Potential benefits of cropping pattern change in the climate-sensitive regions of rice production in China

Rice production is a primary contributor to global greenhouse gas emissions, with unclear pathways towards carbon neutrality. Here, through a comprehensive assessment of direct greenhouse gas (GHG) emission using DNDC model and indirect GHG emission using emission factor methods, we estimated the annual crop yield, GHG emission amount and intensity, and economic benefits of different cropping patterns in the climate-sensitive regions of rice production in China. Through the expansion of single-rice and cropping pattern change from the wheat-rice to wheat-rice-rice in the climate-sensitive regions of single and triple-cropping cultivations, the total grain yield increased by 4.4 % and 4.5 % compared with the current national grain production, the GHG emission would increase by 2.4 % and 5.4 % of the current national GHG emissions from rice and wheat production, the net economic benefits could increase 0.9 % and decrease 2.0 % of the national output value of rice and wheat production. The study takes the entire-life cycle of crop growth as the principal line, and could provide a valuable reference for the regulation of the cropping pattern and the formulation of carbon reduction policies in the climate-sensitive region.

Non-negligible impact of microplastics on wetland ecosystems

There has been much concern about microplastic (MP) pollution in marine and soil environments, but attention is gradually shifting towards wetland ecosystems, which are a transitional zone between aquatic and terrestrial ecosystems. This paper comprehensively reviews the sources of MPs in wetland ecosystems, as well as their occurrence characteristics, factors influencing their migration, and their effects on animals, plants, microorganisms, and greenhouse gas (GHG) emissions. It was found that MPs in wetland ecosystems originate mainly from anthropogenic sources (sewage discharge, and agricultural and industrial production) and natural sources (rainfall-runoff, atmospheric deposition, and tidal effects). The most common types and forms of MPs identified in the literature were polyethylene and polypropylene, fibers, and fragments. The migration of MPs in wetlands is influenced by both non-biological factors (the physicochemical properties of MPs, sediment characteristics, and hydrodynamic conditions) and biological factors (the adsorption and growth interception by plant roots, ingestion, and animal excretion). Furthermore, once MPs enter wetland ecosystems, they can impact the resident microorganisms, animals, and plants. They also have a role in global warming because MPs act as unique exogenous carbon sources, and can also influence GHG emissions in wetland ecosystems by affecting the microbial community structure in wetland sediments and abundance of genes associated with GHG emissions. However, further investigation is needed into the influence of MP type, size, and concentration on the GHG emissions in wetlands and the underlying mechanisms. Overall, the accumulation of MPs in wetland ecosystems can have far-reaching consequences for the local ecosystem, human health, and global climate regulation. Understanding the effects of MPs on wetland ecosystems is essential for developing effective management and mitigation strategies to safeguard these valuable and vulnerable environments.

Livestock intensification and environmental sustainability: An analysis based on pasture management scenarios in the brazilian savanna

Brazil's major beef production occurs in the Cerrado, predominantly as extensive pastures that covers ∼50 Mha of the biome, of which approximately 2/3 show signs of degradation. Pasture recovery is now a key environmental policy, as it improves land use efficiency and soil carbon sequestration. However, as intensification leads to higher cattle stocking rates and external inputs (fertilizers, liming, etc.), the impact of improved pastures on greenhouse gas mitigation is still debatable. This study focused on the Cerrado biome and aimed to (i) quantify soil carbon stock changes under different scenarios of management and recovery of degraded pastures. In addition, (ii) the potential for capturing carbon in the soil to mitigate emissions of greenhouse gases (GHG) by the intensification of pastures was evaluated. Soil C stock changes (0-20 cm) were assessed using the Century model version 4.5, which had been previously validated for the region. Model parameters were adjusted for three pastures classes (degraded, intermediately degraded, and not degraded) within a time-series (1985-2020) of land use maps for the Cerrado, serving as baselines. Scenarios of pasture intensification were modeled against these baselines, and an analysis was carried out on the estimated changes in soil C stock and greenhouse gas balance. Before the intensification scenario (year 2020), the total carbon stock was estimated to be ∼1830 Mt for the whole pasture area, whose spatial distribution corresponded to edaphoclimatic contrasts and pasture conditions. The highest soil organic carbon stocks were observed in the non-degraded pastures. With the increase in carrying capacity, beef production is estimated to potentially increase by 1/3 due to the recovery of degraded areas through intensive management. This increase would be sufficient to meet the projected ∼12% increase in Brazil's livestock production by the end of the decade if all pasture areas are restored, which is much possibly an unrealistic scenario as not all degraded areas are suitable for crops or can successfully improve pasture yield. In addition, the increase in soil C stocks was only sufficient to compensate for 27% and 42% of the GHG emissions resulting from intensification in areas with intermediate and severe degradation, respectively. Therefore, to strike a balance between economic considerations and environmental impact, additional strategies are needed to reduce GHG emissions and/or enhance C sinks, such as increasing tree density on farms. From this perspective, implementing livestock intensification at the landscape scale can promote C stocks and the diversity of ecosystem services, opening the possibility of ecosystem restoration.

Towards low energy-carbon footprint: Current versus potential P recovery paths in domestic wastewater treatment plants

With the unprecedented exhaustion of natural phosphorus (P) resource and the high eutrophication potential of the associated-P discharge, P recovery from the domestic wastewater is a promising way and has been putting on agenda of wastewater industry. To address the concern of P resource recovery in an environmentally sustainable way is indispensable especially in the carbon neutrality-oriented wastewater treatment plants (WWTPs). Therefore, this review aims to offer a critical view and a holistic analysis of different P removal/recovery process in current WWTPs and more P reclaim options with the focus on the energy consumption and greenhouse gas (GHG) emission. Unlike P mostly flowing out in the planned/semi-planned P removal/recovery process in current WWTPs, P could be maximumly sequestered via the A-2B- centered process, direct reuse of P-bearing permeate from anaerobic membrane bioreactor, nano-adsorption combined with anaerobic membrane and electrochemical P recovery process. The A-2B- centered process, in which the anaerobic fixed bed reactor was designated for COD capture for energy efficiency while P was enriched and recovered with further P crystallization treating, exhibited the lowest specific energy consumption and GHG emission on the basis of P mass recovered. P resource management in WWTPs tends to incorporate issues related to environmental protection, energy efficiency, GHG emission and socio-economic benefits. This review offers a holistic view with regard to the paradigm shift from "simple P removal" to "P reuse/recovery" and offers in-depth insights into the possible directions towards the P-recovery in the "water-energy-resource-GHG nexus" plant.

