Efficiency and Carbon Footprint of the German Meat Supply Chain

Article Cite This: Environ. Sci. Technol. XXXX, XXX, XXX−XXX

pubs.acs.org/est

Efficiency and Carbon Footprint of the German Meat Supply Chain Li Xue,†,‡,§ Neele Prass,‡ Sebastian Gollnow,∥ Jennifer Davis,⊥ Silvia Scherhaufer,∥ Karin Ö stergren,⊥ Shengkui Cheng,† and Gang Liu*,‡ †

Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 100101 Beijing, P. R. China SDU Life Cycle Engineering, Department of Chemical Engineering, Biotechnology, and Environmental Technology, University of Southern Denmark, 5230 Odense, Denmark § University of Chinese Academy of Sciences, 100049 Beijing, P. R. China ∥ University of Natural Resources and Life Sciences, Vienna (BOKU), Department of Water-Atmosphere-Environment, Institute of Waste Management, 1190 Vienna, Austria ⊥ RISE Agrifood and Bioscience, SE 402 29 Gothenburg, Sweden

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‡

S Supporting Information *

ABSTRACT: Meat production and consumption contribute significantly to environmental impacts such as greenhouse gas (GHG) emissions. These emissions can be reduced via various strategies ranging from production efficiency improvement to process optimization, food waste reduction, trade pattern change, and diet structure change. On the basis of a material flow analysis approach, we mapped the dry matter mass and energy balance of the meat (including beef, pork, and poultry) supply chain in Germany and discussed the emission reduction potential of different mitigation strategies in an integrated and massbalance consistent framework. Our results reaffirmed the low energy conversion efficiency of the meat supply chain (among which beef was the least efficient) and the high GHG emissions at the meat production stage. While diet structure change (either reducing the meat consumption or substituting meat by edible offal) showed the highest emissions reduction potential, eliminating meat waste in retailing and consumption and byproducts generation in slaughtering and processing were found to have profound effect on emissions reduction as well. The rendering of meat byproducts and waste treatment were modeled in detail, adding up to a net environmental benefit of about 5% of the entire supply chain GHG emissions. The combined effects based on assumed high levels of changes of important mitigation strategies, in a rank order considering the level of difficulty of implementation, showed that the total emission could be reduced by 43% comparing to the current level, implying a tremendous opportunity for sustainably feeding the planet by 2050.

1. INTRODUCTION

For example, the animal production sector occupies about 65% of the arable agricultural land in Europe,6 and also contributes to about 12−17% of the total EU-27 GHG emissions.7,8 While methane from enteric fermentation is the main source9−13 (approximately 65% of the total GHG emissions, with a time horizon of 100 years, of this sector14), methane and N2O emissions from manure management also

The past decades have witnessed an increase of meat production by 15.8% between 1990 and 2016 in the European Union (EU 28), and this increase is expected to continue until 2025.1 The meat consumption in EU 28, on a per capita level, will increase from 63.4 kg in 2010 to 65.8 kg in 2020.2 Such a growing trend of meat consumption leads to aggravated environmental burdens of the animal production sector,3 because meat production requires more natural resources (land, water, and energy) and emits more greenhouse gases (GHGs) than grain-based food.4,5 © XXXX American Chemical Society

Received: November 8, 2018 Revised: March 8, 2019 Accepted: March 13, 2019

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DOI: 10.1021/acs.est.8b06079 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

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Environmental Science & Technology

Figure 1. System definition of the German meat supply chain and its associated energy use and emissions.

contribute significantly with about 10%−18% of the sector’s total emissions.10,15−17 Although the GHG emissions from animal production in total declined by over 20% from 1990 to 2007 in the EU,18 mainly due to the collapse in Eastern Europe, the establishment of the milk quota, and the implementation of the Nitrates Directive and consequent reduction in use of nitrogen fertilizer,19 further reduction of GHG emissions in this sector would still be important for EU’s ambitious climate target in an increasing climate constraint future. The environmental impacts of the animal production sector could be mitigated via different approaches throughout the meat production and consumption chain.

