Nitrogen Footprint Research Articles

An inexact multi-objective mixed-integer nonlinear programming approach for water-soil-fertilizer management under uncertainty considering “footprint family-planetary boundary” assessment

Water, energy, and food (WEF) are interlinked and create a dynamic system that impacts both human well-being and ecology. Given the importance of ecology within the WEF system, water resources serve as the core issue. The allocation of water resources in irrigation districts is a challenging problem for the coordinated development of agricultural production, water resources, and the ecological environment. The integration of stochastic multi-objective programming, fuzzy credibility-constrained programming, and mixed integer programming offers a solution to this issue, with the construction of a fuzzy credibility-constrained stochastic multi-objective mixed-integer nonlinear programming model. The applicability and validity of this model were verified by applying it to the Kaikong Irrigation District (KID) of the Tarim River Basin in northwest China, with notable findings indicating that the optimized system reduces agricultural costs by 5.82%, increases irrigation water use efficiency by 1.80%, and reduces global warming potential by 6.45%. This study investigates the effects of diverse allocation strategies of water and land resources on the social, economic, and ecological subsystems and their interactions by downscaling four subprocesses PBs to the KID scale. The optimization model reveals that only the nitrogen footprint of Kuerle City surpasses the nitrogen boundary of the KID. The proposed solutions based on the model can encourage the green and ecologically-friendly development of agricultural production and can be applied to agricultural systems in arid regions with similar conditions.

The nitrogen footprint and reactive nitrogen reduction potential of cotton production in China

Analyzing the nitrogen footprint (NF) and the potential reduction of reactive nitrogen in crop production and proposing higher N utilization efficiency strategies are important approaches to sustainable crop development. Cotton is an important cash crop in China. However, only a few studies have systematically quantified the NF of cotton production in China, analyzed its temporal and spatial varieties, clarified its main constituent factors and influential factors, and explored its nitrogen emission reduction potential. This study adopts the life cycle method and analyzes the temporal-spatial varieties in the NF of cotton production in China's main cotton planting areas from 2004 to 2018 based on statistical data, analyzes the main components of the nitrogen footprint of China's cotton production, studies the main driving factors of China's cotton nitrogen emissions based on principal component analysis, simulates the nitrogen emissions of China's cotton production combined with the STIRPAT model, and comprehensively analyzes the potential nitrogen emission reduction of China's cotton production. The results indicated that the average nitrogen footprint per unit area (NFa) of cotton planting districts in Northwest China (Nw.CPD), the Yellow River Basin (Yel.RCPD) and the Yangtze River Basin (Yan.RCPD) was 112 kg Neq·ha−1, 65 kg Neq·ha−1 and 155 kg Neq·ha−1, respectively, and the NFa of cotton production in Hunan was the highest. In terms of spatial distribution, the NFa, NFy and NFv of cotton production in Yan.RCPD were higher than those in Yel.RCPD and Nw.CPD, and the NF of cotton planted in Yel.RCPD was the lowest. The NFa of cotton planting in China increased continuously, and the NFa in Nw.CPD showed an increasing trend, while the NFa in Yel.RCPD and Yan.RCPD showed a decreasing trend. Principal component analysis (PCA) showed that fertilizer and the associated reactive nitrogen losses were the main components of the nitrogen footprint. The prediction results of the STIRPAT model showed that compared with 2018, China's cotton production can reduce nitrogen emissions by 54.43 kilotons in 2050 at most. Improved fertilizer utilization efficiency, optimized field management measures and effective policy intervention are effective strategies to reduce the nitrogen footprint of cotton production.