Regional CO2 accounting and market layout of incinerator fly ash management in China

The reduction of greenhouse gas (GHG) emissions from solid waste incinerator fly ash (IFA) management attracts growing interests since China's zero-waste plan and carbon peak/neutral goals. Herein, provincial GHG emissions from four demonstrated IFA reutilization technologies in China were estimated after analyzing IFA spatial-temporal distribution. Results indicate that technologies transition (landfilling-to-reutilization) could reduce GHG except for glassy slag production. IFA to cement option could potentially realize negative GHG emissions. Spatial GHG variation drivers in IFA management were recognized as provincial-different IFA composition and power emission factors. IFA management options were recommended provincially after weighting local development goals related to GHG reduction and economic benefits. Baseline scenario analysis shows that China's IFA industry would reach carbon peak in 2025 (5.02 Mt). 2030's GHG reduction potential (6.12 Mt) is equivalent to that of absorbed CO₂ by 340 million trees annually. Overall, this research could contribute to illustrating future market layout complying with carbon peaking.

Assessing life-cycle GHG emissions of recycled paper products under imported solid waste ban in China: A case study

Changes of raw materials in China's recycled paper industry after the imported solid waste ban affect products' life-cycle greenhouse gas (GHG) emissions as well. This paper presented a case study of newsprint production with prior- and post-ban scenarios with life cycle assessment, including using imported waste paper (P0) and its three substitutions, i.e., virgin pulp (P1), domestic waste paper (P2), and imported recycled pulp (P3). The function unit is 1 ton of newsprint produced in China, and the study is conducted from cradle to grave which consists pulping and papermaking process, from raw material acquisition to manufacturing, with associated energy production and wastewater treatment, transport, and chemicals production. Our results showed that P1 holds the highest life-cycle GHG emission of 2724.91, followed by 2400.88 from P3. P2 has the lowest emission of 1619.27, only slightly lower than 1742.39 before the ban using route P0 (unit: kgCO₂e/ton paper). Scenario analysis showed that current average life-cycle GHG emission for one ton of newsprint is 2049.33 kgCO₂e, increased by 17.62 % due to the ban, while this number could be reduced to 12.22 % or even -0.79 % if switching from P1 to P3 and P2. Our study highlighted the importance of domestic waste paper as a promising way to reduce GHG emissions, which still has great potential to increase if with an enhanced waste paper recycling system in China.

Mediation of gaseous emissions and improving plant productivity by DCD and DMPP nitrification inhibitors: Meta-analysis of last three decades

Nitrification inhibitors (NIs), especially dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP), have been extensively investigated to mitigate nitrogen (N) losses from the soil and thus improve crop productivity by enhancing N use efficiency. However, to provide crop and soil-specific guidelines about using these NIs, a quantitative assessment of their efficacy in mitigating gaseous emissions, worth for nitrate leaching, and improving crop productivity under different crops and soils is yet required. Therefore, based upon 146 peer-reviewed research studies, we conducted a meta-analysis to quantify the effect of DCD and DMPP on gaseous emissions, nitrate leaching, soil inorganic N, and crop productivity under different variates. The efficacy of the NIs in reducing the emissions of CO2, CH4, NO, and N2O highly depends on the crop, soil, and experiment types. The comparative efficacy of DCD in reducing N2O emission was higher than the DMPP under maize, grasses, and fallow soils in both organic and chemical fertilizer amended soils. The use of DCD was linked to increased NH3 emission in vegetables, rice, and grasses. Depending upon the crop, soil, and fertilizer type, both the NIs decreased nitrate leaching from soils; however, DMPP was more effective. Nevertheless, the effect of DCD on crop productivity indicators, including N uptake, N use efficiency, and biomass/yield was higher than DMPP due to certain factors. Moreover, among soils, crops, and fertilizer types, the response by plant productivity indicators to the application of NIs ranged between 35 and 43%. Overall, the finding of this meta-analysis strongly suggests the use of DCD and DMPP while considering the crop, fertilizer, and soil types.

Rice cultivation and processing: Highlights from a life cycle thinking perspective

The agri-food sector needs both water and energy and it also contributes to greenhouse gas (GHG) emissions; among the various activities within this sector, rice production has a particularly significant impact on the environment. Life Cycle Assessment (LCA) is one of the widely used approaches for evaluating the environmental impacts of a product, and as such, it is useful for examining the impacts of the rice industry. In recent years, LCA has been increasingly utilized to provide detailed insight into rice production processes. This review focuses on the application of LCA in rice production. Rice LCA studies were gathered in Scopus®. A total of 76 papers were examined up to the end of 2022. Most studies have evaluated the environmental impact of rice production and identified problem areas and opportunities for improvement. But there is a discrepancy in inputs considered, multifunctionality, emissions estimation and use of FU, which makes it challenging to compare LCA results, while some key aspects such as loss of biodiversity and variation of soil organic carbon and fertility are often not considered or roughly modelled. Only a small number (13 studies) evaluated economic consequences and investigated the impact of rice production on biodiversity (4 studies), indicating a stronger focus on environmental rather than socioeconomic aspects and limitations in evaluating certain environmental effects such as biodiversity and soil fertility.

Financial stability influence on climate risk, GHG emission, and green economic recovery of China

This study examines the nexus between financial stability, climate risks, GHG emission mitigation, and green economic recovery of China. Financing efforts to protect against and reduce the hazards associated with climate change need to consider these risks and resources. Study used the Kalman technique of analysis for empirical inference. This research focuses on the carbon risk in China by employing a Kalman estimation approach. Although environmental mitigation was found to be important at 39%, financial strength and carbon hazards were considerable at 34%. Moreover, the report demonstrates the relationship between climatic threats and environmental drift in China, at a rate of 17%, emphasizing the need to address climate change issues. A state's fiscal health guarantees national economic security while pursuing green economic recovery initiatives. Researchers concluded that precise policy suggestions were needed to promote green economic development.

The climate impact of high seas shipping

Strict carbon emission regulations are set with respect to countries' territorial seas or shipping activities in exclusive economic zones to meet their climate change commitment under the Paris Agreement. However, no shipping policies on carbon mitigation are proposed for the world's high seas regions, which results in carbon intensive shipping activities. In this paper, we propose a Geographic-based Emission Estimation Model (GEEM) to estimate shipping GHG emission patterns on high seas regions. The results indicate that annual emissions of carbon dioxide equivalent (CO₂-e) in shipping on the high seas reached 211.60 million metric tonnes in 2019, accounting for about one-third of all shipping emissions globally and exceeding annual GHG emissions of countries such as Spain. The average emission from shipping activities on the high seas is growing at approximately 7.26% per year, which far surpasses the growth rate of global shipping emission at 2.23%. We propose implementation of policies on each high seas region with respect to the main emission driver identified from our results. Our policy evaluation results show that carbon mitigation policies could reduce emissons by 25.46 and 54.36 million tonnes CO₂-e in the primary intervention stage and overall intervention stage, respectively, with 12.09% and 25.81% reduction rates in comparison to the 2019 annual GHG emissions in high seas shipping.

