Disposal of Surplus Milk Due to COVID-19
Market disruptions due to COVID-19 are resulting in some operations being forced to dump milk. Waste from milk processing, wash water, and disinfectants is considered wastewater and may not be discharged to septic systems, or to waters of the state.
Although wash water is typically transferred to a lagoon, large quantities of milk should not be dumped into a lagoon as it can negatively affect the microbial action in the lagoon. Likewise, the fat in the milk may negatively impact the microbes in anaerobic digesters.
Environmental Impacts of Milk
Milk has a high biochemical oxygen demand (BOD) under aerobic conditions, and a high chemical oxygen demand (COD) under anaerobic conditions. The high BOD of milk can rapidly deplete the free oxygen in water resulting in fish kills and negatively impact aquatic life.
Under anaerobic conditions (as in some manure storages), the microbes that degrade milk produce offensive odors compared to the odors from manure alone. To minimize odors, avoid spraying anaerobically stored milk, or manure and milk mixtures. Anaerobically stored milk should be applied as close to ground level as possible. Fresh milk can be land applied with less of an odor issue, but care needs to be taken to keep milk out of water sources.
Land Application of Milk
The nutrients in milk need to be accounted for just like a manure application. Care should be taken not to exceed crop phosphorus (P) requirements when soil P tests are above 50 ppm. Milk nutrient content is fairly stable. Permitted facilities can follow the nutrient amounts provided in Table 1.
|Table 1. Estimated application rates of total N, P2O5 and K2O for land application of milk.Manure and milk mixtures will likely have lower N, P2O5 and K2O content than listed here.|
|Milk applied (gallons/acre*)||Total N** (lbs/acre)||P2O5 (lbs/acre)||K2O (lbs/acre)|
|*The pH of milk is roughly neutral and chloride content is modest such that the rates, above, will not result in soil acidification or salt limits.|
|**Assumes 3.3% crude protein.|
|Source: Provisional Guidance: Using Surplus Milk as a Fertilizer Due to the COVID-19 Emergency. 2020. New York State Dept. of Agriculture and Markets. Available at: https://custom.cvent.com/1D82EF6865954ABF95C7904CDE2AE18A/files/72c20521c1d447999d6c79077d0dda2f.pdf|