How many chickens does it take to make an egg? Animal welfare and environmental benefits of replacing eggs with plant foods at the University of California, and beyond

Cleveland, David Arthur; Gee, Quentin; Horn, Audrey; Weichert, Lauren; Blancho, Mickael

doi:10.1007/s10460-020-10148-z

Table 2 Impact of reduced egg consumption on animal welfare and the environment

From: How many chickens does it take to make an egg? Animal welfare and environmental benefits of replacing eggs with plant foods at the University of California, and beyond

Scenario, location	Eggs used year⁻¹ at institutional/retail level before change to plant-based alternatives			Net impact year⁻¹ of change to plant-based alternatives to eggs, cradle to farmgate, adjusted for waste
				Chicken welfare (number of chicken in egg industry)^c	Environmental impact^d
	Eggs at institution level^a	Eggs at farm gate^b	50% of eggs at farm gate	Chicken welfare (number of chicken in egg industry)^c	MT CO₂e	m³ water	kg Nr	ha land
Plant-based mayonnaise replaces 100% of egg-based mayonnaise year^−1e
UC Santa Barbara
General dining^f	2,195	2,229		− 14	− 0.11	− 13.70	− 3.99	− 0.03
Residential dining^g	11,818	11,998		− 76	− 0.58	− 73.73	− 21.48	− 0.17
Total	14,013	14,227		− 90	− 0.68	− 87.42	− 25.47	− 0.20
UC, all campuses^h	144,264	146,461		− 924	− 7.02	− 900.01	− 262.19	− 2.06
Tofu replaces 50% of all eggs used year⁻¹ⁱ
On all UC campuses, only for first-year student breakfast ^j	2,885,365	2,929,305	1,464,652	− 9,245	− 85	− 8,213	− 2,627	− 22
On all UC campuses with spillover to all off-campus meals^k	123,997,721	125,886,011	62,943,005	− 397,302	− 3,674	− 352,956	− 112,877	− 926
On all UC campuses with spillover to all off-campus household meals^l	367,033,253	372,622,592	186,311,296	− 1,176,015	− 10,874	− 1,044,749	− 334,117	− 2,741
United States^m	90,730,517,000	92,112,200,000	46,056,100,000	− 290,710,500	− 2,688,043	− 258,261,562	− 82,593,681	− 677,451

^aFor the mayonnaise scenarios the amount at institutional level was based on estimates of the amount of mayonnaise used and the amount of eggs in mayonnaise (see note e below). For UCSB the amount of mayonnaise used was based on purchase data, and for all UC campuses the amount was estimated based on the UCSB amounts per person. For the tofu scenarios the amount at institutional level was calculated from the amount at farm gate adjusted for a loss and waste rate of 1.5%. According to the USDA, in 2017 the loss and waste of based on amount available at the of farm gate was 1.5% to institution/retail, 8.9% at the institutional level, and 28.9% at the consumer level for a total of 39.3%
^bFor the mayonnaise scenarios, eggs at farm gate = the number of eggs produced that result in the number available at retail/institutional level after loss and waste (= 0.015%) (USDA ERS 2019a). For the tofu substitution scenarios, we calculated eggs cap⁻¹ at farm gate by dividing the the total number of eggs produced Dec 2016-Nov 2017 (Table 1) by the US population in 2017 (USCB 2020); we then multiplied the result by the population for each scenario
^cEstimated using 0.0063 chicken lives egg⁻¹ (Table 1, Calculations)
^dEstimates of environmental impact of eggs are for 2010 based on (Pelletier et al. 2014) and (Eshel et al. 2014) (Table S1). Estimates of environmental impact of replacing eggs in mayonnaise with soy protein isolate are based primarily on (Berardy et al. 2015; Braun et al. 2016; Eshel et al. 2014) (Table S2). Estimates of environmental impact of replacing eggs in the diet with tofu are based primarily on (Berk 1992; Eshel et al. 2014; Mejia et al. 2018) (Table S3)
^eEstimate of number of eggs use in mayonnaise based on data for mayonnaise use from general and residential dining, assuming eggs = 6.7% of mass of mayonnaise (Sheldon et al. 2017, p. 29), and weight per egg is mean of the USDA largest + smallest size classes (53.15 g) (USDA AMS 2000). We assumed whole egg used in egg-based mayonnaise, as some use whole eggs plus egg yolks, and ingredient amounts are not available (Table S2). We assumed that eggs are 6.7% of mass of mayonnaise (Sheldon et al. 2017, p. 29) and are replaced by an equal combined mass of soy protein isolate, soybean oil and water in plant-based mayonnaise
^fAssumes all people on campus except first-year students eat their meals with general dining
^gAssumes academic year, and all first-year students eat all of their meals in residential dining
^hUsing estimates of meals eaten by UC population for fall 2018 (Table S4)
ⁱEstimate of number of eggs used in the UC food supply based on the average number of eggs produced annually (Table 1), adjusted for loss and waste from farm gate to the institutional level of 1.5% based on USDA loss-adjusted food availability (LAFA) data (USDA ERS 2019a). Total eggs consumed includes eggs in shell as well as “processed” or “broken eggs,” which comprise about one-third of the eggs consumed in the US, including as liquid, dried, or frozen eggs, for example as ingredients in food products. For on-campus meals we assumed eggs only eaten at breakfast, and therefore used only one meal day⁻¹, and only for first-year students, which underestimates egg consumption because of eggs used in ingredients for foods eaten at lunch and dinner. For spillover to off-campus meals, we used the total per capita egg consumption. We assumed that eggs were replace by an equal mass of tofu, with environmental impacts based on (Mejia et al. 2018) and (Eshel et al. 2014); conversions from https://ussec.org/resources/conversion-table/ (Table S3)
^jSee Table S4 for estimates of number of meals per year on campus. Assumes = distribution of eggs among meals
^kAssumes all 3 meals day⁻¹ for entire year for total UC population, and total egg consumption
^lAssumes household size including the UC person = mean for California 2013–2017: 2.96 persons. (https://www.census.gov/quickfacts/fact/table/ca/PST045217)
^mSee note i above for method used to estimate number of eggs in the US food supply. We used the US population for July 1, 2016 (323,071,342) (https://factfinder.census.gov/faces/tableservices/jsf/pages/productview.xhtml?src=bkmk)

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