Today's food management system is not sustainable in the long term. According to the Study of the UN Food and Agriculture Organization (FAO), there are huge differences among the population in terms of food availability. One part throws away almost a third of the food it uses, while almost 10% of the world's population is starving. One of the most important issues in the domain of the agricultural and food sector is the existence of by-products which in most cases are still treated as waste. By implementing the principles of the circular economy, the loss of their economic value could be prevented by exploiting these products as resources for other processes. Agricultural waste can be turned into products such as fertilizers, new materials, animal feed or can be used to produce energy.

Regenerative food production means growing food in ways that create positive outcomes for nature, such as improved biodiversity, improved air, land and water quality.

By implementing the concept of circular economy, there is a possibility of acquiring the economic value of many by-products in the agricultural and food industry. This approach has numerous possibilities. For example, the statistics indicate that Jakarta, the capital of Indonesia, produces up to 3233 m3 of organic waste, most of which is the result of activities from the agricultural and food industry. This amount is the second largest in the world, and only Saudi Arabia is ahead of it with 427 kg of wasted food per person in one year. Also, according to the report, methane from food waste at the landfill is 21 times more harmful than carbon dioxide in the form of greenhouse gas emissions. So, in addition to obtaining economic value from a large amount of food waste, there is also an opportunity to reduce the emission of greenhouse gases.

According to the research of the United States Environmental Protection Agency on the assessment of food waste from the food retail and food service sectors and households, statistics show that 2.29% of food waste ends up as animal feed, 5% is composted, and 3.53% ends up in biochemical processing. However, the data that almost 60% of waste from these sectors ends up in landfills is worrying.

There are numerous approaches for implementing the concept of circular economy in the agricultural and food sector such as:

• Composting of organic waste that can be used as fertilizer;
• Use of by-products in the processing of wheat for animal feed; 
• Utilization of waste from one industry as raw material for another industry - e.g. using pig's blood and fat.

The advantages of these approached, for example the company De Clique from the Netherlands which collects food by-products such as coffee grounds, orange peels and other food waste, are the following:

• For every 1 kg of food waste turned into compost, which is later sold to consumers or used to grow tea and mint, the emission of 0.6 kg of CO2 is avoided.
• For every 1 kg of orange peel converted into products such as flavours, essential oils, dietary fibres and candied peel, the emission of 0.7 kg of CO2 is avoided.
• For every 1 kg of spent coffee grounds used as a medium for growing oyster mushrooms or for compost production, the emission of 4.6 kg of CO2 is avoided.

Waste from plant production can be a complete meal or a supplement to concentrated animal feed, depending on the content of nutrients and digestible substances. Oat straw stands out for its high nutritional value, followed by barley, while rye has the lowest nutritional value. Dry corn pulp, especially from fresh sweet corn biomass, has bigger nutrition value. The harvest residues of buckwheat and grain legumes, although rich in proteins, show a lower digestibility value due to the increased level of alkaloids. Increasing the nutritional value of these secondary products includes recommended preparation methods such as chopping, soaking in hot water or fermentation with chemical preparations. Chopping straw, for example, reduces feed losses by approximately 30%, ensuring that animals consume the entire biomass. When straw is chopped into smaller pieces, it is easier for animals to consume, leading to more complete utilization of the available biomass. This means that animals are less likely to selectively eat only certain parts of the feed, ensuring a balanced diet and getting all the nutrients needed for growth and health. 

The best secondary agricultural products include small and damaged grains separated before milling, together with the bran that represents the seed coats after the yields have been dehulled. Called animal meal, these residues serve as concentrated low-protein animal feed.

Residues from oil pressing or oil cakes represent energy-rich secondary agricultural products, rich in protein and with a minimal amount of oil, especially soybean oil cakes. They serve as vital sources of vegetable proteins for domestic animals and are essential in concentrated animal feed for different species and categories of animals.

In the field of sustainable agriculture and food production, the concept of circular economy has emerged as a source of hope, promising economic growth, but also care for the environment. Within this paradigm, the use of food residues and by-products has enormous potential, especially in sustainable animal feed production. Through innovative practice and technological progress, such residuals are transformed from ordinary waste into valuable resources, creating a closed-loop system where nothing goes to waste.

By diverting these materials from landfills and incinerators, we not only reduce greenhouse gas emissions, but also reduce pressure on limited resources such as land, water and energy. Moreover, converting food residuals into animal feed reduces the need for conventional animal feed ingredients, thus mitigating the environmental impact associated with their production, such as deforestation and destruction of animal habitats.

Furthermore, the integration of food residues and by-products into animal feed offers economic benefits to both farmers and producers. By reducing feed costs, farmers can improve their competitiveness and resilience to market fluctuations.

However, realizing the principles of the circular economy in the agriculture and food sector requires harmonized efforts from different parties, including policy makers, industry and consumers. Governments must implement supportive policies and regulatory frameworks that encourage the adoption of these practices and promote investment in research and infrastructure. Similarly, industry stakeholders must embrace innovation and collaboration to develop effective technologies and solutions that facilitate the integration of food residues into animal feed production. Finally, consumers play a key role in driving demand for sustainably produced food products and encouraging responsible consumption habits.