Impact of energy efficiency, technology innovation, institutional quality, and trade openness on greenhouse gas emissions in ten Asian economies

Despite the fact that Asian economies have experienced robust economic growth in recent decades, rising pollution emissions have raised worries among policymakers about the long-term stability of this output growth. Knowing this fact, the present study attempts to empirically analyze the impact of some important factors, e.g., energy efficiency, technology innovations, trade openness, and institutional quality, on environment in 10 Asian economies over the period 1995-2018. Taking into account the slope heterogeneity and cross-sectional dependence present in the data, Westerlund and Edgerton (2008) and Banerjee and Carrion-i-Silvestre (2017) cointegration techniques and cross-sectionally augmented autoregressive distributed lag model (CS-ARDL) estimation are applied. For robust analysis, augmented mean group (AMG) and common correlated effects mean group (CCEMG) are also employed in the study. The empirical findings provided by selected variables reveal that both trade openness and institutional quality have detrimental impact, whereas energy efficiency and technology innovations have favorable impact on environmental quality in the selected economies. Empirical findings are robust to various policy recommendations. To create a sustainable future environment, Asian economies should focus on the improvement of their institutions quality and increase investments in technology innovations. The Asian countries must encourage trade-related environmental regulations and energy efficiency policies for better and sustainable environmental quality.

Factors Influencing Gaseous Emissions in Constructed Wetlands: A Meta-Analysis and Systematic Review

Constructed wetlands (CWs) are an eco-technology for wastewater treatment and are applied worldwide. Due to the regular influx of pollutants, CWs can release considerable quantities of greenhouse gases (GHGs), ammonia (NH₃), and other atmospheric pollutants, such as volatile organic compounds (VOCs) and hydrogen sulfide (H₂S), etc., which will aggravate global warming, degrade air quality and even threaten human health. However, there is a lack of systematic understanding of factors affecting the emission of these gases in CWs. In this study, we applied meta-analysis to quantitatively review the main influencing factors of GHG emission from CWs; meanwhile, the emissions of NH₃, VOCs, and H₂S were qualitatively assessed. Meta-analysis indicates that horizontal subsurface flow (HSSF) CWs emit less CH₄ and N₂O than free water surface flow (FWS) CWs. The addition of biochar can mitigate N₂O emission compared to gravel-based CWs but has the risk of increasing CH₄ emission. Polyculture CWs stimulate CH₄ emission but pose no influence on N₂O emission compared to monoculture CWs. The influent wastewater characteristics (e.g., C/N ratio, salinity) and environmental conditions (e.g., temperature) can also impact GHG emission. The NH₃ volatilization from CWs is positively related to the influent nitrogen concentration and pH value. High plant species richness tends to reduce NH₃ volatilization and plant composition showed greater effects than species richness. Though VOCs and H₂S emissions from CWs do not always occur, it should be a concern when using CWs to treat wastewater containing hydrocarbon and acid. This study provides solid references for simultaneously achieving pollutant removal and reducing gaseous emission from CWs, which avoids the transformation of water pollution into air contamination.

Transforming agrifood systems in a win-win for health and environment: evidence from organic rice-duck coculture

BACKGROUND

Rice-duck coculture is an ecological agricultural mode; however, the nutritional and environmental benefits of transforming from conventional rice monoculture to rice-duck coculture are unknown. Based on survey data and the life-cycle assessment approach, this study conducted a carbon footprint evaluation of conventional rice monoculture (CR), organic rice monoculture (OR), and organic rice-duck coculture (ORD) using different functional units.

RESULTS

The carbon footprint per hectare of ORD (7842 ± 284 kg CO₂ eq ha^-1 ) was slightly lower than that of CR (7905 ± 412 kg CO₂ eq ha^-1 ), while higher than that of OR (7786 ± 235 kg CO₂ eq ha^-1 ). Although the rice yield of ORD was slightly lower than that of CR, its nutrient density unit (NDU) did not decrease significantly due to the additional duck yield. Thus, the carbon footprint per NDU of ORD was significantly lower than that of OR by 24.3% (P < 0.05) and was 5.8% higher than that of CR, but this was not statistically significant. Due to the higher economic profits of ORD, its unit of carbon footprint per economic profit was significantly reduced (by 47.1-75.7%) compared with the other two farming modes, while the net ecosystem economic budget was significantly increased by 98.5-341.9% (P < 0.05).

CONCLUSION

Transforming from a rice monoculture to a coculture system will contribute to a win-win situation for human health and environmental sustainability. This study highlighted the abundant nutritional output function of the rice-duck coculture and analyzed the urgency and necessity of transitioning from traditional agriculture to ecological agriculture from the production and consumption perspectives. © 2022 Society of Chemical Industry.

Identifying greenhouse gas emission reduction potentials through large-scale photovoltaic-driven seawater desalination

To widely promote freshwater production through seawater desalination, renewable energy is expected to replace traditional fossil energy to drive seawater desalination. Based on the input list of components and materials, this study attempts to quantify greenhouse gas (GHG) emissions of photovoltaic-driven seawater desalination projects through replacing traditional thermal power plants and evaluate GHG emission reduction potentials by comparing the thermal- and photovoltaic-driven seawater desalination projects. The GHG emission of photovoltaic-driven seawater desalination project could be reduced by 94.97 % compared with the thermal-driven seawater desalination project, and the GHG emission per unit water production is reduced by 9.8 kg CO₂-eq/ton, which could greatly reduce GHG emissions in the whole life cycle. In addition, it is estimated that the large-scale implementation of photovoltaic power stations in LT-MED seawater desalination project can reduce GHG emissions from 1.61E+05 to 3.86E+06 t CO₂-eq per year. Through the payback period assessment, the combination of photovoltaic power stations and thermal power plants to drive the seawater desalination project can offset the GHG emission of 7.94E+03 t CO₂-eq, and the payback period of photovoltaic-driven seawater desalination project is estimated to be 0.33 years. Using renewable energy instead of traditional thermal energy can reduce the fossil fuel combustion and GHG emissions during the water desalination process, which provides essential references for the low-carbon transition and energy saving in seawater desalination projects in China's coastal areas.

Impact assessment of the EU import ban on Indonesian palm oil: Using environmental extended multi-scale MRIO

Under the Renewable Energy Directive (RED) II, the EU will phase out the use of palm oil for biodiesel feedstock. Environmental concerns are the main reasons for the EU to implement this initiative. This study analyzes the economic and environmental impact of EU import ban to Indonesia at provincial level, using 2 scenarios (a direct and direct-indirect import ban). The analysis is performed using a global-subnational Multi-Regional Input-Output (MRIO) with environmental extensions. This study shows that a direct (combined) import ban of palm oil by the EU will reduce Indonesia's GDP by -0.2 % (-0.26 %) and employment by -0.12 % (-0.54 %) from baseline. At provincial level, Riau, North Sumatra, Lampung, Central Kalimantan and South Kalimantan experience the highest impact on their domestic product (more than -0.5 %). Under a direct import ban, job losses mostly happen in outside Java (96.26 %) and in the oilseeds sector (75.21 %). Low and middle skilled jobs decline more than high skilled jobs and count for 95 % of the total loss. This study also shows that a direct (combined) import ban reduces national GHG emissions by -0.19 % (-0.24 %) and total land use by -0.48 % (-0.6 %). Potential carbon sequestration can be 34.55 (42.27) million tons C equivalent to 149.74 (182.67) million tons CO₂e under assumption a full rewilding from the reduction of land use in oilseed. Our study shows that an EU import ban on Indonesian palm oil has relatively small economic and environmental impacts at national and provincial level. Yet, this policy can create potential carbon sequestration that can absorb CO₂ by vegetation and soil.

