Sustainability in dairy farming

What are the environmental impacts of milk production and dairies?

Milk production consumes many resources. Cows require feed, water, pasture, stables, and care. The cultivation of feed such as corn or soy requires a lot of land, often in monocultures, which depletes the soil, reduces biodiversity, and necessitates more fertilizers and pesticides. Cows themselves produce greenhouse gases like methane (CH₄) and nitrous oxide (N₂O). Dairies also consume a lot of energy: milk must be cooled, heated, separated, and pumped. Processes involving high temperatures, such as milk preservation, require particularly large amounts of energy. Furthermore, a significant amount of wastewater is produced, containing milk residues and traces of cleaning agents, which requires extensive treatment before it can be released into the environment. The production of milk itself already heavily burdens the environment – and its further processing into dairy products adds to that. Therefore, it is all the more important that as much of the milk as possible is utilized.

How are milk residues processed further today?

Residues from milk are often utilized in biogas plants. There, microorganisms break down the substances and produce biogas, which mainly consists of methane (CH₄) and carbon dioxide (CO₂). The methane is burned to generate electricity and heat – directly for the dairy or for the power grid. What’s special about biogas: the energy comes from substances that previously absorbed CO₂ from the air. In the case of milk, this happens via the cows’ feed. The CO₂ that plants absorbed while growing is thus contained in the milk and its residues (Image 8). When the methane is burned, this CO₂ is released back into the atmosphere. Unlike coal or oil, biogas does not release old CO₂ that was stored in the ground for centuries. Biogas is therefore more climate-friendly. Nevertheless, CO₂ is released into the atmosphere, and too much of it harms the environment. Moreover, the valuable ingredients of the milk residues are lost through decomposition. Proteins, sugars, and minerals are composed of many different chemical building blocks and therefore have high material value. CO₂ and methane, on the other hand, are simple molecules – they provide energy, but you cannot produce food or valuable substances from them. A truly sustainable approach would be not to break down the by-streams, but to continue using them. Research and creative ideas can ensure that today’s “waste” becomes tomorrow’s valuable raw materials. At the same time, the dairy industry can become more sustainable if individual production steps are designed to be more energy-efficient and environmentally friendly.

How can a dairy make its production steps more sustainable?

An important point is to consume less energy and water. Regarding energy consumption, it is worthwhile to check process temperatures. Many steps in cheese production have been carried out at specific temperatures for generations. Today, we know: in many cases, slightly lower temperatures are sufficient – and this saves a lot of energy (Image 9A). Since cooling also requires energy, these temperatures should also be questioned. Another important measure is to avoid heat loss. If heat is lost, it must be replenished, which requires additional energy. Well-insulated pipes, boilers, and machines help reduce such losses (Image 9A). Furthermore, waste heat can be utilized. Waste heat is heat generated, for example, during the operation of machines. Since this waste heat is often not warm enough for many industrial processes, heat pumps can raise it to a higher temperature, making it usable (Image 9A). If heat pumps are powered by electricity from renewable sources, it is particularly environmentally friendly. A great deal of energy can be saved if heating and cooling are considered together. In the dairy, for example, cold milk is first heated, and after cheese production, the warm whey is cooled again. Energy is required for both processes. With the help of a so-called heat recovery system, however, the two processes can be combined: the whey transfers its heat to the milk and cools down in the process, thereby saving heat and cooling energy. There are also savings opportunities for water consumption, for example, through the treatment and reuse of water or through more efficient cleaning processes. If excess milk is first removed from pipes with a strong airflow, less milk remains in the pipes, and less water is needed for cleaning (Image 9B). However, implementing such changes is often complex. Dairies have grown over many years, and the individual steps are closely linked. Even small changes can have significant impacts on the overall process and costs, as well as cause complications. This can quickly disrupt the production workflow.

What components of milk end up in cheese and which in whey?

During the separation of milk into curd and whey, the components are unevenly distributed between two phases: a solid and a liquid. The solid phase, the curd, is formed by the cross-linking of casein into a kind of matrix. A large portion of the milk fat gets trapped in this network, as does some of the minerals. The fat-soluble vitamins are also predominantly enclosed in the curd because they are bound to the milk fat. How much water remains trapped depends on further processing – this leads to different types of cheese. Whey, on the other hand, is the liquid part that drains out of this matrix. It consists mainly of water and contains primarily the substances that cannot be incorporated into the solid matrix. These include, in particular, milk sugar (lactose) and whey proteins, which are too small and too soluble to be retained in the curd. Water-soluble vitamins and some minerals also pass into the liquid. Thus, from the same milk, two very different products are created: a solid, structurally rich cheese and a thin, but still nutrient-rich whey.

How is whey turned into a sustainable food?

This is precisely what Infinite Roots and the Institute for Biocatalysis are researching from 2025 to 2027 – they use whey as a nutrient for fungal mycelium, which is further processed into a new food product. From 2027, you can discover this exciting topic on Kniffelix.de.