Abstract
Dairy farms are challenged to increase productivity while achieving environmental sustainability, where greenhouse gas (GHG) emissions are at the center of the discussion. The U.S. dairy industry leadership has committed to a Net Zero Initiative to achieve GHG neutrality, but the specifics on how to achieve this are still uncertain. Life cycle assessment methods were used to quantify GHGs and net energy intensity (NEI) of a large (1000 cows) and a small (150 cows) farm in Wisconsin. The GHGs are 1.0 and 1.3 kg CO2-eq/kg FPCM and the NEI is 2.4 and 3.2 MJ/kg FPCM for the large and small farm, respectively. The GHG benefits from anaerobic digestion (AD, sized to process all manure on both farms) and PV (sized to match AD electricity production) are not enough to achieve GHG neutrality. Increasing the capacity of these systems showed that AD is more cost-effective for the larger farm, but the challenges and costs related to securing and disposing the extra manure needed for energy production limit its feasibility. For the smaller farm, the total annualized costs to achieve GHG neutrality are lower for PV vs. AD, even before accounting for any transportation costs related to handling the extra manure.
Highlights
In 2020, the Innovation Center for U.S Dairy set forth the “Net Zero Initiative” (NZI)to achieve greenhouse gas (GHG) neutrality and other environmental stewardship goals related to water and manure nutrient use by 2050 [1]
Embedded GHG emissions and energy consumed during the production of material and energy inputs are included as this study considers a life cycle approach
net energy intensity (NEI) is expressed in MJ and defined as the difference between the life cycle energy required by the system and the energy supplied by the system
Summary
To achieve greenhouse gas (GHG) neutrality and other environmental stewardship goals related to water and manure nutrient use by 2050 [1]. In 2019, agriculture contributed 9.6% of total U.S GHG emissions, with dairy being a major contributor [2]. Consumers have been shifting their buying preferences and behavior toward more sustainable products. Between 2017 and 2019, the percentage of consumers purchasing products classified as “sustainable” because of earth/environmental reasons rose from 31% to 51%, surpassing family and community reasons [3]. Capper et al [4], and Capper and Cady [5] quantified continuous efficiency improvements in the U.S dairy industry from 1944 to 2017, resulting in reduced GHG emissions per unit of milk produced, achieving GHG neutrality will require additional improvements
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