Reduce GHG Emissions Research Articles

Balancing Economic Growth and Emission Reductions: Policy Trade-offs in India’s Power Sector Towards Achieving the 2070 Net-Zero Goal

India faces significant policy trade-offs between raising living standards for 1.4 billion people and reducing global GHG emissions. While the government has introduced policies to promote renewable energy and reduce coal dependency, numerous efforts are required to meet the 2070 net-zero target. Cutting emissions will likely slow short-term growth and affect coal-dependent communities. However, the right policies can minimize these costs. This paper reviews India’s current climate policies and models emission trajectories under various policy scenarios to explore ways to reduce GHG emissions effectively.

Pathways in the governance of shipping decarbonization from perspective of balancing the conflicting interests

The shipping industry is featured by high carbon emissions. The 2023 IMO Strategy on Reduction of GHG Emissions from Ships sets forth the global goals of shipping decarbonization. Shipping decarbonization involves complicated issues of economy, technology, policy and law etc., and implies the conflicts between economic interests and environmental interests, between individual interests and public interests, between individual States’ interests and international common interests and between current interests and long-term interests. This research suggests that balancing such conflicting interests need to follow the principle of prioritizing the international public environmental interests while taking into account the other interests because protection of environmental interests should be taken as the basic value orientation in shipping decarbonization governance and the principle of collaborating governmental intervention and market mechanisms by reference to the theory on the relationship between government and market in economics. Under the guidance of these principle, by reference to the equilibrium analysis method in economics and following the progressive decision theory in management, this research demonstrates that the main pathways in achieving such balance may include: making strategic plan and basic policy for reducing GHG emissions from ships by the government, implementing economic incentive policies such as tax incentives and fiscal subsidies, implementing ship energy efficiency measures, prudently implementing shipping carbon emissions trading mechanism, accelerating the establishment of alternative marine fuel supply chain, innovating alternative marine fuel technology and ship propulsion technology, and actively engaging in international cooperation.

Decreasing the carbon footprint of food through public procurement—A case study from the municipality of Härnösand

Eating habits are among the strongest drivers of negative environmental impact. Public procurement has been suggested as an efficient lever to catalyze changes within the food system. This study examines alternative purchase processes that may decrease the carbon footprint of publicly procured food through a case study of a municipality in the Northern part of Sweden. The GHG emissions associated with the current food service in the case study were 2.2 kg CO2e per kg food and must be reduced by 40.9% by 2030 to comply with the Paris Agreement; 76% of the emissions derive from food of animal origin (44% from unprocessed red meat). Three alternative diet scenarios, “zero red meat,” “−50% red meat,” and “flexitarian free from red meat,” were explored. Only 6% of the total purchased food kilograms were altered, yet the cutback of meat caused GHG emissions reductions turned out to be as high as 44%. The Swedish Law on Public Procurement, deficient infrastructure, unsustainable food culture, and local politicians' reluctance to change were mentioned as the main obstacles to materializing necessary changes in the food procurement system. The respondents also pointed out essential policy changes at the national and municipal levels.

The benefits and burdens of wind power systems in reaching China’s renewable energy goals: Implications from resource and environment assessment

