Valorization of spent coffee grounds for biogas production: A circular bioeconomy approach for a biorefinery

Eyas Mahmoud, A. E. Atabani, Irfan Anjum Badruddin

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


As a by-product of coffee consumption, millions of tons of spent coffee grounds (SCG) are produced annually. SCG can be recycled in a biorefinery-based process to produce biofuels and value-added products, avoiding the environmental issues, hazardous emissions and costs associated with its disposal. The recycling potential of SCG into biogas by the anaerobic digestion (AD) and co-digestion was reviewed in this work. Such types of review papers are novel and not much work was done on this aspect. The AD of SCG produces 0.500–0.598 m3/kg dry organic matter of biogas with a methane (CH4) concentration of 55–61 %. Nevertheless, the long-term mono-digestion of SCG has been linked with instability and volatile fatty acid (VFA) accumulation. Co-digestion with other waste streams, such as waste activated sludge, food waste and spent tea waste, resulted in the same or larger amounts of CH4 emission. Additionally, the defatted spent coffee grounds (DSCG) have been reported to have advantage over the SCG as the average CH4 yield was 336 ± 7 CH4 mL/g vS compared to 310 ± 2 CH4 mL/g vS from SCG. Additionally, the positive impact of the pretreatment process in increasing the CH4 yield during the AD of the SCG has been observed. Based on the presented work, it is clear that recycling SCG and DSCG is a worthwhile option that can help taxpayers save money on landfill operations and maintenance besides protecting the environment from numerous hazardous emissions. Valorization of biogas products and approaches to enhance the economics of the SCG/DSCG-based biorefinery are indicated in this review as areas where future work in biogas generation from SCG and DSCG can be done. In conclusion, this paper suggests further investigation of the techno-economic analyses and life cycle assessment (LCA) of a biorefinery based on the AD of the SCG and DSCG with other organic waste streams.

Original languageEnglish
Article number125296
Publication statusPublished - Nov 15 2022


  • Biogas
  • Biorefinery
  • Co-digestion
  • Recycling
  • Spent coffee grounds
  • Valorization

ASJC Scopus subject areas

  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Organic Chemistry


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