**1. Introduction**

Biomass sources, especially vegetable oils have received much more attention as an alternative source of energy [1]. But its higher viscosity rises some problems like filter clogging, carbon deposition on injector nozzle, compression ring groove piston lend etc. [2, 3]. To solve these problems following methods have been adopted to make it usable in the engine such as blending in small ratio with standard diesel fuel, emulsification, cracking and conversion into biodiesel through transesterification [4]. As per ASTM standard biodiesels are monoalkyl of long chain fatty acid [5].

Biodiesel is an alternative diesel fuel made from renewable biological sources such as vegetable oils and mineral oil [6, 7]. It is biodegradable, nontoxic, renewable and environment-friendly [8–10]. Biodiesel makes the environment fairly less hazardous compared to petroleum diesel, such as decrease acid rain and greenhouse effect caused by combustion. Renewability, biodegradability, sustainability, and environment-friendly properties make it an advantage to that of fossil fuel [8]. Besides this, it protects the global from the exponentially increasing emission, such as CO2, SOx and unburned hydrocarbon (HC) during the combustion process [11]. India is a seventh largest and developing country in the world needs a large amount of energy source to sustain their social and economic growth in 2010 India was the world fifth largest net importer of oil, imported more than 2.2 million bbl/d (Barrel per day), or about 70% of consumption [12]. It implies a dependency on petroleum imports. The supply of part of the demand with biodiesel can contribute to decreasing this dependency.

Many authors have reported that blends of vegetable oils (edible or non-edible) based biodiesel with diesel when used in a diesel engine, a reduction in emission and comparable performance were achieved [13, 14]. Nabi et al. [15] conducted an experiment with Neem oil biodiesel blend in the comparison of diesel fuel on four-stroke natural aspirated (NA) direct injection (DI) diesel engine. Blend showed lower carbon monoxide (CO) emission but higher NOx emission compared to conventional diesel. Later in the second phase, NOx emission was slightly reduced compared to diesel when the engine was applied Exhaust gas recirculation (EGR). Atul Dhar et al. [16] evaluated performance, emission and combustion characteristics of Neem oil biodiesel in a constant speed direct injection (DI) diesel engine. Brake thermal efficiency of all biodiesel blend was found to be increased compared to mineral diesel however specific fuel consumption for biodiesel and its blends were higher than mineral diesel. CO and HC emissions for biodiesel were lower than mineral diesel while NOx emissions were higher for biodiesel blends. Combustion was started earlier for higher blends while for lower blends combustion was slightly delayed in comparison to standard diesel. All biodiesel blends were shown almost same heat release trend and shorter combustion duration in comparison of standard diesel.

In his study, the biodiesel from nonedible Mahua oil has been produced by two step acid-alkaline base catalyst transesterification. There has been substantial research on other non-edible oils like Jatropha, Pongamia, Karanja, and Sunflower for their suitability in Indian conditions and also to meet the automobile blending requirements. However, we are required to be focused on the Mahua oil. It is mainly a nonvolatile oil compressed from Mahua (*Madhuca longifolia*). Mahua is perhaps the widely grown tree in India after mango and almost all parts of Mahua tree are saleable.

### **2. Methodology**

Mahua oil was purchased from a local general store in Uttar Pradesh market, chemical items which play an important role in converting fatty acid content of oil into ester like methanol (CH3OH), (KOH) and H2SO4.

#### **2.1 Biodiesel production and specifications**

The biodiesel fuel used in this study was produced from the two-step acid-base catalyst transesterification of crude Mahua oil with methanol (CH3OH) catalyzed by sulfuric acid in the first step called esterification process followed by the second *Performance, Emissions, and Combustion Evaluations of a Diesel Engine Fuelled with Biodiesel… DOI: http://dx.doi.org/10.5772/intechopen.83845*

step called transesterification process in which esterifies crude oil Mahua with methanol was catalyzed by potassium hydroxide (KOH). In first step acid quantity and methanol to oil molar ratio both were varied but another reaction parameter as reaction time 1 h stirrer speed 300 rpm and reaction temperature 60°C were kept constant. Acid quantity 0.8% wt of oil and molar ratio of 18:1 was obtained as an optimized parameter at which maximum yield of esters was obtained. This oil had an initial acid value of 29 mg KOH/g, corresponding to a free fatty acid (FFA) level of 14.5%, which is far above the 1% limit for satisfactory transesterification reaction using an alkaline catalyst. The process of transesterification is complicated if oil contains large amounts of acid value that will form soap with an alkaline catalyst. The soap can rise difficulties or prevent separation of the biodiesel from the glycerol [17]. Therefore, free fatty acids were first converted to esters in a pretreatment process, an acid value of crude Mahua oil reduced to below 1 mg KOH/g approximate and completed transesterification with an alkaline catalyst to produce biodiesel [18, 19]. A titration was performed to determine the amount of KOH needed to neutralize the free fatty acids in esterified crude sunflower oil. The amount of KOH needed as a catalyst for every liter of crude Mahua oil was determined as 9.9 g. For transesterification, 250 ml CH3OH (molar ratio 6:1) plus the required amount of KOH were added for every liter of esterified CNO, and the reactions were carried out at 60°C for 1 h. The mixture was stirred at a constant speed of 300 rpm continuously and then allowed to settle under gravity in a separating flask. Two separate layers form due to gravity settling after 24 h. The upper layer was of ester and the lower layer was of glycerol. The lower layer was separated out. The separated ester was mixed with some warm water at (40–42°C) around 30% volume of ester to remove the excess catalyst present in ester and allowed to settle under gravity for 4–6 h. At least three times this washing was done to ensure no catalyst present in esters. The catalyst got dissolved in water, which was separated and removed from the ester. After washing, a drying process was followed to make ester moisture free in which washed ester was allowed to heat at (100–120°C) for (1–1.5) h. The important properties of Mahua oil biodiesel are taken from references [20] and compared with those of diesel fuel [21] in **Table 1**. Some properties like density, viscosity acid values of Mahua oil biodiesel were found out at NIT-Hamirpur, Himachal Pradesh, India (177005). Then Mahua oil biodiesel was mixed with standard diesel in various concentrations such as B10, B20, B30, B40 and B50 for preparing biodiesel blends for conducting various engine tests.