The Extension of Vegetable Production to High Altitudes Increases the Environmental Cost and Decreases Economic Benefits in Subtropical Regions

Global warming has driven the expansion of cultivated land to high-altitude areas. Intensive vegetable production, which is generally considered to be a high economic value and high environmental risk system, has expanded greatly in high-altitude mountainous areas of China. However, the environmental cost of vegetable production in these areas is poorly understood. In this study, pepper production at low (traditional pepper production area) and high (newly expanded area) altitudes were investigated in Shizhu, a typical pepper crop area. The output and environmental cost at the two altitudes were identified. the influence of resource inputs, climate, and soil properties on pepper production was evaluated. There were obvious differences in output and environmental cost between the two altitudes. High-altitude pepper production achieved a 16.2% lower yield, and had a higher fertilizer input, resulting in a 22.3% lower net ecosystem economic benefit (NEEB), 23.0% higher nitrogen (N) footprint and 24.0% higher carbon (C) footprint compared to low-altitude farming. There is potential for environmental mitigation with both high- and low-altitude pepper production; Compared to average farmers, high-yield farmers groups reduced their N and C footprints by 16.9–24.8% and 18.3–25.2%, respectively, with 30.6–34.1% higher yield. A large increase in yield could also be achieved by increasing the top-dress fertilizer rate and decreasing the plant density. Importantly, high-altitude pepper production was achieved despite less advanced technology and inferior conditions (e.g., a poor road system and uneven fields). It provides a reference for the study of the environmental cost of other high-altitude regions or other crop systems at high-altitude areas.

Regional Analysis of Nitrogen Flow within the Chesapeake Bay Watershed Food Production Chain Inclusive of Trade.

In the Chesapeake Bay Watershed, excess nitrogen has contributed to poor water quality, leading to nitrogen mitigation efforts to restore and protect the watershed. The food production system is a top contributor to this nitrogen pollution. While the food trade plays a vital role in distancing the environmental impacts of nitrogen use from the consumer, previous work on nitrogen pollution and management in the Bay is yet to carefully consider the effect of embedded nitrogen found in products (nitrogen mass within the product) imported and exported throughout the Bay. Our work advances understanding across this area by creating a mass flow model of nitrogen embedded in the food production chain throughout the Chesapeake Bay Watershed that separates phases of the production and consumption processes for crops, live animals, and animal products and considers commodity trade at each phase by combining aspects of both nitrogen footprint and nitrogen budget models. Also, by tracking nitrogen embedded in products imported and exported in these processes, we distinguished between direct nitrogen pollution and nitrogen pollution externalities (displaced N pollution from other regions) from outside of the Bay. We developed the model for the watershed and all its counties for major agricultural commodities and food products for 4 years 2002, 2007, 2012, and 2017 with a specific focus on 2012. Using the developed model, we determined the spatiotemporal drivers of nitrogen loss to the environment from the food chain within the watershed. Recent literature leveraging mass balance approaches has suggested that previous long-term declines in nitrogen surplus and improvements in nutrient use efficiency have stagnated or begun to reverse. Our results suggest that within the Chesapeake Bay, increased corn and wheat acreage and steadily increasing livestock/poultry production may have led to the stagnation in decreasing N loss trends from agricultural production observed over the past two decades. We also show that at the watershed scale, trade has reduced the food chain nitrogen loss by about 40 million metric tons. This model has the potential to quantify the effect of various decision scenarios, including trade, dietary choices, production patterns, and agricultural practices, on the food production chain nitrogen loss at multiple scales. In addition, the model's ability to distinguish between nitrogen loss from local and nonlocal (due to trade) sources makes it a potential tool to optimize regional domestic production and trade to meet local watershed's needs while minimizing the resulting nitrogen loss.

Effects of nitrogen fertilizer substitution by cow manure on yield, net GHG emissions, carbon and nitrogen footprints in sweet maize farmland in the Pearl River Delta in China

