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THE MEASURE OF MEAT:

EFFICIENCY OR ECOLOGY? By Ted Schettler | March, 2017 | White Paper

Summary:

A summary of this white paper is available here.

Meat consumption in countries around the world

Whether or not these can fulfill completely the anticipated meat demand is debatable, but they can be much more sustainable over the long term, providing abundant nutritious diets that will undoubtedly include more plant-based proteins [7]. Since the consequences of the choices we make among models differ, it’s worth considering how they will be assessed.

varies more than 30-fold, with the US near the top [1]. Our appetite for meat, estimated to be on average 137-250 pounds per person annually, exceeds nutritional recommendations [2, 3]. Meanwhile many people in other countries, some long-deprived of meat’s benefits, want more. Some estimates predict a near doubling of global demand by 2050, fueled more by economic than population growth [4, 5, 6]. This anticipated change in the diet of a dominant planetary species is unprecedented historically in time or scale. Implications for human, ecosystem and planetary health are profound.

Efficiency and economic return on investment are common metrics for evaluating alternative production systems. For example, the concepts of carbon efficiency—greenhouse gas emissions/kg meat—and feed conversion efficiency are liberally imbedded in studies of agricultural animal production. But, instead of focusing primarily on efficiency, others begin by asking first about the effectiveness of alternative livestock and crop production systems [8]. What do we want them to do? Produce the most product per dollar input? Rebuild soil? Promote biodiversity? Protect air and water quality? Increase resilience and buffering capacity against climate change, drought, or

Scaling up meat production can take different approaches. An industrial model features production efficiencies, intensive confined animal feeding operations, and externalized costs. Other approaches incorporate animal agriculture into more context-specific, integrated farming systems that are less destructive and help to restore soil quality, biodiversity, and ecosystem health.

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economic shock? Support community? If we were to clarify what we want agricultural systems to do, we would have a better idea of how to evaluate their costs and benefits.

varies—most growing animals are transferred to feedlots for more intensive finishing with mixtures of forages, silage, and grain—often supplemented with hormones and other growth-enhancing technologies. Cattle that are grass-fed throughout their lives—an extensive system—are a relatively small part of US beef production. In other countries, more extensive, grazing systems have been the norm. With transitions from extensive to more intensive systems, land use changes have very different impacts on climate-changing GHGs, water, and soil than in countries where beef production is already fairly intensive [9].

The growing demand for meat: at what cost? Estimating the cost of food is a contentious boundary problem. What to consider? The price to consumers at the time of purchase? Opportunity costs—what is not produced when something else is? All costs from a full life cycle perspective? In the more expansive analysis, animal agriculture entails costs associated with climate-changing greenhouse gas (GHG) emissions, loss of biodiversity, water consumption, pollution, and soil degradation. Although these vary with production methods, many are not accounted for in retail prices. Rather, they are externalized to the extent possible, putting them onto remote balance sheets of the public more generally.

In the US, the Environmental Protection Agency (EPA) attributes about 8.5 percent of all GHG emissions to agriculture (see figure 1) [10]. But, this is a strikingly incomplete picture. The five categories include only non-carbon dioxide emissions from the various sources. Rather than attributing CO2 emissions associated with agriculture here, the EPA’s inventory assigns those related to production of energy-intensive nitrogencontaining fertilizers to the industrial sector, carbon releases from agriculture-related land use change to a land-use change category, and carbon from on-farm energy use and food transport to the energy sector. They simply do not appear in the agricultural GHG accounting budget.

Climate and water impacts of meat production are illustrative examples.

Climate change, agriculture and meat: In the US most pork and poultry production involves confined animal feeding operations (CAFOs)—often referred to as intensive systems—for most of the animals’ lives. Beef production usually begins with cow-calf operations on pasture and forage. At some point after weaning—the timing

Figure 1: 2014 US Agriculture Greenhouse Gas Emission Sources (MMT CO2 Eq.) [11]

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Agriculture contributes three GHGs—carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Their turnover rates and global warming potentials (GWP) differ. For a 100-year timeframe, equivalent masses of CH4 and N2O have an estimated 23 and 300 times the GWP, respectively, compared to CO2 [12].

mature pastures can help reduce methane production [17, 18, 19, 20].