Climate-smart planting for potato to balance economic return and environmental impact across China

Potato production plays an important role in safeguarding food security in China since the central government implemented the 'Potato-as-Staple-Food' policy in 2015. However, a key challenge facing China's potato production is to realize a tradeoff between economic return and environmental impact. Effective strategies for reducing carbon emission without compromising potato yield remain to be developed. This study conducted a comprehensive assessment by integrating climate, soil, crop, and agricultural input data, crop model and life cycle impact assessment model to quantify potato yields, GHG emission amounts and intensities (GHGI), and economic benefits under the conventional planting pattern (CPP), the lowest GHG emission pattern (LEP), and the highest yield pattern (HYP) across China's potato planting regions including four sub-regions, i.e., North Single planting region (NS), Central Double planting region (CD), South Winter planting region (SW), and Southwest Mixed planting region (SWM). Averaged fresh potato yield, GHG emission amount, and GHGI under the CPP were 21.7 t ha^-1, 2815.1 kg CO₂eq ha^-1, and 137.3 kg CO₂eq t^-1, respectively, in China's potato planting region. Compared with the CPP, averaged GHG emission amount and GHGI under the LEP could be decreased by 48.2 % and 51.5 % respectively while the fresh potato yield and economic benefit could be enhanced by 8.1 % and 18.5 %, respectively. For the HYP, averaged GHG emission amount and GHGI could be decreased by 24.2 % and 39.8 % respectively while the fresh potato yield and economic benefit could be enhanced by 18.7 % and 39.6 %, respectively, compared with the CPP. Across the four potato planting regions, SW had the largest potential in reducing GHG emissions owing to a high reduction amount of nitrogen application rate. Our study demonstrates that optimizing agronomic management could reduce environmental impact without compromising economic benefit and provides a scientific method for assessing crop potential to realize the climate-smart planting.

Lessons from farmers' adaptive practices to climate change in China: a systematic literature review

Due to the vulnerability and exposure of agriculture, farmers' adaptive strategies to climate change are important to food security and sustainable environment development. However, a systematic review is still absent, though there are many studies about farmers' adaptations to climate change, and few studies discuss their potential impacts on climate change. This article analyses farmers' adaptation strategies and their heterogeneities across regions in China via a systemic literature review. Then we also discuss possible driving factors of these adaptations and their potential impacts on greenhouse gas emissions. We follow the updated Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) guidelines to identify and screen publications. A total of 448 relevant records were identified from the Web of Science, Elsevier ScienceDirect, and China National Knowledge Infrastructure (CNKI). We include peer-reviewed publications focusing on farmers engaged in crop farming in China, with survey data and specific adoption ratio analysis of adaptations to climate change. After screening, 27 articles were finally analysed. Our results show that crop variety management, rescheduling farming, increasing production inputs, increasing irrigation, and crop structure management are prevalent strategies reported in the existing literature. However, sustainable adaptations such as improving farmland's ecological environment and agronomic water-saving irrigation gain less attention. Besides, farmers in northern China adapt to climate change more actively compared to their counterparts in southern China. Moreover, some adaptations with high adoption ratios, such as increased chemical inputs, might increase greenhouse gas emissions and accelerate climate change. Our findings have important implications for food security and sustainable agricultural development.

Preparation for Denitrification and Phenotypic Diversification at the Cusp of Anoxia: a Purpose for N2O Reductase Vis-à-Vis Multiple Roles of O2

Adaptation to anoxia by synthesizing a denitrification proteome costs metabolic energy, and the anaerobic respiration conserves less energy per electron than aerobic respiration. This implies a selective advantage of the stringent O₂ repression of denitrification gene transcription, which is found in most denitrifying bacteria. In some bacteria, the metabolic burden of adaptation can be minimized further by phenotypic diversification, colloquially termed "bet-hedging," where all cells synthesize the N₂O reductase (NosZ) but only a minority synthesize nitrite reductase (NirS), as demonstrated for the model strain Paracoccus denitrificans. We hypothesized that the cells lacking NirS would be entrapped in anoxia but with the possibility of escape if supplied with O₂ or N₂O. To test this, cells were exposed to gradual O₂ depletion or sudden anoxia and subsequent spikes of O₂ and N₂O. The synthesis of NirS in single cells was monitored by using an mCherry-nirS fusion replacing the native nirS, and their growth was detected as dilution of green, fluorescent fluorescein isothiocyanate (FITC) stain. We demonstrate anoxic entrapment due to e^--acceptor deprivation and show that O₂ spiking leads to bet-hedging, while N₂O spiking promotes NirS synthesis and growth in all cells carrying NosZ. The cells rescued by the N₂O spike had much lower respiration rates than those rescued by the O₂ spike, however, which could indicate that the well-known autocatalytic synthesis of NirS via NO production requires O₂. Our results bring into relief a fitness advantage of pairing restrictive nirS expression with universal NosZ synthesis in energy-limited systems. IMPORTANCE Denitrifying bacteria have evolved elaborate regulatory networks securing their respiratory metabolism in environments with fluctuating oxygen concentrations. Here, we provide new insight regarding their bet-hedging in response to hypoxia, which minimizes their N₂O emissions because all cells express NosZ, reducing N₂O to N₂, while a minority express NirS + Nor, reducing NO₂^- to N₂O. We hypothesized that the cells without Nir were entrapped in anoxia, without energy to synthesize Nir, and that they could be rescued by short spikes of O₂ or N₂O. We confirm such entrapment and the rescue of all cells by an N₂O spike but only a fraction by an O₂ spike. The results shed light on the role of O₂ repression in bet-hedging and generated a novel hypothesis regarding the autocatalytic nirS expression via NO production. Insight into the regulation of denitrification, including bet-hedging, holds a clue to understanding, and ultimately curbing, the escalating emissions of N₂O, which contribute to anthropogenic climate forcing.

Food, Energy, and Water Nexus at Household Level: Do Sustainable Household Consumption Practices Promote Cleaner Environment?

Governments around the globe are trying to find sustainable solutions for lessening pressure on natural resources and reducing carbon emissions. Daily household consumption of food, energy, and water has an impact on stocks of natural resources, environmental quality, and climate change. Households have significant potential for increasing conservation actions for efficient use of natural resources and greenhouse gas emissions. Households could contribute to a clean and healthy environment by adopting sustainable household practices through lower per capita consumption and carbon emissions. This study explored the role of different sustainable household consumption practices in promoting a clean environment as well as the factors affecting the adoption of these practices in Pakistan. Factor analysis and an ordered probit model were used to analyze the data from 1424 participants chosen through a multistage random sampling technique. The factor analysis identified 35 sustainable household practices for sustainable consumption. These 35 practices were grouped into the underlying factors of "Food" (14 items), "Energy" (12 items), and "Water" (9 items). The results from the econometric model showed a significant relationship between gender, education, residential area, family size, and income and the adoption of sustainable household consumption practices. Statistically, higher levels of reported sustainable consumption practices were apparent among females, households living in urban areas, more educated people, individuals of large family sizes, and more affluent households. Therefore, public policies for taking care of the environment need to put households at the center while at the same time promoting mass uptake of sustainable consumption practices related to food, energy, and water. In addition, the sector-specific policies also need to be augmented through focus on household-level consumption and production dynamics for achieving the UN's SDGs.

