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Food waste and the embedded phosphorus footprint in China
Journal Pre-proof Food waste and the embedded phosphorus footprint in China
Bing Li, Tailai Yin, Isuru A. Udugama, Shou Long Dong, Wei Yu, Yue Fei Huang, Brent Young PII:
S0959-6526(19)34779-1
DOI:
https://doi.org/10.1016/j.jclepro.2019.119909
Reference:
JCLP 119909
To appear in:
Journal of Cleaner Production
Received Date:
26 October 2019
Accepted Date:
27 December 2019
Please cite this article as: Bing Li, Tailai Yin, Isuru A. Udugama, Shou Long Dong, Wei Yu, Yue Fei Huang, Brent Young, Food waste and the embedded phosphorus footprint in China, Journal of Cleaner Production (2019), https://doi.org/10.1016/j.jclepro.2019.119909
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Journal Pre-proof
Food waste and the embedded phosphorus footprint in China Bing Li1,2,3*, Tailai Yin4, Isuru A. Udugama5, Shou Long Dong6**, Wei Yu3, Yue Fei Huang2, Brent Young3 1School
of Biological and Chemical Engineering, Nan Yang Institute of Technology, Nan Yang, Henan, China 2Department of Hydraulic Engineering, Tsinghua University, China 3Department of Chemical & Materials Engineering, The University of Auckland, New Zealand 4College of Water Conservancy, North China University of Water Resources and Electric Power, China 5Department of Chemical and Biochemical Engineering, Technical University of Denmark, Denmark 6School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China *[email protected],
**
[email protected]
Abstract The increasing food waste volume causes inadequate resource usage and results in partially avoidable environmental degradation. Although previous research has developed cost-effective processes for food waste treatment, the significance of embedded resources in food waste, especially the unreplaceable and depleting phosphorus, has been overlooked. This paper quantifies food waste in China at the provincial level by considering both at-home and away-from-home consumption, where phosphorus loss factor derived from substance flow analysis will be used to estimate phosphorus loss along the food supply chain. The results provide meaningful information regarding the volume and composition of food waste, as well as its impact on phosphorus resource and the environment at the provincial level. The calculation 1
Journal Pre-proof confirmed that at-table food waste was 53.7 million tons in 2015, while the embedded phosphorus was 86,300 tons. The off-table phosphorus loss was then back-calculated along the food supply chain, showing a total phosphorus loss of 424,400 tons, which was equivalent to 16.4% of the total mineral phosphate fertilizer consumption in China. Given China’s importance on the global food cycle, effective phosphorus management along the food supply chain, at-table food waste minimization and phosphorus recovery are recommended to close the current imbalanced phosphorus cycle. Keywords: Food waste, phosphorus, food supply chain, substance flow analysis
1. Introduction Phosphorus is a major nutrient supporting plant growth, a key element involved with biological metabolism (Rahman et al., 2019) and an essential input for agricultural production (Neset et al., 2019). Currently, almost all consumed phosphorus is sourced from phosphate rock, a non-renewable resource that is predicted to run out in the next 100 to 150 years (Li et al., 2018). The ineffective phosphorus utilization and uncontrolled food waste along the food supply chain have aggravated the phosphorus resource depletion and caused environmental problems such as eutrophication, ride tide and unnecessary greenhouse gas emissions (Xue et al., 2017). Food waste is the unconsumed safe and nutritious food at the table. It not only hinders the food availability for countries with limited food supply, but also causes inefficient water and land usages around the globe. As estimated, 30%, 23%, 20% and 10−20% of the purchased food in Finland, Denmark, Norway and Sweden have been thrown away 2
Journal Pre-proof from households (Gjerris et al., 2013). The UK alone generated 7.2 million tons of food waste in 2012, over 60% of which was avoidable (WRAP, 2014). Globally, one-third produced food is lost or wasted (Gustavsson et al., 2011), which is equivalent to 4.4 gigatons CO2 emission, accounting for 8% of our total greenhouse gas emission. Moreover, food waste has a substantial economic impact. For example, 27 billion USD of food is wasted in Canada each year (Xue et al., 2017), 200 billion Yuan-worth food is thrown away in China (Li et al., 2016), and 750 billion USD-worth food is wasted around the world (Papargyropoulou et al., 2014). Due to its significant wastage and substantial economic impact, a growing body of literature has quantified the volume of food waste across the food supply chain at global, regional, and national levels in the past decade (Li et al., 2019d). Based on these researches, many counties and organizations have added food waste minimization on their international and national political agenda. For example, the UN’s Sustainable Development Goals (SDG) have planned to halve the global food waste at retail and consumer levels and reduce food losses along the supply chain by 2030. This has been adopted by the European Union, the United States and the African Union (Porter et al., 2016). Food is also a vehicle of nutrition, water and land (Sun et al., 2018). To this end, the reduction of food waste could also reduce fertilizer utilization, water consumption and greenhouse gas emission (Yuan et al., 2019). Therefore, there are increasing scholars investigating the environmental footprints of water and energy within food production systems. Foley et al. (2011) and Vermeulen et al. (2012) estimated that the global 3
Journal Pre-proof agriculture consumed 70% of the world's freshwater, 38% of the land area and produced 25% of the world's greenhouse gas emission. Sedghamiz et al. (2018) developed a multi-objective model to allocate agricultural and environmental water. To date, most food types have been included for the water and energy assessment by using life cycle analysis and Input-Output Analysis, based on which the carbon footprint change pattern could be quantified (Wu et al., 2013; Striebig et al., 2019). China is a vast agricultural country producing a tremendous amount of food. With the rapid development of the chinese economy, the over-fertilized cropland and increasing food waste have become more serious. As a result, the food supply chain has caused environmental problems such as water and land shortage, non-point source pollution, and phosphate rock reserve depletion. The quantification of natural resource embedded in food waste can clarify the specific factors of resource loss and its impact on natural resources and the environment. However, there is currently little such research available (Reutter et al., 2017). Liu et al. (2013) assessed the impact of vegetable losses and waste on water and land in China. Song et al. (2015) combined the survey data with life-cycle assessment and concluded that the embedded carbon, water and ecological footprints in at-home food waste is 40 kg CO2e, 18 m3 and 173 gm2, respectively. Sun et al. (2018) evaluated the impacts of food waste on water resources in China. These studies have provided valuable examinations of water and energy embedded in food waste. However, as a significant nutrient for agricultural production and an essential element that will be depleted within the next 100 years, little research evaluates the impact of food waste on the phosphorus resource. 4
Journal Pre-proof When food waste is reduced, lower demand for food production is conceivable. Consequently, there will be a lower pressure on the natural phosphate rock resource. To achieve this, the amount of at-table food wastage in 31 provinces of mainland China was firstly estimated based on at-home and away-from-home food consumption. This is different from most previous estimations, where only at-home food waste is considered. Substance flow analysis was then used to estimate the phosphorus utilization efficiency along the food supply chain. Based on these, the volume and composition of food waste, as well as the amount of embedded phosphorus and its destinations could be determined. This research will not only provide vital information for embedded phosphorus within the food waste in China, but also help policymakers to manage the phosphate rock resource effectively and reduce agricultural phosphorus runoff. 2. Methodology This paper aims to quantify the amount of wasted phosphorus embedded in food waste in China. According to Liu et al. (2013), it is important to differentiate the terminology between food loss and food waste in order to analyze their relative significance. Here, food loss refers to food that is wasted during on-farm production and processing (including postharvest handling - PH, processing-PR, storage - ST and distribution-DI, which are shown in the processing block in Figure 1). Food waste is the thrown-away food that could have been eaten (shown in the consumption stock in Figure 1, which is quantified by considering at-home and away-from-home food consumption). Food supply chain here is a series of processes from food production to intake (or from farm 5
Journal Pre-proof to table). The overall research methodology was highlighted in Figure 1. Different stages of the food supply chain (highlighted by dash lines in Figure 1), and the major phosphorus flows in China (processes related to phosphorus extraction, production and consumption) are shown in Figure 1, where the light blue blocks represent the plant food production, and the dark grey blocks represent the animal food production.