Manure management: Livestock manure is a double-edged sword. It contributes vital nutrients to soil and can improve soil quality and fertility. Soil fertilized with manure is more biologically active than soil fertilized by mineral fertilizers alone [21]. Manure can build the carbon storage potential of the soil and help remove carbon from the atmosphere [22]. As a natural source of nitrogen and other mineral inputs, manure helps avoid the need to produce, transport and use energy-intensive synthetic fertilizers.

Animal agriculture in the US accounts for about half of EPA’s limited inventory of agriculture-related GHG emissions, although globally livestock are responsible for about 14 percent of all GHG emissions [13]. In addition to methane releases from fermentation in ruminants, much of meat’s large climate footprint globally comes from the release of enormous amounts of carbon stored in forests and grassland soils converted to corn and soybean production for animal feed to satisfy the world’s rapidly growing appetite for meat. In the US, vast areas of grassland in the Midwest and Plains were plowed and planted in crops long ago but even today, additional grassland is being converted to corn and soy production to meet the demands for animal feed and biofuels [14, 15].

As with synthetic fertilizers, however, manure emits N2O and CH4 as it is stored and breaks down in the soil [23]. Emissions are particularly problematic in intensive livestock systems that produce large amounts of manure, often stored in lagoons and spread on nearby land. Manure management accounts for about 14 percent of the total greenhouse gas emissions in the EPA’s agriculture inventory in the US. Manure storage methods and exposure to oxygen and moisture affects how these greenhouse gases are produced. Methane is produced by organisms in manure slurries under anaerobic conditions. High temperature, high moisture levels and neutral pH favor methane production [24].

Enteric fermentation of feed in cattle and sheep is the largest source of agriculture-related CH4 in the US, representing nearly 25 percent of total methane emissions from anthropogenic activities. About 80 percent of all N2O emissions come from fertilized soil, nitrogen runoff, and manure [16]. Finishing beef cattle on corn, grains, and oils in feedlots brings them to slaughter weight at a younger age, resulting in less CH4 production per animal over a lifetime. But two important caveats must be kept in mind: 1) If this approach enables higher stocking rates in feedlots, total CH4 emissions may increase; 2) N2O and CO2 emissions from animal feed crop production and land clearing for additional area devoted to those crops must also be considered. Further research and may help identify where climate benefits from reduced methane production are offset by increased N2O and CO2 from grain production and transport, but there will be considerable variability at the farm- and region-scale when all factors are taken into account.

Nitrous oxide is also produced during the storage and treatment of manure and urine largely under aerobic conditions. Direct emissions occur through nitrification and denitrification while indirect emissions occur through volatilization, leaching and runoff [25]. Higher N2O emissions are related to intake of feed with higher nitrogen concentration. Manure stored for long periods of time results in relatively high emissions of N2O. Low pH, high temperature, increased aeration and low moisture content favor production of N2O in managed manure. Since conditions and practices that reduce methane emissions are likely to increase N2O emissions, manure management to reduce GHG emissions is challenging.

Feeding forage with lower fiber and cellulose, higher soluble carbohydrates or grazing on less 3

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Overall, lowering the concentration of nitrogen in manure by reducing dietary protein nitrogen, preventing anaerobic conditions, or reducing the concentration of degradable manure C
 are successful strategies for reducing GHG emissions from manure applied to soil [26].

This shows that beef and lamb have larger carbon footprints than pork or poultry. And all are more carbon intensive than plant-based proteins. Expressed as CO2e/kg protein (rather than product), beef is responsible for 50-600 kg CO2e/ kg protein, varying with feeding and production practices, pork for 20-55, poultry for 10-30, and pulses—e.g. lentils, chickpeas, dry beans—for 4-10 [31]. The smaller carbon footprint for plant-based proteins is a consistent finding and is essential to keep in mind as we consider the re-design of food systems on a planet with more than 7 billion people, likely to exceed 9 billion by 2050.