Long-term excessive nitrogen (N) application in sweet maize farmland in the Pearl River Delta in China has caused huge greenhouse gas (GHG) and reactive nitrogen (RN) emissions in the region. This study compared the effects of N fertilizer replaced by cow manure at 20.00% (CD20) and 50.00% (CD50) ratios on crop yield, on-field N2O, CH4 and CO2 emissions, soil organic carbon (SOC) concentration, GHG emission intensity and carbon footprint (CF) and nitrogen footprint (NF) based on field research carried out for four consecutive cropping seasons during 2020–2021. The results showed that, compared with conventional nitrogen application (CK), CD20 could reduce N2O emissions by 6.65% and increase the SOC concentration by 48.08% when ensuring yield, although GHG emissions and intensity were both increased by 36.13%–36.44%. The CD50 lowered the crop yield 8.77% as the GHG emissions and intensity increased by 74.32%–74.58% at the same time compared to the CK, although the SOC concentration in farmland was significantly improved by 295.82% due to the higher substitution ratio of N fertilizer. Moreover, the CFs based on the area and yield of CD20 and CD50 were 23.22%–135.52% lower than CK. The NF of CD20 based on area and yield was 10.81%–16.35% lower than that of CK, but the NF of CD50 based on area and yield was 4.82%–14.90% higher than that of CK. In conclusion, replacing 20% synthetic nitrogen with cow manure in sweet maize farmland in the Pearl River Delta could achieve the synergistic technical effects of maintaining crop yield, improving the soil carbon sink and decreasing GHG and RN emissions at the life cycle level. We suggest the application of this method as an alternative fertilization practice for realizing a sustainable sweet maize cultivation system in South China. This study provided a research basis for developing the sustainable sweet maize farming system in the Pearl River Delta in China. It would also provide valuable information for the development of clean agricultural production in typical subtropical area in East Asia.

Food Nitrogen Footprint Increased by 35% on the Third Pole During 1998-2018.

The N footprint is considered as an indicator of potential environmental damage from N. Quantitative analysis of N footprint distribution, sources and drivers can help mitigate its negative impacts and promote sustainable N management. In this study, we constructed a city-scale food N footprint (FNF) framework for the Qinghai-Tibet Plateau (QTP) using a N mass balance approach. We quantitatively analyzed the FNF during food production and consumption on the QTP from 1998 to 2018. We used the logarithmic mean Divisa index decomposition method to analyze the driving forces of the FNF, and the decoupling of the FNF. The results showed that the per capita FNF of the QTP increased from 24.92kgN cap-1 in 1998 to 27.70kgN cap-1 in 2018, and the total FNF increased by 35.11% from 1998 to 2018. The spatial distribution of the FNF was uneven, with N losses from crop production and animal production being the leading contributing source to the FNF (86%). Economic development and urbanization were the main driving forces behind the FNF increase, while N consumption intensity inhibited the growth of the FNF. With the rapid growth of GDP, the FNF in the eastern part of the QTP grew relatively slowly, indicating a gradual decoupling of the FNF from economic development. To reconcile the relationship between socioeconomic drivers and the FNF, it is necessary to focus on coupling relationships between subsystems within the food production and consumption system to promote N recycling.

Resource use efficiencies, environmental footprints and net ecosystem economic benefit of direct-seeded double-season rice in central China

Intensive cropping systems with two or three harvests per year are vital to produce sufficient food for the growing population. Improvements in the sustainability of these systems are critical for global food security. Transplanted double-season rice (TPD), an important cropping system in China, is seriously threatened by various challenges such as labor shortage, poor resource use efficiency, high environmental footprint, and low profitability. These challenges could be potentially alleviated by shifting TPD to direct-seeded double-season rice (DSD). Due to the limited thermal energy, ultrashort-duration cultivars matured within 95 days have to be used in DSD in central China. However, it is unknown whether DSD with ultrashort-duration cultivars (DSDS) can improve resource use efficiency and reduce environmental costs compared with TPD in this region. This study aimed to compare the resource use efficiency (energy, water, labor, and fertilizer), carbon and nitrogen footprints, and net ecosystem economic benefit of DSDS and TPD with ultrashort-duration (TPDS) and medium-duration cultivars (TPDM). Results showed that total energy output was 222.0 GJ ha−1 in DSDS, which was comparable to that of TPDM but was significantly increased by 9.5% compared with TPDS. Compared with TPD (i.e. both TPDS and TPDM), the total energy input, labor input, water input, and nitrogen surplus in DSDS reduced by 16.9%, 53.2%, 36.8%, and 31.4%, respectively, leading to significant increases in energy use efficiency, labor productivity, water use efficiency, and nitrogen use efficiency. Furthermore, DSDS decreased direct CH4 and NH3 emissions and indirect carbon emission and reactive nitrogen losses from agronomic inputs, and consequently reduced carbon footprint by 28.6–42.7% and nitrogen footprint by 12.9–14.8% compared with TPD. As a result, the net ecosystem economic benefit in DSDS was significantly increased by 65.9–188.2% relative to TPD. These findings suggest that DSDS is a highly promising strategy to maintain high productivity with less resource inputs and environmental pressures but high economic benefits in central China.

