Phosphorus (P) is one of the most critical elements of biological building blocks and plays a crucial role in the cellular energy metabolism of all living organisms. Since no other element can substitute for P in biochemical processes, humans ultimately rely on P availability. Modern farming relies heavily on phosphorus, which is derived from phosphate (Pi) fertilizers, to enhance agricultural production in soils. Therefore, P availability is critical to our present and future food security. Moreover, P is widely used in industry as an essential element. It constitutes an important raw material for a variety of industrial products, including electronics, chemical catalysts, food additives, flame retardants and pharmaceuticals.

Asia, the largest continent in the world, where 60% of the current global population resides, is now the largest consumer of Pi rock and fertilizer. The two most populous countries, China and India, are the largest consumers of P fertilizers, accounting for about 60% of global consumption. Furthermore, Asia's rapid growth and fast economic development are increasingly boosting P demand in the region. Although China holds large Pi rock reserves, large parts of Asia are almost totally dependent on imports of P from other countries. South Asia, in particular, has the largest global share in Pi rock imports, at approximately 25%. Since P use in Asia can have enormous leverage over global food security, a solid understanding of P flows, fertilizer applications and the implementation of P recycling in Asia is critical for achieving global P sustainability in the future.

This special issue deals with the sustainable use of P in East and South Asian countries, including China, Korea, Taiwan R.O.C., Vietnam, Thailand and Japan. China is the largest producer and consumer of P in the world. Korea, Taiwan R.O.C. and Japan are relatively large consumers, depending almost entirely on imported P. Thailand and Vietnam possess the highest growth potential for the fertilizer industry in Asia.

Most of the contributions to this special issue are extended versions of papers presented at the 1st and 2nd International Workshops on Sustainable P Governance from Asian Perspectives. The workshops were held at Tohoku University, Sendai, Japan, May 28, 2012 and at Keio University, Yokohama, Japan, November 20, 2012. They were organized by Dr. Kazuyo Matsubae and Prof. Tetsuya Nagasaka of Tohoku University and supported by Japan’s Ministry of the Environment and JST-RISTEX. The papers have been significantly expanded in content by the authors to highlight emerging issues in P use in Asia.

This special issue is the first collection of papers dealing with sustainable P use from Asian perspectives. We would like to express our great appreciation to those who contributed to the success of the workshops and this special issue. We would also like to extend our sincere thanks to Professor Hiroyoshi Higuchi of Keio University and editorial board members of the journal for giving us the opportunity to guest-edit this special issue. We hope that this issue will provide a valuable reference and perspective to sustainable P use in Asia.

Hisao OHTAKE

Kazuyo MATSUBAE

Masaru YARIME

This work examines recent historical phosphate rock production and determines possible identifiable trends. The difficulties of identifying trends from short time-series are described. Statistical analysis alone cannot be definitive in identifying a trend. These results, however, can be supported by information about sources of increasing global demand. A bilinear model was developed that indicates global per-capita phosphate rock production was essentially steady from 1993 to 2006 at an average annual 22.58 kilograms per capita. Since 2007 there has been strong growth at an average annual rate of 5.1 percent per year. This, combined with a population growth rate of 1.14 percent per year, yields a growth rate in the total phosphate rock production of 6.3 percent per year. Even if further growth in per-capita production is linear at current rates and not exponential, total global phosphate rock production would have to increase by a factor of 3.6 to satisfy the demand by the year 2050. Whether such an increase would be expected to continue to this extent or not, this increase should provide motivation to begin the implementation of significant conservation measures. Underlying drivers of per-capita demand suggest that strong growth is likely to continue.

In just about every aspect of life, dependency can be equated with vulnerability, and in the case of phosphorus, this vulnerability potentially puts whole nations at significant risk. Phosphorus is vital in the semi-conductor industry, automobile industry, fertilizer industry and all aspects of agriculture. With one third of the world’s population housed in Asia and the numbers steadily rising, the demand for phosphorus is growing rapidly. The cultural shifts and changes in consumption that come with economic improvements and urbanization throughout Asia are pushing the demand for phosphorus to grow at an ever faster rate. Confidence that the rising populations of Asia will have sufficient food in the future can only come from the knowledge that the necessary phosphorus will be readily available. In order to ensure this and to ensure industry will have the phosphorus it requires, it is essential to understand the flow of phosphorus in the region and the nature and risks associated with phosphorus dependence.