Figure 1： Conceptual model for food waste and phosphorus estimation, definitions of different symbols are shown in Table 1. 2.1 Data The base year of 2015 was used for wasted food and phosphorus quantification in this 6
Journal Pre-proof paper. The geological boundaries are the 31 provincial administrative districts in mainland China. Hong Kong, Taiwan, Macao and marine environments are excluded due to the lack of information. Food referred in this paper is a combination of plant and animal food, while the former includes vegetables, fruits and cereals, and the latter includes pork, beef, mutton, poultry, eggs, fish and dairy products. Major food import, export, production and at-home consumption data are derived from the China Statistical Yearbook (e.g. population, urban and rural food consumption), the China Agriculture Yearbook (e.g. fertilizer and pesticide usage, crop and livestock production) and the United States Geological Survey database (e.g. phosphate rock production). The ratios of at-home food waste, meals away-from-home and away-from-home food waste are derived from the Li et al. (2017), Ma et al. (2006), and Zhang et al. (2016a), respectively. 2.2 Food waste quantification To address the significant food consumption difference caused by the economic growth and socio-demographic changes in China, food waste is estimated based on athome and away-from-home consumption. Food waste from the tourism industry is also considered because of its enormous amount prepared by the various foodservice providers (Zhang et al., 2017). The amount of at-table food waste, Wtf, can be estimated using Equation 1: 31
𝑊𝑡𝑓 = ∑𝑖 = 1(𝑊𝑎𝑡,𝑖 + 𝑊𝑜𝑢𝑡,𝑖 + 𝑊𝑡,𝑖)
(1)
where, Wat, i is the at-home food waste generated in province i, Wout,i is the away-fromhome food waste, Wt,i is the food waste from the tourism industry. i ranges from 1 to 31, representing different provinces in China. The at-home food waste gernerated in a 7
Journal Pre-proof province could be calculated using the following equation: 10
𝑊𝑎𝑡 = ∑𝑛 = 1(𝐹𝐴𝑛,𝑟𝑢𝑟𝑎𝑙 × 𝑅𝑛,𝑟𝑢𝑟𝑎𝑙 + 𝐹𝐴𝑛,𝑢𝑟𝑏𝑎𝑛 × 𝑅𝑛,𝑢𝑟𝑏𝑎𝑛)
(2)
where, FAn,rural is the at-home food consumed in the rural area for food species n, which can be estimated based on the per capita food consumption of rural residents and the population. Rn,rural is the at-home food waste ratio in the rural area for food species n, and is derived from Li et al. (2017). Similarly, FAn, urban is the at-home food consumed in the urban area and is calculated based on urban food consumption and population. Rn,urban is the at-home food waste ratio in the urban area, and is assumed to be 20% higher than Rn,rural due to their economic and social difference. n is from 1 to 10, representing cereals, vegetable, pork, beef, mutton, poultry, eggs, dairy products, fruits and other (fishery product and cooking oil) food, respectively. The away-from-home food waste in each province could be estimated by Equation 3: 10
𝑊𝑜𝑢𝑡 = ∑𝑛 = 1(𝑅𝑂𝑢𝑟𝑏𝑎𝑛 × 𝑃𝑢𝑟𝑏𝑎𝑛 × 𝐹𝑂𝑢𝑟𝑏𝑎𝑛,𝑛 × 𝑘𝑢𝑟𝑏𝑎𝑛 + 𝑅𝑂𝑟𝑢𝑟𝑎𝑙 × 𝑃𝑟𝑢𝑟𝑎𝑙 × 𝐹𝑂𝑟𝑢𝑟𝑎𝑙,𝑛 × 𝑘𝑟𝑢𝑟𝑎𝑙)
(3)
where, ROurban and ROrural are the ratios of food away-from-home in the urban and rual area, kurban and krural are the ratios of meals away-from-home per person per day, FOurban,n and FOrural,n are the amount of food waste for species n in the urban and rural area. Due the lack of data, this paper assumes that FOrural,n has the same value as FOurban,n. The values of ROurban, ROrural, kurban, krural and FOurban,n are derived from Zhang et al. (2016a). Purban and Prural are the urban and rural population in each province and is derived from the China Statistical Yearbook 2015. Similarly, food waste from the tourism industry could be quantified by Equation 4, 10
𝑊𝑡 = ∑𝑛 = 1(𝑇 × 𝑅𝑇𝑠 × 𝐹𝑂𝑢𝑟𝑏𝑎𝑛,𝑛 × 𝑆𝑠 + 𝑇 × 𝑅𝑇𝑚 × 𝐹𝑂𝑢𝑟𝑏𝑎𝑛,𝑛 × 𝑆𝑚)
(4) 8
Journal Pre-proof where, T is the total number of tourists each year, RTs and RTm are the ratios of the one-day tour and overnight visitors. These values are derived from the China Tourism Statistics Yearbook 2016. Ss and Sm are the number of meals for the one-day tour and overnight visitors, which is estimated based on the work of Zhang et al. (2017) and Gao et al. (2019). 2.3 Phosphorus loss factor calculation Phosphorus loss factor in this manuscript is defined as the percentage of phosphorus that is not converted to an expected product along the food supply chain. For example, phosphorus loss during animal farming is everything except the products for human consumption. Although some animal waste (e.g. excrement) could be recycled to fertilize the cropland, they are considered as a loss because it is not an expected product. To calculate the phosphorus loss factor, quantification of phosphorus footprint using substance flow analysis is required (Jiang et al., 2019). Substance flow analysis is a mass-balance-based framework to track how a substance flows within the defined boundaries. Typically, the total amount of substance stored or accumulated in a subprocess is named as ‘subsystem’ (e.g. block B in Figure 1), and the mass of substance within the process is defined as ‘flow’ and is also called phosphorus footprint in this paper (e.g. BD in Figure 1). Detailed information of substance flow analysis could be found in Li et al. (2019a). Based on the above, the phosphorus loss factor, μ, in different industries along the food supply chain could be calculated using Equation 5, 𝑥
𝜇=1―
∑𝑥 = 1𝐹𝐸,𝑥 𝑝
∑𝑝 = 1𝐹𝑖𝑛,𝑝
(5)
9
Journal Pre-proof where, FE,x is the phosphorus footprint of expected products in a subsystem, Fin,p is the phosphorus footprint of all input flows, p and x are the numbers of flows for expected and total input flows. The subsystems and flows considered in this paper are highlighted in Figure 1, with their definitions listed in Table 1. The discharge of untreated wastewater (T1), treated wastewater (T2) and landfill waste (T3) from each subsystem are combined into ‘XW’, where X is the symbol of each subsystem. In summary, there are seven subsystems and 23 flows in the proposed framework The phosphorus footprint in each flow, Ta, is calculated by multiplying phosphorus associated material mass flow data, Ca, and their corresponding phosphorus concentration Pa, which is shown in the following equation, 𝑇𝑎 = ∑𝑃𝑎 × 𝐶𝑎
(6)
Most material mass flows are derived from the China Agriculture Yearbook and the United States Geological Survey database. Some material mass flow data are estimated based on animal and human population. For example, animal excreta are estimated by multiplying the population of a specific type of animal with its average excretion amount derived from the literature. The phosphorus concentrations are acquired from Li et al. (2015). Due to the data uncertainty, each phosphorus flow was cross-checked by comparing with values from at least two sources where possible, the average value of different flows was used for calculation. For flows with no available data from the literature, the mass balance of a subsystem could be used for quantification by using Equation 7 𝑝
𝑞
∑𝑝 = 1𝐼𝑁 = ∑𝑞 = 1𝑂𝑈𝑇 +∑𝑆𝑇𝑂
(7) 10
Journal Pre-proof where, IN, OUT and STO are the phosphorus input, output and accumulation in a specific subsystem, p and q are the number of input and output flows. The at-table phosphorus loss will also introduce emissions along the food supply chain, which could be determined by using the following equation: 𝑃𝑇𝑜𝑡𝑎𝑙 =
𝑊𝑡𝑓 × 𝑃𝑛 𝑞
∏1(1 ― 𝐿𝑗)
(8)
where, PTotal is the phosphorus loss in stage q, Lj is the phosphorus loss factor for different stages and Pn is the phosphorus concentration for different food species. 3. Results and discussion 3.1 Sanity check To check the reliability of the proposed quantification method, a consistency check of the calculated food waste values was conducted. Different kinds of food waste (e.g. national or regional, at-home or away-from-home) used for the comparison are listed as the following. Based on these assessments, there is a good agreement of the calculations made by this work and the available literature. 1) The away-from-home food waste in the urban area calculated from this research is 14.7 million tons, which is similar to the estimates of China City Food and Beverage Waste Report (WWF, 2018), indicating that food wastage from restaurants in Chinese cities is around 17 to 18 million tons in 2015. 2) Zhang et al. (2016b) estimated that the total food waste in Beijing is around 0.4 million tons, while the current research shows a value of 0.27 million tons. 3) De Clercq et al. (2016) reported a total amount of 56.5 million tons of food waste in 2015, and the proportions of food waste produced in the east and northeast China 11
Journal Pre-proof were 43.2% and 8%, respectively. In this paper, the total amount of food waste was calculated to be 53.7 million tons, and the proportions of east and northeast China account for 43.8% and 7.8%. 4) Total food waste in Beijing in 2015 is 956, 300 tons (De Clercq et al., 2016), which is at the same magnitude of 837, 700 tons as calculated in this paper. 5) Li et al. (2018) applied food waste generation, gross domestic product (GDP) per capita and annual disposable personal income as indicators for food waste estimation, and concluded that the annual food waste in China was around 56.6 million tons, which was similar to 53.7 million tons presented in this study. 3.2 Quantification of food waste Chinese people consume a variety of plant and animal food. The results show that more than 53.7 million tons of food is wasted at the table, with a per capita wastage of 39.2 kg. Among them, vegetable, cereal and fruits correspond to 24.5, 9.6 and 8.0 million tons, respectively, while pork and poultry waste are 2.1 and 1.7 million tons, respectively. Food waste and its corresponding sources are shown in Figure 2, where a color change from light blue to dark blue indicates the food waste volume at the provincial level (million tons per year) and the pie charts represent different sources of food waste. As can be seen, Sichuan is the largest producer of food waste (4 million tons) because of its large population and food consumption habits. Tibet, is the smallest one, accounting for 0.18 million tons per year. Food waste in each of the economically developed regions (i.e. Guangdong, Jiangsu, Shanghai and Shandong) or the population 12
Journal Pre-proof concentrated regions (i.e. Henan, Sichuan, Hebei and Henan) is over two million tons per year, which is almost equal to the net food production of Sub-Saharan Africa (Secondi et al., 2015).