Biochar combined with N fertilization and straw return in wheat-maize agroecosystem: Key practices to enhance crop yields and minimize carbon and nitrogen footprints

Straw incorporation is widely applied to improve crop productivity, and biochar amendment may be an effective countermeasure for mitigating greenhouse gas (GHG) emissions; however, the comprehensive evaluation of straw return and biochar amendment coupled with different N application rates on soil organic carbon (SOC) sequestration rate, GHG emissions, and reactive N losses have been inadequately recorded. Consequently, the field experiment had six treatments and three replications including two mineral N fertilization rates (conventional N fertilizer application (N1) and 30% reduced N fertilizer application (N0.7)) and three types of straw and biochar management variations (no straw incorporation (S0), straw incorporation (S), and straw incorporation with biochar amendment (SB)) and the results were based on three years of soil SOC and GHGs emission data in wheat-maize agroecosystem. Our finding revealed that N0.7 reduced the GHG emissions (CO2: 13.9%; N2O: 34.2%; CH4: 32.5%), greenhouse gas intensity (GHGI; 32.7%), carbon footprint (CF; 35.1%) and nitrogen footprint (NF; 24.5%), but had no significantly different crop yields compared with N1 (p > 0.05). Straw incorporation had no significant impact on CF and yield-scaled CF but increased NF (29.7%) because the stimulated GHG emissions would be offset by SOC sequestration. Under S, the wheat and maize yields increased by 9.7% and 5.4%, respectively, whereas the GHGI increased by 59.6% compared with S0. Biochar amendment reduced GHG emissions (CO2: 19.9%; N2O: 29.9%), GHGI (32.7%), CF (26.7%) and yield-scaled CF (29.2%), while improving crop yields (wheat: 5.8% (p < 0.05); maize: 1.5% (p > 0.05)) and SOC sequestration rate (74.5%) compared with that under S. Overall, N0.7SB exhibited enormous potential for enhancing wheat-maize agroecosystem productivity and drastically mitigating their CF and NF in the semi-arid conditions of the Guanzhong Plain.

Accounting for the nitrogen footprint of food production in Chinese provinces during 1998–2018

Excessive emission of reactive nitrogen (Nr) in the environment has a negative impact on human health and biodiversity and aggravates the greenhouse effect. Food production and consumption is the primary source of anthropogenic Nr emissions. Currently, the research on China's nitrogen footprint lacks the exploration of regional differentiation, and the local virtual Nitrogen factor (VNF) is also insufficient. In this study, we developed localized VNF at the provincial level in China and then applied them to measure the per capita food production Nitrogen footprint of 31 provinces in mainland China from 1998 to 2018 by employing a modified N-Calculator model. We found that the national per capita food production N footprint varied from 15.30 to 21.09 kg/year over the past 20 years. Per capita food production N footprint of 29 provinces increased, ranging from 13% to 113%. The dominance of the food production N footprint of meat gradually increased, and the differences between regions showed a decreasing trend. Finally, we compared the results with different countries based on VNF and 2018 food consumption data. Although the limitations of the underlying data and parameters pose challenges to the accuracy of the estimation, our study provides an original data contribution to nitrogen footprint research to scientific communities and policymakers.

