Indicators for resource recovery monitoring within the circular economy model implementation in the wastewater sector.

The European Union is currently in the process of transformation toward a circular economy model in which different areas of activity should be integrated for more efficient management of raw materials and waste. The wastewater sector has a great potential in this regard and therefore is an important element of the transformation process to the circular economy model. The targets of the circular economy policy framework such as resource recovery are tightly connected with the wastewater treatment processes and sewage sludge management. With this in view, the present study aims to review existing indicators on resource recovery that can enable efficient monitoring of the sustainable and circular solutions implemented in the wastewater sector. Within the reviewed indicators, most of them were focused on technological aspects of resource recovery processes such as nutrient removal efficiency, sewage sludge processing methods and environmental aspects as the pollutant share in the sewage sludge or its ashes. Moreover, other wide-scope indicators such as the wastewater service coverage or the production of bio-based fertilizers and hydrochar within the wastewater sector were analyzed. The results were used for the development of recommendations for improving the resources recovery monitoring framework in the wastewater sector and a proposal of a circularity indicator for a wastewater treatment plant highlighting new challenges for further researches and wastewater professionals.

Impact of utilizing solid recovered fuel on the global warming potential of cement production and waste management system: A life cycle assessment approach.

Cement production is responsible for a significant share of global greenhouse gas (GHG) emissions. A potential option to reduce the cement production emissions is to use alternative fuels which can have also an impact on emissions from the waste management sector. This work investigates the change in global warming potential (GWP) of ordinary Portland cement (OPC) production and affected waste management systems when conventional fuels are partially replaced by solid recovered fuel (SRF) made from commercial and industrial waste (C&IW). A life cycle assessment (LCA) was conducted with a functional unit of 1 metric tonne of OPC production and treatment of 194 kg of C&IW. Data from an existing cement plant have been used, where the share of SRF from total fuel energy demand increased from 0% to 53% between 2007 and 2016. Four scenarios were established with varying waste treatment methods and SRF share in the thermal energy mix of cement production. It was found that GHG emissions decreased by 20% from 1036 kg carbon dioxide (CO2), eq. (functional unit)-1 in Scenario 1 to 832 kg CO2, eq. (functional unit)-1 in Scenario 3. Furthermore, it is possible to reach a reduction of 30% to 725 kg CO2, eq. (functional unit)-1 in Scenario by increasing the share of SRF to 80%. In conclusion, significant GHG emissions reduction can be achieved by utilizing SRF in cement production. Especially in the middle-income and low-income countries where waste is dumped to the open landfills, emissions could be reduced without huge investments to waste incineration plants.

Life cycle assessment of alternative pulp mill sludge treatment methods in Finland.

Proper management of wastewater treatment plant side streams in pulp and paper mills is a matter of great interest. This study evaluates the environmental impact of different strategies in the management of biosludge from pulp and paper mills in Finland through a Life Cycle Assessment methodology. The base industrial standard practice, biosludge incineration for energy recovery and ash landfill disposal (Scenario 1), was compared to the alternative process of hydrothermal carbonization. The hydrochar generated from hydrothermal carbonization was evaluated for energy recovery through incineration (Scenario 2), or for use in composting for nutrient recovery (Scenario 3). The results showed that the hydrothermal process improved the overall environmental performance of the sludge management, particularly in terms of energy consumption and greenhouse gas emissions. The use of hydrochar as a soil amendment in composting also resulted in a significant reduction on the environmental impact compared to the other two scenarios. Overall, this study highlights the potential of hydrothermal carbonization and hydrochar utilization as sustainable options for managing biosludge from pulp mills.

Long-term evolution of the climate change impacts of solid household waste management in Lappeenranta, Finland.