Germany is the most populated country in Europe, with a population of 81.7 million in 2015.30 Germany was ranked 23rd in meat consumption per capita (87.5 kg) in the world in 2013, more than double of the world’s average (41.9 kg/cap).31 This number has stagnated in the past decade (2005−2016), but the consumption structure has changed: per capita consumption of beef and poultry have increased by 14.6% and 18.1%, respectively, while that of pork has decreased by 8.6%. To meet the huge demand of meat and meat products, 55% of the agricultural land in Germany is used for cereal cultivation, and in the total cereals production about 57.4% is used for feeding cows, pigs, and chickens.32 Germany has become the biggest producer of meat (18.3% of total production) in the EU in 2016.33 Meanwhile, Germany is also experiencing a high level of food loss and food waste along the entire food supply chain (about 18 Mt), accounting for almost one-third of the current food consumption.34 Households make up the largest share of food waste with 61%.35 While the major types of food waste in household are vegetables, fruits, and cereals, meat does present 11.8% of the total food waste.36 Policies and regulations have been implemented at both the EU and Member States level for the management and treatment for food waste. For example, Regulation (EC) 1069/2009 and Commission Regulation (EU) 142/2011 of the European Parliament address specifically animal waste or animal byproducts treatment,37 and the EU Waste Framework Directive (2008/98/EC)38 has laid down a five-step waste hierarchy on biowaste management. Recently, in line with the 2030 Sustainable Development Goals (SDGs) Target 12.3 set by the United Nations,39 the revised EU Waste Framework Directive (2018/851/EC) calls on Member States to reduce food waste along the food supply chain.40 In Germany, the national Waste Management Act (KrWG) was enacted in 2012, which requires that biowaste should be collected separately from January 1, 2015 for circular economy promotion.41 The Biowaste Ordinance (2017)42 also regulates the collection and treatment of biowaste in more detail. In this work, using Germany as an example, we aim to map the efficiency of a national whole meat supply chain and inform its decarbonization strategies. Such a mapping could add value to the literature because most existing studies43 on food loss and waste quantification (including for Germany) concentrate

• On the production side, GHG emissions can be mitigated through improved animal productivity, reduced enteric methane production through adapted breeding and feeding, covering of manure stores,20 as well as limiting manure application rates to plant requirements21,22 and local conditions.21 • From a consumption perspective, dietary change would have great effect on the reduction of GHG emissions.23 For example, it was reported that a potential GHG reduction of 25% per capita in the UK could be achieved by shifting the current U.K.-average diet to the vegetarian diet (replacing meat by plant-based alternatives).24 Hallström et al. (2015)25 came to a similar conclusion based on a review of the sustainable food consumption literature. • In addition, reducing meat loss and waste is often considered as a strategy to help reduce GHG emissions as well because food waste leads to both indirect embedded emissions in production, processing, distribution, and consumption, as well as direct emissions in waste disposal.26 However, such a whole chain efficiency of meat production and consumption and meat waste related GHG emissions reduction potentials have been less understood and characterized in the literature.27,28 It was reported that meat waste related GHG emissions were estimated to be as high as 186 Mt CO2-eq in Europe, or nearly 16% of the entire food supply chain emissions.29 B


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Environmental Science & Technology on individual stages only (mainly households44,45) and only a few studies have covered the whole agrifood supply chain or provide a higher resolution of insights on a specific product. This would also enable an integrated analysis of the environmental impacts of different types of mitigation strategies, such as process and technology efficiency, waste reduction and valorization, trade pattern change, and dietary shift, and thus inform future policy making in climate change mitigation of the animal production and meat processing sector.

