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22 pages, 1084 KiB

Open AccessFeature PaperArticle

Environmental and Economic Performance of Sludge Composting Optimization Alternatives: A Case Study for Thermally Hydrolyzed Anaerobically Digested Sludge

by Irina Kliopova, Edgaras Stunžėnas, Jolita Kruopienė and Rimas Pranas Budrys

Water 2022, 14(24), 4102; https://doi.org/10.3390/w14244102 - 15 Dec 2022

Cited by 4 | Viewed by 2777

Abstract

Composting is one of the ways to return sewage sludge nutrients to the soil and thus keep them in the economic cycle. This well-known technique is still being developed in search of more advanced, optimal solutions. This study presents the results of an environmental and economic analysis of the sludge treatment processes used in a municipal wastewater treatment plant. The sludge (up to 4700 m³ per day) is subjected to thermal hydrolysis before anaerobic treatment. The energy produced is lower than consumed, mainly since 59% of the digested sludge is also dried. An even bigger problem is that the treated sludge does not meet the criteria for fertilizing products and can only be used for energy forests. Thus, three alternatives for composting thermally hydrolyzed anaerobically treated dewatered sludge with green waste from public areas were researched. The analysis revealed the environmental and economic benefits of such a decision, especially when using microbial inoculants in open composting and maintaining semi-anaerobic conditions. An increase in humic acids (by 63.4%) and total nitrogen (by 21.8%) concentrations, a minimization of NH₃ emissions (by 26.6%), and the lowest cost price (53 EUR tonne⁻¹ of sludge dry matter) are among the benefits. Full article

(This article belongs to the Special Issue Utilization and Treatment of Sewage Sludge)

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16 pages, 3963 KiB

Open AccessEditor’s ChoiceArticle

Environmental and Economic Implication of Implementation Scale of Sewage Sludge Recycling Systems Considering Carbon Trading Price

by Jiawen Zhang, Zhiyi Liang, Toru Matsumoto and Tiejia Zhang

Sustainability 2022, 14(14), 8684; https://doi.org/10.3390/su14148684 - 15 Jul 2022

Cited by 6 | Viewed by 3408

Abstract

With China’s ongoing economic development and increasing emphasis on environmental protection, the number and treatment capacity of sewage plants is increasing annually. Simultaneously, sludge production is increasing. In recent years, researchers have investigated various approaches to the environmental and economic analysis of sludge treatment and recycling systems (STRS). These investigations did not take the universal law of different capacities for environmental impact and STRS economics into account. The aim of this study was to analyze the scale effect of STRS with different technologies (i.e., incineration, aerobic composting, used in material (brick), anaerobic digestion) on the environment and economy. Moreover, the cost–benefit impact of introducing a carbon- trading mechanism into the STRS to achieve carbon neutrality was analyzed. After reducing carbon emissions through by-products of STRS, the carbon emission quota can be sold, which will generate income. The results show that the break-even scales for incineration, anaerobic composting, used in building material (brick), and anaerobic digestion are 54,899, 6707, 48,775, and 4425 t/y, respectively. The break-even scale of each system decreased after the introduction of the carbon trading system into the STRS. These findings could provide critical technical information for superior decision-making in sewage sludge recycling systems. Full article

(This article belongs to the Collection Waste Management towards a Circular Economy Transition)

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31 pages, 4393 KiB

Open AccessArticle

Regionalized Strategies for Food Loss and Waste Management in Spain under a Life Cycle Thinking Approach

by Daniel Hoehn, Jara Laso, Jorge Cristóbal, Israel Ruiz-Salmón, Isabela Butnar, Aiduan Borrion, Alba Bala, Pere Fullana-i-Palmer, Ian Vázquez-Rowe, Rubén Aldaco and María Margallo

Foods 2020, 9(12), 1765; https://doi.org/10.3390/foods9121765 - 28 Nov 2020

Cited by 16 | Viewed by 5454

Abstract

Food loss and waste (FLW) has become a central concern in the social and political debate. Simultaneously, using FLW as a bioenergy source could significantly contribute to closing the carbon cycle by reintroducing energy into the food supply chain. This study aims to identify best strategies for FLW management in each of the 17 regions in Spain, through the application of a Life Cycle Assessment. To this end, an evaluation of the environmental performance over time between 2015 and 2040 of five different FLW management scenarios implemented in a framework of (i) compliance and (ii) non-compliance with the targets of the Paris Agreement was performed. Results revealed savings in the consumption of abiotic resources in those regions in which thermal treatment has a strong presence, although their greenhouse gas (GHG) emissions in a scenario of compliance with climate change targets are higher. In contrast, scenarios that include anaerobic digestion and, to a lesser extent those applying aerobic composting, present lower impacts, including climate change, suggesting improvements of 20–60% in non-compliance and 20–80% in compliance with Paris Agreement targets, compared to the current scenarios. Full article

(This article belongs to the Special Issue Sustainable Utilisation and Management of Food Waste)

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