Carbon Footprint Analysis Research Articles

Carbon Footprint of Electric Vehicles—Review of Methodologies and Determinants

The carbon footprint of a product and organization is one of the most important environmental indicators in many sectors, including transport. Consequently, electric vehicles (EV) are being introduced as an alternative to achieve decarbonization targets. This article presents an overview of methodologies for assessing the carbon footprint of electric vehicles, including a review of concepts, methods, standards, and calculation models based on the life cycle of the carbon footprint. The article also includes a systematic review of the results of EV carbon footprint analyses. The analysis of current knowledge on the carbon footprint focuses on road transport vehicles: Battery Electric Vehicles (BEV), Fuel Cell Electric Vehicles (FCEV), Hybrid Electric Vehicles (HEV), and Plug-in Hybrid Electric Vehicles (PHEV). Additionally, a review of factors determining the carbon footprint assessment of electric vehicles, considering their entire life cycle, has been conducted.

Analysis of Carbon Footprint from a Drilling Project in Niger Delta, Nigeria

Abstract: The oil and gas industry plays a significant role in the release of carbon emissions into the atmosphere. Therefore, it is crucial to accurately gauge and minimize its carbon footprint which requires the thorough measurement of emissions and the identification of the primary sources of carbon emissions. By doing so, we can then determine the most effective methods for reducing these emissions. This study aims to precisely quantify and decrease the carbon footprint associated with drilling operations. To achieve this, we evaluated the diesel and petrol consumption from an onshore drilling project in the Niger Delta and used an emissions model to assess carbon dioxide (CO2) emissions from a drilling rig, thus gaining a comprehensive understanding of current emission levels and the potential for reduction. The data collected included the daily fuel consumption for power generation, transportation, and handling vehicles. The CO2 emissions resulting from fuel consumption were calculated and measured to be 103.5 metric tonnes. Our analysis determined that the primary contributor to the emissions was the energy generation on the site, primarily from the generators. Additionally, it was found that the circulating system on the rig was the main source of CO2 emissions. The study underscores the necessity for long-term impact assessments of drilling fluids and new technologies, emphasizing the need for innovative solutions to further decrease emissions.

Effect of alternative dosing strategies of pembrolizumab and nivolumab on health-care emissions in the Netherlands: a carbon footprint analysis

Hospitals contribute substantially to greenhouse gas emissions and face a moral obligation to prioritise emission reduction. Drugs constitute an important component of the greenhouse gas emissions of hospitals. Alternative dosing strategies (ADS) have been implemented to improve the cost-effectiveness of pembrolizumab and nivolumab. However, the impact of these ADS on greenhouse gas emissions remains unknown. Therefore, we aimed to analyse the effect of ADS implementation on the carbon emissions of treatment with pembrolizumab and nivolumab. We used a process-based lifecycle assessment to quantify the environmental impact of pembrolizumab and nivolumab, focused on equivalent carbon dioxide emissions (CO2e). Lifecycle inventory and impact data from Erasmus University Medical Center (Rotterdam, Netherlands) were used to calculate the CO2e for pembrolizumab and nivolumab, their dosing intervals, and the impact of ADS on CO2e. The functional unit of the study was the administration of a single dose of pembrolizumab or nivolumab. In 2022, the annual carbon emissions related to pembrolizumab and nivolumab treatment in the Erasmus University Medical Center were 445 tons of CO2e, averaging 94 kg of CO2e per dose. Pharmaceutical production was the main driver of treatment-related carbon emissions (mean 92·9% of total emissions). Applying ADS resulted in 21-26% and 9-11% CO2e reductions for pembrolizumab and nivolumab, respectively. This study shows the environmental impact of pembrolizumab and nivolumab treatment and calls for further implementation of ADS for pembrolizumab, nivolumab, and other anti-PD-(L)1 monoclonal antibodies, and more sustainable pharmaceutical production processes. Our findings create environmental awareness and contribute to the promotion and understanding of health-care practices with lower carbon emissions. None.

