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Article

Estimation of the Potential Global Nitrogen Flow in a Nitrogen Recycling System with Industrial Countermeasures

by
Kiyotaka Tsunemi
1,*,
Tohru Kawamoto
2 and
Hideyuki Matsumoto
3
1
Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8569, Japan
2
Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan
3
Department of Chemical Science and Engineering, Tokyo Institute of Technology, Tokyo 152-8550, Japan
*
Author to whom correspondence should be addressed.
Sustainability 2023, 15(7), 6042; https://doi.org/10.3390/su15076042
Submission received: 2 March 2023 / Revised: 24 March 2023 / Accepted: 27 March 2023 / Published: 31 March 2023
(This article belongs to the Special Issue Sustainable System Transitions toward a Circular Economy)
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Abstract

:
This study proposes a nitrogen recycling system that collects and recycles nitrogen compounds from waste gases in the industrial sector, such as those from stationary sources, from industrially processed wastewater containing livestock effluent, and from household wastewater. Multiple scenarios are set, and the potential global flows of anthropogenic nitrogen in 2050 are estimated and compared to assess the effects on the largest planetary boundary problem. In contrast to the business-as-usual (BAU) scenario, in which environmental conditions are worsened through a 47% increase in nitrogen emissions by 2050 above the 2010 levels, the agricultural countermeasures scenario produced a reduction in emissions which was less than the 2010 levels. The industrial countermeasures scenario proposed in this study achieved comfortable reductions in nitrogen production by constructing a nitrogen recycling system that installs the nitrogen compounds to ammonia (NTA) technologies. Combining the agricultural and industrial countermeasures achieves a 66% reduction in nitrogen emissions compared with the BAU scenario in 2050. The combination of both countermeasures with a high installation rate of NTA technologies can achieve the reduction of nitrogen emissions beneath the planetary boundary.

