Biodiesel can be produced from vegetable oils and also from waste fats. Biodiesel is a mono-alkyl-ester of long chain fatty acids derived from renewable feedstock such as vegetable oils by transesterification process. The esterified cotton seed oil, pungam oil, rice bran oil, and tamanu oil are chosen as the Alternative Fuels. Among these oils, tamanu oil is considered for the first time as an Alternative Fuel. An experiment is conducted to obtain the operating characteristics of the variable compression ratio (VCR) engine run by chosen esterified oils, and the results are compared with esterified tamanu oil. From the comparison of results, it is inferred that the engine performance is improved with significant reduction in emissions for the chosen oils without any engine modification. The effective compression ratio can be fixed based on the experimental results obtained in the engine since the findings of the present research work infer that the biodiesel obtained from tamanu oil is a promising Alternative Fuel for direct-injection four-stroke VCR engine.

Nowadays, increased attention has been focused on internal combustion engine Fuels. Regarding environmental effects of internal combustion engines particularly as sources of pollution and depletion of fossil Fuels, compressed natural gas has been introduced as an Alternative to gasoline and diesel Fuels in many applications. A high research octane number which allows combustion at higher compression ratios without knocking phenomenon and with good emission characteristics of unburned hydrocarbons and carbon monoxide are major benefits of compressed natural gas as an engine Fuel. In this paper, natural gas as an Alternative Fuel in a spark ignition engine, has been considered. Engine performance and exhaust emissions have been experimentally studied for both natural gas and gasoline Fuels in a wide range of engine operating conditions.

Concerns for climate change, reduction of greenhouse gas emission and environmental pollution, besides economically dependency on fossil Fuels and political aspect motivate governments and policy makers to take into account replacing usual vehicle with Alternative Fuel vehicles (AFVs) such as Compressed Natural Gas Vehicles (CNGV) and Gasoline-Electric Hybrid Vehicles (GEHV). The air pollution in Tehran is a serious concern that based on this problem, CNGV has been introduced to Iranian market from 10 years ago. On the other hand, with the approval and notification of the removal of the electric vehicle importation’, s tariff law, GEHV has been entered into the market of Iran as a new entrant. The purposes of this paper is to identify the effective factors to choose AFVs for drivers in Tehran and the assessment of the incentive policies that increase AFV shares and computing their willingness to pay (WTP) for AFV under different incentives. This study designed a questionnaire which includes 3 parts: current vehicle features, dominant travel characteristics, socio-economic properties and the prioritization of effective factors on new vehicle purchase, and the tendency of AFVs choice with different scenarios representing different features. A random sample of 365 respondents was interviewed in a face-to-face survey in February 2016 in the technical inspection centers and in compressed natural gas stations. Finally, for the determination of effective factors on current and new vehicle purchase with revealed preference information and the assessment of AFVs usage tendency with stated preference information, the Multinomial Logit models have been used and WTPs are calculated. The incentive policy in Tehran, like previous studies, was the most influential factor in motivating consumers to buy AFVs in comparison to improvement of AFV specifications. The results show that drivers’,WTP is 5 million toman (MT) for free access to even-odd area for CNGV and 12 MT for GEHV, also WTP for free access to pricing area in Tehran central business district is equal to 10 MT for CNGV,i. e. people tend to pay this extra cost for AFVs to access to pricing areas. These values are comparable with similar studies in cities located in developed countries. However, the results of this study show that WTP for Fuel cost in Iran is considerably less than WTP of people driving in developed countries. The Fuel cost and access time to gas stations are influential variables on CNGV choice. The vehicle acceleration and driving range are influential variables on GEHV choice.