Better and even faster, instead of taking dung (which has fewer micro-organisms necessary for facilitation of biogas production), just go to the nearest slaughter house. Pick the semi-processed material from the stomach, that green half digested grass they remove from the ruminants after slaugher to get matumbo; and start adding starch on it. By the end of day 2, you will start getting biogas. I dont know how efficient the ready made products are, but l know the entire set-up is costly (around 40-50k). You can buy materials and do your own at 15k at home; and it'll give you enough gas to cook for the extended family!
The laudable is more often than not rendered laughable by overclaim