1. Introduction

Massive amounts of ammonia have been produced using the Haber–Bosch process (N2 + 3H2 → 2NH3, referred to as HB-NH3 below) and used as fertilizer and chemical feedstock [1]. As of 2010, ammonia, a basic chemical product of reactive nitrogen, is produced globally at a rate of 120 million tons-N per year, of which approximately 80% is used in nitrogen fertilizers and approximately 20% is used as feedstock in the manufacture of chemicals [2,3]. This nitrogen is used by humans in food and products, and the lives of around half of humanity are made possible by Haber–Bosch nitrogen [4]. Therefore, world fertilizer nitrogen consumption in 2010–2011 leached 110 million tons-N per year into the environment [5].
The waste gas, effluent, and residues created by using this nitrogen contain harmful nitrogen compounds such as nitrogen oxides (NOx), organic nitrogen, ammonia nitrogen (e.g., NH4+ and NH3), and nitrates (NO3-). Nitrogen in sewage is detoxified through a nitrification/denitrification reaction, such as the activated sludge process, which converts it to N2 and releases it into the atmosphere. Waste is incinerated, detoxified, converted to N2, and then released into the atmosphere. However, because not all emission sources can be sufficiently detoxified, some nitrogen compounds are released into the environment. Additionally, NH3 gas is released from livestock agriculture. Internal combustion engines, such as combustion thermal power stations, also emit NOx, some of which is released into the environment.
Ammonia production through HB-NH3 uses fossil fuels as natural gas, oil, and coal; thus, HB-NH3 is currently one of the largest global energy consumers and greenhouse gas emitters, responsible for 1.2% of the global anthropogenic carbon dioxide (CO2) emissions [6]. Furthermore, detoxifying processes, such as incineration and the nitrification/denitrification of waste gases and wastewater containing nitrogen compounds, require large energy inputs for aeration and combustion, and release large amounts of CO2.
There are major concerns about the impact the release of HB-NH3 has on the eutrophication of lakes, marshes, and coastal regions, and on acid rain and climate change. Rockström et al. [7] and Steffen et al. [8] found that human perturbations risk exceeding planetary boundaries in terms of climate change, biosphere integrity, land-system change, and biochemical flows, and that human activity has reached levels exceeding the safe operating zone for global societal development. Their analyses revealed that the accelerating extinction of species and the nitrogen cycle have reached the high-risk area beyond the zone of uncertainty. Moreover, with a 60% growth in demand for grains by 2050 due to the increase of global population and a shift in dietary habits, the global demand for chemical fertilizers will further expand [9], and environmental pollution is anticipated to grow in severity with a 50% increase in the production of nitrogen compounds by 2050 [10].
There are global efforts to reduce the environmental impact of nitrogen, and Western countries among others have set goals to reduce the release of harmful nitrogen compounds. The United Nations Environmental Programme Colombo Declaration [11] at an international event in October 2019 stated the ambition to halve nitrogen waste by 2030. The EU’s National Emission Ceilings Directive [12] has set reduction targets by 2030 of 63% for NOx and 19% for NH3 below 2005 levels. China’s Three-Year Blue-Sky Protection Plan (2018–2020) set the goal of a 15% reduction in NOx below the 2015 level [13]. Japan’s long-term strategy for growth, based on the Paris Agreement [14], aims to reduce the release of substances that can damage natural cycles and the delicate balance of ecosystems into the environment in order not to exceed the pace that nature can absorb and detoxify them.
A conventional proposal was put forward on the agricultural sector for reducing HB-NH3 production through improvements to human dietary consumption efficiency by decreasing fertilizer use and food loss and waste [10,15]. In 2019, the World Resources Institute advocated setting a Global Action Agenda to halve food loss and waste by 2030, and expects large benefits from avoiding the conversion of ecosystems to agricultural land. Current nitrogen flows used for food have also been estimated at the national and city levels [16,17,18,19].
However, countermeasures to improve dietary consumption efficiency through better agriculture and distribution technology may be insufficient alone to achieve the reduction in the amount of nitrogen compounds to remain within planet boundaries if current dietary habits are sustained. In contrast, were humanity to adopt policies that greatly alter our dietary habits, such as ceasing the consumption of meat and shifting to a vegetarian diet, the amount of nitrogen fertilizers required for food production could be greatly reduced, but this is not realistic because meat, egg, and milk consumption increase with economic growth through dietary changes [20].
Gu et al. [21] estimated that approximately 25 million tons-N/year of reactive nitrogen was used in industrial products (e.g., nylon) globally in 2008. However, there is almost no discussion of decreasing this consumption or recycling ammonia as the basic chemical product in industrial applications.
A new policy is required that can achieve reductions while maintaining the amount of ammonia used in industry, and not force humanity, including those in developing nations, to alter their dietary habits dramatically to adopt vegetarianism. This study proposes a nitrogen recycling system that collects and recycles nitrogen compounds from waste gases emitted in the industrial sector and from livestock effluent and household wastewater. By estimating potential global flows of anthropogenic nitrogen, we predict the effects that countermeasures have on the planetary boundary problem.

