Reducing the land use of EU pork production: where there's swill, there's a way.

Livestock production occupies approximately 75% of agricultural land, consumes 35% of the world's grain, and produces 14.5% of anthropogenic greenhouse gas emissions. With demand for meat and dairy products forecast to increase 60% by 2050, there is a pressing need to reduce the footprint of livestock farming. Food wastes have a long history as a source of environmentally benign animal feed, but their inclusion in feed is currently banned in the EU because of disease control concerns. A number of East Asian states have in the last 20 years, however, introduced regulated, centralised systems for safely recycling food wastes into animal feed. This study quantifies the land use savings that could be realised by changing EU legislation to promote the use of food wastes as animal feed and reviews the policy, public, and industry barriers to the use of food waste as feed. Our results suggest that the application of existing technologies could reduce the land use of EU pork (20% of world production) by one fifth, potentially saving 1.8 million hectares of agricultural land. While swill presents a low-cost, low-impact animal feed, widespread adoption would require efforts to address consumer and farmer concerns over food safety and disease control.

Introduction

Livestock production has a large and growing environmental impact. While providing one-third of all protein consumed by mankind (Herrero et al., 2009), livestock production occupies 75% of agricultural land (Foley et al., 2011), contributes 14.5% of anthropogenic greenhouse gas emissions (Gerber et al., 2013), and drives agricultural expansion in the tropics through the global trade in animal feed (Karstensen et al., 2013, Nepstad et al., 2006). With demand for meat and dairy products forecast to increase 60% by 2050 (Alexandratos and Bruinsma, 2012), there is growing recognition of the need to reduce the environmental impact of meat and dairy production.

Three principal strategies have been proposed to reduce the environmental impact of livestock: (1) reducing demand (Bajželj et al., 2014, Eisler et al., 2014, Fairlie, 2010; zu Ermgassen et al., 2014), principally in the developed world where meat and dairy consumption makes up a high proportion of food intake (Bonhommeau et al., 2013); (2) increasing efficiency, i.e. reducing the quantity of feed required per kg of meat or dairy produced (Garnett, 2013); and (3) changing animal diets to low-impact alternatives. Proposed novel, low-impact animal feeds include insects (Makkar et al., 2014), legumes (Jezierny et al., 2010), algae (Holman and Malau-Aduli, 2013), and bacteria (Byrne, 2014).

Low-impact animal feeds need not, however, be novel. Food waste has historically been recycled as livestock feed, particularly for pigs – cooked food waste fed to pigs is colloquially known as “swill”. Pigs are a monogastric species whose digestive system is well adapted for the conversion of food waste into animal protein (Westendorf, 2000a); food waste produced in early human settlements is thought to have attracted wild pigs, leading to their domestication around 10,000 years ago (Fairlie, 2010). Swill can be a high-quality animal feed that requires no additional land to be brought into production, and hence has minimal or even positive environmental impact (food waste otherwise posing a disposal challenge). However, the use of swill is controversial in some countries and there is marked geographic variation in its acceptance and regulation. Though the recycling of food waste as swill is actively promoted in many nations, including South Korea, Japan, Taiwan, and Thailand (Menikpura et al., 2013), it was banned in the European Union (EU) in 2002 after the UK foot-and-mouth disease epidemic, which is thought to have been started by the illegal feeding of uncooked food waste to pigs. Proponents claim that swill is a cheap, environmentally benign animal feed (Fairlie, 2010, Stuart, 2009, Wadhwa and Bakshi, 2013), but critics claim that it is unsafe and produces pork of poor quality (Garcia et al., 2005, House of Lords, 2014).

In this paper we address some of the controversies surrounding the recycling of food waste as animal feed and quantify the potential for food waste to replace conventional animal feed and reduce the environmental impact of meat production. First, we provide an overview of the history and regulation of swill feeding, focusing on the contrasting approaches taken by the EU and two East Asian states: Japan and South Korea. Second, we consider the role that swill can play in reducing the land required for meat production, through a quantitative case-study of pork production in the EU. We then discuss the impact of swill on other environmental impacts, including greenhouse gas emissions, before reviewing the barriers to swill feeding in Europe. We focus on the potential concerns of pig producers, the public, and policy makers. To finish, we briefly discuss the legal status of swill in other parts of the world, focussing on the world’s two largest pork producers: the USA and China.

