Biochar utilisation in the anaerobic digestion of food waste for the creation of a circular economy via biogas upgrading and digestate treatment

Jonathan T.E. Lee, Yong Sik Ok, Shuang Song, Pavani Dulanja Dissanayake, Hailin Tian, Zhi Kai Tio, Ruofan Cui, Ee Yang Lim, Mui Choo Jong, Sherilyn H. Hoy, Tiffany Q.H. Lum, To Hung Tsui, Chui San Yoon, Yanjun Dai, Chi Hwa Wang, Hugh T.W. Tan, Yen Wah Tong

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)


A wood waste-derived biochar was applied to food-waste anaerobic digestion to evaluate the feasibility of its utilisation to create a circular economy. This biochar was first purposed for the upgrading of the biogas from the said anaerobic digestion, before treating and recovering the nutrients in the solid fraction of the digestate, which was finally employed as a biofertilizer for the organic cultivation of three green leafy vegetables: kale, lettuce and rocket salad. Whilst the amount of CO2 the biochar could absorb from the biogas was low (11.17 mg g−1), it could potentially be increased by modifying through physical and chemical methods. Virgin as well as CO2-laden biochar were able to remove around 31% of chemical oxygen demand, 8% of the ammonia and almost 90% of the total suspended solids from the digestate wastewater, which was better than a dewatering process via centrifugation but worse than the industry standard of a polytetrafluoroethylene membrane bioreactor. Nutrients were recovered in the solid fraction of the digestate residue filtered by the biochar, and utilised as a biofertilizer that performed similarly to a commercial complete fertilizer in terms of aerial fresh weight growth for all three vegetables cultivated. Contingent on the optimal upgrading of biogas, the concept of a circular economy based on biochar and anaerobic digestion appears to be feasible.

Original languageEnglish
Article number125190
JournalBioresource technology
Publication statusPublished - 2021 Aug

Bibliographical note

Funding Information:
This research is supported by the National Research Foundation, Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme. This study was also funded by the National University of Singapore (NUS) grant, From Food Waste to Sustainable Food Production: NUS As Test Bed For The Nation with the grant number R-154-000-A97-133. The work of Shuang Song was supported by a Research Scholarship of the National University of Singapore. The work of Yong Sik Ok was carried out with the support of “ Cooperative Research Program for Agriculture Science and Technology Development (Project No. PJ01475801 ),” Rural Development Administration, Republic of Korea.

Publisher Copyright:
© 2021 Elsevier Ltd


  • Anaerobic digestate utilisation
  • Biochar
  • Biogas upgrading
  • Circular economy
  • Resource recovery

ASJC Scopus subject areas

  • Bioengineering
  • Environmental Engineering
  • Renewable Energy, Sustainability and the Environment
  • Waste Management and Disposal


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