Oxygen dynamics, organic matter degradation and main gas emissions during pig manure composting: Effect of intermittent aeration

To investigate the effect of intermittent aeration on oxygen dynamics, organic matter degradation and main gas emissions, a lab-scale pig manure composting experiment was conducted with intermittent aeration (I_A, 30-min on and 30-min off) and continuous aeration (C_A). Although aeration volume and oxygen supply of I_A was only half of C_A, I_A could obviously enhance the oxygen utilization efficiency by 96.67 % and reduce energy dissipation for aeration by 50.87 %. Based on the comprehensive analysis of total organic matter, total carbon, total nitrogen, cellulose, hemicellulose and lignin contents, there was no significant difference in organic matter degradation between I_A and C_A (p > 0.05). Moreover, a reduction of 21.71 %, 38.93 %, 44.40 % and 62.19 % of CH₄, N₂O and the total GHG emission equivalent as well as NH₃ emissions was realized, respectively, in I_A compared with C_A. Therefore, adopting intermittent aeration was a useful strategy and choice for high-efficiency, high-quality and environment-friendly composting.

Estimating Nitrogen Use Efficiency, Profitability, and Greenhouse Gas Emission Using Different Methods of Fertilization

Fertilization is a way to better use nitrogen fertilizers and increase productivity, but in another way, fertilization is also a source of anthropogenic greenhouse gas emissions. The study was carried out to measure the profitability ratio, technical efficiency, and CO₂ from the top dressing (TD) and deep placement (DP) fertilization. The study was based on primary data, which were collected from different respondents and areas through a well-designed questionnaire. The study finds that DP fertilization is more profitable, least costly, and more efficient than TD fertilization. The finding observed that the yield of the TD growers is 727.82 kg/ha more than that of TD respondents. The efficiency score shows that to reach the 90% efficiency level, the farmers of TD need to use DP fertilization. The farmers of TD and DP can still increase their efficiency up to 12% and 9% by using the same inputs. The findings also clarify that manufacturing of synthetic nitrogen (N), direct use of N, Yield, and Area-Scaled greenhouse gas (GHG) emissions from the use of synthetic N through TD fertilization are greater than that of the DP group. The farming community needs to be aware of greenhouse gas emissions and how they can be reduced. It is also suggested that farmers need to shift toward DP fertilization to increase yield, profit, efficiency, food security, and reduce GHG emissions.

Analytic assessment of renewable potential in Northeast India and impact of their exploitation on environment and economy

The need for electricity all over the world is enhancing significantly. A major portion of this demand is met by fossil fuels leading to substantial mining, environmental pollution, and increment in global warming. The escalating rate of extraction is declining their reserves at an alarming rate and enhancing their price as well. Thus, it has become essential to shift to alternative resources for power generation. Northeast India has a superfluous reserve of renewable energy which can competently fulfill the electricity requirement in the region. The surplus can significantly contribute to supplying the demand of other states in the country. In addition, the use of clean energy can conserve fossil fuels and expenditure and at the same time can slow down environmental pollution. This paper comprehensively analyzes the potential of perennial assets in this area; projects their economic and ecological benefits; and also makes a  brief comparison of the conventional systems with the probable green alternatives. Renewable capacity in this regime is found 66,682 MW out of which 99.51% is yet to be explored and Rs. 5.66 × 10¹² will be required to extract them. Utilization of these boons can save 187.39 Mt of combustibles and 648.61 Mt of greenhouse gasses from emission. Capital, energy, and carbon that will be invested during the installation and operation of the systems will be paid back in 3.6, 2.3, and 2.25 years, respectively. The average levelized cost of this unremitting energy will be Rs. 4.80/kWh.

Perceptions of GHG emissions and renewable energy sources in Europe, Australia and the USA

People's sentiments and perceptions of greenhouse gas emission and renewable energy are important information to understand their reaction to the planned mitigation policy. Therefore, this research analyzes people's perceptions of greenhouse gas emissions and their preferences for renewable energy resources using a sample of Twitter data. We first identify themes of discussion using semantic text similarity and network analysis. Next, we measure people's interest in renewable energy resources based on the mentioned rate in Twitter and search interest in Google trends. Then, we measure people's sentiment toward these resources and compare the interest with sentiments to identify opportunities for policy improvement. The results indicate a minor influence of governmental assemblies on Twitter discourses compared to a very high influence of two renewable energy providers amounts to more than 40% of the tweeting activities related to renewable energy. The search interest analysis shows a slight shift in people's interest in favor of renewable energy. The interest in geothermal energy is decreasing while interest in biomass energy is increasing. The sentiment analysis shows that biomass energy has the highest positive sentiments while solar and wind energy have higher interest. Solar and wind energy are found to be the two most promising sources for the future energy transition. Our study implies that governments should practice a higher influence on promoting awareness of the environment and converging between people's interests and feasible energy solutions. We also advocate Twitter as a source for collecting real-time data about social preferences for environmental policy input.

Perceptions of GHG emissions and renewable energy sources in Europe, Australia and the USA

People's sentiments and perceptions of greenhouse gas emission and renewable energy are important information to understand their reaction to the planned mitigation policy. Therefore, this research analyzes people's perceptions of greenhouse gas emissions and their preferences for renewable energy resources using a sample of Twitter data. We first identify themes of discussion using semantic text similarity and network analysis. Next, we measure people's interest in renewable energy resources based on the mentioned rate in Twitter and search interest in Google trends. Then, we measure people's sentiment toward these resources and compare the interest with sentiments to identify opportunities for policy improvement. The results indicate a minor influence of governmental assemblies on Twitter discourses compared to a very high influence of two renewable energy providers amounts to more than 40% of the tweeting activities related to renewable energy. The search interest analysis shows a slight shift in people's interest in favor of renewable energy. The interest in geothermal energy is decreasing while interest in biomass energy is increasing. The sentiment analysis shows that biomass energy has the highest positive sentiments while solar and wind energy have higher interest. Solar and wind energy are found to be the two most promising sources for the future energy transition. Our study implies that governments should practice a higher influence on promoting awareness of the environment and converging between people's interests and feasible energy solutions. We also advocate Twitter as a source for collecting real-time data about social preferences for environmental policy input.

