Black liquid soap, by-product of homemade bio-diesel production. Mostly composed of used cooking oil, traces of methanol and caustic soda present. I have used this for years to clean cars, work clothes, bio-diesel apparatus. and used on kids slippery dip many times. no adverse effects to grass. The process is called transesterfication,google it. Only interested in parting with large amonts, 20-100 litres.