Utilization of by-products and food waste in livestock production systems: a Canadian perspective

Food waste produced across the supply chain poses negative environmental, social, and economic consequences. Livestock can play a key role in using food waste and by-products by converting low-value materials into high-quality products. Challenges regarding utilization of food waste include regulatory restrictions, safety concerns, and logistics associated with collection, transport, and handling. Addressing these challenges ensures improved stability and resiliency of Canada’s food supply chain, which will be increasingly threatened by global political unrest and climate change. Increasing demand for food coupled with higher environmental standards is shaping agricultural activities toward ecologically sustainable and efficient systems (McGuire, 2015). However, food waste remains a global dilemma, with negative environmental, social, and economic consequences (Spang et al., 2019) associated with estimated annual losses of approximately one-third of all edible food (1.3 billion metric tonnes, MMT) across the supply chain (FAO, 2011). More recently, the FAO (2019) has defined food waste using two indices: food lost in production or in the supply chain before it reaches the retail level (Food Loss Index) or food that is subsequently wasted by consumers or retailers (Food Waste Index). Fourteen percent of the world’s food is lost before it reaches the retail level, but the contribution associated with the Food Waste Index is still being explored (FAO, 2019). In the United States alone, food loss streams have been estimated at 35.9 MMT from production/processing of vegetables, fruit, and meat/poultry/fish, whereas total retail and consumer waste are estimated at 19.5 MMT and 40.8 MMT, respectively (Dou et al., 2016). In Canada, total annual loss and waste along the food value chain equates to 35.5 MMT, of which 11.2 MMT (32%) is avoidable, valued at $49.5 billion, and representing 51.8% of the food dollars spent in retail stores in 2016 (Gooch et al., 2019). As described above, food loss is typically associated with loss of quality or low-quality by-products during the production, processing, and distribution stages of the supply chain, whereas food waste or surplus food is defined as food that is not consumed at the retail, food service, and consumer stages of the food supply chain and is related to consumer behavior (Dou et al., 2016). By-products include a wide range of feedstuffs obtained from 1) cereal grain and oilseed cleaning, milling or extraction; 2) brewery, distillery, or ethanol production; 3) vegetable, fruit, and sugar processing, and 4) livestock processing. Often, a collective term, “food loss and waste,” refers to both indices (Gooch et al., 2019). The term surplus, although perhaps more socially acceptable, was purposefully avoided as it implies that producers and the associated food supply chain are using land and resources in excess of demand. Furthermore, it mitigates the shared responsibility to address loss and waste across the supply chain, from the producer to the consumer. Estimates of food loss and waste are dictated by methodology, with potential overestimates because 1) food redirected for less productive uses, such as fertilizer and animal feed, is deemed as lost; 2) farm losses are monetized at retail-level prices (Bellemare et al., 2017); and/or 3) an inability to accurately determine consumer waste, which can be impacted by many factors including consumer affluence (van den Bos Verma et al., 2020). Minimizing food loss is an important avenue to improve global food security and improve management of land, water, and energy resources in food production systems. Indeed, it has become a global priority formalized by the United Nations (UN) 2030 goal to “…halve per capita global food waste at the retail and consumer levels and reduce food losses along production and supply chains, including post-harvest losses” (UN, 2015). Options to reduce food loss and waste have been described using a “hierarchy of recovery” (Figure 1) which include 1) reduction at source, 2) recovery/redistribution to address hunger, including utilization in animal diets, 3) recycling into pharmaceuticals, cosmetics, fertilizers/compost, as well as biodiesel or natural gas production through anaerobic digestion, and finally, 4) disposal in landfills or via incineration (ECCC, 2019). These options, however, vary broadly by country according to technological development, regulations restricting rendering of animal products into animal feed, as well as consumption. Although countries with higher per capita consumption have higher food waste production (van den Bos Verma et al., 2020), many also have efficient livestock production systems based on emissions per unit of commodity (Gerber et al., 2011). Canada, for example, has highly efficient livestock production systems, but produced 961 kg of waste per capita in 2014 at a cost of $85/capita for nonhazardous waste management (Richter et al., 2018). Many Canadian communities utilize landfills for disposal as a consequence of the availability of significant tracts of undeveloped land (Bruce et al., 2016). Therefore, diverting food loss and waste toward livestock and poultry feed is a logical solution to reduce use of landfills as a strategy for disposal. Numerous studies have addressed food loss and waste in terms of food security, food safety, public health, and the environment, but there are a limited number of North American reviews (Dou et al., 2018), examining conversion to feed for food-producing animals. Modeling efforts have demonstrated that if livestock were removed from the landscape in the United States, 43.2 × 109 kg of human-inedible food and fiber by-products would no longer be converted into human-edible food, pet food, or industrial products (White and Hall, 2017), highlighting the importance of food loss and waste utilization as an ecosystem service associated with livestock production. Unusable by-products present a liability and their disposal has an associated environmental footprint. Hierarchy of solutions to address food loss and waste (adapted from ECCC, 2019). Utilizing food loss and waste in animal diets addresses waste management, food security, resource and environmental challenges. Livestock as “up-cyclers” play a critical role in the solution to reducing food loss and waste (Figure 2), with the potential to convert inedible foods into high-quality protein in the form of meat, eggs, and milk, while addressing waste management, food security, resource and environmental