The production of biodiesel from safflower (Carthamus tinctorius L.) oil as a potential feedstock and its usage in compression ignition engine: A comprehensive review

Highlights

• This paper presents a comprehensive review of safflower as a potential biodiesel feedstock.

• One of the countries that have the greatest potential to produce this crop on a commercial scale is Turkey.

• High oil ratio and quality of its characteristics of the oil makes it a choice to produce biodiesel.

• The physico-chemical characteristics of the safflower oil biodiesel are studied in a detail.

• Safflower oil biodiesel and its blends can be used in different types of engines without any modification on the engine.

Abstract

Nowadays, energy consumption is progressively boosting in all sectors because of the rising in population and enhancing lifestyle. The dependency over fossil-based fuels has been increasing due to the ever-growing need for energy. The declining characterization of such energy sources and the increment nature of energy demand have led to vital apprehensions of energy regarding future energy safety. Keeping this in mind, the usage of alternative fuels such as biodiesel can be one of the possible solutions in order to accomplish the future energy demand. In this context, the biodiesel production is an attractive way for researchers. Biodiesel is non-toxic, biodegradable and renewable fuel that can be produced from vegetable oils, animal fats and also their wastes by applying different techniques. Contrary to the advantages, the biggest disadvantage of biodiesel is that costs are largely dependent on the feedstock. Although it has the nature of the food, safflower (Carthamus tinctorius L.) can be utilized as a feedstock for biodiesel production because its oil consumption is limited and it can be grown in arid and dry areas all over the world. This review paper has presented a detailed overview of safflower plant, the physicochemical properties of safflower oil and its biodiesel, the performance, emission and combustion characteristics of the safflower oil biodiesel when used in a diesel engine. The findings of the present work revealed that biodiesel production from safflower oil is possible and the observations from the literature resulted in comparable fuel properties, engine performance and emission parameters with those of diesel.

Introduction

The total worldwide energy consumption has been significantly increasing day by day owing to the increment of the world population, increasing trade and production as a result of industrialization and technological developments. The main problem is that a large part of the energy consumed in the world has been supplied from fossil-based energy sources like petroleum, coal and natural gas. Fossil-based fuels have played a very important role in the world energy market. According to the International Energy Agency (IEA), 81% of the total energy demand was provided from fossil-based resources in 2017. This quantity has maintained stability over a period of more than thirty years [1]. Furthermore, it can be clearly stated that fossil-based fuels have still prevailed in the world energy market, which is worth 1.5 trillion dollars [2].

The proved global petroleum reserves in the world decreased slightly to 1696.6 billion barrels at the end of 2017. It has been reported that this amount could be sufficient to satisfy the 50.2 years of global production at the 2017 level [3]. In addition to this, approximately 87.11 million barrels of petroleum in 2007 were consumed per day in the world, which was realized to be at 98.19 million barrels in 2017 [4]. It has been indicated that the consumption of petroleum will continue to increase in the near future. In this case, it is not possible for the petroleum reserves in the world to meet the requirements.

One of the biggest consumers of fossil-based fuels has been the transportation sector. Diesel fuel has got more market share than gasoline in terms of energy perspective, especially in developing countries [5]. Moreover, the share of demand for diesel fuel in the transportation sector is projected to rise at different ratios further in many countries. It is also expected that diesel fuel will account for 70% of the demand in transportation fuels until 2040 on a global scale [6].