2. Materials and Methods

2.1. Setting Scenarios

Appropriate goals have been set for reduction of anthropogenic emissions of nitrogen compounds and strategies are required to achieve these goals. It is estimated that in the Earth’s environment in 2050, 300 million tons-N per year of nitrogen compounds in nature (e.g., soil, oceans) will be decomposed and purified, whereas 220 million tons-N per year will be generated naturally through reactions in soil, oceans, and lightning strikes [3]. Thus, the set amount of nitrogen compound stock in the environment will be 80 million tons-N per year (=300 million tons-N per year–220 million tons-N per year), which is approximately the permissible limit for anthropogenic nitrogen compounds.
Steffen et al. [8] reported 62–82 million tons-N per year of anthropogenic nitrogen fixed through the Haber-Bosch process as the planetary boundary objective, and estimating a proxy parameter for the amount of nitrogen emissions into the environment yields a permissible emissions value close to 80 million tons-N per year. Releasing nitrogen into the environment above this value would likely worsen the eutrophication of lakes, marshes, and coastal areas. Therefore, in this study, we set a target of 80 million tons-N per year of anthropogenic nitrogen emissions into the environment.
We set various scenarios and estimate the global flows of anthropogenic nitrogen for each scenario. First, we review data from Galloway et al. [3] and Fowler et al. [2] for global flows of anthropogenic nitrogen as of 2010. Based on these data, global flows of nitrogen are estimated for 2050. The first scenario is the business-as-usual (BAU) scenario, in which no countermeasures are taken from the current circumstances. The global population is expected to approach 9 billion in 2050, and global NH3 production is forecasted to be 165 million tons-N per year owing to the increase in nitrogen fertilizer for food production [3]. Nr creation by cultivation-induced biological nitrogen fixation is estimated to be 50 million tons per year, and anthropogenic Nr creation by fossil fuel combustion is estimated to be 52 million tons per year [3]. We used these values for global nitrogen flow in 2050.
In the second scenario, improvements to dietary consumption efficiency by humans reduce the waste accompanying the processing of livestock for food [15]. Efforts to improve dietary consumption efficiency would be focused on policies that change the dietary habits of humans from eating meat to primarily eating vegetables, making further reductions to food waste and improving fertilizer application efficiency. To save the Earth from food crises, agricultural mechanization is in definite need, especially in developing countries. As the population continues to grow, it is expected to work more on precision agriculture [22]. Utilization methods of agricultural and animal wastes for biogas production have been developing recently and the produced digestate can replace the use of fertilizers from the Haber–Bosch process [23]. In this study, it is considered an important option of the agricultural countermeasures.
In the third scenario, industrial countermeasures are put in place. The details of these countermeasures are described below.

2.2. Overview of Industrial Countermeasures

The industrial countermeasures scenario aims to contribute greatly to decreasing the inflow of nitrogen into the environment by changing from a detoxifying process to a recycling process for nitrogen compounds in wastewater processing and NOx released into the air through combustion. In both methods, the original conversion to nitrogen is changed to the conversion to ammonia solution, a valuable resource, which is used for energy, such as in internal combustion engines.
NOx in the gas effluent of thermal power stations is denitrified using NH3 as a reductant. A new method under development converts NOx to NH3 (NOx to ammonia; NTA) by a new catalyst at low temperature with oxygen coexistence and achieves denitrification without using an external source of NH3 [24,25]. The NH3 collected and recycled can be reused as chemical feedstock or fuel. The NH3 in the exhaust gas of composting facilities and chemical factories is also used as fuel and feedstock. It was revealed that this NTA method has the potential to decrease environmental impact compared with traditional methods [26].
The aqueous nitrogen compounds in wastewater are currently converted to N2 and detoxified mainly through biological denitrification. However, massive amounts of electricity are required in this process, and unprocessed water is released without passing through a removal process. A wastewater treatment system that controls the outflow of nitrogen compounds completely can be achieved by an NTA technology converting the nitrogen compounds in wastewater to ammonia [27,28,29] and collecting the ammonia through adsorptive enrichment [30]. Moreover, the surplus heat and electricity can also be supplied to the surrounding region.
The novel nitrogen recycling system shown in Figure 1 could be built by combining these NTA technologies. The use of this system has multiple potential effects, including greatly reducing the energy required to detoxify nitrogen compounds, reducing the production yield of HB-NH3, collecting energy through combustion, and reducing greenhouse gas emissions.