Exergy-economic based multi-objective optimization and carbon footprint analysis of solar thermal refrigeration systems

The increasing carbon footprint associated with conventional cooling methods underscores the urgent need for sustainable alternatives. This study investigates the economic and environmental advantages of various solar-thermal cooling systems, with a focus on optimizing their performance across different climate conditions. Employing a multi-objective approach, the research emphasizes exergy-economic indices to optimize selected cycles. The analysis covers multiple refrigeration technologies, including liquid absorption, solid adsorption, and solid desiccant cycles. Results indicate that the liquid absorption cycle performs optimally in hot, arid climates, reducing the payback period to approximately 8 years when optimized. In hot and humid regions, the solid desiccant cycle proves most effective due to its superior humidity control, yielding a payback period of 5.3 years. For cold and mountainous areas, the solid adsorption cycle is preferred, with a payback period of 13.5 years, while moderate and humid climates benefit from the solid desiccant cycle for both cooling and humidity regulation. The exergy-economic factors for the solar refrigeration systems across semi-arid, hot and arid, hot and humid, cold and mountainous, and moderate and humid climates are 0.758, 0.602, 0.698, 0.74, and 0.575, respectively.

Comparative techno-economic and carbon footprint analysis of 2,3-butanediol production through aerobic and anaerobic bioconversion of carbon dioxide with green hydrogen

Renewable CO2 and hydrogen have the potential to be the feedstocks of a decarbonized chemical industry, and biochemical conversions offer new alternatives for the industry. There are two options among chemolithotrophic bacteria capable of CO2 fixation: under aerobic conditions, through the use of the Calvin-Benson-Basham cycle, known to produce large-chain compounds, and under anaerobic conditions, through the Wood-Ljungdahl pathway, known to produce short-chain organic molecules. Here, we report a comparison of both bioconversions, made at a simulated industrial scale, considering techno-economic and environmental variables, and using renewable CO2 and H2 as feedstocks. 2,3-butanediol, a mid-range chain compound that can be produced via both routes, was selected for comparison. The comparison was set up in Chile due to expected low-cost renewable hydrogen and renewable CO2 availability. The assessment showed that the minimum selling price of 2,3-butanediol in the anaerobic case was higher (3.91 (USD kg−1)) than in the aerobic case (3.36 (USD kg−1)), with hydrogen being the largest expense in both processes (50 % and 70 % of total expenses respectively). Further, owing to metabolic restrictions, the anaerobic process required almost five times more CO2 than the aerobic process to produce the same amount of 2,3-butanediol. A Monte Carlo analysis showed that in most scenarios the aerobic process was more economically favorable. In environmental terms, the aerobic process had a smaller carbon footprint in all the evaluated scenarios. Therefore, the results suggest that the aerobic process is a more suitable alternative to anaerobic bacteria-based processes for producing 2,3-butanediol from renewable CO2 and hydrogen.

Sustainability Assessment of Agricultural Waste Biogas Production System in China Based on Emergy and Carbon Evaluation Methods

Biogas production is widely recognized as an effective solution for addressing agricultural waste treatment in rural areas. However, its development is often hindered by economic and environmental constraints. This study combined emergy evaluation and carbon footprint analysis methods to establish a new environmental radius assessment model for evaluating the ecological performance and optimization direction of an agricultural waste biogas production system, using a biogas production company in China as a case study. Compared with the straw return model and straw power generation model, the results of emergy indicators and carbon accounting showed that the biogas production model had a lower environmental load and higher economic output and level of emergy sustainability. Additionally, the biogas production system was found to reduce 0.47 kg of carbon emissions per 1 kg of agricultural waste utilized. The application of the biogas production model in rural areas had high ecological sustainability and carbon emission reduction benefits. Environmental radius assessment results confirmed that the reasonable changes in resource collection distance could further enhance the ecological sustainability, carbon mitigation ability, and economic benefits of the biogas production system. The environmental radius assessment method offers a new approach to the location planning of agricultural waste biogas utilization companies in rural areas.