Figure 2: Total and decomposition of food waste in each province (million tons) Urbanization in China has increased in speed following the initiation of the reform and opening policy, making the urban area a hot spot for food consumption and therefore a major contributor to food waste generation. Figure 2 confirms this statement and indicates that over 60% food waste is sourced from the urban area. China's urban population will hit the one billion mark by 2030, which in turn will further increase the amount of wasted food. This provides an opportunity for centralized food waste management, where food waste prevention from food providers and consumers, as well 13
Journal Pre-proof as food recycling, reuse and resource recovery could be regulated less costly. It is worthwhile to mention that the proportion of food waste from the tourism industry is also significant in Yunnan and Guizhou (20% and 29%), mainly caused by a large number of tourists all year round. This might challenge their future waste management plans because their natural landscape-based tourism industry usually is far away from the urban area and is lack of waste collection and treatment facilities. Moreover, the results indicate that away-from-home food waste accounts for onethird of its total volume in the urban area. The increases in Chinese economy and household income have resulted in a continuing booming of the catering and hospitality industry, meaning a lower eat-at-home ratio and higher amount of food wastage in restaurants if no proper actions are taken. Considering China’s significant role in achieving the global sustainability, such a trend will raise severe concerns for food security, resource scarcity, and environmental sustainability for both China and the whole world (Wang et al., 2017). Decomposition of food waste in each province is shown in Figure 3. As can be seen, the amount of plant food waste is twice as animal food waste. Regarding the plant food waste, the leftover of vegetables is a key contributor (accounting for 40 – 50% in most provinces). It should be noted that wasted vegetable in Tibet shows a much lower proportion (23%) than in other provinces. This might be caused by the higher vegetable price, where only a few vegetables can be produced locally, especially in winter. The high transportation cost increases the price and changes the diet structure. Cereals are the second-largest food waste in most provinces (around 20% of the total food waste) 14
Journal Pre-proof due to its significant consumption amount. The high cereal wastage ratios in Tibet and Neimenggu are mainly caused by their special food structure. Pork takes up the majority share of meats wasted in China, accounting for 40%. This is comparable to that reported by Sun et al. (2018), stating that pork accounts for 44% of the total animal food consumption in China. Besides, animal food waste demonstrates a noticeable regional difference because of the diverse cultural, economic and social backgrounds. For example, beef, mutton and dairy wastes account for a more significant proportion in the ethnic minority regions such as Tibet (47.1%), and Xinjiang (36%).
Figure 3: Decomposition of food waste in each province Taking these values into account, the per capita food waste across China is calculated by dividing the food waste volume with its corresponding resident population, which could be used to guide the food waste treatment facility capacity design in the future. The results and food consumption preference in each province are shown in Figure 4. 15
Journal Pre-proof Interestingly, it was found that although the total food waste in less developed regions (e.g. Tibet, Xinjiang, Neimenggu) are insignificant (from Figure 2), their average food wastes per capita are among the highest in the country (from Figure 4). Such inconsistency might come from a large number of tourists in these regions, which was ignored during the calculation of average food wastage. By combining Figure 2 and 4, it can be concluded that Sichuan and Hunan are both high in total food waste volume and per capita food wastage, which is believed to be caused by their food consumption habits and large population.
Figure 4: Average food waste and food consumption preference in each province (kg) A qualitative description of food flavors in different regions are highlighted in Figure 4 (information adapted from Li et al. (2017)). It can be concluded that food flavor has a significant impact on the average food waste. For example, the average food waste 16
Journal Pre-proof rates in all umami regions (Fujian, Guangdong and Hainan) are below 40 kg per person per year. Instead, most regions preferring hot (e.g. Sichuan, Chongqing, Hunan and Hubei) and sweet (e.g. Shanghai, Jiangsu and Zhejiang) food are over 40 kg per year. On the other hand, the influence of staple food (e.g. rice, noodle and meat) of a region on its average food waste is insignificant. For example, the average food wastage for regions where rice is the staple food (mainly in the south and northeast China) ranges between 31.9 (Yunnan) and 55.6 kg (Chongqing), for the rest of China (noodle is the staple food), the average food wastage ranges between 31.3 (Henan) and 54.3 kg (Tibet). 3.3 Effect of at-table food waste on phosphorus footprint Food production is a phosphorous-intensive process that not only consumes a large amount of phosphate rock but also discharges tremendous wasted phosphorus that threatens the natural environment. This paper applied the phosphorus footprint theory to evaluate phosphorus wastage. Definitions and values of phosphorus flow calculated from the substance flow analysis are shown in Table 1. Table 1. Definitions and values of phosphorus flows (Unit: 1,000 tons phosphorus) Symbol Name
Value
Symbol
3423
DW
Name
Value
P rock for fertilizer AB
P runoff from cropland
378
production AC
P rock for feed additives
598
Accumulation Accumulated P in cropland
744
Animal faeces for AW
Waste from mining
558
ED
1339 agriculture
AEX
Exported P rock
41
EG
Meat for food
391 17
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Consumed fertilizer
2578
EW
Waste from animal farms
1653
388
FH
Crops for consumption
573
Exported P fertilizer
397
FE
Crops for animal feeding
1737
CE
P for animal feed
543
FW
Waste from crop processing
30
CW
Waste from feed processing
12
Import
Imported food
960
CEX
P in exported animal feed
42
GH
Meat for consumption
314
Waste from fertilizer BW manufacturing BEX
Waste from meat DE
Pastures for animal
1028
GW
77 processing
DF
Crop production
2145
The calculation of phosphorus embedded in at-table food waste shows a total amount of 86,300 tons, which is around 4.3% of China’s mineral phosphate fertilizer consumption in 2010 (Li et al, 2015a; Li et al., 2015b, Bai et al., 2016). When considering the phosphorus loss across the food supply chain (more discussions are provided in Section 3.4), 424, 400 tons of phosphorus is wasted. This number is 16.4% of the total mineral phosphate fertilizer consumption in China in 2010 and is eight times of the imported phosphorus in Singapore in 2012 (Pearce and Chertow, 2017).
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Figure 5: Total and decomposition of at-table phosphorus loss from food wastage in each province (Unit: 1,000 tons) In terms of the regional distribution, developed provinces (e.g. Guangdong and Jiangsu) and those with large populations (e.g. Sichuan, Shandong and Hunan) have larger phosphorus footprints (Figure 5). As known, in wealthy and affluent societies, consumers are living in a “culture of abundance”, making it easier and less costly to waste and overeat (Liu et al., 2013), while few people considered the environmental cost behind the tag of the items. From our calculation, the phosphorus footprint related to food waste in Sichuan is 7,000 tons, accounting for the largest share in China. The phosphorus footprint in Ningxia is 289 tons, taking up the least share. This is in accordance with the total food wastage shown in Figure 2, with the slight differences 19
Journal Pre-proof caused by the variation of diet structure. In China, people usually order more than enough food when they host guests to show their hospitality, resulting in a much higher away-from-home food waste rate than athome. This is in agreement with findings from Figure 5, indicating that most of the attable phosphorus waste comes from the urban area across the country. For Guizhou and Yunnan, 38.3 and 29.1 % of the wasted phosphorus are sourced from the tourism industry, which should be considered by the local governments when addressing their water and resource challenges.
Figure 6: Decomposition of at-table phosphorus waste in each province The decomposition of at-table phosphorus waste in each province is shown in Figure 6. When compared to Figure 3, the percentage of plant food waste is still higher than the animal food waste, but the share of vegetable has been reduced significantly due to its low phosphorus content. As have been noted, phosphorus wasted in cereals in Tibet 20
Journal Pre-proof and Neimenggu is much higher than other provinces (over 40%), which might be caused by their high cereal consumption rate. Moreover, the wasted phosphorus in animal food follows a similar trend to that in Figure 3, where pork alone accounts for 50% of the total phosphorus wastage. The average at-table phosphorus waste is shown in Figure 7. Again, it is noticed that provinces with a lower amount of total phosphorus waste have higher average at-table waste rate due to the ignorance of tourism population. For example, the total amount of at-table phosphorus waste is 375 tons in Tibet, taking one of the least shares in the country, while its per capita phosphorus waste is 111 grams, which is one of the highest. The ratios of embedded phosphorus in wasted plant food and animal food (PMR) are shown in Figure 7. The result confirms that most at-table phosphorus waste comes from plant food, which is preferred over meat because of its lower nutrient consumption and greenhouse gas emissions along the food supply chain. Moreover, it is observed that most developed regions have a lower PMR value (e.g. Beijing, Tianjin, Guangdong). As with the economic growth and the changing from a current plant-based to meat and dairy-based diet structure, the PMR ratio will decrease. In turn, this will increase the off-table phosphorus loss significantly.