Intensively managed grazing practices can also play a role in reducing N2O emissions including 1) reducing the amount of nitrogen excreted by grazing animals, 2) optimizing soil management and nitrogen inputs, 3) optimizing pasture renovation, 4) manipulating soil nitrogen cycling processes through soil additives, 5) selecting for plants and animals that maximize nitrogen utilization, and 6) altering grazing and feeding management [27].

Fertilizer: Fertilizer production is a highly energy-intensive process with natural gas as a feedstock. Nitrogencontaining fertilizers are used in large amounts on corn, about 36 percent of which is processed for animal feed in the US. About 13 percent of US corn is exported and most of that is also used as animal feed [32].

For cattle, manure management strategies to reduce GHG emissions include shifting from liquid to solid systems, aeration to reduce anaerobic methane production, compaction and composting. Composting aerobically, however, can result in increased N2O production. Using a digester for methane capture and combustion to produce energy is an option but requires capital investment [28, 29].

In the US inorganic fertilization accounts for about a third of total energy input to crop production [33]. According to the US Energy Information Administration, in 2010 the nitrogenous fertilizer industry consumed more than 200 trillion Btu of natural gas as feedstock and another 152 trillion Btu for heat and power [34]. A cradle-to-farm gate analysis found that nitrogen had the largest impact on energy use and GHG emissions for a wide range of crops resulting from the large energy requirements to produce nitrogen fertilizers through the Haber-Bosch process (55 MJ per kg) and from the large global warming potential associated with N2O emissions [35]. GHG emissions from crop inputs ranged from 847 to 3283 kg CO2e per ha per year. Soybeans had the lowest input, largely because soy is a legume and does not require nitrogen fertilizer. Corn grain and corn silage, dependent on Nfertilizer, accounted for the largest input-related emissions.

Summary of Life Cycle Analyses: In a review of land use and carbon footprints of animal food products and their substitutes, Nijdam et al. summarized numerous studies of life cycle analyses [30]; farm to retail; not taking into account soil carbon changes or GHG footprint of fertilizer production:

aCO2e

= CO2 equivalents. Since CO2, methane and nitrous oxide have different global warming potentials, the latter are typically converted to CO2 equivalents so that they can be included in a common metric. *square meters during some period of a year/kg product.

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Soybeans for animals: Soybeans are the second-most-planted field crop in the United States after corn, with over 83 million acres planted in 2016. Of that, 94 percent was planted in herbicide-resistant varieties. Fewer than one percent of total soybean acres were organic production. Corn-soybean rotations are common. More than 80 percent of soybean acreage is in the upper Midwest although significant amounts are planted in the South and Southeast. Processed soybeans are the world's largest source of animal protein feed and the largest source of edible vegetable oil in the US. Soybeans comprise about 90 percent of U.S. oilseed production, while other oilseeds-including peanuts, sunflower seed, canola, and flax--make up the remainder. About 85 percent of the world’s soybean crop is processed into meal and vegetable oil, and virtually all of that meal is used in animal feed. About two percent of the soybean meal is further processed into soy flours and proteins for food use.  Approximately six percent of soybeans is used directly as human food. USDA: https://www.nass.usda.gov/ Statistics_by_Subject/index.php http://www.soyatech.com/soy_facts.htm

In the US, over 90 million acres of land are planted in corn, producing about 14 billion bushels annually, about one-third of which goes to animal food domestically— approximately 9 percent to beef cattle, 6 percent to dairy cattle, 8percent to hogs, and 9 percent to poultry [36]. About 11 percent of total corn production is exported and much of that goes to animal feed as well. In the US, corn is typically grown with intensive fertilizer application, accounting for about 40 percent of fertilizer consumption [37]. According to one analysis, corn grain production results in 2500 kg CO2e emissions/ha [38]. In 2015, 32.7 million hectares of land were planted in corn in the US. This resulted in nearly 82 MMT CO2e attributable to corn grain production, cradle-to-farm gate.b In 2015, 2.5 million hectares were used to produce corn silage, resulting in about 8 MMT CO2e attributable to corn silage. About 36 percent of corn production plus distillers grains left from ethanol production goes to animal feed in the US. Assuming that 80 percent of exported corn goes to animal feed, this results in about 46 percent of US corn fed to animals. Therefore, roughly 41 MMT CO2e emissions are attributable to corn production for animal feed annually. Taking into account transportation from farm to feedlot in the US and abroad, corn-related GHG emissions are even higher. These do not appear in the agriculture GHG budget.