With phosphorus (P) one of the three essential nutrients for plant growth on Earth, global P scarcity and sustainable P management are emerging as two of the greatest challenges facing humans in the 21st century. China is the biggest producer and consumer of phosphate fertilizer, exerting profound influence on the sustainability of global P flows. This paper depicts the static P flow in China in 2012 from the production perspective, including the mining and extraction of phosphate rock (PR) ores, manufacturing of intermediate and end-use products and waste discharge. The results show that, with the second largest P mining resources in the world, China is also confronting a serious P scarcity problem. It is predicted that the current P reserves could sustain only the next three generations in China. In 2012, 1 g of P consumed domestically in China re quired 2 g of P extraction throughout the production chain, and the life-cycle P-use efficiency (PUE) is much higher than those of the food production system in China, the United States and worldwide. The P supply chain also saw waste production of 2,369 Gg P in 2012, with only 20% of the wastes recycled. The current recycling activities, however, lock in P instead of recovering it, which does not serve the purpose of mitigating P scarcity.

Phosphorus is an essential substance in organisms and has been widely used in industries and agriculture. The consumed phosphate rock, however, is nonrenewable. To use phosphorus more sustainably, knowledge of phosphorus flows is necessary. This study aims at exploring phosphorus flows at national and local scales. Exploration at the national scale was implemented to describe overall consumption, whereas exploration at the local scale was done to examine ways of using phosphorus sustainably. Hence, in this study, the spatial scopes of the inventory analyses are Taiwan (national scale) and a farm in Chiayi County (local scale), a major district with high fertilizer consumption. The results indicate that crop production and livestock farming were the major processes associated with huge phosphorus flows and these two activities also delivered the most phosphorus throughput into waste streams. In Taiwan, all phosphate rock is imported, and some of the phosphorus constituents are exported with products. Phosphorus has been accumulating in the soil and hydrosphere, especially in sediment. Examination of sinks in the environment showed that adding phosphorus stock to these sinks has had serious environmental impacts such as eutrophication. Nevertheless, phosphorus chemicals are crucial input to several industries that make great contributions to the GDP. Therefore, society will be at risk if the phosphorus supply falls short in the future. The results of our analysis provide some visions for sustainable management of phosphorus.

Phosphate is a key contaminant that induces eutrophication in rivers, ponds and reservoirs. To control phosphates in wastewater, we developed a chitosan-bead-based ion exchanger using Cu2+ for immobilization. Changing the initial conditions, we investigated its phosphate removal efficiency from solutions. The optimal initial concentrations of chitosan, acid and base were determined to be 2.5% (w/w) chitosan, 1% (v/v) HCl, and 1M NaOH to maintain bead shape. The additional step of crosslinking reduced uptake (efficiency) by up to 10% due to the loss of amino group active sites. The phosphate removal efficiency was proportionally increased by copper uptake. A concentration of 5,000 mg/L of copper could achieve stable physical strength. The maximum phosphate uptake was 89 mg/g, fitted with a Langmuir equation. When 10% NaCl was used as a regenerate, the regeneration efficiency gradually decreased from 75% to 40% through seven cycles.

To transition to efficient fertilizer use for promoting food production, a wide range of stakeholders need to know nutrient demands for meeting crop yield potentials over an agricultural region. Knowledge about spa tial patterns of these demands, however is often deficient in developing countries. This study (1) assesses the nutrient demands of potential crop productions in two intensive agricultural regions in Vietnam (Dong Nai and Bac Ninh provinces), and (2) provides public access to the output. We calculated the nitrogen (N), phosphorus (P) and potassium (K) demands for reaching crop yield potentials over the farmlands in the two provinces, taking soil nutrient balances into account. The balance calculations considered the effects of natural nutrient supplies (e.g., from soils), and different natural nutrient losses (e.g., by volatilization, erosion, leaching, runoff and crops’ uptake with different fertilizer use efficiencies). The results were spatially explicit, presented at a map scale of 1:100,000, and managed by a Web-based Geographic Information System (GIS). The web-based GIS allows lay users to query the results at different levels of aggregation (i.e., farm, com mune, district and province) in a responsive and iterative manner.

