Due to the reduction of fossil fuels’ resources and their contribution to environmental problems, biodiesel fuels have attracted significant attention as substitutes for diesel fuels. However, since their NOₓ emissions are higher than that of diesel fuels in most cases and also because of their higher viscosity than diesel, fuel additives are used to enhance their properties and reduce emissions. In this study, the effect of n-hexane and n-hexadecane addition to biodiesel and diesel fuels on exhaust emissions and performance of a single-cylinder diesel engine was investigated by using grey-based Taguchi method. Fuel additive, the additive amount, and fuel type were considered as the operating parameters. Three fuel types including diesel, rapeseed oil biodiesel, and cottonseed oil biodiesel were used in this investigation, while n-hexane and n-hexadecane were considered as the two fuel additives. As well as, three levels were assigned to the additive amount which were 4, 8, and 12%. Based on the operating parameters and their levels, the plan of experiments was generated according to L₁₈ orthogonal array. Using grey relational analysis, this multi-response optimization problem was first transformed into a single response optimization. Then, this single system response, which is known as grey relational grade, was utilized in Taguchi approach for statistical evaluations. The results demonstrated that rapeseed was the best selection for fuel type compared to cottonseed and diesel in order to have the optimum system responses and hexadecane gave better results for system optimization in comparison with hexane additive. As well as, the analysis of variance showed that fuel type was the predominant operating factor influencing the grey relational grade which means fuel type was the most important parameter in the simultaneous optimization of exhaust emissions and engine performance. The Taguchi results also revealed that the optimum condition of engine performance and exhaust emissions happened when engine was fueled with rapeseed biodiesel containing 12% hexadecane as an additive. The confirmation test result validated the reliability of Taguchi approach in this investigation.

Ruminant livestock production processes are the major sources of methane production in agriculture sector triggering global environmental pollution. Above 90% of world buffalo population present in Asian countries, India ranks first and contributes significantly to the environmental pollution by enteric methane emissions. In this study, we examined the effect of dietary composite feed additive supplementation on ruminal methane production, nutrient utilization, milk production and immune status of buffaloes (Bubalus bubalis). Eighteen lactating Murrah (Bubalus bubalis) buffaloes at early stage of lactation were divided into two groups of nine animals and fed a composite feed additive [consisted of (%, w/w) dried and ground leaves of Cordia dichotoma and Holoptelea integrifolia, 31.4 each; garlic oil, 0.6; sodium nitrate, 3.1; magnesium sulphate, 8.4; mustard oil, 12.6 and cottonseed oil, 12.5] which contained an ideal combinations of methane inhibitors, alternate hydrogen sinks and rumen stimulating agents to treatment (CFA) group animals along with basal feed of chaffed green sorghum (Sorghum bicolor) fodder, chaffed wheat straw and concentrate mixture for maintenance and milk production. The results showed a decrease (44.6%) in methane concentration in exhaled air of CFA group buffaloes with increase (p < 0.05) in digestibility of feed in comparison to control (CON). Total digestible nutrient (TDN) content of the ration fed to buffaloes of CFA group was significantly (p < 0.05) increased. The daily milk yield, 6% fat corrected milk (FCM) yield and immune response were also increased (p < 0.05) in CFA group. The study suggests that the supplementation of composite feed additive was effective to reduce enteric methane emissions and improvement in production performance and immune status of buffaloes.