Phosphorus flow analysis in the maize based food-feed-energy systems in China.

Phosphorus (P) is an essential and limiting nutrient for agricultural systems, where the demand for agricultural products such as food, feed, and bio-fuel are the major drivers of the intensification of agricultural production systems. Globally, maize is one of three main cereal crops, a main feedstock for animal production and a substrate for the production of bio-ethanol. This study investigated P flows through the multiple utilization systems of maize (as represented by the subsystems of food, feed and energy production) at a crop level of 2016 as reference year and made future predictions of P flows for the year 2030 based on different scenarios for food-feed-energy systems in China. For 2016, the subsystem of animal production resulted in the highest waste of P due to inappropriate manure management, but the subsystem of value-added products (Bio-fuel production, distillers dried grains with solubles (DDGS), maize-oil) showed the lowest P use efficiency (39%). From the value-added subsystem, 17% of P from the process flow to the subsystem of animal production as DDGS, and 61% of P is wasted associated with wastewater and sludge. Future scenarios of structural adjustments in the maize consumption system predict that the supply of maize for animal feed will be threatened if the policy of the Biofuel National Promotion before 2020 is fully implemented in China, as current maize production will not meet the future demand of food, feed and energy simultaneously. The results emphasized the use of P waste resources and better sludge management from a systems perspective. This also implied the importance of exploring coordinated development and integrated strategies for sustainable P flow management in multiple utilization systems.

Phosphorus flow characteristics in the waste system of Poyang Lake Watershed over the past 70 years.

With the intensification of human activities, the amount of phosphorus (P)-containing waste has increased. When such waste is not recycled, P is released into the environment, leading to environmental issues such as the eutrophication of water bodies. In this study, based on the material flow analysis method, a P Waste Flow analysis model (P-WFA) was developed to analyze the P flow in the waste system of Poyang Lake, the largest freshwater lake in China. To address the research gap in long-term P flow analysis at the watershed scale, this study quantified the P content in the waste system of the Poyang Lake Watershed from 1950 to 2020. The analysis revealed that from 1950 to 2020, the total P input into the waste system increased from 5.49 × 104 tons in 1950 to 2.28 × 105 tons in 2020. The breeding industry system was identified as the primary source, accounting for 25.19-41.59 % of the total waste system. Over the past 70 years, P loss to surface water from waste systems has been primarily facilitated by manure from the breeding industry, as well as drainage from crop farming systems (77.74 % in 2020). At the same time, the P recycling rate (PRR) of the waste system exhibited an initial increase followed by a decrease, increasing from 44.14 % to 47.75 % before dropping to 44.41 %. Population growth, urbanization, and changes in consumption levels in Jiangxi Province have led to changes in the dietary structure and fertilizer use, consequently affecting the P cycling pattern. This study presents a comprehensive P flow model for waste systems in the Poyang Lake Watershed. This model can be used as a reference to enhance P cycling and manage P loss in other large freshwater lakes.

Analyzing the phosphorus flow characteristics in the largest freshwater lake (Poyang Lake) watershed of China from 1950 to 2020 through a bottom-up approach of watershed-scale phosphorus substance flow model.

Understanding the historical patterns of phosphorus (P) cycling is essential for sustainable P management and eutrophication mitigation in watersheds. Currently, there is a lack of long-term watershed-scale models that analyze the flow of P substances and quantify the socioeconomic patterns of P flow. This study adopted a watershed perspective and incorporated crucial economic and social subsystems related to P production, consumption, and emissions throughout the entire life cycle. Based on this approach, a bottom-up watershed P flow analysis model was developed to quantify the P cycle for the first time in the Poyang Lake watershed from 1950 to 2020 and to explore the driving factors that influence its strength by analyzing multi-year P flow results. In general, the P cycle in the Poyang Lake watershed was no longer a naturally dominated cycle but significantly influenced by human activities during the flow dynamics between 1950 and 2015. Agricultural intensification and expansion of large-scale livestock farming continue to enhance the P flow in the study area. Fertilizer P inputs from cultivation account for approximately 60% of the total inputs to farming systems, but phosphate fertilizer utilization continues to decline. Feed P inputs have continued to increase since 2007. The expansion of large-scale farming and the demand for urbanization are the main factors leading to changes in feed P input patterns. The P utilization rate for livestock farming (PUEa) is progressively higher than international levels, with PUEa increasing from 0.64% (1950) to 9.7% (2020). Additionally, per capita food P consumption in the watershed increased from 0.67 kg to 0.80 kg between 1950 and 2020. The anthropogenic P emissions have increased from 1.67 × 104 t (1950) to 8.73 × 104 t (2020), with an average annual growth rate of 2.41%. Watershed-wide P pollution emissions have increased by more than five-fold. Population growth and agricultural development are important drivers of structural changes in P flows in the study area, and they induce changes in social conditions, including agricultural production, dietary structure, and consumption levels, further dominating the cyclic patterns of P use, discharge, and recycling. This study provides a broader and applicable P flow model to measure the characteristics of the P cycle throughout the watershed social system as well as provides methodological support and policy insights for large lakes in rapidly developing areas or countries to easily present P flow structures and sustainably manage P resources.

