Do investments in phosphorus recovery from dairy processing wastewater pay off?

While phosphorus fertilizers contribute to food security, part of the introduced phosphorus dissipates into water bodies leading to eutrophication. At the same time, conventional mineral phosphorus sources are increasingly scarce. Therefore, closing phosphorus cycles reduces pollution while decreasing trade dependence and increasing food security. A major part of the phosphorus loss occurs during food processing. In this article, we combine a systematic literature review with investment and efficiency analysis to investigate the financial feasibility of recovering phosphorus from dairy processing wastewater. This wastewater is particularly rich in phosphorus, but while recovery technologies are readily available, they are rarely adopted. We calculate the Net Present Value (NPV) of investing in phosphorus recycling technology for a representative European dairy processing company producing 100,000 tonnes of milk per year. We develop sensitivity scenarios and adjust the parameters accordingly. Applying struvite precipitation, the NPV can be positive in two scenarios. First, if the phosphorus price is high (1.51 million EUR) or second if phosphorus recovery is a substitute for mandatory waste disposal (1.48 million EUR). However, for a variety of methodological specifications, the NPV is negative, mainly because of high input costs for chemicals and energy. These trade-offs between off-setting pollution and reducing energy consumption imply, that policy makers and investors should consider the energy source for phosphorus recovery carefully.

Extreme heat reduces insecticide use under real field conditions.

Insecticide use and its adverse environmental and health effects are expected to further increase in a warming climate. We here show that farmers' insecticide use, however, declines substantially when facing extreme heat. Using the example of Colorado potato beetles (Leptinotarsa decemlineata) in Switzerland, we find an 11.5% reduction of insecticide use for each day and degree that maximum temperatures exceed 34 °C in the potato growing season. Importantly, our analysis accounts for farmers' behavior under real field conditions, considering the potential adaption of farming practices to extreme heat. It, therefore, highlights how to combine methods to assess and improve our knowledge on the combined major challenges of reducing pesticide risks and coping with the effects of climate change on agriculture while accounting for human behavior. In the analysis, we provide various robustness checks with regard to the definition of temperature extremes, pesticide use indicators, and the chosen statistical model. We further distinguish the principal drivers of the identified effect and find strong evidence that insecticide use reductions are mainly driven by heat-induced decreases in pest pressure rather than heat-induced yield losses that render insecticide applications too expensive. We conclude that similar investigations for other crops and countries are required to assess and understand farmers changing pesticide use decisions under climate change.