previously used is now disposed of as waste, such as incineration.46 The animal byproducts industry handles all the raw materials that are not directly destined for human consumption. The Regulation (EC) 1069/2009 and Commission Regulation (EU) 142/2011 of the European Parliament govern the use and disposal routes permitted.37 Animal byproducts are divided into three categories according to the level of their risk. Category 1 byproducts (Cat 1) refer to materials of high risk, while Category 2 byproducts (Cat 2) and Category 3 byproducts (Cat 3) are with medium and lease risk, respectively.37,47 It is assumed that edible animal fat (EAF) is a part of Cat 3. The categorization determines the processing and possible utilization options for the material. The detailed definition of byproducts is in SI section 1. According to these risk levels-based categories of meat byproducts, we assumed that animal byproducts occurred at the production, slaughtering, and processing stages. All dead cattle bodies (in rearing) are classified as Cat 1, and dead pig, chicken, turkey, duck, and goose are considered as Cat 2. The slaughtering stage covers all the three categories, and the meat processing stage generates only Cat 3 of animal byproducts (SI Figure S1). In addition, meat waste refers to meat discarded or spoiled during the retailing and consumption stages due to expiration, negligence, and other stakeholder or consumer behaviors. It is assumed that such kinds of meat waste are collected by the municipal waste management associations and thus further treated by either incineration, composting, or anaerobic digestion. 2.2. Data Collection and Model Quantification. The dry matter (DM) balance and related energy and emissions of the whole system were calculated based on the MFA principles. Primary data were collected from German statistical databases (e.g., Statista), industry reports, and scientific articles. Several federal organizations associated with agriculture processes (e.g., Federal Ministry of Food and Agriculture, BMEL), biodegradable waste, and food waste were targeted. The reference year for data collection is 2016. The starting point of the mass flow analysis was animal production in live weight equivalent, which was calculated based on the carcass weight data obtained from BMEL (SI Table S4). Two markets (live animals and meat products) and corresponding import and export flows were quantified based on trade statistics. The three categories of animal byproducts processed into protein and fat for various further uses were calculated by transfer coefficients. The energy within the mass was calculated based on their corresponding energy coefficients (caloric value). The data sources and calculation processes are detailed in the SI Sections 2.1 (mass) and 2.2 (energy). The GHG emissions from each stage were calculated based on emission factors of meat reported in the literature. The environmental impacts and benefits of rendering byproducts and meat waste treatment were also considered. For food (mainly EAF can be produced from byproducts Cat 3), feed, biodiesel production, and composting, the substitution of palm oil, soymeal, fossil fuel, and fertilizer, respectively, were modeled. We replaced palm oil based on the caloric content, while soymeal based on the protein content since for feeding energy more local feed can be used than soymeal, such as cereals, grass, potatoes, associated with lower emissions. The efficiency of food and feed production was assumed at 33%.48 For incineration and biogas production, heat and electricity

2. MATERIALS AND METHODS 2.1. System Definition. 2.1.1. Meat Categories and Meat Supply Chain. Three major categories of meat products were included: beef, pork, and poultry (including chicken, turkey, duck, and goose). We used a Material Flow Analysis (MFA) approach to quantify the dry matter (DM) balance of meat and meat products, which includes animal production, slaughtering, processing, retailing, consumption, trade of animal and meat products, and byproducts rendering and waste management (Figure 1). Specifically, various byproducts and waste treatment routes were considered, such as composting, incineration, biogas production, biodiesel production, industry use (e.g., soap and pharmaceuticals production), animal feeding, and food use (e.g., edible animal fat like lard used as a frying agent). 2.1.2. Energy and Emission Accounting Framework. The energy layer was then additionally calculated based on the mass layer, containing both the gross energy of biomass itself and the process energy (PE) used to process the goods (e.g., fossil fuel and electricity). Further, the emissions layer encompasses the consequent GHG emissions along the meat supply chain, which includes all emissions from animal production (those related to feed production, enteric fermentation, manure management, N2O emission, fertilizer production, and cultivation of organic soils) and related to process energy use in other stages. The trade-embodied emissions for live animals and meat products were calculated by considering the production and processing emission intensity of the trading countries. Due to lack of data and large variation for animals as well as meat products, energy use for transportation and related emissions in all stages were not considered; nor were packaging-related emissions in the meat processing accounted. There are two types of emission accounting approaches, depending on how the international trade of live animals and meat products was considered. A territory-based accounting includes emissions occurring within the German national boundary only, while a consumption-based accounting encompasses emissions from domestic final consumption of meat, and thus those caused by the production of its imports elsewhere. We have tested both accounting approaches in our analysis. The consumption-based emissions were presented in our results aiming to reveal the efficiency of the meat supply chain and explore mitigation options linked to consumption. The territory-based accounting results were detailed in the Supporting Information (SI) section 5.4. 2.1.3. Definition of Meat Byproducts and Waste. Byproducts in the meat supply chain include edible materials such as tongue, edible fats, and casings, as well as hides/skins and other nonfood materials. In recent years, especially because of bovine spongiform encephalopathy (BSE), the value of byproducts has reduced substantially and much of the material C


