Environmental and Economic Effects of Changing to Shelf-Stable Dairy or Soy Milk for the Breakfast in the Classroom Program

Abstract

Objectives. To estimate economic and environmental effects of reducing milk waste from the US Breakfast in the Classroom (BIC) School Breakfast Program by replacing conventional milk with shelf-stable dairy or soy milk.

Methods. We estimated net greenhouse gas emissions (GHGE; kg CO₂ equivalents [e]) from replacing conventional milk with shelf-stable dairy or soy milk by adapting existing life cycle assessments and US Environmental Protection Agency Waste Reduction Model estimates to BIC parameters. We estimated net cost with school meal purchasing data.

Results. Replacing conventional dairy milk with shelf-stable dairy or soy milk would reduce milk-associated GHGE by 28.5% (0.133 kg CO₂e) or 79.8% (0.372 kg CO₂e) per student per meal, respectively. Nationally, this equates to driving 248 million or 693 million fewer miles annually, respectively. This change would increase milk costs 1.9% ($0.005) or 59.4% ($0.163) per student per meal, respectively.

Conclusions. Replacing conventional milk with shelf-stable dairy or soy milk could substantially reduce waste and concomitant GHGE in BIC; switching to shelf-stable dairy has low net costs. Pilot tests of these options are warranted to optimize the nutritional value, cost, and sustainability of BIC.

US schools have offered liquid dairy milk in the national school meal programs for nearly a century. Under current offer-versus-serve policy, children can refuse the milk (i.e., the milk is offered but not served).¹ One quarter of cartons offered were refused in a recent Breakfast in the Classroom (BIC) School Breakfast Program study.² Because milk is taken out of the schools’ refrigerators to be brought to classrooms for BIC, unwanted cartons are discarded unopened because of food safety concerns. This unopened milk has substantial economic and global warming effects.² Reducing food waste in US Department of Agriculture (USDA)–administered national school meal programs is a national priority; the 2016 National Environmental Policy Act (NEPA) mandates that all federal agencies, including the USDA, incorporate environmental considerations in their planning and decision-making.³

Shelf-stable dairy and soy milk may be good alternatives to conventional milk because they can meet USDA nutritional requirements for the milk component of school meals¹ and can be offered at a later meal if children do not take them at breakfast. To our knowledge, this study is the first to estimate the environmental and economic effects of eliminating unopened milk waste from BIC by replacing conventional milk with shelf-stable dairy or soy milk.

METHODS

We adapted existing life cycle analyses of dairy and soy milk production,^4–7 packaging production greenhouse gas emissions (GHGE),⁸ and end-of-life effects from the US Environmental Protection Agency (EPA) Waste Reduction Model⁹ to BIC parameters. For our analysis, we defined system boundaries as cradle to grave, and the functional unit was 8 ounces (237 mL) of milk offered in BIC. We calculated the net effect of replacing conventional milk with shelf-stable dairy or soy milk given (1) milk consumption rates consistent with previously measured levels² (i.e., 75% of students take a milk and dispose 25% of its contents; the other 25% of students do not take a milk, and their cartons are disposed unopened), and (2) unopened shelf-stable milk would be saved and offered at a later meal. National annual GHGE estimates (kg CO₂ equivalents [e]) were based on national School Breakfast Program participation (14.2 million children/day)¹⁰ and the proportion of US school districts participating in the School Breakfast Program that offer BIC (29.7%).¹¹ We equated milk-related GHGE to passenger vehicle miles by using the EPA estimate of 4.08 × 10⁻⁴ metric tons of CO₂e per mile.¹²

We divided the life cycles of dairy and soy milk into the following stages:

1. on the farm,

2. transport from farm to processor,

3. milk processing,

4. distribution, and

5. disposal.

When life cycle analyses were not available for specific post–farm gate steps, we used proxy estimates from dairy^4,5 and tofu⁶ life cycle analyses. For example, there were no existing estimates of the effect of soy milk distribution, so we applied the GHGE for shelf-stable dairy milk distribution to shelf-stable soy milk distribution given the similarities in packaging and refrigeration requirements. Also, no estimates of GHGE of milk handling in schools were available, so we assumed effects were similar to those in retail. Finally, we considered only landfill disposal. Most paperboard cartons for conventional milk are diverted to landfills in the United States,⁴ and schools are unlikely to recycle shelf-stable cartons because of budget constraints.

We calculated cost per student per meal with price estimates for the northeastern United States: $0.27 per carton of conventional milk,² $0.37 per carton of shelf-stable dairy milk (P. Logan, Diversified Foods, personal communication, November 9, 2017), and $0.58 per carton of shelf-stable soy milk. Landfill fees were $32 per US ton.²

RESULTS

Switching from conventional milk to shelf-stable dairy or soy milk would reduce milk-associated GHGE by 28.5% (0.133 kg CO₂e per student per meal) or 79.8% (0.372 kg CO₂e per student per meal), respectively (Table 1). With 4.2 million BIC meals served each school day, this is similar to reducing passenger vehicle miles traveled by 248 million miles or 693 million miles annually, respectively.

