Sjaak Twisk has a Demeter certificate besides his organic certificate. In the summer his cows graze in the adjoining nature reserve. In the winter they are housed in the stables which have recently been rebuilt and have solar cells on the roof. These solar cells provide a sizeable chunk of the energy used on the farm. Sjaak Twisk is specialised in the long term (mechanical) storage of onions and shallots, which requires quite a bit of energy.