Comparative Analysis of Carbon Footprints from Away and Home Matches: A Study on Leading Basketball and Football Teams in Türkiye

Problem: Basketball and football teams in Türkiye have the capacity to travel hundreds of kilometres for league matches. In general, such major leagues and leading teams travelling from Türkiye have not been sufficiently researched in the context of Türkiye’s leading leagues and teams. In this context, the aim of this study is to assess and compare the carbon footprint of the transport activities of basketball and football teams in Türkiye for their home and away matches for the 2023–2024 season. Methods: The research is based on EN 16258 and ICAO carbon emissions methodologies. This study aims to calculate and compare the carbon footprint of different transport methods, including bus and plane, used by five basketball and football teams in Türkiye. Results: The findings show that there are significant differences between the teams in terms of travelling distances and carbon footprints. Trabzonspor from the Black Sea region released the highest CO2 emissions from air travel with a total of 91,667.1 kgCO2e, while Fenerbahçe Beko had the lowest CO2 emissions with 5316.72 kgCO2e. In terms of bus travel, Gaziantep FK led the CO2 emissions with 4356.45 kgCO2e, while Türk Telekom was the team with the lowest CO2 emissions with 1233.225 kgCO2e. The findings also reveal a notable difference in the number of trees teams need to plant to offset their carbon emissions. Because of their travel patterns, Antalyaspor would need to plant 3481 trees, whereas Fenerbahçe Beko would only need to plant 348 trees. Conclusions: Air travel is emerging as the dominant source of CO2 emissions and has a greater impact on the environmental impact of teams that rely heavily on airplanes. In this study, the league structure and duration play a critical role in shaping the carbon footprint of sports teams. The football season, which is longer compared to basketball, requires more frequent travel, especially for teams in more remote regions, resulting in higher carbon emissions than basketball. The dominance of Marmara region teams in basketball has a negative impact on the carbon footprint since these teams generally have shorter travel distances.

Sustainable Energy Solutions in Sub-Saharan Africa: Integrating Indigenous Knowledge and Climate Resilience for Lower Carbon Emissions

Promoting sustainable energy solutions in sub-Saharan countries is crucial for addressing energy poverty, reducing carbon emissions, and fostering long-term environmental and economic sustainability. This study explored using indigenous knowledge and emerging technologies to reduce carbon footprints and GHG emissions in Africa's climate hotspots in sub-Saharan countries. The study revealed that operating institutions utilize various applications to ensure that energy management resources can mitigate the effects of carbon emissions. The study revealed that the most efficient use of natural resources for energy production requires collaboration among governments, private sectors, NGOs, and local communities. By adopting a holistic and inclusive approach, one can work toward a more sustainable and low-carbon energy future. This paper focuses on carbon footprint analysis and proposes solutions to address environmental issues in implementing sustainable energy solutions in sub-Saharan countries. A multifaceted approach involving effective strategies is needed to lower the carbon footprint. The contribution of this study is to improve energy consumption in communities in Africa by integrating climate resilience considerations into sustainable energy projects to ensure long-term viability. This will involve planning for changing climate conditions, such as extreme weather events, and designing infrastructure that can withstand and adapt to these challenges. It has been concluded that carbon footprint analysis is useful for determining the impacts of carbon particles in the world’s atmosphere. The role of energy management operations seeks to improve the assessment and analysis of carbon footprints by allowing atmospheric measurements of carbon.

