A closed loop case study of decentralized food waste management: System performance and life cycle carbon emission assessment

Hailin Tian; Miao Yan; Jieyu Zhou; Qinglian Wu; Yong Wei Tiong; Heng Thong Lam; Jingxin Zhang; Yen Wah Tong

doi:10.1016/j.scitotenv.2023.165783

A closed loop case study of decentralized food waste management: System performance and life cycle carbon emission assessment

Sci Total Environ. 2023 Nov 15:899:165783. doi: 10.1016/j.scitotenv.2023.165783. Epub 2023 Jul 24.

Authors

Hailin Tian¹, Miao Yan², Jieyu Zhou³, Qinglian Wu⁴, Yong Wei Tiong³, Heng Thong Lam³, Jingxin Zhang⁵, Yen Wah Tong⁶

Affiliations

¹ Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China; Environmental Research Institute, National University of Singapore, 1 Create Way, 138602, Singapore; Energy and Environmental Sustainability for Megacities (E2S2) Phase II, Campus for Research Excellence and Technological Enterprise (CREATE), 1 Create Way, Singapore 138602, Singapore.
² Environmental Research Institute, National University of Singapore, 1 Create Way, 138602, Singapore; Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China.
³ Environmental Research Institute, National University of Singapore, 1 Create Way, 138602, Singapore; Energy and Environmental Sustainability for Megacities (E2S2) Phase II, Campus for Research Excellence and Technological Enterprise (CREATE), 1 Create Way, Singapore 138602, Singapore.
⁴ Environmental Research Institute, National University of Singapore, 1 Create Way, 138602, Singapore; State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150000, China.
⁵ China-UK Low Carbon College, Shanghai Jiao Tong University, Shanghai 201306, China.
⁶ Environmental Research Institute, National University of Singapore, 1 Create Way, 138602, Singapore; Energy and Environmental Sustainability for Megacities (E2S2) Phase II, Campus for Research Excellence and Technological Enterprise (CREATE), 1 Create Way, Singapore 138602, Singapore; Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive, 117585, Singapore. Electronic address: chetyw@nus.edu.sg.

PMID: 37495140
DOI: 10.1016/j.scitotenv.2023.165783

Abstract

Food waste (FW) has become a worldwide issue, while anaerobic digestion (AD) has appeared as a widely adopted technology to recover energy and resources from FW. Compared to many existing case studies of centralized AD system, the comprehensive study of decentralized micro-AD system from both system energy efficiency and carbon emission perspective is still scanty, particularly system operated under ambient temperature conditions. In this study, an actual decentralized micro-AD system with treating capacity of 300 kg FW/d for a local hawker center in Singapore was reported and evaluated. The results showed that 1894.5 kg of FW was treated and 173 m³ biogas with methane content of 53 % was produced during the experimental period of 75 days. The methane yield results showed a high FW degradation efficiency (87.87 %). However, net energy consumption and net carbon emission were observed during the experimental period. Nevertheless, energy self-efficiency and carbon neutrality, even net energy output and carbon reduction, can be achieved by increasing daily FW loading and biogas engine efficiency. Specifically, the FW loading for system energy self-efficiency was identified as 159 kg/d for engine efficiency of 35 % at a high kitchen waste/table waste ratio (63 %/37 %, with covid-19 dine-in restrictions); while they were 112 and 58 kg/d for engine efficiency of 25 % and 35 %, respective, at a low kitchen waste/table waste ratio (31 %/69 %, without covid-19 dine-in restrictions). The carbon emission ranged from 156.08 kg CO₂-eq/t FW to -77.35 kg CO₂-eq/t FW depending on the FW loading quantity and engine efficiency. Moreover, the sensitivity analysis also showed that the used electricity source for substitution influenced the carbon emission performance significantly. The obtained results imply that the decentralized micro-AD system could be a feasible FW management solution for energy generation and carbon reduction when the FW loading and engine electrical efficiency are carefully addressed.

Keywords: Anaerobic digestion; Carbon emission; Decentralized system; Energy efficiency; Food waste.

MeSH terms

Anaerobiosis
Biofuels
Bioreactors
COVID-19*
Carbon
Carbon Dioxide
Food
Humans
Methane
Refuse Disposal*
Waste Management*

Substances

Biofuels
Carbon
Carbon Dioxide
Methane