Swill in the EU, Japan, and South Korea

Although it is the archetypal pig feed, swill has been in and out of fashion in Europe. Swill was the prevalent pig feed in the early 20th century and was actively promoted by the UK government during the Second World War as a means of attaining food security (Fairlie, 2010). The popularity of swill feeding decreased in the late 20th century as the availability of abundant cheap grains led the pig industry to focus on increasing production efficiencies through grain- and soybean-based diets. The risks of uncooked swill were demonstrated in 2001 when a UK farmer illegally fed uncooked food waste to pigs, precipitating the 2001 foot-and-mouth disease outbreak, which cost the UK economy £8 billion (UK House of Commons report, 2002). In response, swill feeding was banned in the UK in 2001, with the ban extended across the EU the following year (EC, 2002). The ban still permits the feeding of some food wastes where it can be demonstrated that there is no risk of contamination with meat products, but this represents only a small proportion of all EU food waste (see Appendix A for further details of EU regulation and food waste recycling).

Today, the EU produces more than 20% of world pork, 34 kg of pork meat/person/year (FAO, 2014a), and relies on grain- and soybean-based feed, which has a sizeable environmental footprint. A life cycle assessment (LCA) of European pork production found that pork production causes €1.9 of damage to the environment (from eutrophication, acidification, land use, and greenhouse gas emissions) per kg of pork produced – in comparison, it costs the farmer on average €1.4 to produce each kg of pork (Nguyen et al., 2012). Most (75.4%) of this environmental burden stems from feed production – in particular, the farming of soybean meal. The expansion of soybean farming in South America to meet international demand for animal feed poses a significant threat to biodiversity and is a large source of carbon emissions from deforestation (Godar et al., 2015, Karstensen et al., 2013, Nepstad et al., 2006, Richards et al., 2014).

Not all modern pig production is reliant on grain and soybean feed. In the same year that the UK banned swill, the Japanese government introduced the opposite policy, promoting the inclusion of food waste in animal feed (Takata et al., 2012). South Korea and Taiwan have introduced similar food waste recycling systems (in 1997 and 2003, respectively). While the feeding of uncooked meat wastes to pigs can transmit diseases including foot-and-mouth and classical swine fever, appropriate heat treatment deactivates these viruses and renders food waste safe for animal feed (Edwards, 2000, Garcia et al., 2005, OIE, 2009). In these countries, the industry is tightly regulated: the heat treatment of food waste is carried out by registered “Ecofeed” manufacturers (see Appendix B for details of food waste recycling practices in Japan and South Korea). Where Japan and South Korea formerly sent substantial quantities of food waste to landfill, in 2006–07 they respectively recycled 35.9% and 42.5% of food waste as animal feed (Fig. 1) (Kim and Kim, 2010, MAFF, 2012a, MAFF, 2011).

Fig. 1

The end-uses of food waste in South Korea 2001–06, the most recent available data (Kim and Kim, 2010). After the introduction of food waste recycling legislation in 1997, South Korea achieved substantial increases in food waste recycling. The recycling of food waste for animal feed is shown as a solid line.

The potential for swill to reduce the land use of EU pork

To estimate the potential land use saving of a change in EU regulation to promote the recycling of food waste as animal feed, we performed three complementary analyses. (a) We estimated the current land use of EU pork production; (b) we used data from feed trials comparing food waste and conventional diets to determine how the incorporation of food waste in pig diets affects the amount of feed and land required for pig production; and (c) we estimated the availability of food waste suitable for pig feed in the EU. We then combined these results to estimate the potential impact of promoting swill on the land use of EU pork production.

In this analysis we use land use as a footprint metric to assess the potential environmental benefits of the re-legalisation and promotion of swill in the EU. While measuring land use alone does not capture all of the environmental impacts of meat production, we consider land use an informative (though incomplete) metric for this analysis because (a) land use represents the majority (55%) of the environmental costs of European pork production (Nguyen et al., 2012); and (b) land use is a valuable indicator of the biodiversity impacts of products (Mattila et al., 2011). While other biodiversity metrics have been used in life cycle assessment (LCA), there remains no consensus on their relative validity (Souza et al., 2015).

The land use of EU pork production

To estimate the land use of EU pork, we calculated the land required across the entire lifecycle of pork production (breeding sows, piglets, and young and mature slaughter pigs) to grow the feed necessary to produce the 21.5 million tonnes of pork (live weight) which is produced in modern, large-scale pig production systems in the EU each year (for more details see Appendix C). The calculation was based upon weighted mean values of EU production statistics (e.g. the number of piglets weaned per sow per year, piglet mortality rates) and representative diets from the five leading producers of pork in the EU: Germany, Spain, Denmark, France, and Poland. These member states together represent >64% of EU pork production (Appendix C, Fig. A3).

Fig. A3

The number of slaughter pigs (all pigs reared for slaughter, excluding breeding animals and piglets <20 kg) reared on farms with different herd sizes in the EU in 2010. DE = Germany, ES = Spain, DK = Denmark, FR = France, PL = Poland, other country codes listed in electronic supplementary material, Table A3. Source: (Eurostat database, 2014).