LCA-based carbon footprint analysis of anaerobic digestion of coffee husk waste

While studies have shown that anaerobic digestion (AD) with energy generation of agricultural residues have many benefits, it is still unclear the extent to which this technology can reduce greenhouse gas (GHG) emissions, particularly in the context of coffee husk wastes. To address this knowledge gap, this work explored three scenarios of coffee husks as an energy source: 0) business-as-usual (landfilling); 1) AD with energy generation; 2) same as the previous one, adding a hydrothermal hydrolysis pre-treatment step. The study adopted a Life Cycle Assessment (LCA) methodology to estimate the environmental impacts of this technology in terms of GHG emissions. The results indicate that the main benefit of using AD is to avoid the impacts of landfilling, as the carbon footprint for the landfilling scenario was more than 13 times higher than the others. The emissions from digestate management were the main source of the overall emissions, accounting for 34 %. However, its use to replace chemical fertilizers affected the environmental performance positively. The inclusion of the pre-treatment was a key factor in making the bioenergy from coffee husks less carbon-intensive than natural gas and oil, although common renewable sources such as wind and hydropower tend to have lower GHG emissions. Sensitivity analyses indicate that this type of bioenergy can mitigate GHG emissions from energy generation in coffee-producing countries with fossil-based energy mixes. Overall, this work fills a knowledge gap by providing empirical evidence to the potential benefits of using coffee husks in the world's transition to a low-carbon economy.

Spent lithium-ion battery recycling: Process optimization and carbon footprint analysis based on thermal mechanical force

ABSTRACT With the increasing number of spent lithium-ion batteries, the development of efficient and environmentally friendly recycling technologies has become a key research focus. This study aims to establish a physical recycling method that integrates thermal treatment and mechanical separation to enhance the recovery rate of LiFePO4 materials while minimizing environmental impact. The process combines thermal treatment, mechanical separation, and air separation, with key factors influencing material separation and recovery efficiency analyzed through single-factor and variance analyses. Additionally, the carbon footprint of the recycling process was assessed using SimaPro software. The experimental results indicate that within a temperature range of 270°C–300°C, thermal treatment effectively separates LiFePO4 from aluminum foil, achieving a recovery rate of 96.88%. The air separation experiments further demonstrate that at an airflow speed of 20 m/s, the cathode material and current collector can be efficiently separated. Moreover, the carbon footprint analysis shows that this method significantly reduces carbon emissions.

Exploring the feasibility of home-delivered capsule endoscopy with 5G support: innovations and carbon footprint insights.

Colorectal cancer (CRC) poses a significant global health threat, necessitating early detection. Traditional diagnostic tools like optical colonoscopy have limitations prompting our '5G-SUCCEEDS' initiative to explore a novel approach involving remote colon capsule endoscopy (CCE). This prospective feasibility study was conducted at a single hospital in England. Between December 2022 and September 2023, we introduced a remote CCE service within the 5G-SUCCEEDS framework. We undertook a feasibility study of CCE in patients with low-risk/moderate-risk CRC stratified by faecal haemoglobin. Outcomes included carbon footprint analysis (outlined through three potential clinical pathways) and patient-reported outcomes through structured questionnaires and interviews. Among 25 participants, 88% expressed satisfaction with remote CCE. 82% were willing to have remote CCE if clinically indicated in future. CCE findings included adenomatous polyps (58%), normal results (17%) and diverticulosis (21%), with no cancers identified in this pilot. Notably, we found that the carbon footprint associated with delivery of CCE at home (pathway 3) was lower compared with CCE delivered in a clinical setting (pathway 2). A fully optimised, automated scaled-up pathway would combine the delivery and collection of CCE equipment within a local area to reduce the carbon footprint of the travel element by 75%. Moreover, the conversion rate into a colonoscopy pathway is not static and clinicians acknowledge that this could be as low as 28%. Carbon footprint is more favourable for home-delivered CCE in the optimised scenario, while less so when considering the need for additional procedures (colonoscopy conversion). The 5G-SUCCEEDS initiative highlights the feasibility and advantages of home-based diagnostics using CCE.

