The popular narrative of climate change often posits production of milk and meat as a key culprit of greenhouse gas emissions (GHG). Cattle indeed significantly contribute to the amount of GHG from agriculture. The biggest share of the pie comes from methane emissions that occur in cattle bodies and deposit in manure. Besides GHG, cattle are also blamed for other environmental burdens such as land degradation, biodiversity loss, and water usage.

The top four emitters from agriculture are China, India, Brazil, and USA - countries that the have largest cattle inventories in the world. Intensive farms with a large number of cattle—which are mostly found in China and USA—import maize and soybean to feed cattle, leading to GHG from production and transportation of those crops. Specifically, meeting the demand for soybean through production in Brazil—the biggest soybean exporter—drives deforestation to expand soybean plantations. In addition, cattle ranching in Brazil is also another reason of land clearing and a cause of GHG from land use change.

Is this happening all around the world?

I did a research on smallholder dairy farms in Indonesia. The largest proportion of national milk supply comes from this typical farm in which the farmers keep 2 or 3 cows and occupy only 0.5 hectares of land. The cattle are confined in the barn while the farmers cut and carry grass from the land to feed their cattle. The small size of the land yields a limited amount of grass, so the farmers need to buy compound feed and by-products from agriculture or food industries to supplement the dairy cattle, such as rice straw, by-products of tofu, tapioca, soy sauce, and beer. In addition, the compound feed is made of by-products of wheat flour, rice milling, coffee processing, and oil extraction such as palm oil and coconut oil.

I happened to observe the utilization of different by-products to feed dairy cattle in other regions. For instance, sweet potato vine is commonly fed to dairy cows in Kenya. Because sweet potatoes are an annual crop, the amount of the residue is abundant after the harvest, and the farmers make silage from sweet potato vine to preserve it. A country that exports fruits like Costa Rica produces by-products from fruit plantation and processing. In this way, banana crop residue, pineapple fruit residue, and citrus pulp become feedstuff for Costa Rican dairy farms.

Feeding by-products to dairy cattle complies with one of the principles in circular agriculture, which prompts recycle of waste into food systems. Implementing this principle will reduce nutrient losses from agriculture that cause pollution in the environment. By-products are inedible for humans, but cattle can consume them to produce milk and meat. Hence, by-products are an alternative that allows to avoid feeding human-edible crops to cattle.

“Feeding by-products to dairy cattle complies with one of the principles in circular agriculture, which prompts recycle of waste into food systems”

The challenges of feeding by-products to cattle

Although the nutrients of the by-products are still valuable, the quality might be lower than what found in the main product. The quality of by-products, in fact, is determined by their chemical composition. Some by-products from agriculture are also classified as crop residue with high content of fiber that reduce digestibility and consequently milk production. This is also the case of the hull of grain, a by-product from the milling industry. Depending on the treatment, by-products can be contaminated by toxic substances produced by fungi that are harmful for the cattle.

To transport by-products from crop fields or food industries is another challenge. The high water content of by-products, in fact, hampers the handling during transportation, which can become a laborious process. Distance between the origin of by-products and cattle farms is another issue, especially without good road integration. These issues in the transportation stage potentially lead to losses of by-products.

The availability of by-products is potentially fluctuating because it depends on the production of main products. Across food supply chains, by-products are created from the stage of crop production to the stage of end-users consumption (e.g. retail, household). The by-products are defined as unintended materials that cannot be avoided during production, or former main products with poor quality that are rejected by the market. Many factors are associated with the occurrence of by-products at each stage and classified into internal and external factors. The internal factors are related to management of production or transportation, while the external factors are the result of market conditions.

Moving towards circular agriculture

Feeding by-products is expected to reduce land use expansion due to feed production. Simultaneously, it is in line with another principle of circular agriculture which prioritises the allocation of arable land for food production. Cattle who mainly consume grass must be reared in marginal land. The definition of arable and marginal land does not rely upon the fertility per se, but is regional and functional context-dependent. Thus, policies should be in place to safeguard land allocation for food and feed production, and also for all the other societal functions.

Some strategies to overcome the challenges related to the quality and quantity of by-products need to be explored. It is essential to present this information as transparent as possible for farmers and animal nutritionists who take decisions about feeding management in farms. Quality control is critical to maintain security of by-products. Because the nutrient components of by-products vary over time, a rapid tool, for example near infrared reflectance spectroscopy (NIRS), must be deployed along the supply chain. Similar to the quality control, a forecast to inform quantity of by-products should be accessible so alternatives will be determined immediately when a particular by-product is lacking.

“It is essential to present this information as transparent as possible for farmers and animal nutritionists who take decisions about feeding management in farms”

To realize circularity, dairy farms close the loop through the contribution of manure to soil. However, some farms may not be capacitated to manage manure because of small land size as occurs on smallholder dairy farms. In this case, manure is potentially exported to other farms such as crop and horticulture. Manure management on dairy farms has been implemented successfully through regulatory enforcement, for example the rules on animal manure management in Netherlands.

Nutrient flow is the keyword in circular agriculture. Shifting toward circular agriculture aims to efficiently utilise nutrients within the agricultural systems, so losses in the environment are minimal. Nutrients are also outputs from agriculture as part of food systems. Since the spatial boundary of food systems is drawn from local to global, utilisation of nutrients requires strategic mapping of the resources that allow subsequent parties to obtain the information about the availability of the nutrients. To involve many parties within food systems, a good partnership must be established. Last but not least, we need to put in place attractive business models and present lucrative scheme of nutrients recycling in food systems.

By Titis Apdini

February 2021