We found relatively little variation in the estimated land use across all five sets of diets (4.02 m2/kg pork; range: 3.6–4.3 m2/kg) and determined that the land required to grow feed for EU pork was ca. 8.5 million ha (±0.7 Mha s.d.). Soybean production in 2010 represented ca. 15% of the total land area required for EU pig feed production, an area of 1.2 million ha (±0.2 Mha s.d.).

The effect of swill on land required for pig production

To determine how the inclusion of food waste in pig feed influences the land required for pork production, we conducted a comprehensive literature review (Appendix D) to identify 18 feed trials comparing the growth performance of pigs on 23 conventional and 55 food waste-based diets. For each diet, we recorded the proportion of the diet that was food waste (on a dry matter basis) and calculated the land use per kg of pork (Appendix D). We found a strong linear relationship between the land use per kg of pork and the proportion of the diet made up by food waste (r = 0.97, n = 78, P < 0.0001; Fig. 2).

Fig. 2

The inclusion of food waste in pig diets linearly reduces the land required per kg of pork live weight; r = 0.97, n = 78, p < 0.0001. This linear relationship reflects that the inclusion of food waste in pig feed (a) has no effect on the feed conversion efficiency (it substitutes conventional feed almost 1:1 on a dry matter basis (t = 1.15, p = 0.26)), and (b) does not have a large effect on growth rates (for more details see Appendix D). Some diets have a land use of zero, without being 100% swill: they contain a small amount of other ingredients, such as vitamins and minerals, which also do not require agricultural land.

The availability of food wastes in the EU

An estimated 102.5 million tonnes of food were wasted in the EU in 2015 (202 kg per person) (EC, 2010), from four principal waste streams: households (42%), manufacturing (39%), the food service/catering industry (14%), and retail (5% of food waste). These waste streams span the food supply chain, and so our definition of food wastes includes so-called “food losses” (food wasted during the post-harvest and processing stages; Parfitt et al., 2010), but excludes co-products (Appendix D) and agricultural wastes. The estimates of food waste are uncertain because of differing food waste definitions used by member states (e.g. classifications of green wastes), but are the best available data. We believe these figures are conservative estimates of EU food waste because they do not include agricultural wastes, which make up ca. 34% of all European food waste (Kummu et al., 2012), and we therefore used them as lower-bound estimates of the availability of food waste for use as pig feed in the EU.

Before estimating the quantities of food waste available for swill feeding, we made three adjustments. First, we subtracted the 3 million tonnes of manufacturing food waste (known in the processing industry as former foodstuffs) that are currently included in livestock feed in the EU (EFFPA, 2014). It is not clear whether these are excluded from the EU food waste data, so subtracting them makes our estimates of food waste available for pig feed conservative. Second, we allow for the fact that not all food waste defined by these statistics is available or suitable for pig feed. Only 35.9% and 42.5% of food waste is converted to animal feed in Japan and South Korea, respectively (Kim and Kim, 2010, MAFF, 2012a, MAFF, 2011). We assumed that a similar proportion can be used for the EU and took the mean of these two values (39.2%) to be the proportion of food waste available for recycling into animal feed, if swill feeding were legalised in the EU. Third, in the analyses above (Section ‘The effect of swill on land required for pig production’) we calculated the proportion of animal feed that is food waste on a dry matter basis. To calculate the proportion of EU pig feed that could be replaced by swill we therefore converted our waste estimates into tonnes of dry matter (Appendix E).

Finally, for comparison with the proposed EU swill-feeding scenario, we also calculated the potential for increasing the use of legal food wastes as animal feed under the current legislation. In this scenario, we estimated the land use savings of including in animal feed an estimated 2 million further tonnes of manufacturing food waste which are not currently used for animal feed but which could legally be fed to livestock (EFFPA, 2014).

The potential for swill in the EU

We then used the results from Sections ‘The land use of EU pork production’, ‘The effect of swill on land required for pig production’ and ‘The availability of food wastes in the EU’ to estimate the potential for swill to reduce the land use of EU pork production (Appendix F). Our results indicate that if swill feeding were legalised and food waste recycled into animal feed at rates similar to those in Japan and South Korea, the land requirement of EU pork production could shrink by 1.8 million ha (1.7–2.0 Mha; 95% CI), from 8.5 to 6.7 million ha. This represents a 21.5% (19.6–23.5%; 95% CI) reduction in the current land use of industrial EU pork production. In doing so, swill would also replace 8.8 million tonnes of human-edible grains currently fed to pigs (Appendix F) – equivalent to the annual cereal consumption of 70.3 million EU citizens (FAO, 2014a).

Under the current EU legislation, only a small increase in the quantity of food waste used in animal feed is possible. These legal food wastes could reduce land use by 1.2% (1.0–1.4% or 0.08–0.12 million ha; 95% CI). While this legislation stands, efforts to promote the inclusion of legal food waste in animal feed should be supported in order to realise these modest improvements in environmental impact; our results suggest, however, that far greater gains could be achieved by re-legalising and promoting the use of swill.