Waste management processes have developed significantly in recent decades and will continue to change alongside the associated environmental impacts. This paper examines the climate change impacts of historical development in waste management, which has not received significant attention in the existing literature, while also exploring possible future developments. The city of Lappeenranta in Finland was selected as a case study, and the climate impacts of household waste (HW) management were calculated for the actual situations in 2009 and 2019 and the foreseen situation in 2029. Separately collected waste fractions of mixed residual waste (MRW), biowaste, cardboard, plastic, metal, and glass were included in the analysis. The results show that the net climate change impact decreased considerably from 945 kgCO2-eq./tHW in 2009 to -141 kgCO2-eq./tHW in 2019 mainly by directing the MRW to energy recovery instead of landfill. The emissions responsible for climate change could be further reduced in 2029 by directing biowaste to digestion instead of composting and by directing more fractions to recycling; e.g., plastic, the impact of which is affected by the demand for recycled plastic. For the year 2029, the net climate change impact was -181 kgCO2-eq./tHW when heat produced from MRW displaced natural gas and was as high as 142 kgCO2-eq./tHW if the heat substituted biomass heat. The findings reveal that as energy production mixes and materials become less fossil carbon intensive, they have a significant impact on the net climate impacts of waste management.

Climate impacts of source-separated biowaste from small neighbourhoods in Finland based on pilot experiments for novel biowaste collection systems.

The climate impacts of biowaste collection and utilisation were assessed based on data from two regional pilots. The EU's waste legislation will require biowaste source separation and collection from detached houses in communities with over 10,000 inhabitants starting from 2024 onwards. Two novel biowaste collection approaches were piloted in two Finnish case regions. One with biowaste collection to larger biolinks with a van and another with composting biowaste bins. The biolink approach reduces the need for waste truck driving, while composting biowaste bins enable an extended collection period. A life cycle assessment method was applied to assess the climate impacts of biowaste collection options and utilisation compared with current practices. The results show that source separation of biowaste and direction to biogas production leads to lower overall greenhouse gas (GHG) emissions at the system level compared with the current waste incineration option. Waste logistics has only a minor role in total GHG emissions, but a system based on biolinks and biowaste collection using a van led to the lowest GHG emission levels. Therefore, from a GHG emissions perspective, encouraging people to source separate their biowaste should be made as easy and encouraging as possible, no matter how the actual logistics is provided. However, novel and improved approaches for source-separated biowaste collection provide the potential for additional GHG emissions reductions.

Consequential life-cycle assessment of treatment options for repulping reject from liquid packaging board waste treatment.

Liquid packaging board is one of the highly demanded packaging mediums for liquid food and beverages, generating substantial waste each year. Even though the fibre part of the liquid packaging board is recycled through a repulping process, the plastic and aluminium are usually used for energy recovery and as alternative raw materials in cement factories. This practice reduces the life span and economic value of plastic and aluminium, which does not fit within a circular economy. The plastic and aluminium from liquid packaging board waste can be recycled mechanically and chemically. This study used the consequential life-cycle assessment method to compare the environmental impact of the recovery options of rejected materials from liquid packaging board waste treatment. Four scenarios were established: (1) energy recovery by waste incineration, (2) composite pallet production by mechanical recycling, (3) plastic pallet production by mechanical recycling, and (4) plastic pallet production by chemical recycling. The study showed that when the consumed energy was supplied from renewable sources, plastic pallet production by mechanical recycling process had the lowest environmental impact, and energy recovery by waste incineration had the highest impact. A sensitivity analysis revealed that composite pallet production by mechanical recycling process showed the best impact if the energy was sourced from the average production mix, and plastic pallet production by chemical recycling had the lowest impact when mechanically recycled plastic substituted for 0%, 30%, and 50% of virgin plastic. These results should be of interest to liquid packaging board manufacturers and other related stakeholders.

Potential of energy and nutrient recovery from biodegradable waste by co-treatment in Lithuania.

