Agriculture Resilience Act of 2021 This bill establishes, expands, and revises multiple programs and activities of the Department of Agriculture (USDA) primarily to reduce carbon emissions from the agriculture sector. Specifically, USDA must finalize and implement a plan to achieve net-zero emissions from the sector by 2040. USDA must periodically review and revise the plan, as necessary, and annually report on its implementation. Additionally, the bill expands the scope of various USDA research, extension, and education programs; conservation programs; and livestock programs to incorporate climate change adaptation and mitigation. Expanded activities include efforts to improve soil health and preserve farmland and grassland. Further, the bill changes programs that support renewable energy in rural areas to address carbon emissions in the agriculture sector. Among these changes, the bill provides statutory authority for a program for reducing methane emissions from livestock waste that is carried out by the Environmental Protection Agency and transitions the program to USDA. The bill also addresses food waste, for example, by (1) standardizing the voluntary labels used by food producers to indicate the date by which food should be used or discarded, and (2) making composting activities eligible for support through USDA conservation programs. Moreover, the bill establishes grants to reduce and prevent food waste in landfills and in schools.