Use of swill might also help reduce the impact of EU pork production on global ecosystems. The inclusion of food waste in pig feed would reduce the area of soybean required by 268,000 ha (0.25–0.29 Mha; 95% CI) (Appendix F). In Brazil, the source of the majority (60%) of EU soybean (FAO, 2014a), soybean production is forecast to expand by 10.3 Mha by 2023 (MAPA, 2014). While Brazil is not the sole source of EU soybean meal, the potential for EU swill-feeding to reduce demand for up to 268,000 hectares of soybean production could mitigate ca. 2.6% of the forecast expansion of soybean, reducing pressure on high-biodiversity tropical biomes accordingly.

Swill: beyond land use

The substitution of conventional feed with food waste has the potential to reduce not only the land requirement for pork production, but also other environmental impacts associated with the production of animal feed, including greenhouse gas emissions and eutrophication The impacts of swill feeding on these other environmental effects are more difficult to estimate. For greenhouse gas emissions, while eight LCA studies have compared the recycling of food waste into animal feed with other food waste disposal practices (including incineration, anaerobic digestion, and composting), the calculated emissions vary substantially and are sensitive to local conditions and study assumptions (Fig. 3; Bernstad and la Cour Jansen, 2012). In particular, only one of these studies considers emissions associated with land use change, with the remaining studies therefore underestimating agricultural emissions of feed ingredients, such as soybean meal, by up to nine times (van Middelaar et al., 2013). Two multi-criterion LCAs have been conducted in the European context. Vandermeersch et al. (2014) compare two scenarios in Belgium: (1) sending retail food waste for anaerobic digestion and (2) recycling 10% as animal feed, with the rest sent for anaerobic digestion. This study found that the food waste feeding scenario scored better on 10 of 18 environmental criteria (including land use, marine eutrophication, and freshwater ecotoxicity), with anaerobic digestion scoring better on 8 criteria (including greenhouse gas emissions, ozone depletion, and freshwater eutrophication). Tufvesson et al. (2013) compare the use of manufacturing food wastes (such as bread wastes and fodder milk) for biofuel or animal feed in Sweden. They find that the use of these wastes as biofuel only results in environmental benefits (measured by greenhouse gas emissions, eutrophication, and acidification) if you do not take into account their potential use as animal feed. That is to say, they recommend the use of these wastes as animal feeds, instead using dedicated biofuel crops for biofuel (though this study did not take into account greenhouse gas emissions from indirect land use change resulting from the expansion of crop-based biofuels, nor the potential use of those biofuel crops as animal feed). As evidenced by the caveats above and the variable results presented in Fig. 3, the results of LCAs are often location, assumption, and study-dependent (Bernstad and la Cour Jansen, 2012). Future work should therefore analyse swill feeding and other uses of food waste in other EU member states, using alternative food waste sources, and taking into account all agricultural emissions.

Fig. 3

Results of six LCA studies reporting the greenhouse gas emissions per tonne of food waste for different disposal options, including recycling food waste as swill. Negative emissions mean that the process has a net negative carbon balance, ie the emissions avoided are larger than emissions released. Swill, for example, avoids emissions associated with the production of conventional feed, and anaerobic digestion (AD) avoids emissions from the fossil fuels it replaces. Where a study reported emissions for multiple food waste types, the mean emissions are shown, and none of the studies shown include land use change, a major source of agricultural emissions, when calculating the emissions avoided from swill feeding. The swill data for Vandermeersch et al. (2014) are for a 10% swill, 90% anaerobic digestion scenario. Gaps are left where studies did not report particular food waste disposal options, and the country of study is listed under each reference. Two further LCA studies (Ogino et al., 2012, Tufvesson et al., 2013) use different units (reporting results per kg of animal feed and per MJ of fuel energy, rather than per tonne of food waste) and so cannot be displayed for comparison. (Eriksson et al., 2015, Kim et al., 2011, Lee et al., 2007)

Barriers facing swill in the EU

While our EU-wide analysis is inevitably constrained by the available data, in particular by uncertainty about the quantity of food wastes produced in the EU and their nutritional content, we are confident that our principal conclusion is robust: a policy promoting the recycling of food waste as pig feed has substantial potential to reduce the global land use of EU pork production. When selecting animal feeds, however, there are many more considerations than simply their environmental impact. The adoption of swill feeding in the EU would require backing from pig producers, the public, and policy makers. We next consider the potential barriers from each interest group in turn.

Support from pig producers

Pig producers want to produce pork of high quality, at affordable prices, with reliable profit margins, and the highest standards of food safety.

