A food system is composed of several stages where inputs, agricultural commodities, processed food, and wastes are moving downward and upward a commodity chain:
- Nutrient management. The biological conditions supporting food production, such as soils and water reservoirs, which are directly related to key environmental characteristics such as temperature and precipitation. These tend to occur naturally, unless the conditions in which food is grown have been substantially modified, such as for aquaculture and greenhouses.
- Farm inputs. The inputs that are provided through capital and labor (more than often mechanized) include irrigation, seeds, fertilizers, and the equipment required to prepare, maintain, and harvest crops. The manner in which these inputs are organized is linked to different forms of farming, such as subsistence farming, commercial agriculture, and corporate farming.
- Production. The activities involved in harvesting food from crops (e.g. grains) or collecting food from their natural or artificial habitat (e.g. cattle or seafood). These activities are becoming increasingly mechanized.
- Transportation and storage. Food that has been harvested or collected for commercial purposes needs to be transported and stored. For instance, grain elevators are nearby transport facilities such as rail or ports. The scale and condition in which food can be transported and stored is a function of how perishable and fragile it is.
- Processing. The transformation of agricultural products into food involves a highly diversified range of activities, scales, methods, and skills. It is usually divided into primary (transforming an agricultural product into food; milling grain into flour), secondary (creating food from ingredients; baking bread), and tertiary (manufacturing; ready-to-eat food) processing.
- Distribution. The range of activities related to food packaging, packing, storage, and distribution for final and intermediate uses. For perishable food, this often involves cold storage facilities and modes. Distribution also includes retailers acting as intermediaries, such as wholesalers, grocers, and restaurants.
- End-use. The consumption of food in a variety of social and commercial settings, including homes, cafeterias, and restaurants. This is linked to cultural preferences and affordability. As societies get wealthier, the consumption of food involves a larger share of meat, a larger caloric intake, more processed food, and an increasing variety of food items.
- Post-use. Discarding and recycling food can be a substantial post-use activity, as about 30% of the food consumed in the world is discarded.
These stages involve complex interactions between biological, economic, and political systems, each subject to risks.