Environmental impact of sewage sludge co-digestion with food waste and fat-oil-grease: Integrating plant-wide modeling with life cycle assessment approach

Systematic review of factors influencing household food waste behaviour: Applying the theory of planned behaviour

Globally, household food waste alone accounts for about $700 billion in environmental costs owing to the resources expended in producing discarded or uneaten food, along with social costs reaching approximately $900 billion. Reducing this waste by 25% could potentially feed 821 million chronically undernourished individuals. This systematic review examines household food waste behaviour using the Theory of Planned Behaviour (TPB). Comprehensive searches were conducted in PubMed and EMBASE using Elsevier supplemented by additional articles from the reference lists. The procedure followed the PRISMA flowchart. A descriptive analysis was conducted to summarize the characteristics of the 42 included studies from 17 countries. Significantly, 95% of these articles were published between 1 January 2010 and 19 April 2024, in Scimago Q1 ranked journals. The findings demonstrate an intersection of TPB components in explaining household food waste behaviour. This study suggests that a holistic strategy targeting attitudes, subjective norms and perceived behavioural control is essential for effectively reducing household food waste. Additionally, tailored interventions that consider demographic and socioeconomic factors are necessary to address the diverse needs of different populations. The study concludes that public education targeting mindful consumption, effective policies and community initiatives can significantly reduce food waste.

Life cycle assessment of anaerobic digestion coupled co-pyrolysis for treatment of food waste

In this study, the environmental impact of anaerobic digestion (AD) coupled co-pyrolysis (PY) to dispose of food waste (FW) was assessed. Four cases (mono AD, mono PY, AD coupled PY and AD coupled co-PY) were analyzed in comparison by life cycle assessment. The results showed that coupling technology was an environmentally viable technology compared with mono AD or PY. Among them, AD coupled co-PY presented the best environmental benefit (-0.0038Pt of total environmental impact potential /t FW), and provided a potential way to treat waste plastics and digestate. Moreover, the optimization of AD technology will enhance the total environmental benefits, while the control of emission at the energy recovery stage and the improvement of electricity efficiency are crucial for sustainability. This study provides potential approaches and environmental support for the treatment of FW.

Biorefinery of waste activated sludge: Nutrient recovery and microbial lipid production by Yarrowia lipolytica

The rising generation of waste activated sludge (WAS) demands a fundamental shift towards resource reuse and recovery. The conventional methodologies used to manage this by-product derived from wastewater treatment plants are increasingly constrained due to stringent regulatory measures aimed at mitigating its adverse impacts on the environment and public health. Therefore, this work evaluated a promising strategy for the efficient management of WAS, transforming it into a valuable renewable source to produce high-value-added compounds, such as lipids and a slow-release fertilizer (struvite). Wet oxidation (WO) was identified as a suitable technique for solubilising WAS while generating short-chain fatty acids (primarily acetic acid). It was found that conducting WO at 200 °C for 120 min resulted in a 65% reduction of the total suspended solids (TSS) content and 87% of the volatile suspended solids (VSS) content. Additionally, under these conditions, 4440 ± 105 mg/L and 593 ± 21 mg/L of acetic and propionic acid were obtained, respectively, which were assimilated by Yarrowia lipolytica to produce biolipids. Furthermore, the rupture of WAS flocs also led to the solubilisation of 980 ± 8 mg/L of ammonium. During the struvite precipitation stage, a NH4:PO4:Mg ratio of 1:1.5:1.5 was found to be the most effective for removing soluble ammonium (97.4 ± 0.8%), resulting in a high-purity struvite formation, and enhancing the carbon/nitrogen (C/N) ratio of the oxidised WAS from 3 to 105. This improvement in the C/N ratio raised the lipid content from 36 ± 1% to 49 ± 1% during the cultivation of Y. lipolytica. The application of the sequencing batch culture strategy further increased lipid content to 59 ± 1%, with 6.0 ± 0.3 g/L as the final concentration after the fifth cycle. The lipids produced, mainly monounsaturated fatty acids with 40% of oleic acid, offer potential as biodiesel feedstock. This lipid composition led to biodiesel properties, including cetane number, iodine value, kinematic viscosity and density that met international standards. Therefore, this research presents a promising alternative not only for WAS management but also for harnessing valuable resources, thereby establishing a basis for large-scale studies.