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Figure 7: Average at-table phosphorus (Unit: gram) and the plant to animal food waste ratio (PMR) 3.4 Wasted Phosphorus along the food supply chain The off-table phosphorus loss was back-calculated by using the phosphorous loss factor derived from the substance flow analysis. The names of different subsystems and their corresponding phosphorus loss factors are shown in Table 2. Table 2: Phosphorus loss factor for different subsystems (for subsystems shown in Figure 1) Subsystem
Name
Phosphorus loss factor
B
Fertilizer manufacturing
0.131
C
Animal feed production
0.022 22
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Cultivated land
0.286
E
Animal farming
0.882
F
Crop processing
0.052
G
Meat processing
0.197
More explanation of results from the substance flow analysis could be found from our previous published paper (Li et al., 2019a, Li et al., 2019c). The phosphorus loss factor is a phosphorus utilization efficiency indicator along the food supply chain, where lower value represents a more efficient phosphorus utilization process during the transformation from raw material to final products. As can be seen in Table 2, the wellindustrialized subsystems (e.g. animal feed production, crop processing and fertilizer manufacturing) have relatively low phosphorus loss efficiency, indicating that less phosphorus was wasted during this process. However, the on-farm production, especially for animal farming, has a high phosphorus loss factor of 0.882. As known, animal farming produces a significant amount of manure with high phosphorus content and is, therefore, ineffective in terms of phosphorus utilization. This paper finds that the phosphorus loss factor during animal farming is 88.2% in China, which is similar to that reported for the UK (83.5%, Cooper and Carliell-Marquet, 2013). Besides, the wasted phosphorus loss from cultivated land is also significant, with a phosphorus loss factor of 0.286 and a total amount of 23,600 tons in 2015. Based on the at-table and off-table phosphorus loss calculation, the total phosphorus loss along is food supply chain is 424,400 tons, by comparing with the total at-table phosphorus loss, over 80% phosphorus loss was derived from food production (284,000 23
Journal Pre-proof tons), which is two times higher than those wasted during at-table food consumption. Such a significant proportion makes the development of effective strategies for manure minimization and reuses urgent. The wastes phosphorus could flow into surface water (T1), wastewater treatment facilities (T2), landfill, composting or incineration plant (T3). A summary of destinations for phosphorus in different subsystems could be found in Figure 8.
Figure 8: Destinations of lost phosphorus in different subsystems (‘other’ means the amount of phosphorus ending up in composting or other unreported processes, ACC represents accumulation in the crop land)
24
Journal Pre-proof By considering both the at-table and off-table phosphorous loss, Figure 8 shows that 160,200, 95,500, and 81,900 tones of phosphorus flows into wastewater treatment plants, landfill sites and the surface water, with another 79,300 tones of phosphorus ended up in either land, incineration process and other processes. It should be noted that these numbers are not representing the final destination, as the phosphorus leaching and exchange (e.g. phosphorus discharge from wastewater treatment plants to surface water or leaching from the landfill site to surface water) are ignored in this paper. As can be seen in Figure 8, nearly one-third phosphorus ends up in the wastewater treatment, providing an opportunity for cost-effective resource recovery because of the fast development of struvite precipitation for phosphorus recovery (Li et al., 2019b; Huang et al., 2019). At the same time, careful attention should be paid to the landfill, which is not only because of its large amount of embedded phosphorus, but also by the fact that phosphorus in landfill sites will decrease the surface water quality if no proper actions are taken. 4.0 Implications Phosphorus is an essential element for living organisms. As a non-renewable resource, it is predicted to be depleted in the next 100 years (Li et al., 2018). Unconsumed food represents an inefficient use of valuable natural resources and will cause partially avoidable environmental degradation (Jalava et al., 2016; Shafiee-Jood and Cai, 2016). As reported by Kummu et al. (2012), food loss and wastage account for 25% water, cropland and fertilizer used for global food crop production. However, most current research focuses on the development of cost-effective phosphorus recovery 25
Journal Pre-proof technologies, while the significance of embedded phosphorus in food waste has been overlooked. This paper provides meaningful information regarding the food waste volume and its composition in China, as well as its impact on phosphorus resource and the environment at the provincial level. The results demonstrate that food waste is a severe concern in China, which could result in a large amount of ineffective phosphorus consumption. This study suggests that improving the phosphorus utilization efficiency in food production and adjusting the dietary structure to plant food-based consumption will reduce the food waste generation and the phosphorus loss. Given the scarcity of the phosphorus resource in both China and the globe, food waste minimization, reuse and recycling are also recommended to enhance food security and environmental sustainability (Shafiee-Jood and Cai, 2016). The substantial environmental costs of food waste (e.g. decrease of biodiversity and degradation of land and freshwater) require both businesses and individuals to minimize their food waste urgently. As reported by Nahman and Lange (2013), food waste reduction at the source could save the energy used for planting and growing, reduce the greenhouse gas emission and chemical fertilizer consumption, and save money through more efficient handling, processing and storage of food. Therefore, enough and proper education programs for food waste minimization and separation in the private sector should be considered. For example, Japan has made impressive progress on waste minimization and recycling since 2001, which is believed to be benefitted from the community level education and a certification system guiding the reuse of food waste for animal feed, fertilizer and the agricultural products (Liu et al., 26
Journal Pre-proof 2015). Regarding the food waste minimization management, four ministries – the Ministry of Housing and Urban-Rural Development, the National Development and Reform Commission, the Ministry of Environmental Protection and the Ministry of Agriculture - are at the same administrative level in China. According to Li et al. (2018), these multiple ministries and agencies currently work somewhat independently, and some of their duties and tasks are interacting and overlapping with each other, which might make the implemented food waste policies and regulations ineffective (Thi et al., 2015). Although some policies and regulations have been launched (i.e. source-separation, collection and local treatment), reasonable integration of different regulations and the co-working of different departments should still be considered. One solution might be the implementation of a single responsible individual and an organization that issues all high-level directives related to food waste in China, while the four ministries have the autonomy to carry them out as they see fit. Besides minimization, the reuse and recycling of wasted food should also be encouraged. The development of centralized livestock and ecological farms reduces the cost of manure and food waste composting, the residual from which could be used as animal feed. However, the balance between supply and demand between regions should be considered as the quantity of available animal manure and food waste vary across the country. Moreover, the bio-safety of reusing food waste as animal feed should also be addressed (Salemdeeb et al., 2017). For example, the use of uncooked food waste to feed pigs in 2001 precipitated in the foot-and-mouth disease epidemic and cost the UK 27
Journal Pre-proof economy £8 billion (UK House of Commons report, 2002). Pilot projects in less developed regions in China (e.g. higher levels animal husbandry) could be launched to address this concern. Meanwhile, support from policymakers, the public and the animal industry are also required. The data quality and system uncertainty are other concerns for effective phosphorus and food waste management. Typically, the data variation in a substance-flow-analysisbased system could come from the lack of knowledge on hidden flows, data deficiency and inconsistency, and uncertainty propagation. For example, some data are outdated but are still used due to the lack of information. To address this, more directly measured data are required, which will help to verify the existing data, improve the accuracy and reliability, and fill in the current missing data (Xue et al., 2017). Consistent food waste reporting framework that is available to the public and stakeholders along the food supply chain is also encouraged. Such information will contribute to the quantification and minimization of food waste, which is crucial for tracking progresses toward the SDG target 12.3 (Benyam et al., 2018). Previous literature has used the Monte Carlo simulation and Bayesian network for uncertainty quantification in less complicated environmental systems (Beaudequin et al., 2016). However, the large number of variables in this paper increases the system complexity and make most simulations difficult to converge. A simple uncertainty estimation method considering standard deviations based on the data source (i.e. from the published paper, government report and website) might be an effective strategy to address this problem (Cooper and Carliell, 2013; Li et al., 2015), which is suggested to be considered in the future research. 28
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5. Conclusion This paper quantified the amount of at-table food waste in China by considering both at-home and away-from-home consumption. The embedded phosphorus, as well as the off-table phosphorous loss, was then estimated based on phosphorus loss factor calculated from substance flow analysis. The result showed an at-table food waste of at 53.7 million tons in 2015, with a per capita wastage of 39.2 kg. Among different species, vegetables and cereals are accounted for the largest shares for plant-based food waste, while pork took up the largest share for meat-based food waste. In terms of phosphorus loss, the at-table lost was 86,300 tons. By considering the off-table phosphorus loss, a total amount of 424,400 tons phosphorus was wasted, accounting for 16.4% of the mineral phosphate fertilizer consumption in 2010. Further analysis indicated that over one-third the lost phosphorus ended up in the wastewater treatment plants, providing an opportunity for cost-effective phosphorus recovery and management. This paper provides an alternative insight into phosphorus consumption which, together with the status quo phosphorus recovery concepts can be developed into a robust framework that addresses phosphorus depletion. References Bai, Z., Ma, L., Ma, W., Qin, W., Velthof, G., Oenema, O., Zhang, F., 2016. Changes in phosphorus use and losses in the food chain of China during 1950–2010 and forecasts for 2030, Nutrient Cycling in Agroecosystems, 104, 3, 361–372. DOI: 10.1007/s10705015-9737-y Beaudequin, D., Harden, F., Roiko, A., Mengersen, K., 2016. Utility of Bayesian 29