Biochar as a Soil Amendment for Restraining Greenhouse Gases Emission and Improving Soil Carbon Sink: Current Situation and Ways Forward

The global exponential rise in greenhouse gas (GHG) emissions over the last few decades has triggered an urgent need to contextualize low-cost and evergreen technologies for restraining GHG production and enhancing soil carbon sink. GHGs can be mitigated via incorporating biochar into soil matrix to sequestrate the mineralized carbon in a stable form upon organic matter decomposition in soil. However, the efficiency of using biochar to offset GHG emissions from soil and terrestrial ecosystems is still debatable. Moreover, in the literature, biochar shows high functionality in restraining GHG emissions in short-term laboratory studies, but it shows minimal or negative impacts in field-scale experiments, leading to conflicting results. This paper synthesizes information on the ability of biochar to mitigate carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions from soil and organic biomass, with an emphasis on cropland soils. The feedstock type, pyrolysis temperature, and application rate factors showed significant effects on controlling the effectiveness of biochar in restraining GHG emissions. Our study demonstrates that biochar, taken as a whole, can be seen as a powerful and easy-to-use tool for halting the rising tide of greenhouse gas emissions. Nonetheless, future research should focus on (i) identifying other indirect factors related to soil physicochemical characters (such as soil pH/EH and CaCO3 contents) that may control the functionality of biochar, (ii) fabricating aged biochars with low carbon and nitrogen footprints, and (iii) functionalizing biologically activated biochars to suppress CO2, CH4, and N2O emissions. Overall, our paradoxical findings highlight the urgent need to functionalize modern biochars with a high capacity to abate GHG emissions via locking up their release from soil into the carbonaceous lattice of biochar.

Agricultural environmental footprint index based on planetary boundary: Framework and case on Chinese agriculture

Agricultural production activity consumes natural resources and generates negative environmental consequences at the same time. An effective tool is required to calculate a comprehensive assessment score for selecting the best agricultural practice or system from others, which could help policy makers or producers to propose a practical and comprehensive solution for development of agricultural systems. Therefore, this study identified an agricultural environmental footprint index (EFI) by integrating footprints indicators, including land, water, carbon, nitrogen and phosphorus footprints, with the planetary boundary (PB) theory. The Chinese agricultural system was selected as a case to demonstrate the rationality and feasibility of the EFI framework proposed in the present case. Results indicated that the EFI could reflect the comprehensive environmental costs of agricultural production activities by a score under the unified system boundary and accounting logic. The case study demonstrated that the EFI based on unit area (EFI) of Chinese agricultural system increased by 9.06% from 2001 to 2020, and the EFI per unit of economic output (EFIY) has decreased by 80.5%. Meanwhile, the EFI of Chinese agricultural system was higher in the south regions and lower in the north regions in China, while the EFIY showed the opposite trend. The results presented the real temporal and spatial variations of environmental performance of agricultural systems in China. In addition, we found that the inputs of fertilizers, cropland and freshwater contributed 81.42%–84.91% of EFI during the study period, illustrating that the EFI framework contributed to finding out the key aspects and sources of environmental costs of Chinese agricultural system. Overall, this study provided a simple tool for policy makers or producers to understand the balance between the useful output and multiple negative environmental costs of the agricultural production activities. It would provide method basis for assessing and regulating the agricultural practices, models and systems, promoting the development of sustainable agriculture.

Amount of Food Groups in a Healthy Diet with Low Environmental Impact: an Analysis Using Nitrogen Footprint

【目的】地球環境と健康の両方に資する食物選択の推進に向けて，環境負荷の少ない健康な食事の特徴を探るため，窒素フットプリント (以下，NF) を用いて健康な食事の食品群別使用状況を調べた。

Desirable Diet to Lower the Japanese Nitrogen Footprint: Analysis of the Saitama Prefecture Nutrition Survey 2017

With the growing interest in healthy and sustainable diets, studying diets with high nutritional quality and low environmental impact is needed. We focused on the nitrogen footprint (NFP)-an indicator of reactive nitrogen loss that causes various environmental impacts-of Japanese diets using individual dietary records and identified the characteristics of lower NFP diets. This cross-sectional study was a secondary data analysis from the 2017 Saitama Prefecture Nutrition Survey. We analyzed the data obtained from a questionnaire and two-day dietary records of 479 men and women aged 30-65 y who had no misreported or missing data. The NFP was calculated using the virtual nitrogen factors of each food group reported in a previous study. After assessing NFP and its contributions, we conducted sub-group analysis for participants with appropriate weight status and adequate protein intake, classifying them into three groups according to tertiles of NFP to protein ratio. We compared NFP, its contributions, and nutrient intake between the groups. The total NFP (kg N/y) was 18.2±5.0 in men and 16.1±4.4 in women. In the sub-group analysis, total NFPs of the lower NFP group were 16.5±3.1 in men and 13.6±2.8 in women. Cereals, pulses, and fish and seafood contributed more significantly to the total NFP in the lower NFP group than in the higher NFP group. These results suggest that adequate protein intake from a variety of food sources is required to lower the environmental impact of adequate diets.

