Spent Coffee Grounds as a Versatile Source of Green Energy

Abstract

The production of energy from renewable and waste materials is an attractive alternative to the conventional agricultural feed stocks such as corn and soybean. This paper describes an approach to extract oil from spent coffee grounds and to further transesterify the processed oil to convert it into biodiesel. This process yields 10-15% oil depending on the coffee species (Arabica or Robusta). The biodiesel derived from the coffee grounds (100% conversion of oil to biodiesel) was found to be stable for more than 1 month under ambient conditions. It is projected that 340 million gallons of biodiesel can be produced from the waste coffee grounds around the world. The coffee grounds after oil extraction are ideal materials for garden fertilizer, feedstock for ethanol, and as fuel pellets.

Effect of Solvent Extraction Parameters on the Recovery of Oil From Spent Coffee Grounds for Biofuel Production

“…The standard deviations calculated from three experimental repeats are also presented, while the oil contents were achieved with a coffee to solvent ratio of 1:9 w/v after 8 h of extraction. The measured SCG moisture contents are similar to those reported by Kondamudi [10] (18-45% w/w) and Ahangari and Sargolzaei (48% w/w) [6,7,9,10,13,16,26]. The variance of the moisture results can be likely attributed to the different coffee brewing procedures that significantly increase the moisture content of SCGs, however there is not a clear difference between ICG and RCG samples (Table 2).…”

“…The lipid content of SCGs on a dry weight basis has been found to range between 7 and 27.8% w/w according to previous studies [6][7][8][10][11][12][13][14][15][16][17] and is significant relative to other major biodiesel feedstocks such as rapeseed oil (37-50%), soybean oil (20%) and palm oil (20%) [18]. Coffee oil consists primarily of triglycerides, diglycerides, monoglycerides and FFAs that combined account for 85-90% of the total lipid content and are principally composed of linoleic, palmitic, oleic and stearic acids in decreasing order of magnitude and in proportions not unlike those found in other common edible vegetable oils [6,11,13,16,19].…”

Evaluation of Spent Coffee Obtained from the Most Common Coffeemakers as a Source of Hydrophilic Bioactive Compounds

“…During last decades, at industrial level several applications have been proposed to add value to coffee by-products originated from the fruit to roasted coffee (coffee pulp, husk, and silverskin) and even soluble coffee (spent coffee). 1, 2 For example, spent coffee from soluble coffee industry might be used for animal feed, 3 biofuel, biodiesel or bioethanol production, 4,5 as adsorbent and activated carbon, 6, 7 but also to extract antioxidants or other bioactive compounds. 8,9 Although the production of soluble (or instant) coffee originates a high effective extraction of coffee bioactive compounds, such as caffeine, chlorogenic acids, etc., limited amounts of these compounds still remains in spent coffee grounds and might be extracted with solvents (ethanol, methanol, etc.).…”

Production of Polyhydroxybutyrate from Crude Glycerol and Spent Coffee Grounds Extract by Bacillus cereus Isolated from Sewage Treatment Plant

“…Coffee is one of the most popular beverages in the world, thus huge amount of waste are released. Annual global production of coffee is estimated to be about 16 billion pounds [12]. Raw coffee beans contain carbohydrates as well as some oil.…”

“…The amount of total carbohydrates is about 60% of coffee [13]. Recently, the waste spent coffee grounds, which contain about 15% of oil, have been examined for biodiesel production through catalytic transesterification [12].…”