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Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
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CRediT author statement Bing Li: Conceptualization, Methodology, Formal analysis, Writing - Original Draft Tailai Yin: Methodology, Formal analysis, Investigation, Writing - Original Draft Isuru A. Udugama: Conceptualization, Investigation, Writing - Review & Editing Shou Long Dong: Methodology, Software, Visualization Wei Yu: Methodology, Validation, Visualization Yue Fei Huang: Conceptualization, Validation, Resources, Supervision Brent Young: Resources, Writing - Review & Editing, Supervision
Bing Li, Tailai Yin, Isuru A. Udugama, Shou Long Dong, Wei Yu, Yue Fei Huang, Brent Young PII:
S0959-6526(19)34779-1
DOI:
https://doi.org/10.1016/j.jclepro.2019.119909
Reference:
JCLP 119909
To appear in:
Journal of Cleaner Production
Received Date:
26 October 2019
Accepted Date:
27 December 2019
Please cite this article as: Bing Li, Tailai Yin, Isuru A. Udugama, Shou Long Dong, Wei Yu, Yue Fei Huang, Brent Young, Food waste and the embedded phosphorus footprint in China, Journal of Cleaner Production (2019), https://doi.org/10.1016/j.jclepro.2019.119909
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Food waste and the embedded phosphorus footprint in China Bing Li1,2,3*, Tailai Yin4, Isuru A. Udugama5, Shou Long Dong6**, Wei Yu3, Yue Fei Huang2, Brent Young3 1School
of Biological and Chemical Engineering, Nan Yang Institute of Technology, Nan Yang, Henan, China 2Department of Hydraulic Engineering, Tsinghua University, China 3Department of Chemical & Materials Engineering, The University of Auckland, New Zealand 4College of Water Conservancy, North China University of Water Resources and Electric Power, China 5Department of Chemical and Biochemical Engineering, Technical University of Denmark, Denmark 6School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China *[email protected],
**
[email protected]
Abstract The increasing food waste volume causes inadequate resource usage and results in partially avoidable environmental degradation. Although previous research has developed cost-effective processes for food waste treatment, the significance of embedded resources in food waste, especially the unreplaceable and depleting phosphorus, has been overlooked. This paper quantifies food waste in China at the provincial level by considering both at-home and away-from-home consumption, where phosphorus loss factor derived from substance flow analysis will be used to estimate phosphorus loss along the food supply chain. The results provide meaningful information regarding the volume and composition of food waste, as well as its impact on phosphorus resource and the environment at the provincial level. The calculation 1
Journal Pre-proof confirmed that at-table food waste was 53.7 million tons in 2015, while the embedded phosphorus was 86,300 tons. The off-table phosphorus loss was then back-calculated along the food supply chain, showing a total phosphorus loss of 424,400 tons, which was equivalent to 16.4% of the total mineral phosphate fertilizer consumption in China. Given China’s importance on the global food cycle, effective phosphorus management along the food supply chain, at-table food waste minimization and phosphorus recovery are recommended to close the current imbalanced phosphorus cycle. Keywords: Food waste, phosphorus, food supply chain, substance flow analysis
1. Introduction Phosphorus is a major nutrient supporting plant growth, a key element involved with biological metabolism (Rahman et al., 2019) and an essential input for agricultural production (Neset et al., 2019). Currently, almost all consumed phosphorus is sourced from phosphate rock, a non-renewable resource that is predicted to run out in the next 100 to 150 years (Li et al., 2018). The ineffective phosphorus utilization and uncontrolled food waste along the food supply chain have aggravated the phosphorus resource depletion and caused environmental problems such as eutrophication, ride tide and unnecessary greenhouse gas emissions (Xue et al., 2017). Food waste is the unconsumed safe and nutritious food at the table. It not only hinders the food availability for countries with limited food supply, but also causes inefficient water and land usages around the globe. As estimated, 30%, 23%, 20% and 10−20% of the purchased food in Finland, Denmark, Norway and Sweden have been thrown away 2
Journal Pre-proof from households (Gjerris et al., 2013). The UK alone generated 7.2 million tons of food waste in 2012, over 60% of which was avoidable (WRAP, 2014). Globally, one-third produced food is lost or wasted (Gustavsson et al., 2011), which is equivalent to 4.4 gigatons CO2 emission, accounting for 8% of our total greenhouse gas emission. Moreover, food waste has a substantial economic impact. For example, 27 billion USD of food is wasted in Canada each year (Xue et al., 2017), 200 billion Yuan-worth food is thrown away in China (Li et al., 2016), and 750 billion USD-worth food is wasted around the world (Papargyropoulou et al., 2014). Due to its significant wastage and substantial economic impact, a growing body of literature has quantified the volume of food waste across the food supply chain at global, regional, and national levels in the past decade (Li et al., 2019d). Based on these researches, many counties and organizations have added food waste minimization on their international and national political agenda. For example, the UN’s Sustainable Development Goals (SDG) have planned to halve the global food waste at retail and consumer levels and reduce food losses along the supply chain by 2030. This has been adopted by the European Union, the United States and the African Union (Porter et al., 2016). Food is also a vehicle of nutrition, water and land (Sun et al., 2018). To this end, the reduction of food waste could also reduce fertilizer utilization, water consumption and greenhouse gas emission (Yuan et al., 2019). Therefore, there are increasing scholars investigating the environmental footprints of water and energy within food production systems. Foley et al. (2011) and Vermeulen et al. (2012) estimated that the global 3
Journal Pre-proof agriculture consumed 70% of the world's freshwater, 38% of the land area and produced 25% of the world's greenhouse gas emission. Sedghamiz et al. (2018) developed a multi-objective model to allocate agricultural and environmental water. To date, most food types have been included for the water and energy assessment by using life cycle analysis and Input-Output Analysis, based on which the carbon footprint change pattern could be quantified (Wu et al., 2013; Striebig et al., 2019). China is a vast agricultural country producing a tremendous amount of food. With the rapid development of the chinese economy, the over-fertilized cropland and increasing food waste have become more serious. As a result, the food supply chain has caused environmental problems such as water and land shortage, non-point source pollution, and phosphate rock reserve depletion. The quantification of natural resource embedded in food waste can clarify the specific factors of resource loss and its impact on natural resources and the environment. However, there is currently little such research available (Reutter et al., 2017). Liu et al. (2013) assessed the impact of vegetable losses and waste on water and land in China. Song et al. (2015) combined the survey data with life-cycle assessment and concluded that the embedded carbon, water and ecological footprints in at-home food waste is 40 kg CO2e, 18 m3 and 173 gm2, respectively. Sun et al. (2018) evaluated the impacts of food waste on water resources in China. These studies have provided valuable examinations of water and energy embedded in food waste. However, as a significant nutrient for agricultural production and an essential element that will be depleted within the next 100 years, little research evaluates the impact of food waste on the phosphorus resource. 4
Journal Pre-proof When food waste is reduced, lower demand for food production is conceivable. Consequently, there will be a lower pressure on the natural phosphate rock resource. To achieve this, the amount of at-table food wastage in 31 provinces of mainland China was firstly estimated based on at-home and away-from-home food consumption. This is different from most previous estimations, where only at-home food waste is considered. Substance flow analysis was then used to estimate the phosphorus utilization efficiency along the food supply chain. Based on these, the volume and composition of food waste, as well as the amount of embedded phosphorus and its destinations could be determined. This research will not only provide vital information for embedded phosphorus within the food waste in China, but also help policymakers to manage the phosphate rock resource effectively and reduce agricultural phosphorus runoff. 2. Methodology This paper aims to quantify the amount of wasted phosphorus embedded in food waste in China. According to Liu et al. (2013), it is important to differentiate the terminology between food loss and food waste in order to analyze their relative significance. Here, food loss refers to food that is wasted during on-farm production and processing (including postharvest handling - PH, processing-PR, storage - ST and distribution-DI, which are shown in the processing block in Figure 1). Food waste is the thrown-away food that could have been eaten (shown in the consumption stock in Figure 1, which is quantified by considering at-home and away-from-home food consumption). Food supply chain here is a series of processes from food production to intake (or from farm 5
Journal Pre-proof to table). The overall research methodology was highlighted in Figure 1. Different stages of the food supply chain (highlighted by dash lines in Figure 1), and the major phosphorus flows in China (processes related to phosphorus extraction, production and consumption) are shown in Figure 1, where the light blue blocks represent the plant food production, and the dark grey blocks represent the animal food production.
