Environmental impacts and nutrient distribution routes for food waste separated disposal on large-scale anaerobic digestion/ composting plants

Wasted Food, Wasted Resources? A Critical Review of Environmental Impact Analysis of Food Loss and Waste Generation and Treatment

Food loss and waste (FLW) comes with significant environmental impacts and thus prevents a sustainable food system transition. Here we conducted a systematic review of 174 screened studies that assessed the environmental impacts of FLW generation and treatment. We found that the embodied impacts of FLW along the supply chain and impacts from FLW treatment received equal attention, but few studies have included both. The reviewed studies show narrow geographical (mostly conducted in industrialized countries) and food supply chain (mostly focused on the consumption stage) coverage. Life cycle analysis (LCA), material flow analysis (MFA), or their combination are the most commonly used to quantify FLW related environmental impacts. More method standardization, integration, and innovation and better FLW data with regional and stage resolution from a first-hand source are badly needed. Among the various proposed mitigation strategies covering technology, economy, behavior, and policy aspects, process optimization and waste management options are the most discussed. Our review calls for a more holistic environmental impact assessment of FLW generation and treatment and analysis of the trade-offs among different environmental impact categories and between supply chain stages, which would better inform relevant policy on effective environmental impact mitigation strategies toward sustainable food systems.

A critical review for the impact of anaerobic digestion on the sustainable development goals

Anaerobic Digestion (AD) technology emerges as a viable solution for managing municipal organic waste, offering pollution reduction and the generation of biogas and fertilisers. This study reviews the research works for the advancements in AD implementation to effectively impact the UN Sustainable Development Goals (SDGs). Furthermore, the study critically analyses responsible waste management that contributes to health and safety, elevating quality of life in both rural and urban areas and, finally, creates a map of AD outputs onto all 17 SDGs. Finally, the assessment employs the three sustainability pillars (i.e., economic, environmental, and social perspectives) to examine the direct and indirect links between AD and all 17 UN SDGs. The findings reveal substantial progress, such as poverty reduction through job creation, bolstering economic growth (SDGs 1, 8, 10, 12), enhancing agricultural productivity (SDG 2), advancing renewable energy usage and diminishing reliance on fossil fuels (SDG 7), fostering inclusive education and gender equality (SDGs 4, 5, 9), combating climate change (SDG 13), transforming cities into sustainable and harmonious environments (SDGs 11, 16, 17), and curbing environmental pollution (SDGs 3, 6, 12, 14, 15). Nonetheless, the study highlights the need for further efforts to achieve the SDG targets, particularly in part of liquid and solid fertilisers as the AD outputs.

Literature review on the potential of urban waste for the fertilization of urban agriculture: A closer look at the metropolitan area of Barcelona

Urban agriculture (UA) activities are increasing in popularity and importance due to greater food demands and reductions in agricultural land, also advocating for greater local food supply and security as well as the social and community cohesion perspective. This activity also has the potential to enhance the circularity of urban flows, repurposing nutrients from waste sources, increasing their self-sufficiency, reducing nutrient loss into the environment, and avoiding environmental cost of nutrient extraction and synthetization. The present work is aimed at defining recovery technologies outlined in the literature to obtain relevant nutrients such as N and P from waste sources in urban areas. Through literature research tools, the waste sources were defined, differentiating two main groups: (1) food, organic, biowaste and (2) wastewater. Up to 7 recovery strategies were identified for food, organic, and biowaste sources, while 11 strategies were defined for wastewater, mainly focusing on the recovery of N and P, which are applicable in UA in different forms. The potential of the recovered nutrients to cover existing and prospective UA sites was further assessed for the metropolitan area of Barcelona. Nutrient recovery from current composting and anaerobic digestion of urban sourced organic matter obtained each year in the area as well as the composting of wastewater sludge, struvite precipitation and ion exchange in wastewater effluent generated yearly in existing WWTPs were assessed. The results show that the requirements for the current and prospective UA in the area can be met 2.7 to 380.2 times for P and 1.7 to 117.5 times for N depending on the recovery strategy. While the present results are promising, current perceptions, legislation and the implementation and production costs compared to existing markets do not facilitate the application of nutrient recovery strategies, although a change is expected in the near future.