Land use; land use change; grazing practices:

Soil, crops, grasslands and forests can be a carbon source or sink, depending on how the land is used, how uses change, and where the baseline for comparison is established. The soil organic carbon (SOC) pool ranges from 40 to 400 Mg C/ha under undisturbed natural vegetation cover [39]. The SOC pool is depleted with conversion to agricultural systems. The loss may be 50-75 percent following 5 to 20 years after deforestation in soils of the tropics, compared with 25-50 percent over 20-50 years in soils in temperate climates. Most soils in agricultural systems have lost 50-75 percent of their pre-agricultural soil C pool, with the magnitude of loss estimated at 30-60 Mg C/ha. SOC depletion is exacerbated by soil drainage, plowing, removal of crop residue, biomass burning, subsistence agriculture, and soil degradation by erosion and other processes. Although much of the land in the US producing corn and soy for animal feed was converted from grassland long ago, with global warming and additional pressure for biofuels, more grassland is being converted to corn and soy production in the Central Plains states, releasing more carbon into the atmosphere [40, 41]. According to the EPA’s GHG inventory, land converted to cropland recently has contributed about 22 MMT CO2 equivalents to total emissions annually. b

One (metric) tonne= 1000 kg; One Megagram (Mg)=one tonne=106 gm; one Megatonne (Mt)=one million tonnes=106 tonnes; one Teragram (Tg)=1012 gm=1 million tonnes (MMT) ; one Petagram (Pg)=1015 gm

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higher productivity or deeper roots will increase soil carbon. Improvement of nitrogen-use efficiency of fertilizer and manure will reduce N2O emissions from soil. By grazing forages at their optimal quality, digestibility is enhanced and methane production reduced [49].

Carbon soil sequestration: Land conversion to improved pastures, forests, agricultural practices, and reduced conversion of grassland to cropland can enhance substantially carbon sequestration in soils [42]. The rate of organic carbon sequestration depends on climate, soil type, and site-specific management. The global potential of SOC sequestration is 0.6 to 1.2 Pg C/yr., which is equivalent to off-setting about 15 percent of global CO2 emissions [43]. Lal et al. estimate the total organic carbon sequestration potential in the US to be 144-432 Mt—45-98 Mt in cropland, 13-70 Mt in grazing land, 25-102 Mt in forests.

Grazing management: Improved grazing management can dramatically reduce emissions of GHG and enhance soil carbon sequestration [50]. When land is overgrazed the combination of vegetative loss and soil trampling can lead to soil carbon losses and the release of CO2. Rotational grazing on rangeland and pasture, adjusted stocking intensity, and prevention of overgrazing can increase soil carbon sequestration. Grasses or legumes with higher productivity or deeper roots will increase soil carbon. Improvement of nitrogen-use efficiency of fertilizer and manure will reduce N2O emissions from soil. By grazing forages at the optimal maturity for increasing forage quality, digestibility is enhanced and methane production reduced [51].

Carbon sequestration in soils is strongly influenced by location, soil quality, crop or grass type, current and historic management practices, leaving crop residues in the field, choosing highresidue crop rotations, optimal plant nutrition, cover crops, applying manure or compost, and low- or no-till systems [44, 45]. The potential for soil carbon sequestration in rangeland not suitable for crops varies considerably with location (e.g. Great Plains vs. desert Southwest vs. coastal California), vegetation, and soil type [46].

Since rainfall, soil type, and vegetative cover (pasture or rangeland) vary from place to place, no single formula will describe best practices for grazing management. Moreover, best grazing practices with animals in an integrated cropping system will be highly context specific. Nonetheless, appropriate grazing practices can increase carbon soil sequestration and help offset GHG emissions associated with ruminant production.