2.3. Method of Calculating Flow Amount

The anthropogenic nitrogen flows as of 2010 were set based on data estimated by Fowler et al. [2]. The oceanic flows were particularly large; however, because the most of them are natural, these were disregarded here. The nitrogen flows between the atmosphere and the oceans were also omitted. The amount of NH3 used in the chemical industry was set as 20 million tons-N [2], and the remaining HB-NH3 was presumed to be used in agriculture and livestock. The inputs and outputs for human, agricultural, and livestock use were calculated based on the nitrogen footprint involved in food production reported by Leach et al. [32]. Of the nitrogen in the manure, 24–60% was discharged into the air through sewage treatment systems [33], thus the volatilization ratio of nitrogen in manure was set to be 40%. The sewage treatment rate was set at 20% [3]. The yield weight of nitrogen in chemical manufacturing using NH3 was assumed to be 90%, and the remaining amount was assumed to be flows into wastewater.
In the 2050 BAU scenario, the anthropogenic nitrogen flows were set based on the data estimated by Galloway et al. [3]. The inputs and outputs for human, agricultural, and livestock use were calculated based on the nitrogen footprint [32] through calculating the required volume of food production by the population growth in 2050. Additionally, the amount of nitrogen used in the chemical industry was assumed to remain the ratio of around 20% [2] to the production volume of HB-NH3 from 2010 to 2050. The sewage treatment rate was set at 20% [3]. Galloway et al. [3] used 52 million tons-N per year of reactive nitrogen emitted by fossil fuel combustion in 2050, which is within the range of the Intergovernmental Panel on Climate Change (IPCC) estimates [34,35]. However, there are large ranges in the estimates of reactive nitrogen emission by fossil fuel combustion in 2050; therefore, nitrogen flows of each scenario were estimated considering the emissions of 38 million tons-N as the minimum value [35], 95 million tons-N as the maximum value [35], and 52 million tons-N as the middle value [3].
In the 2050 agricultural countermeasures scenario, the 2050 anthropogenic nitrogen flows were estimated considering the production yield of HB-NH3 proposed by Steffen et al. [8]. In the scenario of improvements to dietary consumption efficiency by humans from the current 15%–20% to 25% [15], the inputs and outputs for human, agricultural, and livestock use were calculated based on the nitrogen footprint [32]. To reduce the waste accompanying the processing of livestock for food, biogas production plant can be implemented on a small scale in rural areas [23,36]; therefore, the utilization ratio of agricultural and animal wastes for fertilizers was set to be 20%.
In the 2050 industrial countermeasures scenario, the anthropogenic nitrogen flows were estimated based on the 2050 BAU scenario, and the installation rates for the NTA technologies of recycling in exhaust gas and in wastewater with nitrogen in 2050 was set, respectively, at 50% as the median value because it will be difficult to install countermeasures in developing countries smoothly. Additionally, we calculated the nitrogen flows for a scenario that combined the agricultural and industrial countermeasures.

3. Results

Table 1 shows the global anthropogenic nitrogen flow amounts estimated for each of the 2010 and 2050 BAU, agricultural countermeasures, and industrial countermeasure scenarios, with the middle value of reactive nitrogen emission by fossil fuel combustion in 2050. As of 2010, the atmospheric emissions of reactive nitrogen were estimated to be approximately 106 million tons-N per year, and the water emissions were estimated to be 77 million tons-N per year, making the estimated total environmental emissions 183 million tons-N per year.
In the 2050 BAU scenario, the atmospheric emissions of reactive nitrogen were estimated to be approximately 155 million tons-N per year, and the water emissions were estimated to be 102 million tons-N per year, making the estimated total environmental emissions 257 million tons-N per year. This is a total increase of 41% over 2010 levels. Therefore, to achieve the target of 80 million tons-N per year, reductions must be made of 180 million tons-N per year using some sort of measures.
In the agricultural countermeasures scenario, major reductions in the production of reactive nitrogen through the Haber–Bosch process were achieved, and total emissions were estimated to be 154 million tons-N per year which were less than the 2010 emissions. In the industrial countermeasures scenario, there were only slight reductions in the production of reactive nitrogen through the Haber–Bosch process; however, it was highly effective in controlling the environmental emissions of nitrogen compounds, and the total emissions were estimated to be 153 million tons-N per year. This achieved a reduction of environmental nitrogen emissions of 41% of the 2050 BAU scenario, and the emissions were mostly the same as the agricultural countermeasures scenario.
By the scenario of combining the agricultural and industrial countermeasures, reductions in both nitrogen production and emissions were possible. The environmental nitrogen emissions were reduced 95 million tons-N by 63% of the 2050 BAU scenario.
Figure 2 shows a breakdown of the environmental nitrogen emissions by scenario, considering the range of reactive nitrogen emission by fossil fuel combustion in 2050. Emissions were divided into four categories: NOx emissions from stationary and mobile sources, atmospheric nitrogen emissions from agriculture and livestock, hydrospheric nitrogen emissions in agriculture/industry and household wastewater treatment, and watershed nitrogen emissions through fertilizer runoff from farmland.
In the 2010 and 2050 BAU scenarios, these four categories affected environmental emissions. Agricultural countermeasures reduced environmental emissions by reducing the amount of fertilizer used and the production volume of agriculture and livestock. In contrast, industrial countermeasures greatly reduced nitrogen emissions from stationary and mobile sources and wastewater treatment. Combining agricultural and industrial countermeasures achieved well-balanced reductions in emissions across all four categories, and the nitrogen emissions using the minimum value of reactive nitrogen emitted by fossil fuel combustion in 2050 were reduced to be 88 million tons-N per year.