Figure 1： Conceptual model for food waste and phosphorus estimation, definitions of different symbols are shown in Table 1. 2.1 Data The base year of 2015 was used for wasted food and phosphorus quantification in this 6
Journal Pre-proof paper. The geological boundaries are the 31 provincial administrative districts in mainland China. Hong Kong, Taiwan, Macao and marine environments are excluded due to the lack of information. Food referred in this paper is a combination of plant and animal food, while the former includes vegetables, fruits and cereals, and the latter includes pork, beef, mutton, poultry, eggs, fish and dairy products. Major food import, export, production and at-home consumption data are derived from the China Statistical Yearbook (e.g. population, urban and rural food consumption), the China Agriculture Yearbook (e.g. fertilizer and pesticide usage, crop and livestock production) and the United States Geological Survey database (e.g. phosphate rock production). The ratios of at-home food waste, meals away-from-home and away-from-home food waste are derived from the Li et al. (2017), Ma et al. (2006), and Zhang et al. (2016a), respectively. 2.2 Food waste quantification To address the significant food consumption difference caused by the economic growth and socio-demographic changes in China, food waste is estimated based on athome and away-from-home consumption. Food waste from the tourism industry is also considered because of its enormous amount prepared by the various foodservice providers (Zhang et al., 2017). The amount of at-table food waste, Wtf, can be estimated using Equation 1: 31
𝑊𝑡𝑓 = ∑𝑖 = 1(𝑊𝑎𝑡,𝑖 + 𝑊𝑜𝑢𝑡,𝑖 + 𝑊𝑡,𝑖)
(1)
where, Wat, i is the at-home food waste generated in province i, Wout,i is the away-fromhome food waste, Wt,i is the food waste from the tourism industry. i ranges from 1 to 31, representing different provinces in China. The at-home food waste gernerated in a 7
Journal Pre-proof province could be calculated using the following equation: 10
𝑊𝑎𝑡 = ∑𝑛 = 1(𝐹𝐴𝑛,𝑟𝑢𝑟𝑎𝑙 × 𝑅𝑛,𝑟𝑢𝑟𝑎𝑙 + 𝐹𝐴𝑛,𝑢𝑟𝑏𝑎𝑛 × 𝑅𝑛,𝑢𝑟𝑏𝑎𝑛)
(2)
where, FAn,rural is the at-home food consumed in the rural area for food species n, which can be estimated based on the per capita food consumption of rural residents and the population. Rn,rural is the at-home food waste ratio in the rural area for food species n, and is derived from Li et al. (2017). Similarly, FAn, urban is the at-home food consumed in the urban area and is calculated based on urban food consumption and population. Rn,urban is the at-home food waste ratio in the urban area, and is assumed to be 20% higher than Rn,rural due to their economic and social difference. n is from 1 to 10, representing cereals, vegetable, pork, beef, mutton, poultry, eggs, dairy products, fruits and other (fishery product and cooking oil) food, respectively. The away-from-home food waste in each province could be estimated by Equation 3: 10
𝑊𝑜𝑢𝑡 = ∑𝑛 = 1(𝑅𝑂𝑢𝑟𝑏𝑎𝑛 × 𝑃𝑢𝑟𝑏𝑎𝑛 × 𝐹𝑂𝑢𝑟𝑏𝑎𝑛,𝑛 × 𝑘𝑢𝑟𝑏𝑎𝑛 + 𝑅𝑂𝑟𝑢𝑟𝑎𝑙 × 𝑃𝑟𝑢𝑟𝑎𝑙 × 𝐹𝑂𝑟𝑢𝑟𝑎𝑙,𝑛 × 𝑘𝑟𝑢𝑟𝑎𝑙)
(3)
where, ROurban and ROrural are the ratios of food away-from-home in the urban and rual area, kurban and krural are the ratios of meals away-from-home per person per day, FOurban,n and FOrural,n are the amount of food waste for species n in the urban and rural area. Due the lack of data, this paper assumes that FOrural,n has the same value as FOurban,n. The values of ROurban, ROrural, kurban, krural and FOurban,n are derived from Zhang et al. (2016a). Purban and Prural are the urban and rural population in each province and is derived from the China Statistical Yearbook 2015. Similarly, food waste from the tourism industry could be quantified by Equation 4, 10
𝑊𝑡 = ∑𝑛 = 1(𝑇 × 𝑅𝑇𝑠 × 𝐹𝑂𝑢𝑟𝑏𝑎𝑛,𝑛 × 𝑆𝑠 + 𝑇 × 𝑅𝑇𝑚 × 𝐹𝑂𝑢𝑟𝑏𝑎𝑛,𝑛 × 𝑆𝑚)
(4) 8
Journal Pre-proof where, T is the total number of tourists each year, RTs and RTm are the ratios of the one-day tour and overnight visitors. These values are derived from the China Tourism Statistics Yearbook 2016. Ss and Sm are the number of meals for the one-day tour and overnight visitors, which is estimated based on the work of Zhang et al. (2017) and Gao et al. (2019). 2.3 Phosphorus loss factor calculation Phosphorus loss factor in this manuscript is defined as the percentage of phosphorus that is not converted to an expected product along the food supply chain. For example, phosphorus loss during animal farming is everything except the products for human consumption. Although some animal waste (e.g. excrement) could be recycled to fertilize the cropland, they are considered as a loss because it is not an expected product. To calculate the phosphorus loss factor, quantification of phosphorus footprint using substance flow analysis is required (Jiang et al., 2019). Substance flow analysis is a mass-balance-based framework to track how a substance flows within the defined boundaries. Typically, the total amount of substance stored or accumulated in a subprocess is named as ‘subsystem’ (e.g. block B in Figure 1), and the mass of substance within the process is defined as ‘flow’ and is also called phosphorus footprint in this paper (e.g. BD in Figure 1). Detailed information of substance flow analysis could be found in Li et al. (2019a). Based on the above, the phosphorus loss factor, μ, in different industries along the food supply chain could be calculated using Equation 5, 𝑥
𝜇=1―
∑𝑥 = 1𝐹𝐸,𝑥 𝑝
∑𝑝 = 1𝐹𝑖𝑛,𝑝
(5)
9
Journal Pre-proof where, FE,x is the phosphorus footprint of expected products in a subsystem, Fin,p is the phosphorus footprint of all input flows, p and x are the numbers of flows for expected and total input flows. The subsystems and flows considered in this paper are highlighted in Figure 1, with their definitions listed in Table 1. The discharge of untreated wastewater (T1), treated wastewater (T2) and landfill waste (T3) from each subsystem are combined into ‘XW’, where X is the symbol of each subsystem. In summary, there are seven subsystems and 23 flows in the proposed framework The phosphorus footprint in each flow, Ta, is calculated by multiplying phosphorus associated material mass flow data, Ca, and their corresponding phosphorus concentration Pa, which is shown in the following equation, 𝑇𝑎 = ∑𝑃𝑎 × 𝐶𝑎
(6)
Most material mass flows are derived from the China Agriculture Yearbook and the United States Geological Survey database. Some material mass flow data are estimated based on animal and human population. For example, animal excreta are estimated by multiplying the population of a specific type of animal with its average excretion amount derived from the literature. The phosphorus concentrations are acquired from Li et al. (2015). Due to the data uncertainty, each phosphorus flow was cross-checked by comparing with values from at least two sources where possible, the average value of different flows was used for calculation. For flows with no available data from the literature, the mass balance of a subsystem could be used for quantification by using Equation 7 𝑝
𝑞
∑𝑝 = 1𝐼𝑁 = ∑𝑞 = 1𝑂𝑈𝑇 +∑𝑆𝑇𝑂
(7) 10
Journal Pre-proof where, IN, OUT and STO are the phosphorus input, output and accumulation in a specific subsystem, p and q are the number of input and output flows. The at-table phosphorus loss will also introduce emissions along the food supply chain, which could be determined by using the following equation: 𝑃𝑇𝑜𝑡𝑎𝑙 =
𝑊𝑡𝑓 × 𝑃𝑛 𝑞
∏1(1 ― 𝐿𝑗)
(8)
where, PTotal is the phosphorus loss in stage q, Lj is the phosphorus loss factor for different stages and Pn is the phosphorus concentration for different food species. 3. Results and discussion 3.1 Sanity check To check the reliability of the proposed quantification method, a consistency check of the calculated food waste values was conducted. Different kinds of food waste (e.g. national or regional, at-home or away-from-home) used for the comparison are listed as the following. Based on these assessments, there is a good agreement of the calculations made by this work and the available literature. 1) The away-from-home food waste in the urban area calculated from this research is 14.7 million tons, which is similar to the estimates of China City Food and Beverage Waste Report (WWF, 2018), indicating that food wastage from restaurants in Chinese cities is around 17 to 18 million tons in 2015. 2) Zhang et al. (2016b) estimated that the total food waste in Beijing is around 0.4 million tons, while the current research shows a value of 0.27 million tons. 3) De Clercq et al. (2016) reported a total amount of 56.5 million tons of food waste in 2015, and the proportions of food waste produced in the east and northeast China 11
Journal Pre-proof were 43.2% and 8%, respectively. In this paper, the total amount of food waste was calculated to be 53.7 million tons, and the proportions of east and northeast China account for 43.8% and 7.8%. 4) Total food waste in Beijing in 2015 is 956, 300 tons (De Clercq et al., 2016), which is at the same magnitude of 837, 700 tons as calculated in this paper. 5) Li et al. (2018) applied food waste generation, gross domestic product (GDP) per capita and annual disposable personal income as indicators for food waste estimation, and concluded that the annual food waste in China was around 56.6 million tons, which was similar to 53.7 million tons presented in this study. 3.2 Quantification of food waste Chinese people consume a variety of plant and animal food. The results show that more than 53.7 million tons of food is wasted at the table, with a per capita wastage of 39.2 kg. Among them, vegetable, cereal and fruits correspond to 24.5, 9.6 and 8.0 million tons, respectively, while pork and poultry waste are 2.1 and 1.7 million tons, respectively. Food waste and its corresponding sources are shown in Figure 2, where a color change from light blue to dark blue indicates the food waste volume at the provincial level (million tons per year) and the pie charts represent different sources of food waste. As can be seen, Sichuan is the largest producer of food waste (4 million tons) because of its large population and food consumption habits. Tibet, is the smallest one, accounting for 0.18 million tons per year. Food waste in each of the economically developed regions (i.e. Guangdong, Jiangsu, Shanghai and Shandong) or the population 12
Journal Pre-proof concentrated regions (i.e. Henan, Sichuan, Hebei and Henan) is over two million tons per year, which is almost equal to the net food production of Sub-Saharan Africa (Secondi et al., 2015).