Global warming potential and energy dynamics of conservation tillage practices for different rabi crops in the Indo-Gangetic Plains

A field experiment was conducted during 2007-2019 under various rabi (winter) crops (viz., wheat, maize, barley and mustard) on a Vertisol in sub-tropical Indo-Gangetic Plains (IGP) with different tillage systems to assess energy indices, greenhouse gas (GHG) emission and carbon sustainability index in assured irrigated fields. The tillage systems were: no tillage sown by a zero till drill (NT), no tillage with retention of previous crop residues at 6 t ha^-1 and sowing by a happy turbo seeder (HT), and conventional tillage (CT) where sowing was performed by a multi-crop zero till drill after twice harrowing + twice tilling + once rotavator operations. Significantly higher input energy was observed in wheat followed by maize, barley and mustard. Among tillage systems, CT plots consumed higher input energy that was about 20, 21 to 22, 25 to 26 and 20-22% higher than HT and NT in wheat, maize, barley and mustard, respectively. However, output energy and energy use efficiency were highest in HT. The total GHG emission (kg CO₂ equivalent ha^-1) was highest in wheat (2,351) followed by maize (2,274), barley (1,859) and mustard (1,652). Among tillage systems, CT produced about 31-34%, 33-34%, 37-40% and 28-30% higher GHG emission than HT and NT under wheat, maize, barley and mustard, respectively. The CT plots had lower carbon sustainability index and carbon efficiency than ZT and HT in all crops. In short, HT recorded significantly higher energy use efficiency and lower global warming potential (GWP) than CT in all crops. Thus, HT could be a promising agro-technique for production of rabi crops in the IGP. Among rabi crops, barley production was energy efficient and had less GWP. In rabi crop production, the highest energy sources was mineral fertilizer use (25-49%) and second highest source was irrigation water (14-44%). These can be substituted with use of the organic sources of fertilizers and application of solar and wind power in irrigation, respectively.

Estimating greenhouse emissions from sanitary landfills using Land-GEM and IPCC model based on realistic scenarios of different urban areas: a case study of Iran

This study examined the emission of greenhouse gases from municipal solid waste disposal centers in different regions of Iran based on different scenarios. Assuming landfill site opening in 2012 and considering the 20-year plan period for its usage, the amount of wastes entering the landfill site was calculated for 2012-2032. For calculating the production of methane (CH4) and other gases during different years of the project, Land-GEM and IPCC model were used. We defined 9 scenarios for these two models based on the growth rate of population and waste generation. The results revealed that the lowest amount of gas emission in nine scenarios by Land- GEM model was related to non-methane organic compounds (NMOCs). According to the results obtained, the total emissions of greenhouse gases from sanitary landfills for Iran in 2032 were 3,844,000 Mg/year, the largest and lowest amounts of gas emission were related to Tehran region, 860,400 Mg/year, and the South Coast area of the country,138,200 Mg/year, respectively. The major section of the gas production in both landfills was related to greenhouse gas and carbon dioxide emissions. The difference in gas production in the studied regions was due to differences in the percentage of moisture and organic compounds.

Utilization of fruit and vegetable waste as an alternative feed resource for sustainable and eco-friendly sheep farming

Globally, 10-20% of horticultural wastes are disposed in landfills leading to environmental pollution. Recycling these wastes as animal feedstuff will lessen food-feed competition and minimize environmental hazards. The present study was undertaken to determine the nutritional quality of fresh fruit and vegetable waste (F&VW) and their dietary inclusion on nutrient utilization, antioxidant status, greenhouse gases (GHG) emissions and potable water sparing efficacy in sheep. Three dietary combinations were formulated i.e. control (C):70% Cenchrus ciliaris hay +30% concentrate mixture (CM), diet with fruit waste (FWD):70% Cenchrus ciliaris hay +20% CM +10% FW and diet with vegetable waste (VWD):70% Cenchrus ciliaris hay +20% CM +10% VW for in vitro and in vivo evaluation of these wastes as potential livestock feed. Twenty-one adult ewes were allocated into 3 groups C, FWD and VWD and fed on the above three diets. Dry matter and crude protein digestibility were significantly enhanced by 5.5 and 7.2%; 7.3 and 7.6% in F&VW supplemented groups, respectively, without affecting feed intake. Plasma total antioxidant capacity (TAC) was improved by 32.2 and 26.3% in F&VW supplemented groups. Inclusion of F&VW biomass reduced annual methane (CH₄) and nitrous oxide (N₂O) emissions (kg CO₂eq/sheep) by 3.12 and 4.55%; 15.18 and 14.92% and thus contributed to lowering of global warming potential by 4.00 and 5.27%, respectively. Furthermore, there was a net reduction of potable water consumption by 21.78 and 13.92% in F&VW supplemented groups, respectively. Therefore, it can be concluded that F&VW can be a potential feedstuff for ruminants and its efficient reuse would minimize environmental impacts associated with disposal of such waste in the landfills.

ALLODUST augmented activated sludge single batch anaerobic reactor (AS-SBAnR) for high concentration nitrate removal from agricultural wastewater

Nitrate is among the most widespread contaminants that threaten water bodies and waterways. Under favourable environmental conditions, high nitrate concentrations in water can contribute to eutrophication, thus presenting a high potential for risk to ecosystems and human health. Low-cost allophanic soil material and carbon-based bio-wastes have great potential to reduce nutrient concentrations from contaminated waters. This study investigated the mechanisms that underpin the reduction of nitrate concentrations and nitrous oxide (N₂O) emission in the presence of novel developed media in an activated sludge process. A new operating approach, employing a newly developed media (ALLODUST), was evaluated for enhanced NO^-₃-N removal from agricultural wastewater. Two anaerobic-aerobic batch reactors were developed, where the coupled bottom aeration method was used for efficient agitation and aeration in the aerobic reactor. The reactor was run at high NO^-₃-N concentrations (110 mg L^-1), under anoxic conditions at low- to long-term contact times (2, 12, and 22 h), while the aerobic period (clarification) was constant for all the experimental designs (2 h). ALLODUST retained its integrity and stability over the long-term operation. Low ALLODUST concentrations (5.95 g L^-1) removed 87% of the NO^-₃-N from the wastewater within 12 h. Further exploration revealed that the same amount of the media was optimal for decreasing N₂O emissions from the anaerobic activated sludge reactor by 80%.

Development, current state and future trends of sludge management in China: Based on exploratory data and CO2-equivaient emissions analysis

This study statistically reported the current state of sludge treatment/disposal in China from the aspects of sources, technical routes, geographical distribution, and development by using observational data after 1978. By the end of 2019, 5476 municipal wastewater treatment plants were operating in China, leading to an annual sludge productivity of 39.04 million tons (80% water content). Overall, 29.3% of the sludge in China was disposed via land application, followed by incineration (26.7%) and sanitary landfills (20.1%). Incineration, compost, thermal hydrolysis and anerobic digestion were the mainstream technologies for sludge treatment in China, with capacities of 27,122, 11,250, 8342 and 6944 t/d in 2019, respectively. Incineration and drying were preferentially constructed in East China. In contrast, sludge compost was most frequently used in Northeast China (46.5%), East China (22.4%) and Central China (12.8%), while anaerobic digestion in East China, North China and Central China. The capacities of sludge facilities exhibited a sharp increase in 2009-2019, with an overall greenhouse gas emissions in China in 2019 reached 108.18 × 10⁸ kg CO₂-equivaient emissions, and the four main technical routes contributed as: incineration (45.11%) > sanitary landfills (23.04%) > land utilization (17.64%) > building materials (14.21%). Challenges and existing problems of sludge disposal in China, including high CO₂ emissions, unbalanced regional development, low stabilization and land utilization levels, were discussed. Finally, suggestions regarding potential technical and administrative measures in China, and sustainable sludge management for developing countries, were also given.

