Determination of Relationship between Higher Heating Value and Atomic Ratio of Hydrogen to Carbon in Spent Coffee Grounds by Hydrothermal Carbonization

Jung Park,Gi Lee,Ho Kim,Cheol Jeong,Choong Kim

doi:10.3390/en14206551

Abstract

This study was a preliminary investigation of solid recovered fuel production from spent coffee grounds using the hydrothermal carbonization (HTC) technique. The spent coffee grounds (SCGs) were subjected to HTC at 170 to 250 °C. The biochar was characterized by proximate analysis, ultimate analysis, capillary suction time, time to filter, suspended solids, and particle size distribution. The biochar yields decreased with increasing HTC temperature and time. However, the higher heating value (HHV) of biochar increased with the HTC temperature and time. The H/C slop relative to the O/C atomic rate of spent coffee grounds was 0.10 with low decarboxylation selectivity. Considering the HHV of biochar and dehydration capacity depend on ratio of H/C vs. O/C, the optimum reaction temperature of HTC was 200 °C, and the biochar from SCGs is an attractive biochar.

Highlights

The quantity of spent coffee grounds (SCGs) produced has been continuously increasing with the worldwide increase in coffee consumption [1,2,3]
The results indicated that the hydrothermal carbonization (HTC) temperature increased with increased increasing temperature due to the decomposition of hemicellulose and other sugars, which dehydration capacity, and the dewaterability increased with increasing temperature
The energy density in the synthesized biochar increased with increasing reaction temperature and time

Summary

Introduction

The quantity of spent coffee grounds (SCGs) produced has been continuously increasing with the worldwide increase in coffee consumption [1,2,3]. SCGs is generated during the coffee extraction process, creating various environmental problems [1]. Some are landfilled or incinerated depending on the waste disposal standards [2]. Developing a simple, efficient, low-cost method for solving environmental pollution and converting it into valuable energy products is important. SCGs contains 10–20% oil, depending on the extraction method, and can be used for bio-fuel production [5,6]. The solid SCGs before or after oil extraction are used as biochar [7,8]. Biochar from biomass with high calorific fractions of nonhazardous waste materials has been produced to EU specifications (European Committee for Standardization, 2011) and is recognized as a viable alternative to fossil fuels [9]

Methods

Results

Conclusion