In Kees' pigsty, some of the piglets have learnt to pee and poo in separate corners of the pen. The urine can be used directly as an organic fertilizer substitute, but even better is the lack of ammonia emissions. Ammonia is only produced when the urine and faeces come into contact with each other. The faeces-bacteria contain an enzyme called urease which transforms the urea present in the urine into ammonia (NH3). This nitrogen-hydrogen compound does not only cause a bad smell, it also dissipates the valuable nitrogen present as urea into nitrogen-gas, one of the most aggressive greenhouse-gases.

It just so happens that pigs are naturally trained animals. They prefer to poo and pee away from the nest. Pigs are also very smart, and trainable. In 2012, Kees started testing his theory with three pigs, to see if he could train them to poo and pee in different places. He rewarded the pigs with sour sweets, lemon drops. Pigs love the sweet-sour flavour combination, and they don't mind a good crunch either. After five days of sitting by the pen, Kees had trained his first pigs completely. He patented his find in 2015, and since 2018 has set up further tests on a larger scale at his farm.