4. Discussion

Figure 3, Figure 4 and Figure 5 show global anthropogenic nitrogen flow charts for the 2050 BAU scenario, the agricultural countermeasures scenario, and the 2050 industrial countermeasures scenario, respectively. We focus on anthropogenic sources; natural sources, such as oceanic flows and media transitions, are excluded. In the BAU scenario, we clarified that the flow to livestock and agriculture of nitrogen fertilizer sourced from ammonia produced using the Haber–Bosch process was large and that the NOx emissions from internal combustion engines were substantial.
In the agricultural countermeasure’s scenario, although the flow of nitrogen fertilizers can be reduced and a new recycling flow appears from agriculture and food processing, there is a minor change to the flow and emissions structures, and NOx emissions from internal combustion engines remain as the BAU scenario.
In contrast, in the industrial countermeasure’s scenario, a new recycling flow appears laterally across Figure 5, and this indicates a dramatic change in the nitrogen flow structure. Recycled reactive nitrogen can be used in industrial applications, thereby ensuring sufficient nitrogen fertilizer flow and allowing an increase in food production in response to a population increase. The environmental emissions of nitrogen compounds, shown vertically on Figure 5, can also be sufficiently controlled.
Some of the remaining unconsidered challenges in global nitrogen flows are policies to improve the sewage treatment rate around the world, methods to introduce a recycling mechanism into distributed sources, which are internal combustion engines, and reductions to the transition volume of landfilling of waste that contains nitrogen. The uncertainties of the parameters by utilizing alternative energy in the future and the uncertainty of the planetary boundary should also be considered.
In this study, uncertainty analysis of the installation rate of the NTA technologies in the industrial countermeasures was conducted. The installation rates were set as 30%, 50%, and 70%, respectively. Figure 6 shows global anthropogenic nitrogen estimation for the 2050 industrial countermeasures scenario and the combination scenario of agricultural and industrial countermeasures by the installation rates of the NTA technologies.
The global nitrogen emission was estimated to be 186 million tons-N per year as the installation rate of 30%, which was larger than that in the scenario of agricultural countermeasures. The nitrogen emission was reduced to be 120 million tons-N per year as the installation rate of 70%, which clarified that the installation rate of the NTA technologies has a strong effect on the reduction of nitrogen emissions. By the combination of the agricultural and industrial countermeasures, the nitrogen emission was estimated to be 65–124 million tons-N per year; thus, the combination of both countermeasures with a high installation rate can achieve the reduction of nitrogen emissions less than 80 million tons-N per year as the target value of the planetary boundary.