Recognizing the economy’s growing reliance on global energy landscape transformation on wind power deployment, as well as the general reality that renewable facilities require lower operational but higher up-front inputs than fossil-based power systems, this paper focuses on the life-cycle burdens of wind power systems and their substitution benefits compared with coal-fired power systems. The estimation considers the consumption of nonrenewable sources of energy, emissions of greenhouse gases, and other environmental resource factors that have received significantly less research attention, such as industrial land use, water use, PM2.5, SO2, NOX, and Hg emissions. The scope of this study differs from earlier ones in that it includes a comprehensive description of all the equipment, materials, and services used, as opposed to earlier studies that either omit crucial supporting infrastructure or just focus on the plant’s physical structure as its primary materials. Results based on a typical plant in China show that the state-of-the-art onshore wind power systems can provide significant reductions in nonrenewable energy use (9.2 MJ/kWh) and GHG emissions (782.8 GtCO2/kWh). To produce an equivalent amount of electricity, wind power systems require more than three times industrial land use and almost one-third of industrial water use of that for traditional coal-fired power systems. The avoided SO2, Hg, PM2.5, and NOX emissions per unit of electricity generation account for 60.6%-89.3% of the total air pollution emissions induced by supercritical coal-fired power systems. By integrating 3797 operating plant-specific data and fixed-point wind energy information, this study scales up results of the single plant to a country level. The macro picture implies different opportunities born by wind power systems in easing multiple resource and environmental pressures, highlighting the significance of designing hierarchical strategies to improve penetration levels of wind power. By 2050, cumulative climate benefits obtained from onshore wind power technology are predicted to reach 74.2 Gt CO2, achieving around 17.2%-45.5% of the national carbon-neutral goal.

Estimation of carbon sequestration potential and air quality impacts of biochar production from straw in China

Aiming to optimize straw resource utilization and to reduce air pollutant and greenhouse gas emissions in China, the environmental benefits of biochar production using straw and utilization need to be assessed. Two biochar production scenarios were studied: centralized production scenario (CPS) utilizing an industrialized production method with advanced air pollution control devices, and decentralized production scenario (DPS) based on a distributed production method of biochar at the village level, compared to an open-burning scenario (OBS). The potential GHG emission reductions under DPS, including the benefit of soil biochar application, were evaluated as 680 Tg CO2-eq yr-1, which was lower than the reductions under CPS (780 Tg CO2-eq yr-1). Although the attentional centralized production method of biochar has more potential environmental benefits, at present the distributed production method is more practical in China due to its convenience, management ease, and lower costs. Modeling on air quality in China showed that in comparison with OBS, DPS could reduce the average monthly PM2.5 concentration of key regions by 19%, and about 190 Tg yr-1 biochar could be produced with 150 Tg C yr-1 sequestered in biochar. Our findings support widespread biochar use in China for improved air quality and climate neutrality.

Investigating Fuel Reduction Methods Through Propeller Optimization on Coastal Ro-Ro Liner Vessels

In light of efforts to reduce GHG emissions, liner ship operators in coastal navigation are undertaking numerous activities to contribute to the reduction of fossil fuel consumption during the transitional period toward environmentally friendly propulsion systems without compromising their regular operations. Regular ship overhauls, which include removing fouling from the underwater part of the hull and optimizing propellers, also contribute to this goal and are the focus of this research. The ship propeller, as a key component of the propulsion system, plays a significant role in ensuring reliable, safe, and economical navigation. Proper selection and regular maintenance of the propeller are essential for achieving optimal performance. This paper presents the optimization of a fixed-pitch propeller according to the ISO 484/2 standard to Class I using Metrascan 3D technology. This technology enables a detailed analysis of the propeller geometry, identification of irregularities, correction, and adjustment to achieve better hydrodynamic characteristics. The pitch corrections of the propeller resulted in improved overall vessel performance and fuel consumption, as demonstrated by comparing the consumption before and after the optimization.

Environmental regulations’ impact on clean energy consumption: Under the assistance of governance measures

The drastic change in climate augments the importance of clean energy consumption. Therefore, this paper examines how environmental regulations influence the utilization of clean energy under the moderation of governance measures. The 2-Steps System GMM is applied to 26 OECD countries’ data from 1996 to 2019 to analyze the relationship. Our analysis depicts that environmental regulations and GDP significantly enhance clean energy usage in OECD countries. Moreover, economic globalization insignificantly impacts clean energy consumption. On the contrary, financial development in OECD countries significantly leads to a decrease in the consumption of clean energy because renewable energy projects are long-term and more expensive than non-renewable energy generation projects. This paper further discovers that the majority of the governance measures significantly and positively moderate the connection of environmental regulations with clean energy consumption. Consequently, constructive governance measures facilitate the effective implementation of environmental regulations in OECD countries eventually increasing the consumption of clean energy instead of non-renewable energy. To reduce GHG emissions in the environment, the government should encourage the usage of clean energy in their respective countries. Therefore, policymakers promote the practice of clean energy consumption through stringent environmental regulations and effective governance measures.

