Life cycle assessment of sludge management with phosphorus utilisation and improved hygienisation in Sweden

Electrocoagulation in treatment of municipal wastewater- life cycle impact assessment

The purpose of this study is investigation of electrocoagulation (EC) as a treatment of municipal wastewater, integrating life cycle impact assessment (LCIA) for assessing its environmental performance of investigated treatment. The study evaluated the effectiveness of EC in removing physico-chemical and microbial parameters using aluminum (Al) and iron (Fe) electrodes in monopolar and bipolar modes. Bipolar arrangement of Al(-)/Al/Al/Al(+) electrodes achieved the highest removals: 70% COD, 72% BOD5 followed by complete elimination of total phosphorous, turbidity and microbial parameters. This treatment was subject to investigation of the influence of reaction time (t = 10-60 min) on removals at higher current density (CD = 3.33 mA/cm2). In order to reduce energy consumption, the same reaction time range was used with a reduced CD = 2.33 mA/cm2. Following removal efficiencies obtained: 47-72% COD (higher CD) and 53-78% (lower CD); 69-75% BOD5 (higher CD) and 55-74% CD (lower CD); 12-21% NH4- (higher CD) and 7-22% NH4- (lower CD). Total P, NO3- and NO2- compounds showed the same removals regardless the CD. Decrease in current density did not influence removals of total suspended matter, turbidity, salinity as well as microbial parameters. The bipolar arrangement of Al(-)/Al/Al/Al(+) electrodes, assuming a lower CD = 2.33 mA/cm2 and t = 30 min, was assessed with the Recipe 2016Midpoint (H) and USEtox v.2 LCIA methods to explore the environmental justification of using EC for wastewater treatment. The LCIA results revealed that the EC process significantly reduces water eutrophication and toxicity for freshwater and marine ecosystems, but has higher impacts in global warming, fossil fuel consumption, human toxicity, acidification, and terrestrial ecotoxicity due to high energy consumption. This can be mainly explained by the assumption in the study that the EC precipitate is dispersed to agricultural soil without any pre-treatment and material recovery, along with relatively high energy consumption during the process.

How Can Biodigesters Help Drive the Circular Economy? An Analysis Based on the SWOT Matrix and Case Studies

The use of biodigesters and the circular economy (CE) has been gaining attention in recent years. Both biodigesters and CE have the potential to minimize negative impacts—not only environmental, but also economic and social. However, little attention has been paid to the relationship between biodigesters and CE. Therefore, the objective of this paper is to identify and analyze the implications of the use of biodigesters in the light of a CE concept. To do this, a SWOT matrix was developed based on the opinion of experts and two case studies were conducted in companies operating in different sectors in Brazil. The results showed that the use of biodigesters can drive CE through biogas, which is a renewable energy source, closing the cycle of organic materials, increasing the economic power of companies and small producers, improving basic sanitation in remote areas, and stimulating industrial symbiosis. However, this study identified barriers in the use of biodigesters in the context of CE, such as lack of government incentives and composting being shown to be more cost-effective than the use of biodigesters for the treatment of solid waste.

Sustainable Agri-Food Processes and Circular Economy Pathways in a Life Cycle Perspective: State of the Art of Applicative Research

This study aims at providing a systematic and critical review on the state of the art of life cycle applications from the circular economy point of view. In particular, the main objective is to understand how researchers adopt life cycle approaches for the measurement of the empirical circular pathways of agri-food systems along with the overall lifespan. To perform the literature review, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol was considered to conduct a review by qualitative synthesis. Specifically, an evaluation matrix has been set up to gather and synthesize research evidence, by classifying papers according to several integrated criteria. The literature search was carried out employing scientific databases. The findings highlight that 52 case studies out of 84 (62% of the total) use stand-alone life cycle assessment (LCA) to evaluate the benefits/impacts of circular economy (CE) strategies. In contrast, only eight studies (9.5%) deal with the life cycle costing (LCC) approach combined with other analyses while no paper deals with the social life cycle assessment (S-LCA) methodology. Global warming potential, eutrophication (for marine, freshwater, and terrestrial ecosystems), human toxicity, and ecotoxicity results are the most common LCA indicators applied. Only a few articles deal with the CE assessment through specific indicators. We argue that experts in life cycle methodologies must strive to adopt some key elements to ensure that the results obtained fit perfectly with the measurements of circularity and that these can even be largely based on a common basis.

Life cycle assessment of nutrient recycling from wastewater: A critical review

Recovering resources from wastewater systems is increasingly being emphasised. Many technologies exist or are under development for recycling nutrients such as nitrogen and phosphorus from wastewater to agriculture. Planning and design methodologies are needed to identify and deploy the most sustainable solutions in given contexts. For the environmental sustainability dimension, life cycle assessment (LCA) can be used to assess environmental impact potentials of wastewater-based nutrient recycling alternatives, especially nitrogen and phosphorus recycling. This review aims to evaluate how well the LCA methodology has been adapted and applied for assessing opportunities of wastewater-based nutrient recycling in the form of monomineral, multimineral, nutrient solution and organic solid. We reviewed 65 LCA studies that considered nutrient recycling from wastewater for agricultural land application. We synthesised some of their insights and methodological practices, and discussed the future outlook of using LCA for wastewater-based nutrient recycling. In general, more studies suggested positive environmental outcomes from wastewater-based nutrient recycling, especially when chemical inputs are minimised, and source separation of human excreta is achieved. The review shows the need to improve methodological consistency (e.g., multifunctionality, fertiliser offset accounting, contaminant accounting), ensure transparency of inventory and methods, consider uncertainty in comparative LCA context, integrate up-to-date cross-disciplinary knowledge (e.g., agriculture science, soil science) into LCA models, and consider the localised impacts of recycled nutrient products. Many opportunities exist for applying LCA at various scales to support decisions on wastewater-based nutrient recycling - for instance, performing "product perspective" LCA on recycled nutrient products, integrating "process perspective" LCA with other systems approaches for selecting and optimising individual recovery processes, assessing emerging nutrient recovery technologies and integrated resource recovery systems, and conducting systems analysis at city, national and global level.