TABLE 1—

US Climate Change Effect and Cost of Conventional Dairy Milk, Shelf-Stable Dairy Milk, and Shelf-Stable Soy Milk

	Conventional Dairy Milka	Shelf-Stable Dairy Milkb	Shelf-Stable Soy Milkb
On the farm,c kg CO2e/kg milk	1.23	1.23	0.068
Transport from farm to processor,d kg CO2e/kg milk	0.035	0.031	0.038
Milk processing,e kg CO2e/kg milk	0.294	0.313	0.123
Distribution and school storage,f kg CO2e/kg milk	0.190	0.177	0.177
Unopened milk carton disposal,g kg CO2e/kg milk
Milk	0.122	. . .	. . .
LDPE resin	0.000	. . .	. . .
Paper	0.001	. . .	. . .
Aluminum foil	. . .	. . .	. . .
Opened milk carton disposal,g kg CO2e/kg milk
Milk	0.092	0.122	0.122
LDPE resin	0.000	0.000	0.000
Paper	0.004	0.004	0.004
Aluminum foil	. . .	0.000	0.000
Total kg CO2e/kg milk	1.969	1.877	0.531
Greenhouse gas emissions per child per meal, kg CO2e	0.467	0.334	0.094
Cost per child per meal, $	0.274	0.279	0.437

Note. LDPE = low-density polyethylene.

^aAssumes an 8 oz (237 mL) carton of milk per child per meal, with 75% opened and 25% disposed unopened, as was previously observed in Breakfast in the Classroom (BIC).²

^bAssumes an 8 oz (237 mL) carton of milk offered per child per meal, with 75% opened and 25% unopened and offered at a later meal.

^cDairy estimates from Thoma et al.⁴ Soy milk estimate based on US soy production from Mejia et al.⁶ and 0.15 kg soybeans/kg soy milk.⁷

^dDairy estimates from Burek et al.⁵ Soy milk estimate based on transport of soybeans in the United States from farms to tofu processors.⁶

^eDairy estimates from Burek et al.⁵ Soy milk estimate from Birgersson et al.⁷

^fDairy estimates from Burek et al.⁵ The shelf-stable dairy estimate was applied to shelf-stable soy milk.

^gAll estimates from US Environmental Protection Agency Versions of the Waste Reduction Model (WARM) Version 16.⁹ Gable top paperboard containers for 8 oz conventional milk contain 9.9 g of paper and 1.1 g of LDPE. Shelf-stable 250 mL Tetra Pak pull-top cartons contain 2.541 g of LDPE, 0.605 g of aluminum foil, and 7.854 g of paper.⁸

When reducing total milk purchasing by 25% for shelf-stable milk relative to conventional milk by eliminating unopened milk waste, the cost per child per meal, including landfill fees, was $0.274, $0.279, and $0.437 for conventional milk, shelf-stable dairy milk, and shelf-stable soy milk, respectively (Table 1). As such, switching from conventional to shelf-stable dairy or soy milk would increase milk costs by 1.9% or 59.4%, respectively.

DISCUSSION

Although milk is a nutrient-dense food that has long been a central part of school meals, its nutritional potential is not realized when wasted. The environmental effect of milk waste in the 4.2 million daily BIC meals is considerable. An additional 6.5 million daily breakfasts are served as grab-and-go meals,^10,11 which also present a tremendous opportunity for milk waste. Thus, the total effect of milk waste across the School Breakfast Program is likely to be far greater than that of BIC alone.

Switching from conventional to shelf-stable dairy milk could substantially reduce the waste and concomitant environmental effect of milk in the School Breakfast Program at a low cost. Although soy milk is more expensive, if offered alongside dairy milk, it likely would not be a large portion of the milk that students choose and could improve nutrition for students who do not consume dairy milk because of lactose intolerance, allergies, palatability, or cultural or religious reasons. Shelf-stable dairy and soy milk have the added nutritional benefit over conventional milk of potentially being used in efforts to address food insecurity, such as in weekend meals sent home with children in low-income families. Because the added sugar in flavored milks can offset their nutritional benefits, future studies should assess the acceptability of unflavored shelf-stable dairy and soy milk in schools.

This study had some important limitations. First, we relied on the best available estimates for post–farm gate GHGE but could not find estimates specific to school milk. Because most dairy GHGE occur on the farm, we expect discrepancies in post–farm gate stages of the life cycle to have little effect on our findings. Second, we acknowledge that environmental effects are not limited to GHGE; although the scope of this article was limited to this category, we expect similar findings for other environmental effect indicators. Last, we provide a net cost for the northeastern United States; because milk prices vary by geographic region, generalizability of net cost estimates may be limited.

In areas where shelf-stable products may not be economically feasible, schools might consider investing in additional refrigerators or coolers to be used throughout the school to reduce milk waste from BIC, but the expense and environmental effect would need to be considered. Across all regions and milk types, the USDA could limit milk waste by encouraging schools to have students preorder milk before their meals to ensure that all milk purchased is consumed.

PUBLIC HEALTH IMPLICATIONS

Shelf-stable dairy and soy milk have tremendous potential to reduce the global warming effect of milk in the School Breakfast Program while providing nutritious options for children, highlighting the need for work on the acceptability of these milk options in schools. Under NEPA, the USDA should consider shelf-stable milk options as well as policy solutions to optimize the nutrition, cost, and environmental effects of school meals.