Biodegradable waste quantities in Lithuania and their potential for the co-treatment in renewable energy and organic fertilizer production were investigated. Two scenarios were formulated to study the differences of the amounts of obtainable energy and fertilizers between different ways of utilization. In the first scenario, only digestion was used, and in the second scenario, materials other than straw were digested, and straw and the solid fraction of sewage sludge digestate were combusted. As a result, the amounts of heat and electricity, as well as the fertilizer amounts in the counties were obtained for both scenarios. Based on this study, the share of renewable energy in Lithuania could be doubled by the co-treatment of different biodegradable materials.

Environmental performance of dewatered sewage sludge digestate utilization based on life cycle assessment.

Due to the global trend of urbanization, the amount of sewage water is increasing in cities. This calls for efficient treatment of the resulting sewage sludge. To date, in the 27 European Union member countries (EU-27), the prevailing treatment method is application on arable land. Anaerobic digestion is one of the treatment methods being increasingly used nowadays. However, the resulting digestate requires further utilization. Therefore, in this study, the environmental performance of composting, combustion, and pyrolysis options for dewatered sewage sludge digestate is evaluated based on a life cycle assessment. The results show that digestate combustion and composting performed better than pyrolysis for most of the selected impact categories. However, pyrolysis of sewage sludge is still under development, and there are, to some degree, uncertainties in the data related to this technology; thus, more information for the performance assessment of pyrolysis is still required.

Optimizing energy dispersive X-Ray Spectroscopy (EDS) image fusion to Scanning Electron Microscopy (SEM) images.

Fusion and quality enhancement of the low-resolution Energy Dispersive X-ray Spectroscopy (EDS) maps to Scanning Electron Microscopy (SEM) panchromatic images has been proven effective by various pansharpening algorithms. The present paper aims to target the preprocessing of these maps to enhance the efficiency of the pansharpening process, with as little information loss on the chemical distribution, and as little propagated noise as possible. EDS maps present different noise intensities depending on the flatness of the surface of the analyzed object. The uneven surface maps have limited analytical value due to the noise and have not been resolution-enhanced with pansharpening due to the noise propagation limitation. In this paper, different preprocessing methods are evaluated for enabling uneven-surface particles to pansharpening: background removal, upsampling, and noise filtering. The sequence of applying preprocessing steps is analyzed. The optimal order of preprocessing steps is (i) background removal, (ii) noise filtering, and (iii) interpolation. A methodology for each of these steps is presented in the paper. The best performing pansharpening methodology is chosen to be Affinity for individual map analysis and Wavelet for multi-elemental fusion purposes. Following the methodology results in high-resolution EDS maps, even for uneven-surface particles which are, for the first time in literature, subjected to pansharpening.

Carbon footprint of different recovery options for the repulping reject from liquid packaging board waste treatment process.

Liquid packaging board (LPB) is an integral part of storing and transporting liquid food. In addition to its significant advantages, LPB has been challenging the existing waste management sector since its introduction into the market. In most European countries, LPB waste is either incinerated or recycled in the recycling facilities where fibre is recycled, and the repulping reject is separated for incineration. Mechanical recycling and chemical recycling processes are other options for repulping reject treatment. This study used life cycle assessment (LCA) to compare the environmental impacts of three treatment processes, incineration, mechanical recycling and chemical recycling; each was considered with the functional unit of 1 tonne of repulping reject. Furthermore, two sub-scenarios based on the substituted heat produced by energy from the treatment processes were considered. In substituting biomass-based heat sources, chemical recycling generated the lowest greenhouse gas (GHG) emissions, about 560 kg CO2 eq. tonne-1 repulping rejects, followed by the mechanical recycling process (approximately 740 kg CO2 eq. tonne-1 repulping reject). The maximum amount of GHG was emitted from the incineration scenario, which was about 1900 kg CO2 eq. tonne-1 repulping rejects. By substituting natural gas-based heat sources, chemical recycling generated about 290 kg CO2 eq. tonne-1 repulping rejects. On the contrary, the mechanical recycling process generated about 430 kg CO2 eq. tonne-1 repulping rejects and incineration process generated 960 kg CO2 eq. tonne-1 repulping rejects. Uncertainty analysis showed that some assumptions significantly impact the results; however, the chemical recycling process had the lowest environmental impact in almost all uncertainty analysis.

