capacities of the investigated processes which are below 100,000 tonnes/year are likely to result in negative net present values after 10 years of project lifetime.

A design of experiments analysis was performed to investigate the effects of pilot quantity, combustion phasing and exhaust gas recirculation on performance and emissions in a gasoline partially premixed combustion to find out the optimal combination of the all varied parameters. The experimental activities were performed on a light-duty Volvo Euro 6 diesel engine. The test was performed under steady-state operating conditions, nine test points were chosen inside the operating area of the New European Driving Cycle and the Worldwide Harmonized Light vehicles Test Cycles. A fractional factorial analysis in partially premixed combustion on the single and combined effect of the main engine calibration parameters and a global comparison between partially premixed combustion and conventional diesel combustion on the engine performance and emissions adopting the optimal calibration parameters obtained from design of experiments analysis for both combustion modes analysed were presented. The purpose was to obtain the calibration parameters setting that permits to achieve high efficiency and low emissions as well. The partially premixed combustion results show the highest efficiency and lowest NOx emissions adopting a high exhaust gas recirculation rate combined with advanced combustion phasing and lower pilot quantity. Higher efficiency, up to 2.0% units, was obtained in partially premixed combustion with respect to the conventional diesel combustion due to the lower heat transfer loss. Lower soot (about two times) and NOx (about -0.5 g/kWh) levels with partially premixed combustion were obtained and compared to conventional diesel combustion at the same exhaust gas recirculation level. A reduction of about 5% of CO2 and fuel consumption with a 50% of reduction on NOx and soot simultaneously were obtained for partially premixed combustion on the New European Driving Cycle estimation results with respect to the diesel combustion. The information derived from this work are useful to develop and calibrate a light-duty engine that operate in gasoline partially premixed combustion mode achieving NOx close to the Euro 6 limit without adopting any after treatment system.

A design of experiments analysis was performed to investigate the effects of pilot quantity, combustion phasing and exhaust gas recirculation on performance and emissions in a gasoline partially premixed combustion to find out the optimal combination of the all varied parameters. The experimental activities were performed on a light-duty Volvo Euro 6 diesel engine. The test was performed under steady-state operating conditions, nine test points were chosen inside the operating area of the New European Driving Cycle and the Worldwide Harmonized Light vehicles Test Cycles. A fractional factorial analysis in partially premixed combustion on the single and combined effect of the main engine calibration parameters and a global comparison between partially premixed combustion and conventional diesel combustion on the engine performance and emissions adopting the optimal calibration parameters obtained from design of experiments analysis for both combustion modes analysed were presented. The purpose was to obtain the calibration parameters setting that permits to achieve high efficiency and low emissions as well. The partially premixed combustion results show the highest efficiency and lowest NOx emissions adopting a high exhaust gas recirculation rate combined with advanced combustion phasing and lower pilot quantity. Higher efficiency, up to 2.0% units, was obtained in partially premixed combustion with respect to the conventional diesel combustion due to the lower heat transfer loss. Lower soot (about two times) and NOx (about -0.5 g/kWh) levels with partially premixed combustion were obtained and compared to conventional diesel combustion at the same exhaust gas recirculation level. A reduction of about 5% of CO2 and fuel consumption with a 50% of reduction on NOx and soot simultaneously were obtained for partially premixed combustion on the New European Driving Cycle estimation results with respect to the diesel combustion. The information derived from this work are useful to develop and calibrate a light-duty engine that operate in gasoline partially premixed combustion mode achieving NOx close to the Euro 6 limit without adopting any after treatment system.

Thermophilic co-digestion of sewage sludge with three different doses of trapped grease waste (GW) from the pre-treatment of a WWTP has been assessed in a CSTR bench-scale reactor. After adding 12% and 27% of grease waste (on COD basis), the organic loading rate increased from 2.2 to 2.3 and 2.8 kgCOD m-3 d-1 respectively, and the methane yield increased 1.2 and 2.2 times. Further GW increase (37% on COD basis) resulted in an unstable methane yield and in long chain fatty acids (LCFA) accumulation. Although this inestability, the presence of volatile fatty acids in the effluent was negligible, showing good adaptation to fats of the thermophilic biomass. Nevertheless, the presence of LCFA in the effluent worsens its dewatering properties. Specific methanogenic activity tests showed that the addition of grease waste ameliorates the acetoclastic activity in detriment of the hydrogenotrophic activity, and suggests that the tolerance to LCFA can be further enhanced by slowly increasing the addition of lipidrich materials.

Thermophilic co-digestion of sewage sludge with three different doses of trapped grease waste (GW) from the pre-treatment of a WWTP has been assessed in a CSTR bench-scale reactor. After adding 12% and 27% of grease waste (on COD basis), the organic loading rate increased from 2.2 to 2.3 and 2.8 kgCOD m-3 d-1 respectively, and the methane yield increased 1.2 and 2.2 times. Further GW increase (37% on COD basis) resulted in an unstable methane yield and in long chain fatty acids (LCFA) accumulation. Although this inestability, the presence of volatile fatty acids in the effluent was negligible, showing good adaptation to fats of the thermophilic biomass. Nevertheless, the presence of LCFA in the effluent worsens its dewatering properties. Specific methanogenic activity tests showed that the addition of grease waste ameliorates the acetoclastic activity in detriment of the hydrogenotrophic activity, and suggests that the tolerance to LCFA can be further enhanced by slowly increasing the addition of lipidrich materials.

Residential energy consumption in China increased dramatically over the period of 2002-2010. In this paper, we undertake a decomposition analysis of changes in energy use by Chinese households for five energy-using activities: space heating/cooling, cooking, lighting and electric appliances. We investigate to what extent changes in energy use are due to changes from appliances and to change in floor space, population and energy mix. Our decomposition analysis is based on the logarithmic mean Divisia index technique using data from the China statistical yearbook and China energy statistical yearbook in the period of 2002-2010. According to our results, the increase in energy-using appliances is the biggest contributor to the increase of residential energy consumption during 2002-2010 but the effect declines over time, due to energy efficiency improvements in those appliances. The second most important contributor is floor space per capita, which increased with 28%. Of the four factors, population is the most stable factor and energy mix is the least important factor. We predicted electricity use, with the help of regression-based predictions for ownership of appliances and the energy efficiency of appliances. We found that electricity use will continue to rise despite a gradual saturation of demand

Residential energy consumption in China increased dramatically over the period of 2002-2010. In this paper, we undertake a decomposition analysis of changes in energy use by Chinese households for five energy-using activities: space heating/cooling, cooking, lighting and electric appliances. We investigate to what extent changes in energy use are due to changes from appliances and to change in floor space, population and energy mix. Our decomposition analysis is based on the logarithmic mean Divisia index technique using data from the China statistical yearbook and China energy statistical yearbook in the period of 2002-2010. According to our results, the increase in energy-using appliances is the biggest contributor to the increase of residential energy consumption during 2002-2010 but the effect declines over time, due to energy efficiency improvements in those appliances. The second most important contributor is floor space per capita, which increased with 28%. Of the four factors, population is the most stable factor and energy mix is the least important factor. We predicted electricity use, with the help of regression-based predictions for ownership of appliances and the energy efficiency of appliances. We found that electricity use will continue to rise despite a gradual saturation of demand