Dietary trajectory profiles of French adults over time: Multicriteria analysis of sustainability

Abstract Despite the urgent need for sustainable dietary transitions, few studies have examined current dietary trajectories using longitudinal data. This study aimed to identify dietary consumption trajectory profiles over an 8-year period (2014-2022) while assessing their sustainability in a multicriteria approach. Consumption data from NutriNet-Santé cohort participants were collected using FFQs in 2014, 2018 and 2022. Dietary trajectory profiles were modeled using group-based multi-trajectory based on factors from Principal Component Analysis on energy-adjusted consumption data (n = 17,187). Profiles were analyzed for sustainability (environmental and nutritional dimensions) using multi-adjusted mixed-effects models. Six trajectory profiles (P) were identified. P0 (considered as reference) had average consumption for all food groups, with increased plant-based intake over time. In comparison, P1 had the highest baseline alcohol (+301%) and offal intake, increasing processed meat (+74%) and decreasing offal over time. P2 had higher milk (+187%) and sweet drinks intake, increasing animal substitutes (+1737%) and whole-grain products. P3 had higher nuts (+680%) and legumes intake, increasing egg (+166%) and reducing fruit juice. P4 had high fish (+39%) and fruit intake, increasing butter (+53%) and reducing alcohol. P5 had higher pork (+143%) and red meat intake, increasing fish (+31%) and reducing dairy. Initially, P3 and P4 had the lowest GHG emissions (-18%, -49% vs. P0), best nutritional profiles, and higher organic food consumption. P5 had the greatest environmental impact (+51%) and the lowest nutritional scores. Over time, P0 reduced GHG emissions and improved nutritional scores. P3 and P4 showed minimal changes, while P5 had the greatest GHG emissions decrease (-14%) and nutritional quality improvements. Identifying ongoing dietary transition trajectories, our findings contribute to optimizing targeted actions aimed at promoting sustainable dietary consumption habits. Key messages • Regardless of initial dietary preferences, French adults exhibit an overall trend over time towards increased intake of plant-based foods and decreased intake of red meats, at varying scales. • French adults exhibit varying degrees of transition towards more sustainable diets, with an overall decrease in GHG emissions from food consumption and an improvement in their nutritional profiles.

Proposals on Effective Implementation of the Carbon Intensity Indication of Ships

The Carbon Intensity Indicator (CII) regulation is a short-term measure of IMO for reducing GHG emissions from ships. In addition, the 2023 IMO GHG Strategy describes that the CII regulation is anticipated to create a potential synergy effect with other measures. Accordingly, the CII regulation, which took effect in 2023, is forecast to increasingly impact international shipping and the commercial vessel market. However, efforts to improve energy efficiency and implement slow steaming for ships are insufficient to meet the CII regulation that is increasingly stringent over time. Therefore, there is a growing need for fundamental improvements in future response strategies. In this study, major causes of low CII ratings for ships were investigated from a recent consulting project that was conducted to support shipping companies in satisfying the regulation from operational and technical perspectives. Lastly, proposals to implement the CII regulation effectively and to reduce GHG emissions from ships fundamentally were made, taking into account the major causes derived from the consulting.

Responses of yield, CH4 and N2O emissions to ratoon rice cropping and different management practices