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Environmental Science & Technology Table 1. Description of the Individual Scenarios (PE = Process Energy) reduction (%) strategies

symbols

detailed assumptions

low

medium

high

production efficiency process optimization

S1 S2a S2b S2c S3a S3b S3c S4a S4b S4c S5a S5b S5c S5d S5e S5f S5g S6 S7 S8

production emission intensity slaughtering PE processing PE slaughtering and processing PE slaughtering byproducts processing byproducts slaughtering and processing byproducts retailing waste consumption waste retailing and consumption waste animals import from the top 3 GHG emission partner countries animals export to non-EU countries S5a + S5b meat products import from the top 3 GHG emission partners meat products export to non-EU countries S 5d + S5e S5c + S 5f meat consumption beef consumption offal consumed as food less thrown away

5 5

10 10

20 20

5

10

20

10

25

50

25

50

100

10 5 10

25 10 25

50 25 50

food waste reduction

trade pattern change

diet structure change

live animals or meat products, and vice versa.): For import change scenarios we considered the import of live animals and meat products from the top 3 GHG emission partners and their corresponding GHG emission intensities; for export scenarios we considered the export of these products to nonEU 28 countries (decreased export would lead to less meat produced domestically), but the substitutes of the reduced imports (would lead to more meat produced in Germany) from these countries were not considered. 2.3.5. Diet Structure Change. Three types of dietary change were considered: (i) The first one was a diet with less meat consumption. As the study aims to address a consumptionbased approach (the mass of meat consumption stays the same in all scenarios), the reduced meat consumption needs to be replaced by other protein sources. We selected soybeans and nuts as the substitute (while keeping the energy intake constant) and considered their whole life cycle GHG emissions. The consumption structure, energy equivalent of soybean and nuts, and emission intensity data were detailed in the SI Table S34. (ii) The second one was substituting beef by pork and poultry, while the total energy intake remained constant and the ratio of pork and poultry consumption was kept unchanged. A potential decrease of 10%, 25%, and 50% for total meat consumption and a reduction of 5%, 10%, and 25% for beef consumption were assumed, since the German Nutrition Society (DGE) has reported that Germans eat twice as much meat as is recommended from a nutritional standpoint.50 (iii) The third scenario considered that less offal was thrown away and instead could be consumed as food. This would result in a reduction of meat consumption, and we assumed a reduction potential of 10%, 25%, and 50% when keeping energy intake constant. The baseline scenario was the current emissions based on the German meat supply chain in 2016. We first developed individual scenarios as detailed in Table 1 using a one-factorat-a-time approach. The consumption was assumed to be constant for all the scenarios except the three addressing diet structure change (S6, S7, and S8). We then calculated

substitution were considered. More details on emission accounting can be found in the SI Section 2.3. 2.3. Scenarios Development. Different scenarios were developed to quantitatively investigate the emission reduction potentials of different mitigation strategies. These strategies were grouped into five categories as elaborated below: 2.3.1. Production Efficiency. The reduction of GHG emission intensity of production could be achieved, for example, by increasing the efficiency of animal feed production. Previous estimate shows that emissions could be reduced by 17% with improved manure management and energy saving equipment,9 thus scenarios were set for a decreased production emission intensity of 5%, 10%, and 20%. 2.3.2. Process Optimization. Improving the process efficiency in meat slaughtering and processing would mean less meat cut off and byproduct generation. The technology efficiency improvement in, for example, cooling could reduce process energy. According to BMEL,33 the process energy used in the meat processing sector has already decreased by 16.5% between 2006 and 2015. A reduction potential of 5%, 10%, and 20% of energy use was assumed. 2.3.3. Food Waste Reduction. The reduction of avoidable food waste (partly consumed and entirely uneaten food) is already targeted by national food waste prevention campaigns and EU regulations (e.g., the adoption of SDG Target 12.3). If meat can be prevented from being wasted at the consumer stage, then less meat needs to be produced. The reduction of meat waste was also considered to take place in the retailing stage. It was assumed that a maximum of 50% of edible meat waste in households, food services, and retailing can be reduced, because it is reported that approximately 50% of food waste at households is avoidable.49 2.3.4. Trade Pattern Change. Trade patterns matter for emissions of the German meat supply chain, especially with the consumption-based accounting approach, because of the varying emission intensity in different countries. The import and export change scenarios were developed individually (The import remains unchanged when reducing or halting export of D