The 18 studies comparing food waste and conventional feed also reported a range of meat quality measures, allowing us to examine the effect of swill feeding on meat quality and palatability. We used linear mixed models to measure the effect of including food wastes in animal feed on 18 different measures of meat quality, which were each reported by three or more studies. Since pig age and breed, both important determinants of meat quality, varied among studies, study was included as a random effect. Further details of the methods are listed in Appendix G.

While swill does have more variable nutrient composition than conventional feeds (Westendorf, 2000b), swill feeding had little effect on meat quality, with no effect detected for 16/18 measures (Table 1). The two detected effects were weak and did not detrimentally affect pork quality or value. Pigs fed a 50% swill diet had 1.4% higher monounsaturated fats percentages (t = 3.39, data from 6 studies, n = 23, p = 0.017) and 13% greater meat marbling, the presence of streaks of fat within muscle tissue (t = 3.71, data from 6 studies, n = 22, p = 0.014). Pork marbling is known to increase the flavour and tenderness of pork (Brewer et al., 2001). Indeed, three studies intentionally fed food waste diets with a low lysine content in order to increase meat marbling (Witte et al., 2000). Removing these three studies from the analysis abolished the effect (t = −1.24, data from 3 studies, n = 10, p = 0.32). These results suggest that the inclusion of food wastes in animal diets can produce pork of similar quality to conventional diets, which may allay farmer concerns over product quality.

Table 1

Relationships between the proportion of food waste in pig diets and measures of meat quality. P-values also shown for quadratic relationships, where suggested in the literature.

Meat quality (range or measurement units)	Number of studies (points)	Coefficient (SE)	p-Value
Linear model	Quadratic model
Juiciness (0–1)	4 (13)	0.08 (0.04)	0.173	–
Marbling (1–10)	6 (22)	1.30 (0.35)	0.014	–
Dressing percentage (%)	12 (38)	0.89 (0.76)	0.264	–
Meat colour (1–5)	5 (17)	0.21 (0.28)	0.490	–
Meat lightness (L∗ value)	9 (33)	1.42 (0.81)	0.116	–
Meat redness (a∗ value)	9 (33)	−0.01 (0.27)	0.983	–
Meat yellowness (b∗ value)	9 (33)	0.32 (0.28)	0.283	–
Fat lightness (L∗ value)	7 (29)	0.99 (1.21)	0.443	–
Fat redness (a∗ value)	7 (29)	−0.08 (0.50)	0.872	–
Fat yellowness (b∗ value)	7 (29)	−0.39 (0.33)	0.282	–
Fat free lean percentage (%)	4 (15)	1.14 (0.89)	0.280	–
Flavour (0–1)	3 (7)	0.03 (0.02)	0.319	–
Overall palatability (0–1)	3 (7)	0.03 (0.05)	0.584	–
Monounsaturated fats (%)	6 (23)	2.83 (0.83)	0.017	–
Saturated fats (%)	6 (23)	−1.30 (1.01)	0.243	–
Polyunsaturated fats (%)	6 (23)	−1.50 (1.02)	0.186	–
6 (23)	−0.90 (0.55)	–	0.158
Backfat thickness (mm)	15 (53)	−0.58 (1.08)	0.599	–
15 (53)	−0.32 (0.60)	–	0.600
Drip loss (%)	3 (11)	−0.65 (1.33)	0.673	–
3 (11)	−0.32 (0.81)	–	0.729

Farmers are also acutely concerned about the profitability of pork production. Feed makes up 55–72% of the costs of EU pig production and is subject to significant price volatility, with prices of conventional feed rising 70% from 2005–2012 (from $267 to $456/tonne) (AHDB Market Intelligence, 2013, AHDB Market Intelligence, 2006). Low-cost swill might therefore be a welcome alternative to conventional grain-based feed. Our results show that while swill feeding had no effect on feed conversion efficiencies (t = 1.15, p = 0.26), swill feeding did tend to slow pig growth rates (t = −4.71, p < 0.0001), which would necessarily increase labour and housing costs proportional to the number of extra days required to bring animals to slaughter. The relative merit of cheap, slower-growth swill and expensive, faster-growth conventional feed can be explored with a stylised example.