Context or problemConversion from single rice (SR) or double rice (DR) to ratoon rice (RR) is gaining growing popularity in China. Yet, a quantitative synthesis of their impact on greenhouse gas (GHG, including methane (CH4) and nitrous oxide (N2O)) emissions and grain yield has not been conducted. Objective or research questionThe objective was to evaluate the effects of conversion from SR or DR to RR on CH4 and N2O emissions, grain yield, global warming potential (GWP), and greenhouse gas intensity (GHGI) and to investigate the potential responses to different operating practices [alternate wetting-drying irrigation, nitrogen management, rice variety selection, and their multiple treatments (multiple measures)] in RR fields (oRR). MethodsIn this study, a comprehensive meta-analysis of 571-paired measurements from ratoon rice fields was conducted. ResultsOur results showed that the conversion from SR to RR significantly increased CH4 emissions, grain yield, and GWP by 35.4 %, 30.6 %, and 43.3 %, respectively. In contrast, the conversion from DR to RR decreased CH4 emissions, grain yield, and GWP by 23.2 %, 7.4 %, and 30.0 %, respectively. Interestingly, both conversions from SR or DR to RR did not affect N2O emissions but reduced GHGI in paddy fields, suggesting that RR provided an economically and ecologically sustainable rice planting model. Furthermore, on average, oRR further decreased CH4 and N2O emissions and GHGI from RR fields but did not affect grain yield. Among the existing management practices, the overall effect of multiple measures was better than that of alternate wetting-drying irrigation, nitrogen management, and rice variety selection. ConclusionsOverall, ratoon rice cropping decreased CH4 emissions and maintained rice grain yield. However, it is also necessary to further implement comprehensive cultivation strategies in the future to maximize the benefits of grain yield and GHG emissions reduction.

The Triple Bottom Line: Prioritizing CSR, Human Capital, and GHG Reduction for Sustainable Economic Growth in Indonesia

Our study, which covered the years 2008 to 2022, aimed to create “autoregressive vectors” to investigate the interrelationships between corporate social responsibility (CSR), greenhouse gas net (GHG), human capital (HCPT), and human resources in Indonesia. We used data from the World Bank, OECD, and Bank Republic Indonesia to conduct an analysis of the correlation between these variables. Our results showed that there are significant relationships between corporate governance self-assessment (CGS), GHG, and HCPT in Indonesia. The positive correlation between GHG and CGS suggests that as GHG emissions increase, the level of corporate governance self-assessment also increases. This finding implies that companies that prioritize reducing GHG emissions tend to have better corporate governance practices. Moreover, investing in reducing GHG emissions can have a positive impact on human capital development. However, the negative correlation between HCPT and CGS implies that an increase in human capital may result in a decrease in the level of corporate governance self-assessment. This finding highlights the importance of balancing investments in human capital with maintaining good corporate governance practices to ensure sustainable economic growth. Furthermore, promoting corporate social responsibility can enhance companies’ reputation and increase their brand value, which can positively impact their CGS. Therefore, it is essential for companies to prioritize CSR practices, invest in human capital development, and reduce GHG emissions to ensure sustainable economic growth and maintain good corporate governance practices in Indonesia. Keywords: corporate social responsibility, greenhouse gas net, human capital

A GIS-based assessment of the carbon emission reduction potential of the solar-enhanced char-cycling biomass pyrolysis process in China

Bioenergy and solar energy are the two widely used renewable energies, which have great potential to satisfy the global energy demand. Solar enhanced char-cycling biomass pyrolysis (SCCP) was proposed to integrate bioenergy and solar energy, could be used to make bioenergy fully carbon-negative. A geographical information system (GIS) based method was used to assess the GHG reduction potential and biofuel production potential of SCCP in China. Existing datasets were used to obtain geographical potential and biomass resource amount. Process simulation was conducted to obtain the technical data. The geographical potential results showed that with a DNI (direct normal irradiance) threshold of 1400 kWh/m2, the national suitable area for SCCP plant construction was 3.25 % of the total national area, the total convertible biofuel potential ranges from 1.86E+06 to 1.94E+06 GWh with different concentrating solar technologies. When considering biochar sequestration, the GHG emission reduction potential increased further, the total GHG emission reduction potential increased from 13.97 Mt CO2 eq to 15.42 Mt CO2 eq. Notably, Yunnan has the highest GHG emission reduction potential per unit of energy when running the pyrolysis process with solar energy, which was −8.58 g CO2 eq/kWh. The results revealed that the SCCP process could further decarbonize biofuel production in China.