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Figure 2. (a) Mass balance for the meat supply chain in Germany in 2016, on a dry matter basis; (b) byproducts and meat waste treatment; and (c) distribution of protein and fat from animal byproducts, EAF: edible animal fat.

poultry (24% and 29%) and beef (17% and 13%). As to the animal trade, poultry and cattle were exported in large amounts, whereas the import of pig was higher than export. For the trade of meat products, however, a higher import than export can be seen for beef and poultry, and it is the opposite for pork. Altogether, the self-sufficiency for beef, pork, and poultry was about 159%, 170%, and 119% (all on a DM basis), respectively. Figure 2a also shows that the cumulative byproducts and meat waste along the cattle, pork, and poultry supply chain accounts for 74%, 59%, and 56% of the total mass flow in domestic animal production, respectively. The pork byproducts appeared the largest at the animal production, slaughtering, and processing stages, accounting for 59%, 50%, and 67%, respectively, of the total meat byproducts at each sector. All the byproducts made up 44% of the meat entering the slaughtering stage. The waste (including the inedible parts/ unavoidable food waste) from retailing and consumption stages combined made up roughly 27% of the meat products for human consumption. 3.1.2. Waste Management. Figure 2b illustrates the share of different byproducts and waste along the supply chain of

potentials of assumed low, medium, and high levels of reduction for each strategy. In the end we built a combined scenario to discuss the combined effects of some of these mitigation strategies that have more influence on emissions, based on the assumed high levels of changes in Table 1 in a rank order for assumed level of difficulty of implementation (roughly from technology options down to economic measures to human behaviors, SI Table S3). The consequences of these scenarios on larger socioeconomic systems, e.g., changes of emissions in other countries due to trade pattern change, are not considered.

3. RESULTS AND DISCUSSION 3.1. Mass and Energy Balance of the German Meat Supply Chain. 3.1.1. Characteristics of the Mass Balance. The mass flow (all numbers on a DM basis) of the German meat supply chain shows that 2516 kt of meat (CW, including bones) was produced domestically before slaughtering and 1634 kt ended up for human consumption from the retailing sector in 2016 (Figure 2a). Pork made up the biggest share in the production as well as consumption, both of which accounted for about 59% and 58%, respectively, followed by E


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Figure 3. (a) Distribution of GHG emissions in the meat supply chain; (b) LW (total live weight, DM basis) production and GHG emissions in animal production. They are the reference scenario (data for 2016).

In terms of PE (e.g., for heating and lighting), the highest value was in the animal production sector (2.2 × 105 TJ) with a share of 94%, followed by meat processing (5.9 × 103 TJ, 2.5%) and slaughtering (4.2 × 103 TJ, 1.8%). The cumulative PE was 2.3 × 105TJ, which was about 41% of the feed used or roughly three times of the energy equivalent of total byproducts and meat waste. 3.1.4. Data Quality and Uncertainty. This analysis relied on data from multiple sources and various assumptions which unavoidably leads to uncertainties. A qualitative uncertainty evaluation of the data used and corresponding mass flow, energy flow, and GHG emissions were summarized in the SI Figures S8−S10 based on three levels (low, medium, and high) of uncertainty. Data taken directly from governmental statistics (e.g., the amount of CW produced and the trade values of live animals and meat products) was deemed to have low uncertainty. The statistical data can provide an overall picture of the whole country, although they are not always accurate due to data coverage and collection methods. The slightly varying coefficients data found in several references (e.g., meat waste rate in retailing and the energy equivalent of manure) were categorized as medium uncertainty. If only a single reference was identified and the representativeness is unclear (e.g., the ratio of meat consumption in household and out-ofhome and the treatment of meat waste), then the data uncertainty was considered to be high. Despite the limitations and data gaps mentioned above, the entire model was assessed to be sufficiently robust to reveal the whole chain efficiency of the German meat supply chain. The mass balance allowed for cross-checking between mass, energy, and nutrient (e.g., protein and fat). We compared the data of meat for human consumption between results in this study and the numbers reported by BMLE. For example, the calculated value (722 kt) for beef and pork (2829 kt) were within an acceptable range of 10% compared to the BMLE estimate (793 kt, 2974 kt). 3.2. GHG Emissions of the German Meat Supply Chain. Figure 3a shows that the majority of GHG emissions were found in the production sector either for the total meat production (64%) or for individual meat category (65%, 68%, and 45%, respectively, for beef, pork, and poultry) based on the consumption-based accounting. The second largest contributor was the emissions embodied in the import of live animals and meat products, making up 34%, 27%, and 46%, respectively, of the total emissions for the beef, pork, and poultry supply chains. This can be explained by the relatively large amount of