Glomalin, a glycoprotein produced by arbuscular mycorrhizal fungi in soil, accounts for over 25 percent of soil carbon and is a major component of soil organic material [47]. These fungi live on plant roots, using carbon from the plant to make glomalin, and in turn, extend the reach of plant roots to provide more nutrients in a mutually beneficial interaction. Soil and forage management practices that increase glomalin production can significantly increase soil carbon storage although the rate of increase will slowly decline over a number of years as an equilibrium concentration is reached.

The following summaries of three studies illustrate the importance of

Proper grazing land management can increase soil organic carbon, providing a carbon sink and helping to reduce net GHG emissions associated with animal agriculture [48]. Stocking rates, grazing strategies, and proper soil and forage management collectively influence the extent of carbon sequestration. Grasses or legumes with

taking soil carbon sequestration into account when comparing the carbon footprints of cattle-production systems:

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Case Study 1: A study of three grazing management systems in the northern Great Plains included two native vegetation pastures, one heavily grazed and the other moderately grazed, and a heavily grazed wheatgrass pasture [52]. Contributors to GHGs included 1) CO2 emissions associated with nitrogen fertilizer production and application 2) estimates of methane (CH4) production from enteric fermentation 3) change in soil organic carbon content over 44 years using archived soil samples and 4) soil-atmosphere nitrous oxide (N20) and methane (CH4) fluxes over three years estimated from chamber studies. All pastures were significant sinks for organic carbon. Greater nitrogen inputs in the wheatgrass pasture contributed to nearly 3-fold higher nitrous oxide (N20) emissions than the other two pastures. Lower stocking rates on the moderately grazed native pasture resulted in far lower CH4 emissions than in the other two pastures. When factors contributing to global warming potential were summed, the heavily grazed and moderately heavily grazed pasture systems served as net carbon sinks while the wheatgrass pasture was a net source. Net reductions in GHG emissions was most effectively achieved with moderate stocking rates on native vegetation in this study in the northern Plains.

Case Study 2: Capper used a deterministic environmental impact model (EIM)c based on the nutrient
 requirements and metabolism of animals within all sectors of the beef production system to
 quantify the environmental impact of three US beef production systems: “Conventional”, (CON), “Natural” (NAT) and “Grass-fed” (GFD) [53]. The CON system represented the beef production system characteristic of the majority of beef operations: cow-calf operations with animals brought into a feedlot as soon as they had reached sufficient weight, and treated with growth-enhancing hormones, ionophores, and beta-adrenergic agonists. The NAT system was the same as CON except for the use of growthenhancing drugs. The GFD system was defined by a forage-based diet from birth to slaughter without grain or other non-forage supplementation. Animals in the modeled GFD system were supplied with a forage-based diet based on pasture, alfalfa hay, grass hay and wheat straw, adjusted for a pasture-based diet during spring and summer, with conserved forage supplementation during fall and winter. The CON and NAT systems contained some animals from a dairy operation (dairy-culls or calves). Whereas this is a fairly common practice, it does enable re-allocation of some of the resources and waste to dairy and away from beef in the final analysis. How to do this in a life cycle analysis of operations with interlocking parts is challenging and widely debated [54]. No dairy cattle were in the GFD where all resource and waste impacts were assigned to beef. Environmental impact was calculated by comparing annual resource inputs and waste output of each beef production system, expressed per 1.0 × 109 kg of beef (hot carcass weight) produced in 365 days. Environmental impact in this study was defined as “resource use and greenhouse gas (GHG) emissions.” Results: Animals within the CON system had an average slaughter weight of 569 kg and took a total of 444 days to raise from birth to slaughter; compared to 519 kg slaughter weight per animal after a similar time period (464 d) in the NAT system; and 486 kg after 679 d in the GFD system. This means that fewer animals are required to produce the total target beef production in the CON system. Land use requirements, water use, waste output, and total carbon footprint were all lowest in the CON system and highest in the GFD system. (Continued…) c This

is a software-based modeling system (AMTS Cattle Pro ration formulation software) based on animal
 characteristics and dietary nutrient supply, and is not representative of any specific farm.