Can reusable packaging revolutionise e-commerce? Unveiling the environmental impact through a comparative carbon footprint analysis

E-commerce is a rapidly growing, evolving sector. Its environmental impact has also increased, with shipping packaging being a key contributor. The sector is, however, struggling to tackle this environmental impact, as well as to follow new packaging regulations. Previous studies on reusable packaging have predominantly been qualitative or concentrated on material selection, overlooking essential elements of supply chain design and consumer behaviour. Industry reports attempting to quantify the sustainability of reusable packaging have produced varied results that lack generalisability or transferability to other contexts. Consequently, it is difficult to determine the actual environmental sustainability of reusable packaging in e-commerce. In this research, we assess the carbon footprint of reusable packaging in e-commerce, through a comparison of eight case studies. A multiple case study approach is followed, employing an embedded design where more than one unit of analysis is explored in each case. We evaluate the CO2 emissions of all processes related to the circular supply chain of reusable packaging employing a method that can evaluate different solutions and situations and a sensitivity analysis. Findings highlight three specific factors influencing the carbon footprint of reusable packaging: (1) reusable packaging material, (2) return and reuse rate, and (3) supply chain design (i.e., centralised versus decentralised design, travel distance, transport mode). For the same type of reusable packaging, we found that polyester generates 215% more CO2 emissions than cardboard in production and waste management. However, by analysing the same reusable packaging and supply chain, these same emissions can drastically increase if the return and reuse rate decreases. Changes in the return and reuse rate mainly linked, among others, to customer behaviour and involvement. Furthermore, for the same reusable packaging and return and reuse rate, a decentralised supply chain can reduce the CO2 emissions compared to a centralised structure. Interestingly, reusable packaging is environmentally sustainable long before it reaches its maximum life cycle. Most of the analysed solutions were more environmentally friendly than a cardboard box when they reached 10% of their estimated life cycle.

A study on ecological sustainable cities based on LCA-emergy-carbon footprint and geographic information system (GIS) approach

ABSTRACT Sustainable cities, as an effective response to global climate aberrations, have increasingly garnered the attention of researchers. However, due to the wide range of interpretations and applications associated with sustainable cities, diverse methodologies can yield starkly contrasting results. This paper adopts ecological and low-carbon perspectives to evaluate and discuss urban sustainability. The core of this investigation involves quantitatively measuring a city’s sustainability based on the lifecycle metrics of emergy and carbon footprint. The findings reveal that Yangzhou, recognized as a model ecological city by authorities, exhibits an emergy sustainability index below the standard benchmark (ESI = 0.02 < 1). GIS mapping reveals that the city’s largest ecological service system is situated in the northwest water region. Both the emergy and carbon footprint analyses indicate that urbanized areas exert a detrimental influence on the city’s overall sustainability. Additionally, the administrative authorities in Yangzhou have implemented proactive measures to transition the city towards sustainability. Currently, the impacts of clean energy adoption and urban wetland restoration are particularly pronounced. The application of lifecycle emergy and carbon footprint methods offers a holistic approach for urban managers, enabling sustainable urban planning that harmoniously integrates ecological emergy and low-carbon considerations. This approach is instrumental in the realization of sustainable cities.

An integrated environmental-economic assessment of orange production in China during 2010–2020

It is unclear how agricultural materials use affects environmental sustainability, carbon emissions and economic benefit of fruit plantation as well as relationships among the three aspects. To address these issues, Chinese orange production, as a study case, was investigated through combination of emergy method, carbon footprint and economic analysis, as well as the proposed co-benefit index based on emergy-carbon-economy. This evaluation framework was applied to assess orange production in Chinese seven provinces during 2010–2020. On average, Jiangxi has the highest emergy sustainability level (0.14) while Guangxi and Chongqing show the lowest level (0.08). Chongqing and Guangdong achieve the best and the worst economic benefit (3.34 vs. 1.78 in terms of Return on Investment) respectively. Hunan and Guangdong possess the lowest and the largest carbon emission intensity (0.11 vs. 0.90 kg CO2-eq kg −1 product) accordingly. Hunan and Guangdong achieve the best and the worst co-benefit effect (13.52 vs. 0.48 in terms of Co-benefit Index) respectively. Except Hunan and Jiangxi, emergy sustainability adversely affects co-benefit effect of orange production in the other five provinces. Carbon emission intensity reduces co-benefit effect of orange production in Guangdong. Economic benefit weakens co-benefit effect of orange production in Fujian, Hubei, Hunan and Guangdong. The work proposed one feasible framework for investigating comprehensive performance of fruit production based on emergy – carbon - economy.