Applicability of a field portable X-ray fluorescence for analyzing elemental concentration of waste samples.

Determining the chemical properties of waste is crucial to ensure the most effective utilization of waste. The standard laboratory measurements can produce accurate results, but analysis is labor- and time-consuming. The variety of elements that field portable X-ray fluorescence spectrometry (FPXRF) can detect from selected waste materials was studied, including how the results compared with those of inductively coupled plasma mass spectrometry (ICP-MS) measurements. The selected materials were fine fraction reject from solid recovered fuel production, fly ash, biowaste, and compost. Based on the results, FPXRF is reported to be best suited for waste samples, such as ash and compost, because of their physical properties, as follows: not too moist, quite small particle size, and not too heterogeneous. The results obtained from FPXRF showed the lowest relative standard deviation for ash material. The analysis of the limits of agreement between FPXRF and ICP-MS showed that FPXRF was mainly suitable for qualitative assessment. Furthermore, regression analysis showed a linear correlation between FPXRF and ICP-MS results for calcium and zinc in the selected materials. Keeping the limitations in mind, FPXRF could be used for qualitative analysis in waste treatment processes, such as first quality control of waste materials.

Technical implications and global warming potential of recovering nitrogen released during continuous thermal drying of sewage sludge.

Thermal drying and consequent incineration of sewage sludge result in an absolute loss of an important macronutrient - nitrogen. To fulfill the growing food demand, humanity relies more on industrial fixation of nitrogen, primarily via the Haber-Bosch process. The present paper examines the nitrogen release during continuous thermal drying of municipal sewage sludge and its consequent recovery for fertilization. Furthermore, the possibility of nitrogen recovery from condensate is assessed. Finally, the study assesses the global warming potential of the proposed nitrogen recovery system and compares it with the baseline system manufacturing fertilizers from industrially fixed nitrogen. The results of the drying experiments showed that 0.73-1.03 g N-NH3 kg-1 total solids of sewage sludge was released to off-gases during its continuous thermal drying under 160 °C, which corresponds to 41-58% of ionized nitrogen content in raw sewage sludge subjected to thermal drying. The global warming potential of the nitrogen recovery was 28% lower compared to that of the commercial fertilizer production of equivalent properties: 4.1 kg CO2-Equiv. kg-1 N versus 5.7 kg CO2-Equiv. kg-1 N. Still, the sensitivity analysis showed that the results might traverse and lead to a higher global warming potential of 6.2 kg CO2-Equiv. during the nitrogen recovery process under certain process parameters.

Nitrogen behaviour during thermal drying of mechanically dewatered biosludge from pulp and paper industry.

An ongoing call to implement a circular economy is underway in the European Union, and a specific attention has been placed on the forest industry, which seeks additional recycling routes for its side streams, including biosludge. Biosludge is often dried and incinerated, thus wasting the nitrogen contained therein. This paper describes a study in which the release of nitrogen during thermal drying, the impact of the drying temperatures of 130°C, 180°C, and 210°C on the mass of ammonia released, and the potential for recovery of nitrogen from biosludge were examined. The results indicate that 1310-1730 mg kgTS-1 of nitrogen was released, which corresponded to 56-74% of the soluble nitrogen in biosolids or 4.0-5.3% of the total nitrogen. Of this released nitrogen, 83-85% was identified in condensate and absorbing water, thus indicating a high potential for recovering nitrogen from biosludge.

Modeling and comparative assessment of bubbling fluidized bed gasification system for syngas production - a gateway for a cleaner future in Pakistan.