Assume an EU pig farmer is considering converting to a 50% swill-diet. For simplicity, their current cost of production is €1/kg pork (the EU mean is approximately €1.4/kg pork (Nguyen et al., 2012)), of which 60% are feed costs (EU range of 55–72%), i.e. €0.6/kg. Our results suggest that a diet containing 50% food waste produces 13% lower growth rates, and so the farmer’s swill-fed pigs will need 13% longer to reach slaughter weight, making their conventional feed costs equal to €0.34/kg pork (1.13 ∗ 0.3, where 0.3 = the 0.6 of costs due to conventional feed ∗ 0.5, with the other half of the feed being swill). To conservatively estimate the cost savings of swill, we assume that all other costs also increase in proportion to the extra days required to reach slaughter weight (although fixed costs, such as depreciation and financial costs, make up 15–30% of the cost of production (AHDB Market Intelligence, 2013)). The farmer’s non-feed costs would therefore be 1.13 ∗ 40% = €0.45/kg pork. In this case, the farmer will have an overall lower cost of production if swill costs less than 70% the price of conventional feed (calculated as 1 – the cost of swill production/the cost of the equivalent conventional feed ∗ 100: [€1 − €0.34 − €0.45]/€0.3 ∗ 100). In the centralised food waste recycling systems, swill typically costs only 40–60% of conventional feed (20 vs. 50¥/kg in (Takahashi et al., 2012) and 167 vs. 278₩/kg in (Nam et al., 2000) and main text, Fig. 4). For this farmer, swill feeding would therefore improve profitability. Swill has a more variable nutritional content than conventional feeds (Westendorf, 2000b) and will not suit the business models of all farms, but it could help many to improve profitability. This is especially the case if swill-fed pork is marketed as a premium, low environmental impact product, as it is in Japan (“Eco-pork”, see Appendix B). There it receives an associated price-premium, which further boosts farm profits.

Fig. 4

Prices of conventional pig feed and swill (Ecofeed) in Japan. Dry Ecofeed is fed as a dehydrated pellet, liquid Ecofeed is fed as a wet feed. Dotted lines are an interpolation between the 2011 and 2013 values. Data from: (MAFF, 2014, MAFF, 2013, MAFF, 2012b, MAFF, 2011, MAFF, 2010, MAFF, 2009).

While swill feeding could benefit the bottom line of many individual farmers, there is concern that if the legalisation increased the risk of an outbreak of disease, such as foot and mouth or classical swine fever, the overall cost to the industry of such an outbreak could outweigh the financial gains (House of Lords, 2014). This concern is understandable given the £8 billion cost of the UK 2001 foot and mouth outbreak (UK House of Commons report, 2002). It is challenging to quantify the relative risk of a disease outbreak occurring under either of our two different policy scenarios: the status quo ban on swill and the centralised, regulated use of swill, and it is not certain which policy is lower risk. While it may be argued that a total ban on swill feeding is safer than the regulated use of swill, this ignores the illegal feeding of food waste on smallholder farms which occurs under current, “low-risk” legislation. A survey of 313 smallholder farms in the UK, for example, found that 24% of smallholders fed uncooked household food waste to their pigs (Gillespie et al., 2015). A process for the heat treatment and legal use of food wastes may improve on the current uncontrolled situation. It is worth noting that there have been no disease outbreaks linked to the use of swill in Japan and South Korea (Muroga et al., 2012, Park et al., 2013) and that the use of food waste as animal feed has consistently grown in both countries (by 125% in Japan from 2003–2013, Fig. A1 in Appendix B, and by 35% in South Korea from 2001–06, Fig. 1), suggesting strong farmer buy-in.

Fig. A1

Food waste makes up an increasing proportion of animal feed in Japan. Source: (MAFF, 2014).

Finally, food safety precautions should include not only heat treatment but also checks for potential contaminants in food waste. Garcia et al. (2005) performed microbiological and chemical analysis of different Spanish food waste sources and found high levels of heavy metals and dioxins in some household and restaurant wastes. All other food wastes (e.g. retail meat, fruit, vegetable, and fish wastes) were deemed suitable for animal feed. The suspected sources of heavy metals were metal cans and piping. Contamination from these sources could be reduced through better collection, waste sorting, and storage procedures, as required by regulation in East Asian states (Appendix B).

Support from the public

Our results and the East Asian case studies demonstrate that food waste can be safely recycled as pig feed to produce pork of high quality and low environmental cost. Despite this, swill has previously faced resistance because of concerns over consumer acceptability. For example, the co-operative, a UK food retailer, banned pork reared on food waste from shops in 1996 citing it “was not a natural feeding practice” (Stuart, 2009). This is an issue of public awareness, however, not food safety. Pigs were domesticated on a diet of swill, and as such, it could be argued that swill is no less “natural” than the practice of feeding vegetarian diets to omnivorous pigs in modern, industrial systems. Our review included a number of blinded trials finding no difference between the flavour (n = 4), colour (n = 7 for fat; n = 9 for meat), fat composition (n = 6), or overall palatability (n = 4) of conventional- vs. swill-fed pork (Table 1), suggesting that without labelling, consumers would not notice a difference. In fact, improving consumer awareness of swill has had positive effects in Japan, where certification has been introduced. A survey of consumers there found that those most knowledgeable about the pig industry showed the strongest approval of recycling food waste as feed (Sasaki et al., 2011). Public education may be beneficial in promoting the acceptance of swill in the EU.

