Desert Palm Date Seeds as a Biodiesel Feedstock

 Desert Palm Date Seeds as a Biodiesel Feedstock: Extraction, Characterization, and Engine Testing

Abstract: 

The development of alternative fuels is increasingly important in order to maintain ongoing global economic and technological progress in the face of fossil fuel depletion and increasing environmental damage. Desert palm date seeds have clear potential as feedstock for biodiesel production given their high oil content and availability as food waste that requires no further cultivation. In this study we investigated the optimum production processes and conditions for date seed oil biodiesel, including characterizing the intermediate product and correcting its composition to meet international fuel standards. Four biodiesel blends were prepared (B5, B10, B15, and B20) and tested in a compression ignition engine at engine speeds from 1600 to 3600 rpm (200 rpm increments) and three engine loads (50%, 75%, and 100%). The highest oil yield and biodiesel conversion achieved were 10.74 wt.% and 92%, respectively. The biodiesel properties conformed well with the standards; the values for brake power, brake thermal efficiency, and brake specific fuel consumption were comparable with petrol diesel, though the latter was slightly superior. All blends produced lower levels of CO2, CO, and HC but higher levels of NOx emissions. These results demonstrate the fundamental suitability of date seeds as biodiesel feedstock, deserving of further research.

INTRODUCTION

The rapidly increasing global consumption of liquid fossil fuels suggests that oil reserves may soon be depleted; oil supply shortages may occur by 2020–2030. This presents a dual challenge to humanity: To sustain global economic and technological development without compromising resources for future generations. One specific solution to this challenge is to develop renewable fuels and feedstocks in sufficient amounts to partially or fully supply the needs of industry and transportation.

The use of such renewable fuels in combination with proper technology should help end the detrimental environmental consequences of fossil energy use. Renewable energy resources that command a significant share of the global energy market include solar, hydrogen, wind, geothermal, and energy derived from biomass (bioenergy), such as biodiesel. The latter has many advantages as a renewable fuel, including diversified potential feedstocks including an extended array of vegetable oils and animal fats, high cetane number, oxidative stability, biodegradability, lubricity characteristics, and compatibility with existing transportation infrastructure.

However, the production of first-generation biodiesel (produced from vegetable oils and animal fats) can also cause serious problems (such as deforestation, loss of biodiversity, and excessive consumption of water resources, high production cost, and food shortages) that should be addressed before planning any larger-scale implementation in the transportation sector. Most of these concerns can be addressed by considering second-generation biodiesel (produced from non-food feedstocks and waste streams) instead. Food waste is an inherent problem in the global food industry; more than 30% of food is sent to landfills or incinerators. This waste stream represents a promising source of energy, especially for biodiesel production using materials such as spent coffee grounds and used cooking oil.

Recently, desert palm date seeds have also been proposed as a potential parent feedstock for biodiesel production. The date palm tree has been cultivated in the Middle East and North Africa for millennia, and is believed to be the oldest domesticated fruit tree. Traditionally, it was the most precious fruit crop in harsh arid or desert environments where water scarcity and extreme temperatures are common, due to the range of resources it provides. Nowadays, date palm trees are also grown in semiarid environments and other regions including southern Europe, Australia, and the

America. Globally, there are now more than 100 million date palm trees comprising more than 2000 cultivars. The annual average yield of a palm tree is 500 kg of fresh dates; production starts at 5 years and lasts up to 60 years. The global production and consumption of dates has increased rapidly, from 1.88 million t in 1965 to 3.43 million t in 1990 and 8.46 million t in 2016; production is dominated by Middle Eastern and African countries. The fruit ripens in different stages, up to 150 d after pollination. It is a pitted fruit that consists of a core seed surrounded by a fleshy pericarp. The seeds are very hard, range from 5 to 15 mm in length, and have an oblong shape and a ventral groove. On average, they weigh 11–18% of the total fruit mass and contain 4–13% oil. Based on these numbers, an estimated 1.3 million t of date seed and

127,000 metric t of date seed oil (DSO) (and similar amount biodiesel) could be produced annually. This shows the potential for date-based biodiesel, given that the total annual production of biodiesel in the Middle East and Africa in 2015 was 38,700 t.