Scenario analysis of phosphorus flow in food production and consumption system in the Mwanza region, Tanzania.

Since the mineral, phosphorus (P), has dual properties of being limited resources for use, and being a pollutant for studying sustainable management of anthropogenic P flows in wetlands and soils, currently P receives the highest interests among researchers around the world. This study has successfully mapped P flows for a reference year (2017) and a future year (2030) using different scenarios of food production and consumption system (hereafter 'system') in the Mwanza region (Tanzania). The results showed that the total P input and output for 2017 alone were 9770 t and 7989 t, respectively. However, as high as 1781 tP accumulated in the system and the potentially recyclable P found, is yet to be recovered due to economic reasons and the lack of market. The main anthropogenic P input to the system occurred via imported feed, fertilizer, and crop food, accounting for about 99.72 % of the total input flow. The output was comprised of animal products exported with 3428 tP, and various P-contained wastes which were lost to water bodies with 4561tP. Analysis of the 2030 scenario showed that setting P management objectives from different perspectives such as the total P budget balance, potential recyclable P, and P emission, can help develop differentially preferred management strategies and measures in the Mwanza region. The combination of diet change, precision feeding, and integrated waste management practices presents the best prospects for decreasing P budget and losses, and the amount of P that can be potentially recovered from the system. We propose a package of integrated P management measures for the Mwanza region. Given the similarity of regional socio-economic development background around the Lake Victoria basin, the model can be used to guide the study of anthropogenic P flow analysis in other areas along the shore of Lake Victoria (Africa).

Growing phosphorus dilemma: The opportunity from aquatic systems' secondary phosphorus retention capacity.

The essential cause of phosphorus scarcity and phosphorus-induced risks, i.e. phosphorus dilemma, mainly lies in current low phosphorus flow efficiency (PFE) in agricultural systems. Improving PFE largely depends on secondary phosphorus retention along the phosphorus flow chain from phosphate mining to terrestrial agricultural systems, to aquatic systems, and ultimately to seabed deposition. Our review found that aquatic systems will have the opportunity and growing capacity to retain seaward secondary phosphorus carried by the runoff, due to its location between land and water systems, its ability of converting secondary phosphorus from both land and aquatic systems into aquatic products, and its rapid expansion with low PFE. However, a knowledge gap exists in secondary phosphorus retention in aquatic systems compared to in terrestrial systems. Although the phosphorus retention literature continues to grow in environmental and agricultural & biological sciences, only 8.8% of the documents are related to aquatic systems with few quantification studies. Based on the literature with phosphorus retention quantification since 1979, we divided the reported phosphorus interceptors into abiotic and biotic groups, further into 7 categories and more subcategories. By 2020, eight categories of interceptors had been reported, increased from only one interceptor in 1979. However, most of them focused on wetlands, only a few studies on aquatic organisms which concentrated in 8 countries before 2000. Thus, it is urgent to emphasize aquatic systems' secondary phosphorus retention capacity and its systemic benefits for a sustainable phosphorus use.

Assessing the sustainability of phosphorus use in China: Flow patterns from 1980 to 2015.

Phosphorus is vital for living creatures and will run out in the next few hundred years. The imbalanced phosphate rock distribution and inefficient consumption make phosphorus management of great importance. As China has an undeniable influence on global phosphorus production and consumption, understanding its changing historical patterns is critical for phosphorus resource management and water quality improvement. However, most existing research focus on anthropogenic phosphorus flows in the agricultural sector for a specific year, making the evaluation of such changes difficult. Therefore, substance flow analysis and principal component analysis for phosphorus flows between 1980 and 2015 were performed to understand phosphorus consumption structure change and the build-up of legacy phosphorus in China. The results show that although China's phosphorus utilization efficiency has decreased over time, it is still higher than in most other countries. The research also demonstrates the effectiveness of combining multiyear substance flow analysis and principal component analysis to improve the transparency of identifying underlying consumption structure change during resource management.

Assessment of the minimal available phosphorus needs of pullets during the pre-laying period.

