The best crackers we've ever tasted, made from spent grain!
Spent grain is a byproduct of brewing beer, where almost all of the carbohydrates are extracted by steeping grains like barley, wheat, and oats in hot water. The grain is then drained and rinsed (sparged) to get even more of the sugars out to make beer.
For years we just composted most of the spent grain, as the texture is quite coarse and too sticky to make bread (unless you only use 10% or less spent grain in the recipe). One solution, as with many food byproducts, is to feed it to animals, and both the chickens and goats absolutely love it.
However, the most delicious, human-centered use we've found is to make crackers, which are notoriously packaging-heavy to buy, and very expensive too - decent crackers are $50-$80 per kilo!
All credit for the recipe goes to @lucienalperstein, who recommends using around equal quantities of bakers flour and spent grain, a good pinch of salt, and enough whey or water to make a stiff dough. This is kneaded and rolled out, and ideally put through a pasta maker on a fairly low setting (we gradually go from 7 down to 2) to get nice thin sheets, which are baked at 180 degrees Celcius for 10 minutes or so.
If you don't know any brewers, you can use bread flour and any mix of grain, nuts, and spices you like. Depending on what you use you might need to put it through a grinder or food processor first, or a good old-fashioned mortar and pestle.