Cultivating Organic Matter through the Promotion Of Sustainable Techniques Act or the COMPOST Act This bill makes composting a conservation practice and activity for purposes of Department of Agriculture (USDA) conservation programs. The bill also requires USDA to establish a competitive program to award grants and loan guarantees for projects that expand access to food waste composting. In awarding grants and loans guarantees, USDA must prioritize projects that include the greatest number of the following factors: are located in or serving a location with significant access to food waste and no or limited prior access to food waste composting; demonstrate the potential to create new capacity for the volume or weight of food waste collected and processed, or make significant gains in the number of people with access to food waste composting facilities or systems; demonstrate a plan for following best management practices and producing a high-quality compost product; incorporate the participation of small and diverse businesses (e.g., minority-, woman-, and veteran-owned businesses certified by the Small Business Administration); create opportunities for hiring and leadership development practices that are inclusive and provide living wages; serve disadvantaged and low-income communities, engage Black farmers, Indigenous farmers, and other farmers of color, or incorporate an environmental justice plan or principle; and are for a facility or system that accepts or plans to accept and process only source separated organics.