Support for policy change

Although currently illegal, there is some precedent for reappraising the legal status of swill. First, there is a legal mandate for improved food waste recycling under the EU Waste Framework Directive 2008/98/EC (EC, 2008), and second, similar animal feed regulation is being reconsidered in light of the EU’s deficit in protein sources for animal feed (EC, 2013).

The EU Waste Framework Directive stipulates that EU member states apply a waste management hierarchy to select disposal options in order of their environmental impact (Fig. 5). Under this legislation, the preferred options are to avoid food waste altogether or redistribute it to people. Next, the use of food waste as animal feed is preferable to composting, anaerobic digestion, or disposal in landfill (Papargyropoulou et al., 2014), though the legislation is notably not applied in this respect.

Fig. 5

EU food waste hierarchy showing the different levels of waste disposal established under the EU Waste Framework Directive (EC, 2008). Recycling food waste as animal feed is preferable to composting, anaerobic digestion (AD), or disposal in landfill, the latter of which is to be phased out by 2025 under new legislative proposals (EC, 2014). The diversion of food waste for animal feed would not necessarily reduce the availability of inputs for the AD or composting industries, because the inevitable end product of the use of food waste as pig feed – pig manure – is itself highly suitable for both composting and anaerobic digestion (Bernal et al., 2009, Fairlie, 2010, Holm-Nielsen et al., 2009, Stuart, 2009). Image adapted from (Papargyropoulou et al., 2014).

In 2001, the EU banned the use of all processed animal proteins (including pig by-products, such as tendons and trotters, which are fit for human consumption but not eaten by people for cultural or aesthetic reasons) in animal feed, in response to the Bovine Spongiform Encephalopathy crisis (EC, 2001). There are, however, no recorded cases of pigs, poultry, or fish ever naturally developing or transmitting diseases such as BSE (Andreoletti et al., 2007). After a scientific consultation (Andreoletti et al., 2007) and pressure from the animal feed industry (EFPRA, 2011, Searby, 2014), in 2013 the EU re-legalised the use of non-ruminant processed animal proteins in fish farming, and are currently considering its re-legalisation for use in pig and poultry feed (EC, 2013). It is plausible that swill could undergo a similar process of re-legalisation. It is worth noting that the ban on processed animal proteins is still expected to prevent “intra-species recycling”, i.e. the feeding of poultry waste to chickens, or pork waste to pigs. As swill can, and has always, contained pork wastes, swill-feeding legislation in the EU would have to permit this practice, as in the East Asian states described.

Food waste as animal feed: beyond pigs and beyond the EU

This study has focussed on the potential to reduce the land use of EU pork through recycling food waste as swill because of the current EU ban on swill, and because pigs are an omnivorous species with a long history of food waste recycling. Pigs are, however, not the only animal that can consume diets containing food waste. A number of studies have trialled food waste diets for poultry (Boushy et al., 2000, Ruttanavut et al., 2011), fish (Cheng et al., 2014), and ruminants (Angulo et al., 2012, Ishida et al., 2012, Summers et al., 1980), and the environmental gains of food waste feeding for these species represents an area for further work.

The results of this study are also relevant to other parts of the world. We consider briefly here the state of swill feeding in the two largest producers of pork: China and the United States of America (together 55.3% of world production (FAO, 2014a)). By 2001, swill feeding had been banned in more than 18 US states (Spinelli and Corso, 2000, Stuart, 2009), and across the USA swill-feeding has seen a similar historical trajectory as in the EU: the growth of modern industrialised production systems and availability of abundant grain feed led to a decline in the number of pigs fattened on swill from 130,000 in 1960 to less than 50,000 in 1994 (Westendorf, 2000b). By 2012, 95% of US food waste was sent to landfill (US Environmental Protection Agency, 2012). However, swill has recently received renewed interest in the USA. The US Food Waste Challenge, launched in 2013, aims to promote the recycling of food waste, including the use of food waste as animal feed (HLPE, 2014).

In China the use of swill has remained common, and is one of the six highest-volume food waste disposal options nationally (Hu et al., 2012). Swill plays a particularly important role in backyard pig production (30–40% of pigs), where its low cost contributes to smallholder profitability (McOrist et al., 2011). As the Chinese pig industry becomes increasingly industrialised, however, there is a risk that the use of swill may decline (Fairlie, 2010), increasing the environmental impact of pork production, unless systems are put in place to produce swill for industrial pig producers. Centralised food waste recycling may be facilitated by the concentration of many industrial pork producers around densely populated urban areas (Gerber et al., 2005), thereby lowering transport costs and facilitating urban food waste recycling.