Implementing Circular Economy in municipal solid waste treatment system using P-graph

Municipal solid waste (MSW) is one of the issues associated with the growth of economic and urban population. The aim of this study is to develop an integrated design of waste management systems in support of a Circular Economy by P-graph (a bipartite graphical optimisation tool) as an effective decision support tool. The case study considers four MSW compositions based on different country income levels. Solving the P-graph model identifies the most suitable treatment approaches, considering the economic balance between the main operating cost, type, yield, quality of products, as well as the GHG emission (externality cost). The identification of near-optimal solutions by P-graph is useful in dealing with the trade-offs between conflicting objectives, e.g. local policy and practical implementation, that are difficult to monetise. For a lower-income country, the optimal solution includes a combination of at source separation, recycling, incineration (heat, electricity), anaerobic digestion (biofuel, digestate) and the landfill. It avoids an estimated 411 kg CO_2eq/t of processed MSW and achieves a potential profit of 42 €/t of processed MSW. The optimisation generally favours mechanical biological treatment as the country income level rises, which affects the composition of the MSW. The relative prices of biofuel, electricity and heat (>20%) cause a significant impact on the highest-ranking treatment structure and overall profit. This study shows that the developed framework by P-graph is an effective tool for MSW systems planning. For future study, localised data inputs can be fed into the proposed framework for a customised solution and economic feasibility assessment.

Achieving renewable energy, climate, and air quality policy goals: Rural residential investment in solar panel

Heavy dependence on fossil fuels among rural households contributes to GHG emissions and air pollution while increasing landfill loads in Poland. This study examines benefits from the renewable energy utilization support program that subsidized household purchase and installation of thermal solar panels. This review of synergy between energy, climate, and air quality policies focuses on solar panel subsidies funded through the European Union and county governments in Mazowieckie Voivodship in Poland. County government offices, using the unpublished list of households receiving subsidies for thermal solar panel installation, mediated in the implementation of the survey and collected 123 completed questionnaires in May and June 2015. The heteroscedasticity-corrected OLS estimates two equations identifying and quantifying factors influencing the purchase price of solar panels and rural household monthly energy bill savings after installation using the gathered data. Among sociodemographic variables, increasing age was associated with an increasing price paid for the panels, but education was associated with paying a lower price for solar panels and lower self-reported energy bill savings. Panel purchase price increased if the respondent was a farmer, viewed subsidies as important, and preferred domestically manufactured panels. Location of household increased the price as compared to the reference county. Savings on monthly energy bills increased if respondent had a positive view of solar energy, expected a decrease in the bill following the purchase of panels, and heated large areas in the house. Subsidy programs have been important in increased household solar energy utilization, especially among farm households, while self-reported energy bill savings increased with positive attitudes towards renewable energy and the larger heated areas in rural residences.

[Effects of Biochar Application Rates on Greenhouse Gas Emissions in the Purple Paddy Soil]

In order to explore the effects of different amounts of biochar applied in purple paddy soil on greenhouse gas (GHG) emissions, potted experiments using a static opaque chamber and gas chromatography method were used to study the regulations and influences of biochar on soil greenhouse gas emission using five treatments:no fertilizer (CK), conventional fertilization (NPK), 10 t ·hm^-2 biochar+NPK (LBC), 20 t ·hm^-2 biochar+NPK (MBC), and 40 t ·hm^-2 biochar+NPK (HBC). ① Soil CH₄ emission flux reduced significantly with all biochar application treatments; the emission flux followed the order, from large to small, of NPK > CK > LBC > MBC > HBC. The CH₄ emission flux of each treatment showed a single peak curve, and the peak value was mainly concentrated in the late growth stage of the paddy cropland. During the entire observation period, the emission flux of CH₄ was between -0.05 mg ·(m² ·h)^-1 and 47.34 mg ·(m² ·h)^-1. The CO₂ emission flux of each treatment was complicated and ranged from 32.95 mg ·(m² ·h)^-1 to 1350.88 mg ·(m² ·h)^-1. The CO₂ emission flux of the LBC and MBC treatments showed bimodal curves, and the CO₂ emission flux of other treatments showed single peak curves. In addition, all biochar treatments delayed the peak time of the CO₂ emission flux. The N₂O emission flux of each treatment ranged from -309.39 to 895.48 μg ·(m² ·h)^-1, and the N₂O emission flux of the LBC treatment showed a bimodal curve, while other treatments showed single peak curves. ② Compared with the CK treatment, biochar treatment can significantly reduce the cumulative emissions of CH₄ and promote the cumulative emissions of CO₂ and N₂O. The average amount of CH₄ cumulative emissions followed the order CK > LBC > MBC > HBC, while the average amount of CO₂ cumulative emissions followed LBC > MBC > HBC > CK, and the average amount of N₂O cumulative emissions followed HBC > MBC≈LBC > CK. Compared with conventional fertilization treatment, different application rates of biochar addition significantly reduced CH₄ and CO₂ emissions. As more biochar was added, CH₄ and CO₂ cumulative emissions were lower. Although the regulation of N₂O cumulative emissions on biochar addition was not obvious, the application of nitrogen fertilizer could promote the emission flux of N₂O to some extent. ③ Over the time scale of 100 years, the integrated global warming potentials (GWP) of CH₄ and N₂O emission under different biochar treatment were decreased significantly, indicating that biochar combined with chemical fertilizer is an effective GHG emission reduction measure.

Pyrolysis and co-composting of municipal organic waste in Bangladesh: A quantitative estimate of recyclable nutrients, greenhouse gas emissions, and economic benefits

Waste causes environmental pollution and greenhouse gas (GHG) emissions when it is not managed sustainably. In Bangladesh, municipal organic waste (MOW) is partially collected and landfilled. Thus, it causes deterioration of the environment urging a recycle-oriented waste management system. In this study, we propose a waste management system through pyrolysis of selective MOW for biochar production and composting of the remainder with biochar as an additive. We estimated the carbon (C), nitrogen (N), phosphorus (P) and potassium (K) recycling potentials in the new techniques of waste management. Waste generation of a city was calculated using population density and per capita waste generation rate (PWGR). Two indicators of economic development, i.e., gross domestic product (GDP) and per capita gross national income (GNI) were used to adopt PWGR with a projected contribution of 5-20% to waste generation. The projected PWGR was then validated with a survey. The waste generation from urban areas of Bangladesh in 2016 was estimated between 15,507 and 15,888 t day^-1 with a large share (∼75%) of organic waste. Adoption of the proposed system could produce 3936 t day^-1 biochar blended compost with an annual return of US $210 million in 2016 while it could reduce GHG emission substantially (-503 CO₂ e t^-1 municipal waste). Moreover, the proposed system would able to recover ∼46%, 54%, 54% and 61% of total C, N, P and K content in the initial waste, respectively. We also provide a projection of waste generation and nutrient recycling potentials for the year 2035. The proposed method could be a self-sustaining policy option for waste management as it would generate ∼US$51 from each tonne of waste. Moreover, a significant amount of nutrients can be recycled to agriculture while contributing to the reduction in environmental pollution and GHG emission.