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Comments: The focus of this modeling analysis is energy, water, land use requirements, and carbon footprint of three beef production systems. With respect to soil carbon sequestration, the author says, “carbon sequestration into soil and CO2 produced through animal respiration were considered to be equivalent and were therefore not specifically accounted for.” In other words, the study made no attempt to consider opportunities for soil carbon sequestration in a well-managed grass-fed system that can substantially offset GHG emissions [55, 56]. The potential for soil carbon sequestration is particularly significant in land that has been historically poorly managed or plowed and converted to conventional cropping rotations. Capper also says, “Beef production systems that utilize range and pastureland (which is generally unsuitable for human food crop production) gain a sustainability advantage over monogastric production systems that rely upon human-edible grains and legumes. This is discussed at length by Wilkinson [57], who redefined the conventional measures of feed efficiency (7.8 kg feed per kg of gain for feedlotfinished beef) to account for the human-edible energy or protein feed inputs compared to the humanedible energy or protein output from the animal production system. Under these constraints, grassfinished beef…had a favorable human edible feed efficiency ratio whether expressed in terms of energy (1.9 MJ/MJ edible energy in animal product) or protein (0.92 kg/kg edible protein in animal product). Wilkinson’s results appear to imply that grass-fed beef would be environmentally advantageous if competition for feed/food crops is a defining criteria, however, the quantity of land required for differing production systems must be taken into consideration. If the total US beef produced in 2010 (11.8 × 109 kg) was produced by a grass-fed system, the increase in land required compared to conventional production would be 52.2 × 106 hectares, equivalent to 75 percent the land area of Texas.”

Case Study 3: Pelletier et al. used ISO-compliant life cycle assessment (LCA) to compare the cumulative energy use, ecological footprint, greenhouse gas emissions and eutrophying emissions associated with models of three beef production strategies as currently practiced in the Upper Midwestern US [58]. The ecological footprint is an estimate of the area of productive ecosystem required to furnish inputs and waste assimilation for the three productions systems. They examined systems where calves were either weaned directly to feedlots, weaned to out-of-state wheat pastures then finished in feedlots, or finished wholly on managed pasture and hay. They found that impacts per live-weight kg of beef produced were highest for pasture-finished beef for all impact categories and lowest for feedlot-finished beef, assuming equilibrium conditions in soil organic carbon fluxes across systems. Then the authors re-ran the model applying soil carbon sequestration rates of 0.12 tonnes C sequestered/ ha/year for improved pastures (cow–calf system) and 0.4 tonnes C sequestered/ha/year for pastures recently converted to management-intensive grazing (grass finishing). These estimates of carbon sequestration potential were considered realistic for Upper Midwest pastures. In that scenario, estimated greenhouse gas emissions per live-weight kg. produced would be 1.8 kg less for feedlot-finished beef and 8.2 kg less for beef finished on intensively-grazed improved pastures and hay during the transition phase. Here, rather than being 30 percent higher in GHG emissions calculated based on assumed equilibrium conditions, grass-finished beef would be 15 percent less greenhouse gas intensive than feedlot-finished beef. This result illustrates the importance of well-designed grazing strategies and the potential for carbon soil sequestration as a strategy for mitigating GHG emissions from any source.

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Water in animal agriculture: Water footprint

Livestock alone accounts for more than 8 percent of total global water use, most of which goes to irrigate feed crops [59]. Irrigation withdrawals increasingly exceed supply rates, for example, in the Ogallala aquifer underlying the Great Plains [60, 61].

The water footprint of a product is the amount of freshwater used in its production and management of its waste. Water in agricultural is sometimes classified as green, blue, or gray. Green water is from rain, stored in soil, and directly available to plants and animals. Blue water has been taken from surface or groundwater resources and used to produce a product, often taken from one body of water and returned to another, or returned at a different time. Irrigated agriculture has a blue water footprint. Grey water is fresh water required to assimilate pollutants to meet specific water quality standards. The grey water footprint considers point-source pollution discharged to a freshwater resource directly through a pipe or indirectly through runoff or leaching from the soil, impervious surfaces, or other diffuse sources.

