The farm's general manager is quoted as saying that "(a)t least 80% of what our cows eat will be waste products from Rotterdam's food industry....That might include grains discarded by local breweries, leftovers from restaurants and cafes, by-products from local wheat mills, and even grass clippings, all collected and delivered in electric trucks provided by local "green waste" firm GroenCollect." One of the partners,Minke van Wingerden, says that the urine will be used to grow duckweed, which the cows will eat, and the manure will be processed and sold.
I'm curious about space. The article does not mention the area of the project. How many square feet/meters do forty dairy cows need?