Development of sustainable HPC using rubber powder and waste wire: carbon footprint analysis, mechanical and microstructural properties

This research advances the development of eco-friendly high-performance concrete (HPC) by integrating tire rubber powder and waste wire, focusing on both enhanced mechanical properties and reduced environmental impact. Substituting up to 40% of silica sand with rubber powder helps maintain the compressive strength necessary for high-strength concrete applications. The addition of waste wire is designed to improve ductility. A comprehensive evaluation includes mechanical and microstructural analyses, such as compressive, splitting tensile, and flexural strength assessments, in addition to Scanning Electron Microscopy (SEM) and Differential Thermal Analysis (DTA). Environmental implications are assessed by measuring the embodied carbon footprint. Findings indicate that the absence of rubber powder allows for a compressive strength peak of 95 MPa, while 50% rubber content leads to a decrease to 25 MPa, establishing a 40% rubber threshold for optimal strength. Conversely, 3% waste wire reinforcement enhances the strength to 106 MPa. Microstructural investigations reveal that increased rubber content adversely affects compressive strength by weakening the cement matrix, and reducing calcium-silicate-hydrate (C-S-H) formation. Significantly, the study reveals that replacing silica sand with rubber powder, along with waste wire reinforcement, substantially reduces the carbon footprint of the material, contributing to more sustainable construction methodologies.

Optimized reversed phase liquid chromatography methodology for the determination of vonoprazan fumarate impurities: Towards Six Sigma quality standards and sustainability assessment

Vonoprazan fumarate (VPZ), a potent potassium-competitive acid blocker, holds great promise as a therapeutic option for addressing acid-related disorders. This study introduces a refined reversed phase liquid chromatography methodology tailored for the comprehensive analysis of eight related substances, including starting materials, byproducts, and degradants within VPZ. Our approach integrates response surface methodology and tolerance analysis to achieve six sigma quality standards in chromatographic performance. By embedding specifications into the optimization process, we ensure robustness during method development. Chromatographic separation was executed using an XSelect CSH Phenyl-Hexyl column under stepped gradient conditions, employing a mobile phase comprising 0.1 % trifluoroacetic acid aqueous solution and acetonitrile. The flow rate was maintained at 1.3 mL/min, with UV absorbance at 252 nm, and a column temperature set at 25 °C. To evaluate the stability indicating ability of the method, forced degradation studies were conducted. Importantly, identified degradants did not interfere with the accurate quantification of VPZ and its associated impurities. Validation of the method was achieved through accuracy profiles. A greenness assessment was conducted using National Environmental Methods Index (NEMI), carbon footprint analysis, Analytical Greenness Calculator (AGREE), and Complementary Green Analytical Procedure Index (Complex GAPI). Additionally, blueness and whiteness assessments were conducted using the Blue Applicability Grade Index (BAGI) and Red-Green-Blue 12 (RGB 12) algorithms, respectively. The proposed method exhibited a green profile in NEMI and Complex GAPI. The carbon footprint was calculated at 0.055 kg CO2 equivalent per sample. The AGREE score was 0.67, BAGI was 80.0, and the whiteness score from the RGB12 algorithm was 83.5.This methodological framework holds promise for utilization in process development and quality assurance of VPZ in bulk drug manufacturing, particularly in the absence of official monographs within recognized compendia.

