The main reason conventional wisdom recommends against storing potatoes and onions beside each other in a kitchen space is due to the different storage needs of these vegetables. Potatoes will keep longest when you store them between 4.44 and 10 degrees Celsius, while onions keep better when you store them between 10 and 12.8 degrees Celsius. Because most kitchens will not provide these optimal storage temperatures for potatoes and onions, you may find their storage life reduced somewhat from what it would be under ideal storage temperatures.
Place the onions into the large mesh bag. As you place the onions in the bag, check each one for signs of decay or spoilage. If you find onions with soft outer skins or bruising, discard these onions. Additionally, if you smell any onions with a distasteful odour, discard them. Fill the mesh bag with the onions and close the top.
Fill the bin with the potatoes. Examine each potato as you fill the bin and discard any potatoes with bad spots or soft spots. If you detect any spoilage or odours in potatoes, discard them immediately. One bad potato in a bin will quickly spread its decay to other surrounding potatoes.
Hang the onion bag from a location in the kitchen where it will receive ample ventilation. Use the onions before they begin to sprout--within two to three weeks.
Place the potato bin in a cool and dark location in the kitchen. The bottom of a pantry or cupboard may be the ideal spot for storing potatoes in the kitchen. Keep the potatoes away from any potential sources of heat (the oven, the dishwasher or near the area where the refrigerator fan exhausts heat into the kitchen). Use the potatoes within one to two weeks when you store them above 10C.
Do not store potatoes and onions in the refrigerator. The refrigerator temperatures are too cool for optimal onion storage and refrigerator temperature will cause potato starch to turn to sugars (which will affect the way they taste when you cook them).