The nitrogen footprint of Swedish food consumption

Food systems are major drivers of environmental and health impacts. While the emissions and other pressures causing these impacts mainly occur in primary agricultural production, the deeper causes and much of the mitigation potential are distributed throughout food systems, including dietary choices and multiple inefficiencies in the whole chain from agricultural production to consumption and waste management. An environmental indicator based on this systems perspective is the nitrogen (N) footprint, defined as the emissions of reactive N due to the consumption of an individual or other entity. Here, we present a method to estimate the N footprint of Swedish food consumption, using a detailed inventory of agricultural production, food and feed processing, food waste, waste management, and wastewater treatment. Limitations of data sources and methods are discussed in detail. The estimated Swedish food N footprint is 12.1 kg N capita−1 yr−1, of which 42% is emitted in Swedish production, 38% in production abroad, 1% in consumer waste management, and 19% in wastewater treatment. Animal food products account for 81% of the food N footprint and 70% of the protein intake. Average protein intake exceeds nutritional requirements by about 60%, which suggests that at least 35% reduction of food-related reactive N emissions could be achieved through dietary change. Of the apparent food N consumption (6.9 kg N capita−1 yr−1), about 22% is food waste N (1.5 kg N capita−1 yr−1). We estimate that 76% of food waste N is unavoidable (bones and other parts not commonly eaten). Avoidable food waste is about 7% of the edible food supply, implying that a hypothetical complete elimination of food waste would reduce emissions by about 7%. In summary, we present a detailed method, discuss its limitations, and demonstrate possible uses of the N footprint as a complement to existing territorial and sectoral environmental indicators.

Mitigating environmental impacts using net energy system in feed formulation in China's pig production

As the world's largest pork producer, China is facing substantial environmental pressures caused by pig production and the relevant feed production. The net energy (NE) system is promoted as a new evaluation method to evaluate energy content in feed and energy requirements of pigs, but its application lacks of comprehensive and comparative evaluation from the environmental perspective. To identify influence factors and to develop mitigation strategies, the carbon and nitrogen footprints and land use (LU) of pigs (25–120 kg) in China were explored through scenario analysis and cradle-to-farm gate life cycle assessment (LCA). Functional unit (FU) was defined as 1 kg of live weight increase in pig. Among all the procedures of pig production, feed crop production and manure management were the principal contributors to the greenhouse gas (GHG) and nitrogen emissions. As for the carbon footprint, the GHG emissions ranged from 2.37 to 2.55 kg CO2-eq. FU−1 for scenarios using the NE system, 2 % lower than that of the metabolizable energy (ME) system. Cottonseed meal-based scenario generated the lowest GHG emissions, and anaerobic digestion achieved the same effects as other manure management methods. As for the nitrogen footprint, reactive nitrogen (Nr) emissions ranged from 53.4 to 66.2 g Nr FU−1 for scenarios using the NE system, 4 % lower than that of the ME system. Peanut-based scenario won the lowest Nr losses. Moreover, arable LU ranged from 4.63 to 5.85 m2 FU−1 for scenarios using the NE system, 4 % lower than that of the ME system, and economic advantage by using the NE system was also proved. Sensitivity analysis and data quality assessment were conducted to quantify the uncertainties of the above models. In conclusion, the application of the NE system in feed formulation was an effective strategy to improve the environmental sustainability of China's pig production.