From biogas to biomethane: Comparison of sustainable scenarios for upgrading plant location based on greenhouse gas emissions and cost assessments

Addressing the global energy crisis and achieving sustainable development goals (SDGs) necessitates shifting towards renewable energy sources, with biomethane emerging as a viable alternative. This study evaluated three scenarios for biomethane production from biogas: localized upgrading for biofuel use, district upgrading for biofuel use, and district upgrading with grid injection. By utilizing economic assessments and spatial and network analysis, the optimal locations for upgrading plants were identified to minimize transportation costs and GHG emissions (CO2 equivalents). Results indicate that Scenario 1 achieves the lowest emissions and operating costs (41 MEUR), while Scenarios 2 and 3, despite higher initial investments (152–173 MEUR), offer significant economies of scale (1187–1321 MEUR) and substantial annual production capacities (8.8 × 106 Sm³ of biomethane). Comparative and sensitivity analyses show renewable energy sources reduce GHG emissions by up to 83.7% and significantly lower operating costs. This research underscores the critical role of strategic planning and renewable energy integration in optimizing the biomethane value chain for environmental sustainability and economic viability while also emphasizing the need for further research to refine these findings.

Fuel consumption and exhaust emissions from Euro 6d vehicles fueled by innovative LPG/DME blend

The aim of this research was to investigate the exhaust emissions from vehicles when fueled by a new and fully renewable fuel if made of bio-LPG and renewable dimethyl ether (DME), in comparison with standard gasoline. For this purpose, DME was mixed with liquefied petroleum gas (LPG) and used to fuel three bi-fuel LPG/gasoline spark-ignition engines light-duty vehicles. The suitable fuel blend was selected based on several octane tests using CFR engines. Exhaust emissions were tested over the WLTC and over the hot-start CADC cycles, as well as on the road. All Euro 6 standards were well fully met over the WLTC with both fuels. Switching from gasoline to LPG/DME fueling, the CO and NOx emission factors increased for two vehicles, whereas THC and NMHC decreased. Regarding particulates, for two vehicles the emission factors decreased, too. Generally, when the vehicles were driven on the CADC, lower gaseous emissions were observed compared to WLTC: excluding one vehicle, when switching from gasoline to LPG/DME fueling, the overall emission profiles reflected those of the same vehicles run on the WLTC. The unregulated particulate emissions measured over both testing cycles reflect what was detected for the regulated ones. Except for PN10, which was not measured, all regulated emissions were found to meet the (most severe) Euro 7 standards proposed at first by the European Commission. RDE tests showed that all vehicle emissions obtained from on-road tests were also found to meet the RDE standards, regardless of the fueling. Concerning CO2 emissions, LPG/DME fueling guaranteed a systematic decrease for all vehicles and cycles, both on road and in the laboratory. The present investigation aims at demonstrating that the innovative LPG/DME 80 %/20 % (m/m) blend not only can be deemed as potentially suitable for GHG emissions reduction, as long as both DME and propane are obtained from renewable sources, but even compliant with EN 589 and both Euro 6 and part of preliminary Euro 7 exhaust emission proposal.

Health enhancement through activity travel participation and physical activity intensity

IntroductionPast studies investigate the impact of health parameters on activity and transport options. However, limited research has been done on how activity-travel participation influences health outcomes. Physical activity has the potential to improve health characteristics; however, its intensity (duration and frequency) and optimal mode are yet to be determined. Therefore, the current study aims to use physical activity intensity (PAI) as an intermediate variable to study the correlation among daily activities, transport mode choice, and health parameters to pursue sustainable transportation and improve health parameters. MethodsIn September 2013, a multidimensional three-week household survey was used to collect the data containing 191 households and 732 individuals representing 0.029% of the total population of Bandung, Indonesia. SPSS was used for the data normalization and descriptive analysis, whereas R was used for the multilevel regression and structural equation modeling (SEM). Four models were developed between endogenous, mediator, and exogenous variables. ResultsA significant correlation was found between daily activities, transport mode choice, and health parameters with exceptionally acceptable R2 and p-values. The appraised results indicate that strenuous PAI is 2.1% and 0.3% positively correlates with physical health (PH) and social health (SH), showing that it mediates the correlation among transport-related daily activities and health parameters. High-income households are dependent on motorized transport which is 0.1% and 0.2% negatively associated with PH and SH. Whereas, active transport is 2.0% and 0.2% and public transport is 0.2% and 1.5% positively associated with PH and SH. Replacing short car trips with a sustainable transportation system enhances health parameters and reduces GHG emissions from the transportation sector. ConclusionThe current study concluded that the association was mediated by transport-related PAI which enhances health parameters. Policymakers and practitioners promote transport-related physical activity which may help to enhance health parameters and provide a sustainable transportation system.