Carbon footprint and techno-economic analysis to decarbonize the production of linerboard via fuel switching in the lime kiln and boiler: Development of a marginal abatement cost curve

Carbon footprint and techno-economic analysis to decarbonize the production of linerboard via fuel switching in the lime kiln and boiler: Development of a marginal abatement cost curve

Carbon footprint analysis of sugar production in Poland

Food production is a major contributor to greenhouse gas emissions and biodiversity loss, highlighting the need for a comprehensive approach to identify and reduce emissions. Efficient energy use is critical, alongside the adoption of low-carbon technologies that help agriculture and food processing adapt to climate change. Carbon footprint (CF) analysis is a key tool for assessing the environmental impact of food production and distribution, requiring a thorough evaluation of each product's life cycle from production to consumption. This study focused on the sugar production CF in three Polish plants, examining technological processes and creating unit process diagrams of the production cycle. This analysis led to the development of a database to calculate the CF based on production volume. The determined CF was 0.14–0.27 kg CO2eq/kg, and the average CFav: for plant 1–0.18; for plant 2–0.19; for plant 3–0.19 kg CO2eq/kg. Continuous monitoring is essential, allowing production practices to adapt to changing conditions and ensuring quick responses to sustainability needs. Reducing the sugar production CF involves several strategies, including adopting sustainable cultivation practices, optimizing production processes, using renewable energy sources, improving transportation efficiency, and minimizing waste. Together, these measures promote more environmentally responsible sugar production. By prioritizing sustainability and embracing innovative solutions, the food industry can significantly reduce its environmental impact, meeting the challenges of climate change and biodiversity loss.

ESTABLISHING MANGROVE FOREST PRODUCTS FOR ECO-TOURISM ACTIVITY AT KOTA KINABALU WETLAND RAMSAR SITE, SABAH. MALAYSIA

Mangrove forests are found ubiquitously across the global landscape and are known to assume a pivotal role in supporting the surrounding ecosystem. The study purposely estimates the ability of absorption in CO2 towards the subject area to understand the precautions of visitors in future demand. By leveraging the advanced technology of Geographic Information Systems (GIS) and employing carbon footprint analysis, the study estimated the daily footfall to the area and the resultant carbon footprint. The analysis conclusively revealed a surplus of minus 7,957.65 tons/year, indicating that the area can assimilate more CO2. This underscores the wealth of natural resources and the potential to accommodate a larger number of visitors in the future.

Enhancing the performance of microalgal-bacterial systems with sodium bicarbonate: A step forward to carbon neutrality of municipal wastewater treatment

The microalgal-bacterial granular sludge (MBGS) process, enhanced with sodium bicarbonate (NaHCO3), offers a sustainable alternative for wastewater treatment aiming for carbon neutrality. This study demonstrates that NaHCO3, which can be derived from the flue gases and alkaline textile wastewater, significantly enhances pollutant removal and biomass production. Optimal addition of NaHCO3 was found to achieve an inorganic-to-organic carbon ratio of 1.0 and a total carbon-to-nitrogen ratio of 5.0. Metagenomic analysis and structural equation modeling showed that NaHCO3 addition increased dissolved oxygen concentrations and pH levels, creating a more favorable environment for key microbial communities, including Proteobacteria, Chloroflexi, and Cyanobacteria. Confocal laser scanning microscopy further confirmed enhanced interactions between Cyanobacteria and Proteobacteria/Chloroflexi, facilitating the MBGS process. These microbes harbored functional genes (gap2, GLU, and ppk) critical for removing organics, nitrogen, and phosphorus. Carbon footprint analysis revealed significant reductions in CO2 emissions by the NaHCO3-added MBGS process in representative countries (China, Australia, Canada, Germany, and Morocco), compared to the conventional activated sludge process. These findings highlight the effectiveness of NaHCO3 in optimizing MBGS process, establishing it as a key strategy in achieving carbon-neutral wastewater treatment globally.