MABR process development downstream of a carbon redirection unit: opportunities and challenges in nitrogen removal processes

ABSTRACT Carbon redirection has become the desired option for sustainable and energy-efficient wastewater treatment due to its contribution to a circular economy. However, its impact on downstream processes such as nitrification and denitrification requires further investigation. This research characterizes the nitrogen removal performance, footprint, aeration mode, and microbial composition of a flow-through membrane aerated biofilm reactor (MABR) downstream of a chemically enhanced primary treatment (CEPT) carbon redirection unit. The batch and long-term studies demonstrated relatively higher nitrification rates than those reported using conventional primary treated wastewaters. The results indicated that reducing carbon in the liquid train positively impacted nitrification by achieving 87 ± 12% (1.4 ± 0.4 g/m2.d) ammonia removal with an effluent 2.5 ± 2.8 mg/L ammonia concentration at a short hydraulic retention time (HRT) of 2.5 h. Despite the lower (1.9 ± 1) soluble COD:N, up to 75 ± 25% (0.6 ± 0.4 g/m2.d) total nitrogen removal was achieved at 4 h HRT by implementing intermittent aeration. The batch tests using the developed biofilms showed nitrification (denitrification) capacity up to 11 ± 1.7 gNH4-N/m2.d (8.5 ± 0.5 gNO3-N/m2.d) and 2.7 ± 0.6 gNH4-N/m2.d (2 ± 0.3 gNO3-N/m2.d) corresponding to ammonia and nitrate concentrations ranging from 10–30 mg/L and 2–10 mg/L, respectively. Microbial analysis indicated that the nitrifiers such as Nitrosomonas and Nitrospira were the dominant species. The ammonia-oxidizing, nitrite-oxidizing, and denitrifying bacteria relative abundances were 10.3 ± 1.5%, 20.7 ± 1.7%, and 20.0 ± 2.8% under continuous aeration and 1.3 ± 0.07%, 1.8 ± 0.09%, and 40.5 ± 3.1% under intermittent aeration, supporting the observed ammonia and total nitrogen removal processes, respectively. Overall, the results demonstrated that MABR downstream of the CEPT behave differently; thus, design guides should be updated accordingly.

Feeding children with environmentally based dietary guidelines: The Nitrogen Footprint of school lunch menus adhering to the Spanish dietary guidelines

It is at an early development stage the best opportunity for a society to learn the concepts of sustainable production and consumption. Schools can serve as effective and efficient ways for this purpose. This work quantifies the Nitrogen Footprint (NF) of twelve school menus developed following the Spanish dietary guidelines. The analysis considers six fall school menus and six spring school menus for 7 to 12 years old children. Fall menus present higher NF than spring menus, being on average 23 g N and 19 g N, respectively. This is mainly due to the presence of beef dishes in fall menus, which significantly increase the production NF. Menus including non-meat protein sources, such as legumes, exhibit the lowest N pollution. Menus with beef dishes remain the most intensive menus for fall and spring in terms of N pollution and energy intake, being 0.04 g N/kcal. The highest contributing stage to the total NF is the production (92.6 %), followed by consumption (5.8 %), while the distribution and cooking stages present lower contributions. In order to improve the overall NF, some reduction strategies are: (1) substitution of beef with other animal meat sources, (2) substitution of beef with non-meat sources, (3) improvement of wastewater treatment efficiency, and (4) recycling non-edible food. Substituting beef with non-meat sources achieves the highest reduction (76 %) compared to the total NF of the school menus. It is recommendable to include environmental aspects related to N emissions within the school guidelines in order to provide practical information to policymakers and guide-users.

Performance enhancement, membrane fouling mitigation and eco-friendly strategy by electric field coupled membrane bioreactor for treating mariculture wastewater

An eco-friendly strategy for mariculture wastewater treatment using an electric field attached membrane bioreactor (E-MBR) was evaluated and compared with a conventional membrane bioreactor (C-MBR). The removal efficiencies of total nitrogen (TN) and chemical oxygen demand (COD) increased significantly and the membrane fouling rate reduced by 44.8% in the E-MBR. The underlying mechanisms included the enriched nitrifiers and denitrifiers, the enhanced salinity-resistance, the increased activities and upregulated genes of key enzymes involved in nitrification and denitrification for improving the performance of mariculture wastewater treatment, and the enriched extracellular polymeric substance (EPS)-degrading genera, the downregulated EPS biosynthesis genes, the repressed biofilm-forming bacteria, the enhanced zeta potential absolute value and the generated H2O2 for membrane fouling mitigation by electrical stimulation. Compared with the C-MBR, the energy consumption, carbon emissions, and nitrogen footprint were reduced. These findings provide novel insights into mariculture wastewater treatment using an applied electric field.

