Household Supplies is a crafting part in Dying Light. Items that you can find in a regular household - sugar, baking soda, etc. Don't discount the basics because a little do it yourself will go a long way. Household supplies are usually required for exploding throwables like DIY bombs. Household supplies are also sold by traders.
Household supplies farming: A constant supply of household supplies can be found at a safehouse just north of the school. There is a room (next to the room with the trader) where a pack of household supplies can be found placed on a table (next to a coffee machine). If you sleep once (the resting bed is located on the upper floor) the pack will reappear. This process can be repeated to "farm" household supplies.