challenges (Dou et al., 2018). More specifically, the presence of a myriad of microorganisms in the rumen, and to a lesser extent, the large intestine, has the potential to effectively degrade fiber present in human-inedible plants and plant by-products to enable the ruminant host to generate high-quality protein including essential amino acids and fatty acids (Matthews et al., 2019). Animal protein is also an important source of B vitamins, with B12 obtained exclusively from animal sources, as well as A, D, and K2 (organ meats) and various minerals (i.e., zinc, selenium, iron) that are often more available in animal than plant-based foods (Leroy and Cofnas, 2020). Food waste arises from food processors, restaurants, households, and food markets. Some food waste can go directly to livestock farms as feed, whereas others require secondary processing where they are separated from waste, subject to further processing. Streams that are suitable as feed are used on livestock farms, those designated as unsuitable may be directed toward composting or biodigestion. Unrecyclable packaging may be directed toward landfill. Plants that produce bioethanol and vegetable oils produce distillers grains and oilseed meals, which can be used directly by livestock as an important source of energy and protein. Currently, a large portion of the feed utilized in North American livestock production consists of grains, pulses, and oilseeds, as well as other commodities including potatoes that fail to reach the quality grade required for human consumption. This can be the result of harvest failures, crop pests, poor growing conditions due to early frosts, floods or drought, or excess production exceeding storage capacity. For example, in Canada, malt barley commands a price that is 51% greater than feed barley, but over 75% of malt barley fails to meet the criteria necessary for beer-making (Ribeiro and McAllister, 2016) due to factors including sprouting damage or low protein content which interfere with the malting process. However, barley that is rejected for malt production is acceptable as livestock feed. Furthermore, cereal grains and pulses are cleaned of contaminants prior to shipping, generating “grain screenings” consisting of mixtures of broken grains, chaff, weed seeds, and dust. The chemical composition of grain screenings can vary substantially depending on the parental material from which they were derived and their origin during the cleaning process. Screenings that are captured in dust collection systems are often high in minerals and fiber, suitable only as a low-quality feed for ruminants. To improve nutrient consistency and quality, screenings are often blended and pelleted prior to feeding. In addition to on-farm or near farm losses, as much as 30% of global agriculture production results in biomass waste (Ajila et al., 2012) from food and industrial processing, including alcohol and biofuel production, oilseed processing, fruit and vegetable processing, sugar production, root and tuber processing, and herb, spice and tree processing (Salami et al., 2019). Increased production of biofuels in Canada (approximately 1.8 billion liters in 2019; GAIN, 2019a) has generated dried distillers grains, which are rich in energy, protein, and minerals. This by-product can constitute up to 50% of the diet dry matter (DM) for confined cattle (Leupp et al., 2009) and up to 15% and 10% of the diet dry matter for pigs (Beltranena and Zijlstra, 2011) and poultry (Salim et al., 2010), respectively. Expansion of oilseed production in Canada has also resulted in increased availability of oilseed meals. Canola (19 MMT annually) and soybean (6 MMT annually) were the principal oilseeds produced in Canada in 2019 (GAIN, 2019b). Soybean and canola meal are the principal protein sources used in livestock diets, with the fiber being higher and protein content lower in canola than soybean meal. Sunflower, flax, corn, and safflower are also sources of oilseed meals in Canada, but account for less than 1% of meal production. A number of feed sources resulting from the regional processing of crops are often substituted for a portion of the cereal grain in animal diets, many of which have been characterized by Lardy et al. (2015). Milling of wheat to flour produces bran and germ or a mixture of by-products that can be offered to livestock as wheat middlings. Similarly, the hulls of primary crops such as oats, soybeans, and sunflowers may be removed during processing and are frequently used as a fiber source in ruminant diets. Processing by-products of fruits and vegetables including potatoes are also available for utilization in livestock diets. However, their high moisture necessitates immediate use or further treatment (e.g., ensiling) to prevent spoilage. As fractionation of commodities for inclusion in foodstuffs expands due to increased demand for novel products including meat substitutes, the diversity and volume of by-products in livestock diets is expected to increase. For example, pea processing in western Canada has expanded significantly to provide pea isolates used in dairy and meat substitutes (Acheson, 2016; https://www.roquette.com/media-center/news/2020-09-29-roquette-world-largest-pea-protein-plant-portage-canada). Japan and South Korea have been leaders in recycling food waste into animal feed, where as much as 60% of daily municipal food waste is redirected to animal feed (Nguyen et al., 2017). An opportunity for further inclusion of food waste in livestock diets in Canada exists, given that of the 61.12 MMT consisting of dairy and eggs, field crops, produce, meat and poultry, marine, and sugar/syrup entering the Canadian food system in 2016, only 25.58 MMT (41.9%) were consumed, with 31.4% of the remainder deemed as avoidable food waste. The largest volume and value arose from manufacturing, followed by households, and the processing sector (Gooch et al., 2019). Despite the abundance of by-products and food waste available, there are a number of challenges regarding their use in livestock production. Logistics associated with collection, transport, and handling of by-products and food waste may be too cost-prohibitive for use in livestock diets, particularly when considering by-products and food waste. In Canada, food processing such as and waste vegetables, may be at to no cost to livestock farms, that the farms and For livestock farms in to source, these by-products can reduce feed for more by-products such as distillers grains, with cereal grains and protein increased inclusion in livestock diets. 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