The present study explores the potential of MSW gasification for exergy analysis and has been recently given a premier attention in a region like Pakistan where the urbanization is rapidly growing and resources are few. The plant capacity was set at 50 MW based on reference data available and the total exergetic efficiency was recorded to be 31.5 MW. The largest irreversibility distribution appears in the gasifier followed by methanation unit and CO2 capture. The effect of process temperature, equivalence ratio and MSW moisture content was explored for inspecting the variations in syngas composition, lower heating value, carbon conversion efficiency and cold gas efficiency. Special attention of the paper is paid to the comparative assessment of MSW gasification products in four regions, namely Pakistan, USA, UAE and Thailand. This extended study gave an insight into the spectrum of socioeconomic conditions with varying MSW compositions in order to explain the effect of MSW composition variance on the gasification products.

Potential of phosphorus recovery from sewage sludge and manure ash by thermochemical treatment.

All life forms require phosphorus (P), which has no substitute in food production. The risk of phosphorus loss from soil and limited P rock reserves has led to the development of recycling P from industrial residues. This study investigates the potential of phosphorus recovery from sewage sludge and manure ash by thermochemical treatment (ASH DEC) in Finland. An ASH DEC plant could receive 46-76 kt/a of sewage sludge ash to produce 51-85 kt/a of a P-rich product with a P2O5 content of 13-18%, while 320-750 kt/a of manure ash could be supplied to produce 350-830 kt/a of a P-rich product with a P content of 4-5%. The P2O5 potential in the total P-rich product from the ASH DEC process using sewage sludge and manure ash is estimated to be 25-47 kt/a, which is significantly more than the P fertilizer demand in Finland's agricultural industries. The energy efficiency of integrated incineration and the ASH DEC process is more dependent on the total solid content and the subsequent need for mechanical dewatering and thermal drying than on the energy required by the ASH DEC process. According to the results of this study, the treated sewage sludge and manure ash using the ASH DEC process represent significant potential phosphorus sources for P fertilizer production.

Recycling ash into the first stage of cyclone pre-heater of cement kiln.

Fly ash collected from the bag filter could be recycled into the first stage of the cyclone pre-heater of the cement kiln, resulting in the possible enrichment of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). In this study, soxhlet fly ash (SFA) and raw meal (RM) were selected as the basis for the PCDD/F formation experiments. The levels of 2,3,7,8-PCDD/Fs formed on the SFA and RM were observed to be 2550pg/g (157pg I-TEQ/g) and 1142pg/g (55pg I-TEQ/g), respectively. While less 2,3,7,8-PCDD/Fs was detected when SFA was mixed with RM, suggesting that recycling cement kiln ash would not largely increase the concentration of PCDD/Fs in flue gas. Furthermore, the possible influencing factors on the PCDD/F formation were also investigated. The formation of 2,3,7,8-PCDD/Fs was up to 10,871pg/g (380pg I-TEQ/g) with the adding of CuCl2, which was much higher than the results of CuO and activated carbon. Most importantly, the homologue, congener and gas/particle distribution of PCDD/Fs indicated that de novo synthesis was the dominant PCDD/F formation pathway for SFA. Lastly, principal component analysis (PCA) was also conducted to identify the relationship between the compositions of reactant and the properties of PCDD/Fs produced.

Understanding biorefining efficiency--the case of agrifood waste.

The aim of this study was to determine biorefining efficiency according to the choices made in the entire value chain. The importance of the share of biomass volume biorefined or products substituted was investigated. Agrifood-waste-based biorefining represented the case. Anticipatory scenarios were designed for contrasting targets and compared with the current situation in two Finnish regions. Biorefining increases nutrient and energy efficiency in comparison with current use of waste. System boundaries decisively influence the relative efficiency of biorefining designs. For nutrient efficiency, full exploitation of biomass potential and anaerobic digestion increase nutrient efficiency, but the main determinant is efficient substitution for mineral fertilisers. For energy efficiency, combustion and location of biorefining close to heat demand are crucial. Regional differences in agricultural structure, the extent of the food industry and population density have a major impact on biorefining. High degrees of exploitation of feedstock potential and substitution efficiency are the keys.