Figure 2: Total and decomposition of food waste in each province (million tons) Urbanization in China has increased in speed following the initiation of the reform and opening policy, making the urban area a hot spot for food consumption and therefore a major contributor to food waste generation. Figure 2 confirms this statement and indicates that over 60% food waste is sourced from the urban area. China's urban population will hit the one billion mark by 2030, which in turn will further increase the amount of wasted food. This provides an opportunity for centralized food waste management, where food waste prevention from food providers and consumers, as well 13
Journal Pre-proof as food recycling, reuse and resource recovery could be regulated less costly. It is worthwhile to mention that the proportion of food waste from the tourism industry is also significant in Yunnan and Guizhou (20% and 29%), mainly caused by a large number of tourists all year round. This might challenge their future waste management plans because their natural landscape-based tourism industry usually is far away from the urban area and is lack of waste collection and treatment facilities. Moreover, the results indicate that away-from-home food waste accounts for onethird of its total volume in the urban area. The increases in Chinese economy and household income have resulted in a continuing booming of the catering and hospitality industry, meaning a lower eat-at-home ratio and higher amount of food wastage in restaurants if no proper actions are taken. Considering China’s significant role in achieving the global sustainability, such a trend will raise severe concerns for food security, resource scarcity, and environmental sustainability for both China and the whole world (Wang et al., 2017). Decomposition of food waste in each province is shown in Figure 3. As can be seen, the amount of plant food waste is twice as animal food waste. Regarding the plant food waste, the leftover of vegetables is a key contributor (accounting for 40 – 50% in most provinces). It should be noted that wasted vegetable in Tibet shows a much lower proportion (23%) than in other provinces. This might be caused by the higher vegetable price, where only a few vegetables can be produced locally, especially in winter. The high transportation cost increases the price and changes the diet structure. Cereals are the second-largest food waste in most provinces (around 20% of the total food waste) 14
Journal Pre-proof due to its significant consumption amount. The high cereal wastage ratios in Tibet and Neimenggu are mainly caused by their special food structure. Pork takes up the majority share of meats wasted in China, accounting for 40%. This is comparable to that reported by Sun et al. (2018), stating that pork accounts for 44% of the total animal food consumption in China. Besides, animal food waste demonstrates a noticeable regional difference because of the diverse cultural, economic and social backgrounds. For example, beef, mutton and dairy wastes account for a more significant proportion in the ethnic minority regions such as Tibet (47.1%), and Xinjiang (36%).
Figure 3: Decomposition of food waste in each province Taking these values into account, the per capita food waste across China is calculated by dividing the food waste volume with its corresponding resident population, which could be used to guide the food waste treatment facility capacity design in the future. The results and food consumption preference in each province are shown in Figure 4. 15
Journal Pre-proof Interestingly, it was found that although the total food waste in less developed regions (e.g. Tibet, Xinjiang, Neimenggu) are insignificant (from Figure 2), their average food wastes per capita are among the highest in the country (from Figure 4). Such inconsistency might come from a large number of tourists in these regions, which was ignored during the calculation of average food wastage. By combining Figure 2 and 4, it can be concluded that Sichuan and Hunan are both high in total food waste volume and per capita food wastage, which is believed to be caused by their food consumption habits and large population.
Figure 4: Average food waste and food consumption preference in each province (kg) A qualitative description of food flavors in different regions are highlighted in Figure 4 (information adapted from Li et al. (2017)). It can be concluded that food flavor has a significant impact on the average food waste. For example, the average food waste 16
Journal Pre-proof rates in all umami regions (Fujian, Guangdong and Hainan) are below 40 kg per person per year. Instead, most regions preferring hot (e.g. Sichuan, Chongqing, Hunan and Hubei) and sweet (e.g. Shanghai, Jiangsu and Zhejiang) food are over 40 kg per year. On the other hand, the influence of staple food (e.g. rice, noodle and meat) of a region on its average food waste is insignificant. For example, the average food wastage for regions where rice is the staple food (mainly in the south and northeast China) ranges between 31.9 (Yunnan) and 55.6 kg (Chongqing), for the rest of China (noodle is the staple food), the average food wastage ranges between 31.3 (Henan) and 54.3 kg (Tibet). 3.3 Effect of at-table food waste on phosphorus footprint Food production is a phosphorous-intensive process that not only consumes a large amount of phosphate rock but also discharges tremendous wasted phosphorus that threatens the natural environment. This paper applied the phosphorus footprint theory to evaluate phosphorus wastage. Definitions and values of phosphorus flow calculated from the substance flow analysis are shown in Table 1. Table 1. Definitions and values of phosphorus flows (Unit: 1,000 tons phosphorus) Symbol Name
Value
Symbol
3423
DW
Name
Value
P rock for fertilizer AB
P runoff from cropland
378
production AC
P rock for feed additives
598
Accumulation Accumulated P in cropland
744
Animal faeces for AW
Waste from mining
558
ED
1339 agriculture
AEX
Exported P rock
41
EG
Meat for food
391 17
Journal Pre-proof BD
Consumed fertilizer
2578
EW
Waste from animal farms
1653
388
FH
Crops for consumption
573
Exported P fertilizer
397
FE
Crops for animal feeding
1737
CE
P for animal feed
543
FW
Waste from crop processing
30
CW
Waste from feed processing
12
Import
Imported food
960
CEX
P in exported animal feed
42
GH
Meat for consumption
314
Waste from fertilizer BW manufacturing BEX
Waste from meat DE
Pastures for animal
1028
GW
77 processing
DF
Crop production
2145
The calculation of phosphorus embedded in at-table food waste shows a total amount of 86,300 tons, which is around 4.3% of China’s mineral phosphate fertilizer consumption in 2010 (Li et al, 2015a; Li et al., 2015b, Bai et al., 2016). When considering the phosphorus loss across the food supply chain (more discussions are provided in Section 3.4), 424, 400 tons of phosphorus is wasted. This number is 16.4% of the total mineral phosphate fertilizer consumption in China in 2010 and is eight times of the imported phosphorus in Singapore in 2012 (Pearce and Chertow, 2017).
18
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Figure 5: Total and decomposition of at-table phosphorus loss from food wastage in each province (Unit: 1,000 tons) In terms of the regional distribution, developed provinces (e.g. Guangdong and Jiangsu) and those with large populations (e.g. Sichuan, Shandong and Hunan) have larger phosphorus footprints (Figure 5). As known, in wealthy and affluent societies, consumers are living in a “culture of abundance”, making it easier and less costly to waste and overeat (Liu et al., 2013), while few people considered the environmental cost behind the tag of the items. From our calculation, the phosphorus footprint related to food waste in Sichuan is 7,000 tons, accounting for the largest share in China. The phosphorus footprint in Ningxia is 289 tons, taking up the least share. This is in accordance with the total food wastage shown in Figure 2, with the slight differences 19
Journal Pre-proof caused by the variation of diet structure. In China, people usually order more than enough food when they host guests to show their hospitality, resulting in a much higher away-from-home food waste rate than athome. This is in agreement with findings from Figure 5, indicating that most of the attable phosphorus waste comes from the urban area across the country. For Guizhou and Yunnan, 38.3 and 29.1 % of the wasted phosphorus are sourced from the tourism industry, which should be considered by the local governments when addressing their water and resource challenges.
Figure 6: Decomposition of at-table phosphorus waste in each province The decomposition of at-table phosphorus waste in each province is shown in Figure 6. When compared to Figure 3, the percentage of plant food waste is still higher than the animal food waste, but the share of vegetable has been reduced significantly due to its low phosphorus content. As have been noted, phosphorus wasted in cereals in Tibet 20
Journal Pre-proof and Neimenggu is much higher than other provinces (over 40%), which might be caused by their high cereal consumption rate. Moreover, the wasted phosphorus in animal food follows a similar trend to that in Figure 3, where pork alone accounts for 50% of the total phosphorus wastage. The average at-table phosphorus waste is shown in Figure 7. Again, it is noticed that provinces with a lower amount of total phosphorus waste have higher average at-table waste rate due to the ignorance of tourism population. For example, the total amount of at-table phosphorus waste is 375 tons in Tibet, taking one of the least shares in the country, while its per capita phosphorus waste is 111 grams, which is one of the highest. The ratios of embedded phosphorus in wasted plant food and animal food (PMR) are shown in Figure 7. The result confirms that most at-table phosphorus waste comes from plant food, which is preferred over meat because of its lower nutrient consumption and greenhouse gas emissions along the food supply chain. Moreover, it is observed that most developed regions have a lower PMR value (e.g. Beijing, Tianjin, Guangdong). As with the economic growth and the changing from a current plant-based to meat and dairy-based diet structure, the PMR ratio will decrease. In turn, this will increase the off-table phosphorus loss significantly.