Effect of aeration interval on oxygen consumption and GHG emission during pig manure composting

To verify the optimal aeration interval for oxygen supply and consumption and investigate the effect of aeration interval on GHG emission, reactor-scale composting was conducted with different aeration intervals (0, 10, 30 and 50 min). Although O₂ was sufficiently supplied during aeration period, it could be consumed to <10 vol% only when the aeration interval was 50 min, indicating that an aeration interval more than 50 min would be inadvisable. Compared to continuous aeration, reductions of the total CH₄ and N₂O emissions as well as the total GHG emission equivalent by 22.26-61.36%, 8.24-49.80% and 12.36-53.20%, respectively, was achieved through intermittent aeration. Specifically, both the total CH₄ and N₂O emissions as well as the total GHG emission equivalent were inversely proportional to the duration of aeration interval (R² > 0.902), suggesting that lengthening the duration of aeration interval to some extent could effectively reduce GHG emission.

Environmental impact of an agro-waste based polygeneration without and with CO2 storage: Life cycle assessment approach

Life cycle assessment (LCA) is the most scientific tool to measure environmental sustainability. Poly-generation is a better option than single-utility generation due to its higher resource utilization efficiency and more flexibility. Also biomass based polygeneration with CO2 capture and storage may be useful being 'net negative' greenhouse gas emission option. But this 'negativity' should be studied and confirmed through LCA. In this paper, cradle-to-gate life cycle assessment of a straw based polygeneration without and with CO2 storage is studied. Results show that captured CO2 of this polygeneration should be stored to get a net negative energy system. However, biomass distribution density, ethanol production rate and CO2 transportation distance affect the net GHG emission. For this polygeneration system, exergy based allocation should be preferred.

Greenhouse gas emissions from municipal solid waste management in Vientiane, Lao PDR

Municipal solid waste (MSW) is one of the major environmental problems throughout the world including in Lao PDR. In Vientiane, due to the lack of a collection service, open burning and illegal dumping are commonly practised. This study aims to estimate the greenhouse gas (GHG) emission from the current situation of MSW management (MSWM) in Vientiane and proposes an alternative solution to reduce the GHG emission and environmental impacts. The 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories (IPCC 2006 model) are used for the estimation of GHG emission from landfill and composting. For the estimation of GHG emission from open burning, the Atmospheric Brown Clouds Emission Inventory Manual (ABC EIM) is used. In Vientiane, a total of 232, 505 tonnes year(-1) of MSW was generated in 2011. Waste generation in Vientiane is 0.69 kg per capita per day, and about 31% of the total MSW generated was directly sent to landfill (71,162 tonnes year(-1)). The total potential GHG emission from the baseline scenario in 2011 was 110,182 tonnes year(-1) CO2-eq, which is 0.15 tonne year(-1) CO2-eq per capita. From the three MSWM scenarios proposed, scenario S3, which includes recycling, composting and landfilling, seems to be an effective solution for dealing with MSW in Vientiane with less air pollution, and is environmentally friendly. The total GHG emission in scenario S3 is reduced to 91,920 tonnes year(-1) CO2-eq (47% reduction), compared with the S1 scenario where all uncollected waste is diverted to landfill.

Emerging biorefinery technologies for Indian forest industry to reduce GHG emissions

The production of biofuels as alternative energy source over fossil fuels has gained immense interest over the years as it can contribute significantly to reduce the greenhouse gas (GHG) emissions from energy production and utilization. Also with rapidly increasing fuel price and fall in oil wells, the present scenario forces us to look for an alternative source of energy that will help us in the operation of industrial as well as the transportation sector. The pulp mills in India are one of the many options. The pulp mills in India can help us to produce bio-fuels by thermo-chemical/biochemical conversion of black liquor and wood residues. These technologies include extraction of hemi-cellulose from wooden chips and black liquor, lignin from black liquor, methanol from evaporator condensates, biogas production from waste sludge, syngas production from biomass using gasification and bio-oil production from biomass using pyrolysis. The objective of this paper is to overview these emerging bio-refinery technologies that can be implemented in Indian Forest Industry to get bio-fuels, bio-chemicals and bio-energy to reduce GHG emissions.

Enhancement of farmland greenhouse gas emissions from leakage of stored CO2: simulation of leaked CO2 from CCS

The effects of leaked CO2 on plant and soil constitute a key objective of carbon capture and storage (CCS) safety. The effects of leaked CO2 on trace soil gas (e.g., methane (CH4) and nitrous oxide (N2O) emissions in farmlands are not well-understood. This study simulated the effects of elevated soil CO2 on CH4 and N2O through pot experiments. The results revealed that significant increases of CH4 and N2O emissions were induced by the simulated CO2 leakages; the emission rates of CH4 and N2O were substantial, reaching about 222 and 48 times than that of the control, respectively. The absolute global warming potentials (GWPs) of the additional CH4 and N2O are considerable, but the cumulative GWPs of the additional CH4 and N2O only accounted for 0.03% and 0.06%, respectively, of the cumulative amount of leaked CO2 under high leakage conditions. The results demonstrate that leakage from CCS projects may lead to additional greenhouse gas emissions from soil; however, in general, the amount of additional CH4 and N2O emissions is negligible when compared with the amount of leaked CO2.

Greenhouse gas emission and its potential mitigation process from the waste sector in a large-scale exhibition

As one of the largest human activities, World Expo is an important source of anthropogenic Greenhouse Gas emission (GHG), and the GHG emission and other environmental impacts of the Expo Shanghai 2010, where around 59,397 tons of waste was generated during 184 Expo running days, were assessed by life cycle assessment (LCA). Two scenarios, i.e., the actual and expected figures of the waste sector, were assessed and compared, and 124.01 kg CO2-equivalent (CO2-eq.), 4.43 kg SO2-eq., 4.88 kg NO3--eq., and 3509 m3 water per ton tourist waste were found to be released in terms of global warming (GW), acidification (AC), nutrient enrichment (NE) and spoiled groundwater resources (SGWR), respectively. The total GHG emission was around 3499 ton CO2-eq. from the waste sector in Expo Park, among which 86.47% was generated during the waste landfilling at the rate of 107.24 kg CO2-eq., and CH4, CO and other hydrocarbons (HC) were the main contributors. If the waste sorting process had been implemented according to the plan scenario, around 497 ton CO2-eq. savings could have been attained. Unlike municipal solid waste, with more organic matter content, an incineration plant is more suitable for tourist waste disposal due to its high heating value, from the GHG reduction perspective.