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[Display omitted] • GHG emissions from an industrial-scale AD plant were assessed. • The AD process before digestate treatment achieved carbon offset. • Electricity consumption caused the major GHG emissions. • Waste oil recovery and biogas reuse are pivotal for offsetting GHG emissions. • Net GHG emissions from digestate process varies with different final disposal ways. Anaerobic digestion (AD) has been widely applied for treating organic waste and is known as a carbon-offsetting process. However, most studies relied on laboratory-scale experiments or literature to calculate carbon emissions from AD process, and the impact of digestate processing was overlooked. This study assessed the carbon footprint for an industrial food waste co-digestion plant with operational data. The results indicated that carbon emission before digestate treatment is −88.5 ± 4.4 kg CO 2 -eq/t. The major source of carbon emission is electricity provision, followed by fuel combustion, unburned biogas, and fugitive gas emissions, while waste oil recovery and biogas utilization offset the carbon emissions. Considering digestate treatment and disposal options, the plant's net carbon emissions are as follows: −86.1 ± 6.2 kg CO 2 -eq/t (incineration) < -80.7 ± 6.5 kg CO 2 -eq/t (land application) < 6.7 ± 12.2 kg CO 2 -eq/t (landfilling). This work aims at providing a roadmap for making site-specific calculations of the carbon footprint for AD process. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of EPT on sludge solubilisation and digestibility was studied. • EPT effectively destroyed the extracellular polymeric substance matrix. • EPT promoted sludge floc fragmentation. • EPT enhanced the hydrolysis rate of waste activated sludge (WAS). • EPT improved the overall digestibility of WAS. Anaerobic digestion (AD) of waste activated sludge (WAS) is widely used for stabilisation, mass reduction and resource recovery. However, AD performance is often hampered by the poor digestibility and slow degradation rate for WAS. A series of bench-scale tests was conducted using innovative electrochemical pretreatment (EPT) method to enhance the destruction of the extracellular polymeric substances (EPS) matrix and anaerobic digestibility. The results showed that the EPS matrix destruction was enhanced by 15–30% after EPT for 0.5 h at voltages of 8–15 V. The highest improvement in hydrolysis rate and overall digestibility was achieved at EPT of 15 V for 1.5 h, which was determined as 59% (from 0.27 to 0.43 d-1) and 28% (from 105 to 134 mL CH 4 /g VSS added) respectively, compared with the WAS treatment without EPT. The economic analysis showed 1 h, 12 V EPT was more economically feasible. [ABSTRACT FROM AUTHOR]

[Display omitted] • WAS-FW Co-AF with EPT for VFAs production was investigated. • The mechanism of WAS-FW Co-AF with EPT for VFAs production was revealed. • EPT produced RCS to promote disintegration of WAS-FW and biodegradability of DOM. • Residual RCS causes a dramatic shift of microbial community structure. • EPT and the addition of FW synergistically promoted VFAs production. Waste activated sludge (WAS) has low biodegradability that restricts acidogenic fermentation (AF), thereby limiting the high-value volatile fatty acids (VFAs) production. This study investigated an alternative electrochemical pretreatment (EPT) approach that can facilitate AF of WAS and food waste (FW) and therefore enhance VFAs production. The results showed through introducing 50 % volatile solid basis of FW (containing massive chloride) into WAS, a 60-min EPT produced reactive chlorine species (RCS), which diffused into WAS-FW inner layers resulting in cell lysis, therefore significantly promoted and accelerated WAS-FW disintegration, contributing to more soluble and biodegradable dissolved organic matter (DOM). Then during the subsequent 15-day acidogenic co-fermentation (Co-AF), the residual RCS (approximate 5 mg Cl 2 /L) also caused acidogenic bacteria (including Prevotella_7 , Lactobacillus and Veillonella) gradually outcompeted methanogens due to their different tolerance to residual RCS. Consequently, the maximum VFAs yield of the WAS-FW Co-AF with EPT was 40.8 % higher than WAS-AF without EPT. [ABSTRACT FROM AUTHOR]