Lightweighting cost impacts on market adoption and GHG emissions in U.S. light-duty vehicle fleet

Abstract Vehicle lightweighting is a promising strategy that can reduce energy consumption and GHG emissions without compromising vehicle’s performance or size. The cost of lightweighting plays a critical role in determining the adoption of lightweighting technologies by consumers and manufacturers among advanced vehicle technologies. This analysis estimates the cost of lightweighting needed to achieve significant light-duty vehicle adoption to provide reductions in GHG emissions. Three different costs of lightweighting scenarios in the U.S. market including a baseline scenario, advanced technology scenario, and widespread scenario are evaluated employing Automotive Deployment Options Projection Tool (ADOPT). ADOPT leverages a database of over 700 existing vehicle models and options, enabling it to provide a high degree of realism and capture the unique characteristics of popular vehicles and the endogenously evolvement of the vehicle options. For baseline scenario, the lightweighting fraction reached by about 15% and GHG emissions are reduced by more than 50% in 2046 compared to 2015. The widespread scenario further reduces the GHG emissions by about 4% from the additional 10% glider mass reduction compared to the baseline scenario. The benefit came largely from lightweighting being implemented in the large market segment of lower-price vehicles, due to the relatively low lightweighting cost ($5/kg).

Quantitative Study to Assess the Socio-Economic and Environmental Impacts of Implementing the Extended Producer Responsibility (EPR) System for Packaging: Case Study in Morocco

Extended Producer Responsibility (EPR) is an approach to environmental policy that requires producers to assume full responsibility for the costs of managing their products and packaging throughout their useful life. In Morocco, municipalities assume financial and operational responsibility for collecting and eliminating all household and similar waste at considerable expense. In this respect, integrating an EPR system in the Moroccan context, allowing a transfer of responsibility from municipalities to producers is strongly recommended. In this context, the specific research objective is to conduct a quantitative study to assess the socioeconomic and environmental impacts of implementing an EPR system for packaging in the Moroccan context. To accomplish this, the methodology entails estimating the amount of packaging waste generated and the recycled amount based on current recycling ratios. Then, the socioeconomic and environmental impacts are estimated by comparing the business-as-usual scenario (without EPR) and the EPR scenario with improved recycling rates. The implementation of the EPR system allows improving considerably the recycling rates of plastic, cardboard, glass, and metals from 25%, 20%, 14%, and 46% to 50%, 75%, 70%, and 60%, respectively. The estimated amount of household packaging waste (HPW) is about 1,16 million tons/year. The finding results are very encouraging, showing an economic saving of about 482 MDh/year. This saving is mainly related to the avoided cost of landfilling and the loss of revenue resulting from the recyclable material. Therefore, the economic savings exceed 455 Dhs /ton of recyclable HPW, with 2,894 jobs created nationwide. Since the EPR system will simultaneously reduce GHG emissions and prevent ecosystem degradation, it could provide an environmental saving of 196,4 million Dhs. These results underline promising prospects for integrating the EPR system into the transition to more sustainable, responsible, and efficient waste management.