The emissions resulting from the burning of fossil-based fuels adversely affect both the environment and human health [7]. In addition, the concerns about global warming and climate change have been increasing all over the world. The countries have been working harder to tackle these issues. Reducing carbon dioxide (CO₂) emissions, which is a harmful gas, is the most important step in the fight against global warming. CO₂ is mainly caused by the burning of fossil-based fuels. Besides, compression ignition (CI) engines have emitted higher levels of CO₂ and other harmful air pollutants such as nitrogen oxides (NO_X), particulate matter (PM), and sulfur dioxide (SO₂), etc. This fact, along with the recent diesel emission defamation and the widespread deception rumors by the automotive manufacturers, has launched a long debate on the future and sustainability of the diesel engines. The decreasing harmful emissions can be achieved by further developments in engine technology and even by the application of the alternative fuels. Also, the diversity of energy sources needs to be increased in order to achieve low levels of CO₂ emission. On the other hand, the world has faced the risk of depletion of fossil-based fuels for a long time because of unconscious usage. Additionally, the depletion of oil resources in the near future and the increased environmental anxiety in socioeconomic dimensions have led to research to develop sustainable and alternative fuels from inexpensive and environmentally friendly renewable sources. The decline of petroleum reserves and increasing the price have forced people to seek alternative energy sources. For all these reasons, renewable, sustainable and economically viable fuels are urgently necessary to be taken into consideration by the countries. Therefore, there has been a growing interest in alternative fuels such as biodiesel for diesel engine applications all over the world [8].

Biodiesel can be described as a mixture of long-chain fatty acid alkyl esters that meet the specified standards [9]. It can be produced from several feedstocks such as edible or non-edible vegetable oils, animal fats, algal oils and waste oils [10]. On the other hand, more than 95% of world biodiesel production has been made from edible vegetable oils. Although the non-edible oils are considerable raw materials for the biodiesel industry in order to decrease the cost and prevent the food/fuel controversy, the majority of the countries have utilized edible oils because of agricultural productions [11]. Rapeseed, soybean, sunflower, and palm oils have been shown as crucial edible feedstocks when the current potential feedstocks for biodiesel production around the world are evaluated [12,13]. However, safflower (Carthamus tinctorius L.) seed oil is a promising edible raw material for the biodiesel industry in both Turkey and the world due to the various advantages and these are explained in this paper comprehensively.

It has not been reported that the biodiesel has been commercially produced from Carthamus tinctorius oil in the world. However, literature reviews have demonstrated that the production of biodiesel from C. tinctorius oil has increased in recent times. A comprehensive scientometric data analysis concerning biodiesel production from C. tinctorius oil has been performed and for this, SCOPUS database searching could be realized to explain briefly in the following paragraph.

The words of “safflower or Carthamus tinctorius and biodiesel” were searched in SCOPUS, which the largest abstract and citation database of peer-reviewed literature. Based on the article title, abstract, and keywords searching, 78 documents were found to be published between 2009 and 2018. Also, 2 research articles were seen in Article in Press. The research article, conference paper, book chapter, and review shared 81.25%, 6.25%, 3.75%, and 5%, respectively. 1 technical note regarding C. tinctorius published in 2012. A major contribution to the literature was made from Turkey (38.75%) followed by India (13.75%), United States (13.75%), and Brazil (8.75%) [14]. These data were demonstrated that C. tinctorius biodiesel has not shown enough interest in worldwide. Further investigations on this subject and the new and appropriate oilseed crops for biodiesel production have been required. Thus, the present study is conducted in order to fulfill this gap in the literature.

Although C. tinctorius oil possesses an edible feature, the consumption of its oil has been well below expectations in Turkey. Oguz et al. [15] indicated that the safflower can come to the fore in terms of sustainability and fuel properties. Therefore, C. tinctorius oil is an important and economic feedstock in order to acquire biodiesel fuel in our country. It is likely that interest to these oil crops by the authorities will increase in the next years and will be presented as a new raw material to both the food sector and the biodiesel industry with the promotion of this crop. It is obvious that a detailed study has been needed for the literature about C. tinctorius plant and its biodiesel when evaluated in this context.

The present review paper has been organized as follows. Firstly, the general information about the nature of the plant, the oil content of its seed, and the fatty acid composition of safflower (Carthamus tinctorius L.) have been introduced briefly. Secondly, the production methods of biodiesel are explained. Then, the physicochemical properties of safflower oil biodiesel are reviewed in detail. Also, the engine performance and exhaust emission characteristics of biodiesel obtained from safflower oil are examined in light of the recent literature. Finally, the applicability perspectives of safflower oil for biodiesel production as well as the current biodiesel policy in Turkey have been discussed.