Horse chestnuts contains a substance (saponin) that apparently work like soap. If you have heard of soap nuts, this is the same principle. Do like this to make your own “green” laundry detergent:
Harvest chestnuts while they are green. (Four chestnuts equals about 1 liter of detergent. You use up to 0.5 deciliters for one wash.)
Peel off the first (green) and second (brown) layers so only the white insides remains.
Mix chestnuts with 1-liter water per four chestnuts, until the mix is white and foamy. The water cannot be hard (pH above 9) for this to work. Add some vinegar to make it softer, if needed. Crush the chestnuts with a hammer first if you are unsure if your blender is up to the task.
Filter the mix with a sieve and pour into bottles.
I’m not sure how long it lasts. Someone said a month, another a week if stored in the fridge. Perhaps it could be kept in the freezer for longer storage. Let me know if you know. You can also dry and store peeled chestnuts for later use if you make them into granules first.
Disclaimer: I haven’t tried this myself. Chestnuts are out of season. 🙂
Original photo by Andrew Dunn (File:Aesculus hippocastanum fruit.jpg - Wikimedia Commons).