Farm-scale practical strategies to increase nitrogen use efficiency and reduce nitrogen footprint in crop production across the North China Plain

Achieving a pathway for green development is a critically important challenge for agriculture in China and beyond. The current study evaluates the effects of a range of management interventions including planting, fertilizer nitrogen (N) rate optimization and increasing farm size to promote agricultural green development across the North China Plain (NCP) based on large-scale farm surveys. Our results showed that the mean annual N fertilizer rate for wheat-soybean rotation was much lower than that of wheat-maize and wheat-peanut. Interestingly, our study indicated strong pre-crop effects of summer soybean ( Glycine max (Linn.) Merr.) on the following winter wheat ( Triticum aestivum Linn.) in N saving compared to summer maize ( Zea mays Linn.) and summer peanuts ( Arachis hypogaea Linn.), the low N rate for summer soybean and its ‘legume’ carryover effects led to the low N rate, N surplus and N footprint, and high N use efficiency (NUE) in wheat-soybean. The survey results showed that the optimal N rates for achieving maximum yield of summer maize, summer peanuts and winter wheat were 229, 249 and 236–260 kg ha −1 across the NCP, respectively. Moreover, better N management is beneficial for reducing the N surplus and leads to higher NUE and lower N footprint. Generally, large farms applied less N fertilizer than small farms, thus leading to a lower N surplus and higher N partial factor productivity with the same yield level. Here we show for the first time that the combinations of crop rotation design, optimizing N rate application and increasing farm size are very efficient in reducing N fertilizer applications and the N footprint with stable crop yields. N management should play a more important role in agricultural green development across the NCP and similar regions around the world. • The mean annual N rate, N surplus and N footprint of wheat-soybean was lowest among the three major crop rotations. • Pre-crop effects of soybean on winter wheat increased PFP and reduced N footprint without affecting wheat yield. • The optimal N rate for the maximum crop yield of maize, peanut, wheat were 229, 249, 236–260 kg N ha −1 , respectively. • The NUE was higher and N footprint was lower in large farms compared with small farms.

Using the Default Nudge to Increase Plant-based Meal Consumption on College Campuses

ObjectivesClimate, environmental, and nutrition scientists have recommended reduced meat and dairy consumption as key to reducing adverse planetary and human health impacts. We conducted this study to (1) investigate the effect of a default plant-based nudge on participant meal choices at a higher education institution and (2) to project the footprints of these choices: greenhouse gas (GHG) emissions (g CO2-eq), blue water (m3), land use (m2), nitrogen (g N), and phosphorus (g P) usage. MethodsData collection was performed at two student events where catering was provided. We used a randomized controlled trial (RCT) design to determine if students presented with a plant-based meal as the default option were less likely to choose a meat option. At each event, students were randomly assigned to two groups. The control group received a RSVP form that presented a meal with meat as the default option. The intervention group received a form that presented a plant-based meal as the default. To project and compare the environmental impacts of each group, we modeled two plant-based and two meals with meat. Using these meals we calculated the footprints of two 100-person events based on the RCT meal selections. ResultsWe observed a large effect size (p < 0.0001) across both experiments. In the first event (n = 108) the intervention decreased the selection of meat meals by 43 percentage points (85% to 42%). In the second event (n = 81) the intervention decreased meat meal selection by 56 percentage points (83% to 27%). When comparing the projected 100-person events based on the RCT meal selections, we found reductions in GHG emissions (28–59%), land use (24–59%), nitrogen (40–57%), and phosphorus (37–61%) footprints. However, we also found an increase in blue water usage (41–77%). ConclusionsThis intervention is a low-effort, high impact way to decrease the share of meals containing meat in institutional settings. Adopting a default plant-based policy may be an effective way to reduce environmental impact and encourage healthier options while maintaining choice. Funding SourcesBetter Food Foundation, National Science Foundation.