Dietary phosphorus (P) oversupply is costly to the poultry industry and represents a point source of excessive P discharge to the environment via manure application to soils. The current study was conducted to investigate the effects of dietary available P (AP) level on growth performance, plasma biochemistry, bone characteristics, and P flow in order to assess minimal AP needs of pullets during the pre-lay period. A total of 192 Lohmann pullet chicks were randomly allocated to one of 4 treatments with 8 replicate cages of 6 birds per cage. The pullets of Low (L; the lowest AP regimen) were fed diets in a sequence of 0.200, 0.175, and 0.150% AP for the age period of 0 to 4 wk, 4 to 8 wk, and 8 to 16 wk, respectively. The AP level was increased by an increment of 0.1% in each phase in Low-Medium (LM), Medium-High (MH) and High (H), thus making H (control) consisting of 0.500, 0.475, and 0.450% AP. Overall, there were no main effects of treatment on body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR). However, compared with the H treatment, BWG or FI of the L treatment was lower during the first 8 wk post-hatch, but became comparable or higher over the last 8 wk (P < 0.05); FCR of L birds was greater over wk 0 to 4 but became smaller over wk 8 to 16 (P < 0.05). Plasma P was lower in L than H treatments at wk 8 but turned comparable at wk 16 (P < 0.001). Bone characteristics were not different for pullets fed various AP regimens. Total P intake and excretion were reduced with lowering dietary AP (P < 0.001), but its retention percent was not affected. The results indicated that the lowest AP regimen (0.200-0.175-0.150%) in the current study was adequate to support healthy growth and development of pre-lay pullets, while reducing P excretion in manure.

Anthropogenic phosphorus flows under different scenarios for the city of Stockholm, Sweden.

Today, concerns prevail about the unsustainable use of phosphorus and worldwide eutrophication, thus requiring efficient management of phosphorus flows. With increasing population and associated urban growth, urban management of phosphorus flows in the perspectives of recycling, eutrophication and total budget becomes increasingly important. This study mapped phosphorus flows for a reference year (2013) and a future year (2030) using different scenarios for the city of Stockholm, Sweden. The results indicated that the Swedish goal of recycling phosphorus from wastewater would cover the majority of the total phosphorus budget for Stockholm. However, in 2013, only 10% of phosphorus was recycled for agricultural use, around half of which was from sewage sludge and the other half from food waste. Almost 50% of total phosphorus was sent to landfill/mining waste capping with sewage sludge, for economic reasons and lack of market. Among the scenarios of upstream and downstream urban management options studied in combination with population growth, recovery of phosphorus from sewage sludge had the greatest potential to increase the fraction recycled to agriculture. However, only upstream measures, e.g. changed diet, were able to reduce the total phosphorus budget. Urban management of phosphorus flows based on the different perspectives of recycling, eutrophication or total budget was shown to potentially result in different preferred management actions and both upstream and downstream measures need to be considered. Moreover, management needs to pay attention to small but environmentally sensitive flows, particularly when setting city goals on phosphorus recycling by percentage in a large budget.

Phosphorus leakage from fisheries sector - A case study in Thailand.

Although phosphorus (P) is an essential element needed for all lives, excess P can be harmful to the environment. The objective of this study aims to determine P flows in the fisheries sector of Thailand consisting of both sea and freshwater activities of captures and cultures. Currently, the annual fisheries catch averages 3.44 ± 0.50 Mt. Most comes from marine capture 1.95 ± 0.46 Mt, followed by coastal aquaculture 0.78 ± 0.09 Mt, freshwater aquaculture 0.49 ± 0.05 Mt, and inland capture 0.22 ± 0.01 Mt. Of this total, about 11% is contained in fresh products directly sold in local markets for consumption, while 89% is sent to processing factories prior to being sold in local markets and exported. The quantities of P entering the fisheries sector come from captures, import of fisheries products and feed produced from agriculture. This P input to the fisheries sector is found to average 28,506 t P.y-1 based on the past ten-year records. Of this total, P input from captures accounts for 76%; while, 11% represents aquatic feeds from agriculture and animal manures. About 13% is obtained from the imports of fishery products. Coastal and freshwater aquacultures are found to be P consumers because their feeds are almost all produced from agricultural crops grown inland. Moreover, these activities cause most of P losses, approximately 10,188 t P·y-1, which account for 89% of the total P loss from the fisheries sector. Overall, P in the fisheries sector is found to mobilize through three channels: (a) 44% is consumed within the country; (b) about 16% is exported; and, (c) 40% is lost from the ecosystem. Based on the results of this work it is recommended that future research be directed on ways to minimize P loss and maximize P recycle in Thailand's fisheries sector as to enhance its food security and curtail water pollution.

Substance flow analysis of phosphorus within New Zealand and comparison with other countries.

Phosphorus (P) is an essential and non-renewable resource that is estimated to be depleted within the next 70-140 years. Increasing P scarcity and environmental pollution requires the development of a proper P management system. One fundamental step is to understand how P flows within society. Thus, a substance flow analysis (SFA) of P was conducted to distinguish and quantify different P flows within New Zealand, and principal component analysis (PCA) was used to show where the P flow in New Zealand was significantly different from the most efficient P utilization countries. Aside from having low P recovery, New Zealand imports a significant amount of P, while re-exporting a much smaller fraction of it compared with other countries, resulting in a high accumulation. The SFA analysis showed that although diffuse sources of P pollution pose a greater environmental risk to water bodies, promoting P recovery from point sources of pollution, such as from waste treatment facilities and landfill sites, would still improve the P management efficiency in New Zealand, which could decrease the annual P rock imports by 20%.