The water footprints of animal products are largely determined by three main factors—feed conversion efficiency of the animal, feed composition, and origin of the feed—in addition to direct water consumption. The type of production system (grazing, mixed, or confined feedlot) influences each of these [62]. The mix of green, blue, and grey water requirements can also vary considerably with production system and geographic location. Meat and dairy products have especially large water footprints due to the amount of waterintensive feed required to raise the animals. Globally the average water footprint of beef is 15,500 L/kg, sheep 6,100 L/kg, pork 4,800 l/kg, and chicken 3,900 L/kg [63]. The differences can be partly explained by different feed conversion efficiencies of the animals. Beef production, for example, requires 8 times more feed per kilogram of meat than pork, and 11 times more than chicken.

gram of protein is 6 times larger than for pulses. Butter has a relatively small water footprint per gram of fat, even lower than for oil crops. All other animal products, however, have larger water footprints per gram of fat when compared to oil crops. The general conclusion is that from a freshwater resource perspective, it is more efficient to obtain calories, protein and fat through crop products than animal products, although qualities of proteins and fats differ across the different products.

Per ton of product, animal products generally have a larger water footprint than crop products. The same is true for water footprint per calorie. The average water footprint per calorie for beef is twenty times larger than for cereals and starchy roots [64].

In addition, it is important to note that animal feeding differences can significantly influence the distribution of the water footprint among green, blue, and grey water components. For example, ruminants (cows, sheep) raised completely on rain-fed grass (green water) on grazing land unsuitable for alternative crops have a very different impact on water supplies than ruminants finished in CAFOs to which water must be delivered (blue water) and from which waterborne waste/pollutants must be diluted (grey water).

The global average water footprint per ton of crop increases from sugar crops (roughly 200 m3/ton) and vegetables (~300 m3/ton) to pulses (~4000 m3/ton) and nuts (~9000 m3/ton). For animal products, the water footprint increases from milk (~1000 m3/ton) and egg (~3300 m3/ton) to beef (~15400m3/ton) [65]. The water footprint per gram of protein for milk, eggs and chicken meat is about 1.5 times larger than for pulses. For beef, the water footprint per

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Similarly, the region in which crops are grown will influence water footprint distribution. A vast majority of soy in the US is entirely rain-fed and will have little or no blue water footprint during production. It will however, contribute to grey water requirements and require blue water during processing.

more widespread adoption of more ecologicallybased agricultural models already proven to produce abundant nutritious food. Where meat consumption is excessive, beyond nutritional recommendations, individuals, families, communities and institutional purchasers— hospitals, schools, universities, businesses, governments—could choose more plant-based protein alternatives and give preference to meat from ecologically integrated systems, produced in more sustainable, context-appropriate ways. In the end, our growing appetite for meat comes with costs that could far outweigh the benefits, depending on how we respond to the unprecedented demand.

Beef from entirely grass-fed animals has a larger water footprint than that from animals raised intensively in feedlots but the allocation among green, blue, and gray water can differ dramatically. Animals consuming exclusively rain-supplied grass and forage have a far lower blue and grey water footprint than animals in feedlots that consume food from irrigated crops and produce manure requiring grey water for management.

Summary: Analyses of the long-term sustainability of various meat production systems are complex, inconsistent, and often contentious. They deal differently with assumptions, boundaries, uncertainties, tradeoffs and data gaps. In the US, efficiencies in producing abundant, cheap calories and economic return on investment have been the dominant drivers of the prevailing industrial agricultural model. But here and elsewhere these motives have led to excessive air and water pollution, soil and biodiversity loss, climate change, and socioeconomic instability in rural communities while producing abundant cheap calories. These costs aren’t covered in the price of meat. To be sustainable over the long term, the growing global demand for meat should be considered within the context of a goal of providing adequate, culturally-appropriate nutrition to the world’s population, while restoring soil fertility and biodiversity, protecting water, and helping to reduce drivers of climate change. This will likely mean that supply-oriented changes in meat production will not be sufficient without some constraints on demand. Strategic incentives, including full-cost accounting when establishing food prices, could encourage

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