5. Conclusions

We proposed a novel nitrogen recycling system that collects and recycles nitrogen compounds from gases emitted in the industrial sector, such as those from stationary sources, from industrially processed wastewater containing livestock effluent and from household wastewater. By setting multiple scenarios, we estimated and compared the effects of the system in these scenarios on the planetary boundary problem. The 2050 BAU scenario led to a 47% increase in environmental nitrogen emissions above 2010 levels. In contrast, the agricultural countermeasures scenario produced a reduction in emissions beneath the 2010 levels.
The industrial countermeasures scenario proposed in this study achieved comfortable reductions in nitrogen production by constructing a nitrogen recycling system that installs the NTA technologies, and this suggests the system’s potential to reduce environmental emissions of nitrogen compounds substantially.
Combining the agricultural countermeasures scenario and the industrial countermeasures scenario suggested that environmental nitrogen emissions could be reduced by 66% compared with the 2050 BAU scenario, and the nitrogen emissions using the minimum value of reactive nitrogen emitted by fossil fuel combustion in 2050 were reduced to 88 million tons-N per year. The combination of both countermeasures with a high installation rate of NTA technologies can achieve the reduction of nitrogen emissions beneath the planetary boundary.
The installation of these NTA technologies can also yield benefits to those who reuse nitrogen compounds. Nitrogen compounds can be used as fuel to produce heat and electricity, or as a denitrification agent to eliminate the costs of purchasing ammonia. These benefits could incentivize the spread of these technologies and transform the currently costly process of running a detoxification plant into a source of income.
The system we proposed has the potential to reduce emissions of greenhouse gases, thereby creating a clean Earth through the detoxification and recycling of nitrogen compounds and a cool Earth through a major reduction in CO2 emissions. In future work, we intend to perform an inventory analysis and life-cycle assessment based on the development of these NTA technologies.

Author Contributions

Conceptualization, K.T. and T.K.; Methodology, K.T.; Software, K.T.; Validation, K.T.; Formal analysis, K.T.; Investigation, K.T.; Resources, K.T., T.K. and H.M.; Data curation, K.T.; Writing—original draft, K.T.; Writing—review & editing, K.T.; Visualization, K.T.; Supervision, K.T.; Project administration, T.K.; Funding acquisition, K.T., T.K. and H.M. All authors have read and agreed to the published version of the manuscript.

