<strong>A Critical Review on Briquettes Developed from Spent Coffee Ground Wastes</strong>

Abstract

Coffee is regarded as the highly consumed beverage throughout the world and has established a key spot in the world economy as an important commodity for trading. In general, they are produced by brewing their roasted and ground beans, which release aromatic coffee; as well as produce an equivalent amount of spent coffee grounds (SCG). Previously, they were discarded as wastes or used as natural pest repellent or garden fertilizer; however, in recent times, are valorized into biofuels owing to their high calorific value. In fact, SCG briquettes have gained wide attention for supplying energy renewably, especially to the rising energy demand; and also have been identified as an effective measure to reduce their pollution. With this in mind, this present chapter focuses on reviewing the availability and chemistry involved in these SCG wastes, pre-treatments and preparations required for their briquetting, compacting techniques followed, and fuel characteristics of their briquettes, from various available works of literature. Here, their availability showcases the amount of SCG wastes generated with respect to time and consumption, wherein understanding their chemistry helps in deciding the pre-treatments necessary for their briquetting. Meanwhile, preparation techniques briefs about the necessary pre-treatments undertaken before compaction by different researchers; and the fuel characteristics define the physicochemical and mechanical properties of their briquettes, developed using various compaction methods. Besides, combustion behaviors of these briquettes are explained in terms of their burning characteristics and emission levels, as reported in literatures; which help in deciding their suitability as a replacement for existing fossil coal. Eventually, all the reported data were in accordance with their permissible standards and suggested these SCG as a highly renewable solid biofuel.