each meat category to different treatment sectors. At the animal production stage, dead cattle were mostly incinerated (66%) while dead pigs and poultry mainly went for industry use (63%). At the slaughtering and processing stages, most cat 3 were used for feed production, and most cat 2 went for industrial use and biodiesel production. Due to lack of data, most of the meat waste from retailing and consumption was assumed to be mostly incinerated, followed by composting and anaerobic digestion. In total, the majority of byproducts and waste for beef was processed in feed production (33%) and incineration (30%), while for pork and poultry were in feed production (37% and 36%, respectively) and industry use (27% and 23%, respectively). In terms of protein or fat of each byproduct category, the beef supply chain did not generate category 2 byproducts, and the pork and poultry supply chains did not produce category 1 byproducts.51 Figure 2c shows that the protein from category 1 went to incineration plants, protein from category 2 ended up for industry use, and most protein from category 3 was used as feed ingredients. Fat from category 1 and category 2 were mainly for biodiesel production, and most fat from category 3 went to industry use. 3.1.3. Characteristics of the Energy Balance. The largest energy flows of the whole system was related to the production, especially for feed energy flows with 5.6 × 105 TJ in total (SI Figure S2). The energy equivalent of manure accounted for 21% of all feed inputs. As for the individual animal category, the energy equivalent of meat after slaughtering was 10%, 15%, and 9% of the feed input for beef, pork, and poultry, respectively. When it comes to consumption, the energy equivalent of beef, pork, and poultry entering retailing for human consumption represented only 1.3%, 2.1%, and 1.7%, respectively, of the feed used for animal production, indicating an overall low energy conversion efficiency of the meat supply chain (out of which pork was comparatively the most efficient and beef was the least). In terms of byproducts, the energy equivalent of slaughtering and processing byproducts together comprised of 84% of the energy of animals entering slaughtering. In addition, the energy equivalent of meat waste from retailing and consumption processes totaled to 2.9 × 103 TJ (majority in consumption), accounting for 27% of the energy equivalent of meat input to the retailing stage. In total, the energy equivalent of all the byproducts and meat waste represented 14% of the total feed inputs. F


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Figure 4. (a) Different scenarios of GHG emissions in a consumption-based accounting. Negative values mean the reduction percentage compared to the reference scenario, and positive values mean the increase percentage relative to the baseline; (b) the combined scenario result of GHG emissions reduction. S0 is the baseline scenario. The numbers along the vertical arrows represent the absolute amount of GHG emissions reductions and the shares in the total reduction, respectively. SA = S2c, SB = S2c + S4c, SC = S2c + S4c + S5f, SD = S2c + S4c + S5f + S8, SE = S2c + S4c + S5f + S7 + S8, SF = S1 + S2c + S4c + S5f + S7 + S8; (c) net environment benefits from rendering of meat byproducts and meat waste treatment. We assumed food production (mainly EAF) replaces palm oil, feed production replaces soymeal, and biodiesel production replaces fossil fuel.

net trade of live animals and meat products and the varying emission intensity between Germany and trading partners. Then it was followed by emissions from slaughtering (1.1%), processing (1.06%), consumption (1.05%), and retailing (0.5%) stages. In terms of the GHG emissions of each meat category during production, the largest was from the production of beef (48%), followed by pork (46%), and poultry accounted for the least (6%). However, when it comes to the amount of meat produced of each type, about 60% of the LW (DM basis) produced came from pig, followed by poultry (24%), and cattle had the smallest share (Figure 3b). This indicates again the lower efficiency of beef production comparing to pork and poultry. 3.3. Scenarios for GHG Emissions Reduction. Figure 4a shows the percentage change of the total GHG emissions of the whole meat supply chain under different scenarios (as detailed in Table 1) with respect to the reference scenario in

