The inherent conflict between the increase of global energydemand and the depletion of fossil fuels, along with theenvironmental issues related to extensive use of fossil fuels,has necessarily called for renewable and sustainable energysource alternatives. Biowaste (waste biomass) has beenconsidered as a promising resource for liquid biofuelproduction due to its abundance, renewability and carbonneutrality. Hydrothermal liquefaction (HTL) is an innovativetechnology that is able to convert wet biomass (especiallybiowaste) into liquid fuels (called bio-oil) in sub/supercriticalwater medium under conditions of high pressure andmoderate temperature.

Spent coffee grounds (SCG), the waste generated fromcoffee brewing, are abundantly available and have highcontent of lipid and protein (22 wt.%), showing goodpotential in bio-oil production.

Bio-oil Production from Spent Coffee Grounds via Hydrothermal Liquefaction (HTL)

Linxi Yanga, Laleh Nazarib, Zhongshun Yuanb, Kenneth Corscaddena, Chunbao (Charles) Xub*, Quan (Sophia) Hea*

Introduction

Objectives

Evaluate the potential of SCG as a renewable feedstockfor bio-oil production via HTL:

•Effects of various operating parameters, including retentiontimes, reaction temperatures and water/feedstock ratios onthe yields of product fractions were investigated, tomaximize the bio-oil production.

•The properties of the resulting bio-oil (e.g. elementalcomposition, higher heating value (HHV)) werecharacterized.

Methodology

SCG were offered by Tim Hortons

HTL of SCG

Results

Fig 1. Yields of bio-oil, yield residues, WSP, and gas under different retention times (temperature of 300C and water/feedstock ratio of 5:1 (w/w)).

Fig. 2. Yields of bio-oil, solid residue, WSP, and gas at various reaction temperatures (retention time of 10 min and water/feedstock ratio of 5:1 (w/w)).

Highest bio-oil yield(31.63 wt.%) in 10 min

Highest bio-oil yield(35.29 wt.%) at 275℃

SampleElemental compositions, wt.% HHV

(MJ/kg)C H N O

Spent coffee grounds 50.4 7.2 2.1 40.3 20.2

Bio-oil 71.2 7.1 3.0 18.7 31.0

Table 1. Elemental Analyses of SCG and crude bio-oil derived under optimal liquefaction condition.

Note: Bio-oil was derived under such reaction conditions: 275C, SCG and water/feedstock ratio of 20:1, and reaction time of 10 minutes.

Conclusion

SCG is a suitable feedstock for bio-oil production via HTL.Figure 1, 2, 3 shows that the highest yield of crude bio-oil(approx. 47%) was obtained at the conditions of 275C, 10min retention time and water/feedstock ratio of 20:1 (w/w).The HHV of obtained bio-oil (31.0 MJ/kg) is much higherthan SCG (20.2 MJ/kg) (Table 1).

AcknowledgementsWe would like to acknowledge the financial support providedby Growing Forward 2 program, Nova Scotia Department ofAgriculture the NSERC Discovery and BioFuelNet grants; andthe facilities offered by Institute for Chemical and Fuels fromAlternative Resources (ICFAR), Western University.

Fig. 3. Yields of bio-oil, solid residue, WSP, and gas from the liquefaction with various water/feedstock ratios (retention time of 10 min and temperature of 275C).

Highest bio-oil yield (47.28%) with the water/feedstock ratio of 20:1 (w/w)

a Department of Engineering, Faculty of Agriculture, Dalhousie University, Truro, Nova Scotia, Canada B2N 5E3b Institute for Chemicals and Fuels from Alternative Resources (ICFAR), Faculty of Engineering, Western University, London, ON, Canada N6A 5B940

100 ml stainless steel autoclave; in 2MPa initial pressure of

N2