The recovery of phosphorus (P) from secondary resources is critical to closing the anthropogenic P loop. The recovered P should be recycled effectively for agricultural and industrial purposes without jeopardizing human health and the environment. Although various technologies are potentially applicable to P recovery and recycling, their implementation remains hindered by socioeconomic factors such as insufficient policy support, an immature market for recovered P and a lack of public awareness. Recently, Japan has experienced good practices in recycling P in secondary resources despite these hindrances. Japan’s experience may provide a clue on how to develop and implement technologies for P recovery and recycling, even if the legal, social and economic structures are not fully developed for the security of future P supplies.

While some local governments push ahead with recycling phosphorus from wastewater, there has been little progress nationwide. In this study, we analyzed the perceptions and interests of each stakeholder in this issue by conducting interviews to assess recycling approaches. In comparison with recycling in other fields, for instance, industrial materials recycling, the stakeholders involved in phosphorus recycling are far more diverse. This makes it more difficult to coordinate their behaviour. Based on interviews with a wide range of stakeholders, we identified seven dimensions that they consider vital for promoting phosphorus recycling: environment, cost, image, transaction stability, distribution, quantity and quality. Key challenges will be to develop technologies to slash costs, form dosho-imu alliances for simultaneous achievement of multiple objectives, and make bargaining arrangements among local governments, fertilizer manufacturers and cement producers to secure stable volumes.

Phosphorus recycling is essential for the sustainable future of humanity. Phosphite (Pt), a salt of phosphorous acid (H3PO3), is a waste product of the chemical and automotive industries. Pt has to be oxidized to phosphate (Pi) prior to phosphorus recycling. Pt dehydrogenase (PtxD), catalyzing oxidation of Pt to Pi with concomitant reduction of NAD+ to NADH, could have a number of applications in the efficient utiliza tion of Pt waste. The originally isolated PtxD, however, showed both thermosensitivity and mostly insoluble expression in an Escherichia coli recombinant, limiting the practical application of this enzyme. To overcome this problem, we obtained a stable and solubly expressed PtxD from a thermotolerant Pt-oxidizing bacterium. Here we describe three emerging applications of PtxD in (i) an NADH regeneration system, (ii) a dominant selection system for recombinant microorganisms, and (iii) Pt fertilization in plants. Firstly, an NADH regeneration system is necessary for the production of industrially important chemicals by oxidoreductive enzymes. Stable PtxD with Pt as a reducing reagent could be used practically as an NADH regeneration system. We demonstrated production of a chiral compound using a PtxD-driven NADH regeneration system. Secondly, selective cultivation of microorganisms is important to the production of medical and chemical compounds and renewable biofuels. Transfection with ptxD (recombinant PtxD trait) allows selective growth of microorganisms on a medium containing Pt as its sole phosphorus source. Pt could be used as an alternative to antibiotics in large-scale cultivation of ptxD-recombinant microorganisms. Finally, direct utilization of Pt as a fertilizer would be the most cost-effective method for the recycling of Pt waste. Pi, however, is the only chemical form of phosphorus that can be assimilated by plants. We and another group demonstrated that ptxD-recombinant plants can directly utilize Pt fertilizer. These new environmental biotechnologies could contribute to efficient utilization of Pt waste.

To determine the available nitrogen (N), phosphorus (P) and potassium (K) resource budgets (application minus plant uptake), we obtained data on inorganic fertilizers and livestock manure from statistical yearbooks for Japan, the Republic of Korea and China. Uptake of N, P and K via crop production was also calculated us ing national nutrient content factors. From the budget and crop production data, we calculated the N, P and K surpluses and use efficiencies. Japan used too much P, Korea balanced its use of inorganic fertilizer but needed to improve manure use, and China had high nutrient inputs and outputs in crop yield. To improve nutrient use efficiency and decrease the surplus, we set some guidelines, such as N, P and K output by crop yield should be more than 60 percent, 40 percent and 75 percent of applied inorganic fertilizer plus manure, respectively, or the inorganic N fertilizer application level should be around half of the crop yield, with the effectiveness of organic P and K as 100 percent of inorganic P and K fertilizers. Based on this analysis, we found that Japan should apply inorganic P fertilizer primarily to compensate for soil P deficiency, Korea should develop forage crop production and build recycling pathways within the country, and China should re duce its excessive use of N to reduce the N content of crops.