2016. Most scenarios show a gradually increasing reduction potential under different levels of changes (from low to medium to high). The changes of the amount of GHG emissions under different levels, and the changes of total meat CW produced in different scenarios are detailed in the SI Figures S3−S5. The greatest difference to the base scenario was the reduction of meat consumption by 50% (S6), which resulted in a 32% reduction of the GHG emissions (consumptionbased). A diet to a higher amount of offal with less needs to be thrown away (S8) showed the second largest reduction potential or 14% reduction of the original GHG emissions, followed by reducing GHG emissions intensity in production (S1) with a reduction of 13%. In the case of reducing retailing and consumption waste (S4c) by 50%, a reduction of 2747 kt GHG emissions can be achieved. Halting the import of meat products from the top 3 GHG emission partners and the export to non-EU 28 countries (S5f) would also reduce the G


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meat production54 (among which the beef production is the least efficient21,55). This implies that cattle rearing shall be preferably addressed with mitigation strategies (accounting for almost half of total emissions of meat production) and especially enteric fermentation of the digestive system. Improving feed digestibility could be a part of the solution, which not only could contribute to the growth of feed intake efficiency, but also could lower the amount of manure excreted. However, technology efficiency improvement and process optimization are also important strategies for GHG emissions reduction. Reducing meat consumption, in parallel to making meat production more sustainable, would have profound effect on the GHG emissions. Per capita meat consumption in Germany has decreased from 100.4 kg in 1990 to 87.8 kg in 2016 by 12.5% over a period of 26 years,33 due to an increasing number of vegetarians and a general interest among many to shift to a healthier diet. However, the current level is still twice as high as the world’s average and the recommended meat consumption by the German Nutrition Society (DGE).50 A further reduction is necessary but also challenging. An alternative is to substitute beef with pork and poultry; in fact, poultry has become more popular in Germany in recent years. Furthermore, some edible parts of the animal byproducts (e.g., offal, tongue, and casings) are rarely consumed at present due to low demand as food. However, changing marketing strategies, converting them to more appealing food, and raising awareness about the value of such products would provide a great potential to substitute meat consumption and further lower the total GHG emissions of the meat chain. Eliminating the meat waste at the retailing and consumption stages could also achieve a high reduction of emissions. For example, a 25% reduction of retailing and consumption meat waste would almost have the same emissions reduction potential as reducing the total meat consumption by 10%. The majority of meat waste was found at the consumer stage (392 kt in 2016, on a DM basis), especially in the households (259 kt in 2016, on a DM basis). Households can be the focus and many prevention measures are possible (e.g., freezing food leftovers, cooking new meals from meat leftovers, cooking soups with bones and cut-offs, and creating shopping lists to avoid buying food which is not needed). Furthermore, meat waste from out-of-home consumption (e.g., restaurants or hotels) and the retailing sector should not be overlooked, which would be suitable for food donation and redistribution to social organizations. For example, the “Gadda law” of Italy designed to fight against food waste has come into force in 2016, which makes it easier for businesses to donate unwanted food to people in poverty, and helps raise awareness of consumer to waste less food.56 Our results also show that halting the import of meat products from the top 3 GHG emission countries and the export of meat products to non-EU countries would contribute to reducing the GHG emissions in a consumption-based accounting (while emissions increased in a territory-based accounting; SI Figures S6 and S7). But this would also mean that either the production in other countries needs to increase or the consumption in other countries needs to decrease to hold the overall consumption, and what needs to be considered is whether it would be replaced by a system with more emissions. Furthermore, since Germany plays a key role in the European market of animal and meat products, it is