Catalyzing progress: Unveiling the impact of metallic improved cooking stoves on energy security and sustainable development

The global energy crisis, characterized by shortages of fossil fuels, increasing energy needs, and climate change, requires sustainable energy solutions. Renewable energy technologies provide important options to reduce GHG emission and improve energy security. In developing nations, the use of traditional biomass-fueled cooking stoves contributes to environmental damage, deforestation, and health problems. This research evaluates the impact of MICS on Energy Security and Sustainable Development in Bajura District, Nepal, where firewood is the main source of cooking and heating fuel. Employing an Explanatory Sequential Research Design, the study integrated quantitative survey followed by qualitative approach. A household survey was carried out using KoBo Toolbox among 507 households, followed by focus group discussion and in-depth interviews among 63 people. Survey data was analyzed in SPSS to see the impacts of MICS usage. Findings demonstrated significant reduction of firewood by 693.78 tons (33.85 %) and CO2 emissions by 1247.4 tons (60.93 %) per annum improving energy security, and positive socio-economic and environmental impacts. Research emphasizes the significance of MICS on Energy Security and SD, offering valuable insights for decision-makers. Despite the benefits of MICS, only 44 % of households had adopted them due to high costs, lack of awareness, and maintenance challenges as barriers, advocating for policies to increase adoption through subsidies, awareness campaign, and maintenance assistance as 94.5 % of the surveyed population still use firewood for cooking and heating.

A meta-analysis of the schematic design process of deep retrofit projects

Deep retrofits of the existing building stock will be necessary to meet global emissions reductions targets. One building archetype, low-rise MURBs have been neglected in terms of research and funding for deep retrofits. A meta-analysis was conducted that compares and contrasts the schematic design approach taken for six such buildings in British Columbia which are scheduled to undergo deep retrofits with the goal of reducing GHG emissions by 80%. The analysis showed that design teams had converged toward common solutions for each building while achieving the GHG reduction target. The recommended measures include electrification of space and domestic hot water heating, adding insulation through overcladding, air sealing, ventilators for each unit, and double pane windows. A life cycle cost analysis showed that the economic viability of deep retrofits were dependent on energy price forecasts, capital cost reductions through market forces and transformation, or incentives cover the non-monetizable co-benefits of deep retrofits such as improved resiliency to climate-change or reducing overheating and air quality risks. The meta-analysis can help to streamline the early-stage and schematic design process for such buildings, which is critical to increasing the retrofit rate. This process could be replicated for other building types and construction archetypes.

Enclosing gases by gas circulation to establish photosynthetic O2-supported algal-bacterial granular system in pseudo-closed sequencing batch reactors for greenhouse gas emission mitigation

Photosynthetic O2-supported algal-bacterial aerobic granular sludge (AGS) presents great potential in carbon emission mitigation and operation cost saving in wastewater treatment processes. This study used gas circulation to enclose the photosynthetic O2 and the emitted CO2 for the development of photosynthetic O2-supported algal-bacterial AGS in a pseudo-closed sequencing batch reactors (SBR), targeting greenhouse gas emission mitigation (including CO2, N2O and CH4). Results showed that photosynthetic O2-supported AGS with abundant Cyanobacteria were achieved in this pseudo-closed SBR under strong light conditions. Although gas circulation enclosed acidic CO2, excessive Chlorophyll-a (Chl-a) in biomass still led to the increase of pH, followed by the occurrence of CO2 limitation and the loss of functional strains and extracellular polymeric substances, eventually collapsing granular structure. Interestingly, gas circulation can reduce GHG emissions due to prolonged contact time between gases and microorganisms. Chl-a contents showed an inversely proportional relationship with CO2 emission factors (0.04–0.61 kg-CO2/kg-COD), but over-high algae in biomass may induce more N2O emissions (0.45 % to 5.3 %) by affecting nitrification and denitrification processes. Compared to CO2 and N2O, the emission of CH4 was negligible. It was estimated that zero non-CO2 GHG emissions could be achieved when stable granules containing Chl-a content of > 5.8 mg/g-MLVSS. This study proposed that achieving low-carbon photosynthetic O2-supported algal-bacterial AGS requires minimizing the adverse impact of existing algae on denitrification and nitrification.