A way towards zero-waste campaign and sustainability in sugar industries; filter cake valorisation as energy pellets

Abstract

A by-product known as filter cake has been a major problem for sugar industries. Despite its use as fertiliser, millions of tonnes of filter cake have been discarded as waste. Thus, the concept of wastevalorisation is highly essential to the production of useful energy. Filter cake consists of fine particulates with a high moisture content; consequently, crushing is not necessary for pelletisation. A preliminary investigation has demonstrated the tremendous potential of filter cake pellets with a higher heating value of 8–12 MJ/kg, depending on their moisture content. However, pelletisation must be properly optimised. In the present study, the initial moisture contents of filter cake werevaried between 10, 20, and 30%. The physical properties of pellets with these initial moisture levels were then determined and compared with EN 14961-1. Moreover, the relationship between particle and bulkdensities was determined and utilised for optimisation. The results indicated that an initial moisture content between 10 and 20% was suitable for pelletisation, with excellent conformance to the EN 14961-1 standard. The diameter, length, bulk density, particle density, fines, and durability values were 5.90–5.98 mm, 28.11–29.18 mm, 832.6–852.6 kg/m3,1517.3–1626.1 kg/m3, 0.22–0.30%, and 97.8–98.1%, respectively. In addition, a prototype system demonstrated the feasibility of the concept of waste valorisation for a zero-waste campaign. Furthermore, economic analysis indicated that if 2.04 million tonnes per year of filter cake pellets were utilised as fuels in steam power plants, they could generate 2.63x109 kWh of electricity per year, resulting in approximately 318 million US dollars.