Funding

This study was partially funded by the New Energy and Industrial Technology Development Organization of Japan (NEDO), Japan, JPNP18016.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Novel nitrogen recycling system using industrial countermeasures [31].
Figure 1. Novel nitrogen recycling system using industrial countermeasures [31].
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Figure 2. Global environmental nitrogen emissions by scenario considering the range of reactive nitrogen emission by fossil fuel combustion in 2050. Ag.: agricultural; Ind.: industrial.
Figure 2. Global environmental nitrogen emissions by scenario considering the range of reactive nitrogen emission by fossil fuel combustion in 2050. Ag.: agricultural; Ind.: industrial.
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Figure 3. Global flow of nitrogen (2050, BAU scenario; units: million tons-N/year). N2: unreactive atmospheric dinitrogen; Nr: reactive nitrogen; NH3: ammonia; green arrow: Nr production; red arrow: Nr use flow; orange arrow: Nr waste generation flow; black arrow: Nr emission into the air and water.
Figure 3. Global flow of nitrogen (2050, BAU scenario; units: million tons-N/year). N2: unreactive atmospheric dinitrogen; Nr: reactive nitrogen; NH3: ammonia; green arrow: Nr production; red arrow: Nr use flow; orange arrow: Nr waste generation flow; black arrow: Nr emission into the air and water.
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Figure 4. Global flow of nitrogen (2050, agricultural countermeasure scenario; units: million tons-N/year). N2: unreactive atmospheric dinitrogen; Nr: reactive nitrogen; NH3: ammonia; green arrow: Nr production; red arrow: Nr use flow; orange arrow: Nr waste generation flow; blue arrow: Nr recycling; black arrow: Nr emission into the air and water.
Figure 4. Global flow of nitrogen (2050, agricultural countermeasure scenario; units: million tons-N/year). N2: unreactive atmospheric dinitrogen; Nr: reactive nitrogen; NH3: ammonia; green arrow: Nr production; red arrow: Nr use flow; orange arrow: Nr waste generation flow; blue arrow: Nr recycling; black arrow: Nr emission into the air and water.
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Figure 5. Global flow of nitrogen (2050, industrial countermeasures scenario; units: million tons-N/year). N2: unreactive atmospheric dinitrogen; Nr: reactive nitrogen; NH3: ammonia; green arrow: Nr production; red arrow: Nr use flow; orange arrow: Nr waste generation flow; blue arrow: Nr recycling; black arrow: Nr emission into the air and water.
Figure 5. Global flow of nitrogen (2050, industrial countermeasures scenario; units: million tons-N/year). N2: unreactive atmospheric dinitrogen; Nr: reactive nitrogen; NH3: ammonia; green arrow: Nr production; red arrow: Nr use flow; orange arrow: Nr waste generation flow; blue arrow: Nr recycling; black arrow: Nr emission into the air and water.
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Figure 6. Global environmental nitrogen emissions by scenario and the installation rate of the NTA technologies. Ag.: agricultural; Ind.: industrial.
Figure 6. Global environmental nitrogen emissions by scenario and the installation rate of the NTA technologies. Ag.: agricultural; Ind.: industrial.
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Table
Table 1. Global flow amounts of nitrogen for each scenario (units: million tons-N per year) 1.
Table 1. Global flow amounts of nitrogen for each scenario (units: million tons-N per year) 1.
Year 20102050205020502050
Scenario BAUAgricultural MeasuresIndustrial MeasuresAgricultural + Industrial Measures
Reactive N production
Haber–Bosch process1201658613765
Nitrogen fixing by cultivation6077507750
Use of reactive N
Fertilizer from Haber–Bosch1001375813780
Industrial use2028282828
Food3446314633
Industrial product1825252525
Waste generation of reactive N
Crop and feed waste3851195126
Livestock effluent (liquid)3750235022
Industry wastewater23333
Household wastewater2127272727
Waste treatment and recycling of reactive N
Waste water treatment1216104026
Recycling of waste water---4026
Recycling of agriculture and food processing waste--14-15
Recycling of livestock effluent---1710
Recycling of gas effluent from fossil fuel combustion---5128
Environmental emissions of reactive N
Livestock effluent vaporized (air)253315178
Fertilizer loss (water)2635203521
Incineration (air)5170233513
Fossil fuel combustion 2 (air)3052522626
Waste water treatment (water)23200
No treatment of waste water (water)4864424026
Total emissions of reactive N
Atmospheric emissions106155907847
Hydrospheric emissions77102647547
Total environmental emissions18325715415394
1 Only the anthropogenic nitrogen sources were counted. 2 The middle value of reactive nitrogen emissions by fossil fuel combustion in 2050 [3].
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Tsunemi, K.; Kawamoto, T.; Matsumoto, H. Estimation of the Potential Global Nitrogen Flow in a Nitrogen Recycling System with Industrial Countermeasures. Sustainability 2023, 15, 6042. https://doi.org/10.3390/su15076042

AMA Style

Tsunemi K, Kawamoto T, Matsumoto H. Estimation of the Potential Global Nitrogen Flow in a Nitrogen Recycling System with Industrial Countermeasures. Sustainability. 2023; 15(7):6042. https://doi.org/10.3390/su15076042

Chicago/Turabian Style

Tsunemi, Kiyotaka, Tohru Kawamoto, and Hideyuki Matsumoto. 2023. "Estimation of the Potential Global Nitrogen Flow in a Nitrogen Recycling System with Industrial Countermeasures" Sustainability 15, no. 7: 6042. https://doi.org/10.3390/su15076042

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