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Figure 7: Average at-table phosphorus (Unit: gram) and the plant to animal food waste ratio (PMR) 3.4 Wasted Phosphorus along the food supply chain The off-table phosphorus loss was back-calculated by using the phosphorous loss factor derived from the substance flow analysis. The names of different subsystems and their corresponding phosphorus loss factors are shown in Table 2. Table 2: Phosphorus loss factor for different subsystems (for subsystems shown in Figure 1) Subsystem
Name
Phosphorus loss factor
B
Fertilizer manufacturing
0.131
C
Animal feed production
0.022 22
Journal Pre-proof D
Cultivated land
0.286
E
Animal farming
0.882
F
Crop processing
0.052
G
Meat processing
0.197
More explanation of results from the substance flow analysis could be found from our previous published paper (Li et al., 2019a, Li et al., 2019c). The phosphorus loss factor is a phosphorus utilization efficiency indicator along the food supply chain, where lower value represents a more efficient phosphorus utilization process during the transformation from raw material to final products. As can be seen in Table 2, the wellindustrialized subsystems (e.g. animal feed production, crop processing and fertilizer manufacturing) have relatively low phosphorus loss efficiency, indicating that less phosphorus was wasted during this process. However, the on-farm production, especially for animal farming, has a high phosphorus loss factor of 0.882. As known, animal farming produces a significant amount of manure with high phosphorus content and is, therefore, ineffective in terms of phosphorus utilization. This paper finds that the phosphorus loss factor during animal farming is 88.2% in China, which is similar to that reported for the UK (83.5%, Cooper and Carliell-Marquet, 2013). Besides, the wasted phosphorus loss from cultivated land is also significant, with a phosphorus loss factor of 0.286 and a total amount of 23,600 tons in 2015. Based on the at-table and off-table phosphorus loss calculation, the total phosphorus loss along is food supply chain is 424,400 tons, by comparing with the total at-table phosphorus loss, over 80% phosphorus loss was derived from food production (284,000 23
Journal Pre-proof tons), which is two times higher than those wasted during at-table food consumption. Such a significant proportion makes the development of effective strategies for manure minimization and reuses urgent. The wastes phosphorus could flow into surface water (T1), wastewater treatment facilities (T2), landfill, composting or incineration plant (T3). A summary of destinations for phosphorus in different subsystems could be found in Figure 8.
Figure 8: Destinations of lost phosphorus in different subsystems (‘other’ means the amount of phosphorus ending up in composting or other unreported processes, ACC represents accumulation in the crop land)
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Journal Pre-proof By considering both the at-table and off-table phosphorous loss, Figure 8 shows that 160,200, 95,500, and 81,900 tones of phosphorus flows into wastewater treatment plants, landfill sites and the surface water, with another 79,300 tones of phosphorus ended up in either land, incineration process and other processes. It should be noted that these numbers are not representing the final destination, as the phosphorus leaching and exchange (e.g. phosphorus discharge from wastewater treatment plants to surface water or leaching from the landfill site to surface water) are ignored in this paper. As can be seen in Figure 8, nearly one-third phosphorus ends up in the wastewater treatment, providing an opportunity for cost-effective resource recovery because of the fast development of struvite precipitation for phosphorus recovery (Li et al., 2019b; Huang et al., 2019). At the same time, careful attention should be paid to the landfill, which is not only because of its large amount of embedded phosphorus, but also by the fact that phosphorus in landfill sites will decrease the surface water quality if no proper actions are taken. 4.0 Implications Phosphorus is an essential element for living organisms. As a non-renewable resource, it is predicted to be depleted in the next 100 years (Li et al., 2018). Unconsumed food represents an inefficient use of valuable natural resources and will cause partially avoidable environmental degradation (Jalava et al., 2016; Shafiee-Jood and Cai, 2016). As reported by Kummu et al. (2012), food loss and wastage account for 25% water, cropland and fertilizer used for global food crop production. However, most current research focuses on the development of cost-effective phosphorus recovery 25
Journal Pre-proof technologies, while the significance of embedded phosphorus in food waste has been overlooked. This paper provides meaningful information regarding the food waste volume and its composition in China, as well as its impact on phosphorus resource and the environment at the provincial level. The results demonstrate that food waste is a severe concern in China, which could result in a large amount of ineffective phosphorus consumption. This study suggests that improving the phosphorus utilization efficiency in food production and adjusting the dietary structure to plant food-based consumption will reduce the food waste generation and the phosphorus loss. Given the scarcity of the phosphorus resource in both China and the globe, food waste minimization, reuse and recycling are also recommended to enhance food security and environmental sustainability (Shafiee-Jood and Cai, 2016). The substantial environmental costs of food waste (e.g. decrease of biodiversity and degradation of land and freshwater) require both businesses and individuals to minimize their food waste urgently. As reported by Nahman and Lange (2013), food waste reduction at the source could save the energy used for planting and growing, reduce the greenhouse gas emission and chemical fertilizer consumption, and save money through more efficient handling, processing and storage of food. Therefore, enough and proper education programs for food waste minimization and separation in the private sector should be considered. For example, Japan has made impressive progress on waste minimization and recycling since 2001, which is believed to be benefitted from the community level education and a certification system guiding the reuse of food waste for animal feed, fertilizer and the agricultural products (Liu et al., 26
Journal Pre-proof 2015). Regarding the food waste minimization management, four ministries – the Ministry of Housing and Urban-Rural Development, the National Development and Reform Commission, the Ministry of Environmental Protection and the Ministry of Agriculture - are at the same administrative level in China. According to Li et al. (2018), these multiple ministries and agencies currently work somewhat independently, and some of their duties and tasks are interacting and overlapping with each other, which might make the implemented food waste policies and regulations ineffective (Thi et al., 2015). Although some policies and regulations have been launched (i.e. source-separation, collection and local treatment), reasonable integration of different regulations and the co-working of different departments should still be considered. One solution might be the implementation of a single responsible individual and an organization that issues all high-level directives related to food waste in China, while the four ministries have the autonomy to carry them out as they see fit. Besides minimization, the reuse and recycling of wasted food should also be encouraged. The development of centralized livestock and ecological farms reduces the cost of manure and food waste composting, the residual from which could be used as animal feed. However, the balance between supply and demand between regions should be considered as the quantity of available animal manure and food waste vary across the country. Moreover, the bio-safety of reusing food waste as animal feed should also be addressed (Salemdeeb et al., 2017). For example, the use of uncooked food waste to feed pigs in 2001 precipitated in the foot-and-mouth disease epidemic and cost the UK 27
Journal Pre-proof economy £8 billion (UK House of Commons report, 2002). Pilot projects in less developed regions in China (e.g. higher levels animal husbandry) could be launched to address this concern. Meanwhile, support from policymakers, the public and the animal industry are also required. The data quality and system uncertainty are other concerns for effective phosphorus and food waste management. Typically, the data variation in a substance-flow-analysisbased system could come from the lack of knowledge on hidden flows, data deficiency and inconsistency, and uncertainty propagation. For example, some data are outdated but are still used due to the lack of information. To address this, more directly measured data are required, which will help to verify the existing data, improve the accuracy and reliability, and fill in the current missing data (Xue et al., 2017). Consistent food waste reporting framework that is available to the public and stakeholders along the food supply chain is also encouraged. Such information will contribute to the quantification and minimization of food waste, which is crucial for tracking progresses toward the SDG target 12.3 (Benyam et al., 2018). Previous literature has used the Monte Carlo simulation and Bayesian network for uncertainty quantification in less complicated environmental systems (Beaudequin et al., 2016). However, the large number of variables in this paper increases the system complexity and make most simulations difficult to converge. A simple uncertainty estimation method considering standard deviations based on the data source (i.e. from the published paper, government report and website) might be an effective strategy to address this problem (Cooper and Carliell, 2013; Li et al., 2015), which is suggested to be considered in the future research. 28
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5. Conclusion This paper quantified the amount of at-table food waste in China by considering both at-home and away-from-home consumption. The embedded phosphorus, as well as the off-table phosphorous loss, was then estimated based on phosphorus loss factor calculated from substance flow analysis. The result showed an at-table food waste of at 53.7 million tons in 2015, with a per capita wastage of 39.2 kg. Among different species, vegetables and cereals are accounted for the largest shares for plant-based food waste, while pork took up the largest share for meat-based food waste. In terms of phosphorus loss, the at-table lost was 86,300 tons. By considering the off-table phosphorus loss, a total amount of 424,400 tons phosphorus was wasted, accounting for 16.4% of the mineral phosphate fertilizer consumption in 2010. Further analysis indicated that over one-third the lost phosphorus ended up in the wastewater treatment plants, providing an opportunity for cost-effective phosphorus recovery and management. This paper provides an alternative insight into phosphorus consumption which, together with the status quo phosphorus recovery concepts can be developed into a robust framework that addresses phosphorus depletion. References Bai, Z., Ma, L., Ma, W., Qin, W., Velthof, G., Oenema, O., Zhang, F., 2016. Changes in phosphorus use and losses in the food chain of China during 1950–2010 and forecasts for 2030, Nutrient Cycling in Agroecosystems, 104, 3, 361–372. DOI: 10.1007/s10705015-9737-y Beaudequin, D., Harden, F., Roiko, A., Mengersen, K., 2016. Utility of Bayesian 29
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Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
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CRediT author statement Bing Li: Conceptualization, Methodology, Formal analysis, Writing - Original Draft Tailai Yin: Methodology, Formal analysis, Investigation, Writing - Original Draft Isuru A. Udugama: Conceptualization, Investigation, Writing - Review & Editing Shou Long Dong: Methodology, Software, Visualization Wei Yu: Methodology, Validation, Visualization Yue Fei Huang: Conceptualization, Validation, Resources, Supervision Brent Young: Resources, Writing - Review & Editing, Supervision