Luffa (or loofah) is a vine fruit in the same family as the cucumber and they can be used as sponges for cleaning the house, the dishes, and perfect body scrubbers - perhaps you could grow it on your new tunnel trellis!). Best of all, they're a 100% biodegradable and sustainable tool - no plastics are used nor are they fished out of the ocean. You can grow them in your garden!
Simply wait for the fruit to fully ripen, then wait a little longer, until it over-ripens, and when the skin is brown and begins to come away from the inner skeleton or fibres pick the fruit and wait a day or so (perhaps even just one afternoon if its really hot and dry - after all, they come from Summer-fruiting plants), leaving it in the sun so it dries out fully, then break the skin open along a seam that stretches from end to end. Peel away the skin (and compost it) and shake the seeds out. One vine's harvest in the Summer can provide a whole years worth of defoliant bathroom sponges, dish cleaning sponges and general house cleaning scrubbers.
Some have mentioned that after use they can harbour bacteria. Make sure after each use you give it a good clean by rubbing it under running water. They also survive a cycle in the dishwasher. Be that as it may, don't panic... if your loofah sponge is spoiled, compost it and grow some more!