Phosphate rock (PR) is an important strategic material, providing the non-renewable elemental resource phosphorus (P). From the view of geosciences, PR can actually be seen as a special rock rich in the element P. Many studies have reported on PR distribution, but there is little predictive geological research from a metallogenic perspective on the causes of phosphate ore distribution. This paper reviews research on the origin and geological features of the mineralization distribution of phosphate ore resources in China, introduces the main types of P-containing rocks and/or deposits in China, and provides a good understanding of the mode of occurrence, geological setting and phosphogenesis of China’s phosphate resources. It forms an invaluable aid to the search for, and exploitation of, new P resources in China.

The impact of land use for fertilizer production has been evaluated in terms of total material requirement (TMR) with a central focus on phosphorus fertilizers. Three different ammonium phosphates, calcium superphosphate, fused magnesium phosphate, magnesium multi-phosphate and high analysis compound fertilizer were selected as phosphorus fertilizers. For comparison, nitrogen fertilizers such as urea, nitrolime, ammonium sulfate and ammonium chloride, and potassic fertilizers such as potassium sulfate and potassium chloride were chosen as well. Two types of functional units were considered: one was 1 kilogram of the target fertilizer production and the other was 1 kilogram of phosphorus pentoxide (P₂O₅), nitrogen (N), and/or potassium oxide (K₂O). The system boundaries were set from mining to fertilizer production, and all the direct and indirect inputs were considered, along with hidden flows such as tailings and waste rocks. The TMRs of the fertilizers ranged from 5 to 23 kg/kg. It was found that the phosphorus fertilizers, excluding calcium superphosphate and fused magnesium phosphate, showed higher TMR than nitrogen or potassic fertilizers. The annual TMR with respect to fertilizer usage in Japan, which is defined as the product of the estimated TMR and amount of each fertilizer used in Japan in 2012, indicated that phosphorus fertilizers occupy about 69% of the total TMR, with high analysis compound fertilizer and ammonium phosphate in the majority. The TMR and life-cycle carbon dioxide (LCCO₂) were found to be different indicators. Case studies were examined in which improvements in phosphoric acid and sulfuric acid production were considered. Improvements in phosphoric acid production were found to be more effective at reducing the TMR of phosphorus fertilizers. Finally, the following equation was proposed for simple estimation of diverse phosphorus, nitrogen and potassium- based fertilizers: TMR = 2 + 0.34 [%P₂O₅] + 0.15 [%N] + 0.098 [%K₂O]

Phosphorous (P) is an essential nutrient for plant growth. Natural P reserves are being exhausted at an alarming rate due to the intensive use of P as a fertilizer. Globally, 170 million tons of P fertilizer is used each year, with 0.41 million tons (P2O5) of that being used annually in Thailand. The extent of P use is ever rising since food production needs to be increased to feed the ever-increasing the world population. Since P is a finite resource, its sustainable use has become imperative and remains a major challenge these days. Domestic wastewaters are rich in P levels, which are usually not recycled due to the absence of appropriate P recovery techniques. It is estimated that more than 40,000 tons of P could possibly be recovered yearly from domestic wastewater in Thailand. P recovery has been discussed for decades, but actual application of technology is still lacking. Among various reasons, P-recovery technology development has mainly focused on sewers and centralized wastewater treatment systems which are not equally suitable in the context of developing countries, where non-sewer or onsite sanitation systems predominate. Electrochemical methods are being developed to recover P from effluents of onsite and small-scale waste water treatment systems. Furthermore, the current practice of draining domestic greywater directly into ditches or water bodies in Thailand, as well as in other developing countries, needs to be changed since it contains significant amounts of P. We recommend draining greywater through onsite treatment systems fitted with P recovery units before discharging it.

In China, wetlands are being continuously developed for economic reasons, which results in the decrease and fragmentation of habitats of water birds such as cranes. In order to better understand China’s crane populations so that they may be better protected as a resource, we studied the migration and ecology of red-crowned and white-naped cranes as indicator species. Combining satellite-tracking results with a litera ture survey and collection of network information, we reviewed the migration flyways, current status of im portant habitats, and main existing issues that surround the conservation of red-crowned and white-naped cranes in China. Our results demonstrate that, due to the development of agriculture, animal husbandry, and industry, Chinese populations of red-crowned and white-naped cranes are under tremendous threat from habi tat destruction, human disturbance, chemical pollution, and bird poaching. Current conservation measures are unlikely to be effective in the protection of crane populations. In order to ease the survival pressure on cranes, preservation of their habitats, protection of the environment along migration flyways, and development of effective management systems are of paramount importance.