total emissions by 6%.When beef consumption was reduced by 25% (S7), although the emissions from pork and poultry supply chains would increase by 2−3% due to increased consumption of pork and poultry, the total GHG emissions would still decrease by 7% relative to the base scenario. Similarly, halting the import of live animals (S5a) from high intensity emission countries (with the increase of live animal production domestically) would reduce the total emissions by 1% slightly. The energy use reduction by 20% at the slaughtering as well as processing stages (S2c) would also result in a reduction of GHG emissions (117 kt; or 0.4% of the total). However, when halting the import of meat products (S5d) from high intensity emission countries (with the increase of meat production domestically) would increase the total emissions by 2% slightly. Figure 4b shows the combined effects of the important emissions mitigation strategies under the combined scenario described in the SI Table S3. The biggest change (proportionally as 26%) of emissions occurred when offal thrown away in slaughtering stage was reduced by 50% and consumed as food (less animals need to be produced to get the same amount of animal energy consumed) (SD). The second largest reduction of emissions could be seen in the case of reducing meat waste in retailing and consumption stages by 50% (SB), with a share of 23% in the total reduction of emissions, followed by reducing the emission intensity at the production stage by 20% with a share of 22%. Halting the import of meat products from the top 3 GHG emission countries and the export to non-EU countries would also contribute to the reduction of emissions (18%). In total, a combination of process optimization, radical meat waste reduction, trade pattern change of meat products, radical diet structure change with less beef and substituting meat by edible offal, and reducing the emission intensity of meat would largely reduce the climate impacts by 43% relative to the base scenario. Figure 4c shows the net environment benefits of the rendering of meat byproducts and waste treatment by considering credits from the substitution of resources and energy (e.g., soymeal, electricity, and heat). The total GHG emission saving was 1425 kt. The largest came from the feed production with a reduction of 806 kt CO2-eq, accounting for 57% of the total saving, followed by biodiesel production (561 kt, 39%). Although these emissions savings were low (5.2%) compared to the whole supply chain climate impacts, they almost have the same net environmental benefits as reducing meat waste from retailing and consumption stages by 25%. 3.4. Policy Implications. Our mapping of the mass and energy flows of the German meat supply chain provides a detailed understanding of the whole system efficiency of meat products and the generation and destination (e.g., valorization and recycling) of different meat byproducts and waste. The study also presents the comparison of the effects of different GHG emission mitigation strategies based on combined scenario analysis covering production efficiency, process optimization, food waste reduction, trade pattern change, and diet structure change. Such a model framework can be used as a proxy for other countries and agrifood products as well. Although we considered only the climate change impact in this study, other environmental (e.g., water), economic, and social (e.g., animal welfare) implications could also be analyzed and discussed based on the physical mapping. The results reaffirmed the low energy conversion efficiency of the meat supply chain,52,53 and the high GHG emissions at H


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questionable whether a decreasing export would affect the German economy. The meat byproducts rendered can be further used in different sectors. Our results show that most byproducts go to feed production (47%), where protein and fat from Cat 3 are used as feed ingredients due to their nutritional and preservative properties. This is followed by industry use (31%), where fat is used as an ingredient to produce cosmetics, lubricants, and cleaning products. It is stated that 1 t of animal protein equates to 1.7 t of soybeans which stands for 0.66 ha of rainforest in Brazil.57 Using the protein for feed production would not only prevent wasting the high value protein, but also reduce the carbon and land footprint of meat. In addition, the EAF from Cat 3 that is fit for human consumption can reduce the demand of vegetable oil and thus land use for oil crop cultivation. What’s more, about 17% of all the meat byproducts that are unfit for human consumption go to biodiesel production which is less emission intensive than fossil fuels. Therefore, improving the efficiency of meat byproducts rendering and waste treatment is a straightforward yet important strategy to mitigate the climate change impacts of the entire meat supply chain.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.8b06079.

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Detailed description of the system definition, analytical solutions to the system, and data sources (PDF)

AUTHOR INFORMATION

Corresponding Author

*Phone: +45-65009441; e-mail: [email protected] or [email protected]. ORCID

Li Xue: 0000-0002-6802-6034 Gang Liu: 0000-0002-7613-1985 Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work is funded by REFRESH (Resource Efficient Food and dRink for the Entire Supply cHain), under the Horizon 2020 Framework Programme of the European Union (Grant Agreement no. 641933). The views and opinions expressed in this manuscript are purely those of the authors and may not in any circumstances be regarded as stating an official position of the funding agency.

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REFERENCES

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Efficiency and Carbon Footprint of the German Meat Supply Chain

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