Greenhouse gas emissions and energy assessment of modified diesohol using cashew nut shell liquid and biodiesel as additives

Abstract

The development of sustainable biofuel production has been promoted in many countries to reduce the use of fossil fuel. This work analyses the life cycle global warming impact, net energy and fossil energy ratios for two alternatives diesohol (diesel/bioethanol) fuels and a new modified diesohol using distilled cashew nut shell liquid/biodiesel. Owing to the molecular structure, biodiesel and distilled cashew nut shell liquid can be used as emulsifier to stabilise the diesohol as well as to slightly reduce the portion of diesel in the blend. The uncertainty analysis, land use change impact, and cost performance comparison in the life cycle assessment were also considered. The well-to-wheel analysis of the biofuel life cycle was used as a system boundary. The results indicated that the global warming impact and the energy performance were not significantly different among the three diesohol alternatives. The global warming impact of all studied alternative fuels was estimated as 68.22–75.69 kg CO2 equivalent/1000 MJ, which was 18–26% lower than that of conventional diesel. This was due to the environmental benefits obtained from biodiesel, bioethanol, and distilled cashew nut shell liquid, avoiding CO2 emissions from combustion in fuel blends because they are of biogenic origin. The substitution of diesel by fuel blends resulted in the net energy ratios (1.01–1.08) and fossil energy ratios (0.96–1.04) of the three alternatives diesohol fuels that were 14–19% and 9–16% higher than that of the conventional diesel. The fossil energy ratios of fuel blends were slightly lower than the net energy ratios by 3.70–4.95%. The LCIA result showed that, according to the uncertainty analysis, the global warming impact from well-to-wheel analysis of the modified diesohol fuel with 85 vol.% diesel, 15 vol.% bioethanol and 20 vol.% (based on the combined volume of diesel and bioethanol) biodiesel was, with 100% probability, less than that of other disohol alternatives studied. The results indicated that alternative diesohol fuel in the case of 15% bioethanol was an environmental and economic superior choice of all studied alternatives fuels because of its lowest global warming impact (with and without LUC), while providing the highest energy efficiency with the net energy ratio and fossil energy ratio of 1.08 and 1.04, respectively. To improve the performance in terms of environmental and eonomic perspectives, the integration of fossil fuels and biofuels would improve the sustainable choices and promote the value-added domestic materials from renewable resources for transportation fuels in Thailand.