Carbon/nitrogen flows and associated microbial communities in full-scale foodwaste treatment plants

Microorganisms play key roles in the conversion of organic matter in foodwaste. However, both the microbially-mediated element (carbon/C and nitrogen/N) flows and associated microbial communities in foodwaste treatment plants (FWTPs) remain unclear. This study collected samples of different foodwaste treatment units from five full-scale FWTPs to analyze the C/N flows and microbial communities in foodwaste treatment processes. Results showed that 39.8-45.0% of organic carbon in foodwaste was converted into biogas. Hydrolytic acidogenic bacteria (e.g., Lactobacillus and Limosilactobacillus) and eukaryota (e.g., Cafeteriaceae, Saccharomycetales, and Agaricomycetes) were more abundant in feedstock and pretreatment units. Redundancy analyses showed that acidogens were major players in the transformation of foodwaste organic matter. Populations of W27 and Tepidanaerobacter were major contributors to the difference in conversion of C/N in these FWTPs. This study could support foodwaste treatment efficiencies improvement by providing insights into C/N flows and associated microbiota in FWTPs.

Personal GHG emissions accounting and the driving forces decomposition in the past 10 years

Personal greenhouse gas (P_GHG) emissions were crucial for achieving carbon peak and neutrality targets. The accounting methodology and driving forces identification of P_GHG emissions were helpful for the quantification and the reduction of the P_GHG emissions. In this study, the methodology of P_GHG emissions was developed from resource obtaining to waste disposal, and the variations of Shanghainese P_GHG emissions from 2010 to 2020 were evaluated, with the driving forces analysis based on Logarithmic Mean Divisia Index (LMDI) model. It showed that the emissions decreased from 3796.05 (2010) to 3046.87 kg carbon dioxides (CO₂) (2014) and then increased to 3411.35 kg CO₂ (2018). The emissions from consumptions accounted for around 62.1% of the total emissions, and that from waste disposal were around 3.1%, which were neglected in most previous studies. The P_GHG emissions decreased by around 0.53 kg CO₂ (2019) and 405.86 kg CO₂ (2020) compared to 2018 and 2019, respectively, which were mainly affected by the waste forced source separation policy and the COVID-19 pandemic. The income level and consumption GHG intensity were two key factors influencing the contractively of GHG emissions from consumption, with the contributing rate of 169.3% and − 188.1%, respectively. Energy consumption was the main factor contributing to the growth of the direct GHG emissions (296.4%), and the energy GHG emission factor was the main factor in suppressing it (− 92.2%). Green consumption, low carbon lifestyles, green levy programs, and energy structure optimization were suggested to reduce the P_GHG emissions.

● The boundary of P_GHG emissions developed from resource obtaining to waste disposal.

● Shanghainese P_GHG emissions varied from 3004.64 to 3796.05 kgCO₂ in 2010-2020.

● Around 405.86 kg CO₂ decreased with the reduced consumption by COVID-19 lockdown.

● Energy consumption was the main contributor to DP_GHG emissions (296.4%) increase.

● The GHG intensity was the main contributor to IP_GHG emissions reduction (− 188.1%).

Effect of moisture content on the evolution of bacterial communities and organic matter degradation during bioaugmented biogas residues composting

Composting is an excellent way to recycle biogas residues into a stable, non-toxic agricultural end product. In this study, the dynamic changes of physical-chemical parameters and bacterial community in three groups of bioaugmentation composting systems at different moisture contents (MC) of 50% (MC50), 60% (MC60) and 70% (MC70) were monitored. The differences of bacterial communities in composts with different initial MC were compared, and the interaction between biological and non-biological parameters was also explored. The results revealed that after 30 days of composting, the biogas residues compost in MC60 reached highest temperature of 64 °C, total Kjeldahl nitrogen (TKN) of 2%, seed germination index (GI) of 110%, and the longest thermophilic period duration of 5 days (55 °C). Additionally, the result of high-throughput sequencing showed that the diversity of bacterial communities in MC60 was the highest, and the abundance of Actinobacteria (16.93-52.63%), Firmicutes (8.71-56.75%), and Proteobacteria (16.88-46.95%) in all groups were the highest at phylum level. The LEfSe analysis indicated that the abundance of Ochrobactrum and Cellulomonadaceae in MC60 was significantly (p < 0.05) higher than with other treatments. Moreover, canonical correspondence analysis (CCA) indicated thermophilic period duration is significantly (p < 0.05) positively correlated with Paenibacillus. Besides, it was found the relative abundance of Nocardiopsis and Georgenia has a significant (p < 0.01) correlation with the fertilizer efficiency of compost. These results showed that controlling the initial moisture content at 60% can improve the maturity and fertilizer efficiency of compost, and enable the bacteria beneficial to composting to gain the advantage of proliferation.