Conclusions

As the demand for livestock products grows over the next half-century, we must identify strategies to reduce the environmental footprint of current systems of meat production. One strategy is the promotion of low-impact animal diets. Food waste, when heat-treated appropriately, as in the centralised food waste recycling systems of Japan and South Korea, can be a safe, nutritious form of animal feed. In this study we quantified the potential for swill to reduce the land use of EU pork production. While swill feeding is not a substitute for efforts to reduce food waste, our results suggest that changing EU legislation to promote the use of food waste as swill could substantially reduce the land use impacts of EU pork production. These environmental benefits can be achieved while improving the profitability of many farming businesses and delivering high quality pork products. Similar benefits may be seen in other parts of the world, where swill feeding is currently uncommon or illegal.

Funding statement

E.K.H.J.zE is funded by BBSRC grant BB/J014540/1. BP is funded by the Zukerman research fellowship at King’s College Cambridge.

Table A1

Food waste recycling in Japan, from 2001 to 2009, given as the percentage of food waste recycled for all purposes, including the production of Ecofeed, compost, and anaerobic digestion. Retail figures are a mean of wholesaler and retailer food waste recycling rates. Household food waste is not recycled in Japan, but is in South Korea (Stuart, 2009). Modified from (MAFF, 2012b, Takata et al., 2012).

Food waste source	2001	2002	2003	2004	2005	2006	2007	2008	2009
Manufacturing (%)	50	60	65	65	76	76	77	93	93
Retail (%)	23.5	26.5	30	29	42	44	45	48	47
Catering and food service (%)	9	8	11	12	14	16	16	13	16

Table A2

Classification of food wastes under the Ecofeed certification scheme. To be certified, at least 5% of the entire feed must be “promoted” food wastes, with at least 20% of the total feed made up by a combination of both types of food waste. Adapted from Sugiura et al. (2009).

Type of food waste	Example
Ordinary	Distillery waste, beet pulp, rice bran, wheat bran, soybean dregs (excluding imported soybean dregs)
Promoted	Plate scraps, noodle debris, bread crumbs, cake crumbs, gluten debris, bean curd, mushroom-growing bed waste, sake lees, rice vinegar lees, tea dregs, squeezed fruit waste, coffee waste, cacao grounds, dairy plant wastes, frozen food plant wastes, cooking waste, waste oil, waste boxed lunches

Table A6

EU pork production statistic: summary of data listed in Tables A3, A5, and A7 in the electronic supplementary material. These statistics are based on a weighted mean of production statistics from 12 EU member states (representing >92.9% of EU industrial pork production) and representative diets from 5 EU member states (>64% of EU industrial pork production). Dietary ingredients do not sum to 100% because feed ingredients can belong to multiple groups (e.g. wheat bran is both a cereal and a co-product).

Summary statistics from Tables A3, A5, and A7	Value
EU industrial pork production statistics
Weight at slaughter (kg)	114.8
Feed conversion ratio (kg feed/kg pig produced)	2.83
Piglets weaned/sow/year	25.1
Ratio sows:slaughter pigs	1:23.6
EU industrial pork diet ingredients in percent (standard deviation)
Cereals (e.g. oats, corn, wheat)	71.4 (±8.5)
Soybean meal	9.5 (±1.6)
Agricultural co-products (excluding soybean meal, e.g. rapeseed meal, wheat bran, molasses)	14.8 (±5.3)
Vitamin and mineral supplements	3.0 (±1.0)
Other (e.g. peas, cassava, amino acid supplements)	5.0 (±6.0)

Table A10

Fresh weight and dry matter content of EU food wastes in 2015. The EU food waste figures (EC, 2010) assume that food waste was produced in the same proportions in 2015 as in 2006 (ie. households and retail wastes, for example, made up 42% and 5% of food wastes in 2015, as in 2006). The 39.2% figures (second row) represent the proportion of food wastes potentially recyclable as animal feed.

	Manufacturing food waste	Retail food waste	Catering food waste	Household food waste
EU food waste (tonnes)	38,786,404	5,122,616	14,343,324	43,029,974
39.2% of food waste recycled as feed (tonnes)a	15,204,271	2,008,065	5,622,583	16,867,750
Dry matter content (%) of food waste (95% CI)	29.8 (24.7–36.8)	23.3 (18.0–30.4)	21.5 (20.1–23.0)	26.0 (24.3–27.6)
Food waste recyclable as feed (DM tonnes)	4,530,873	467,879	1,208,855	4,385,615

The figure for the percentage of manufacturing food wastes available for recycling excludes the 3 million tonnes of former foodstuffs which are already used for animal feed in the EU.

Table A11

Parameters used in land use calculations (Eq. (S2)).

Parameter	Value (95% confidence intervals)
LU_kgporkEU	8.5 million ha
coef_FW	−1.06
FWprop_household	0.084 (0.079–0.089)
FWprop_manufacturing	0.087 (0.070–0.104)
FWprop_retail	0.009 (0.007–0.011)
FWprop_catering	0.023 (0.022–0.025)
FWprop_currentlegislation	0.011 (0.009–0.014)