Dung Plus Kitchen Waste: A Co-Digestion Bound and a Bucket Rule for Households

Adding kitchen waste to a cattle-dung digester raises gas yield, but two separate limits restrict how much can be added. This simulated study, not a measurement, states a carbon-to-nitrogen ratio of 25 for cattle dung and 14 for mixed kitchen waste, with a target window of 20 to 30, and a stated acidification criterion based on the buffering capacity of dung. The carbon-to-nitrogen limit alone allows kitchen waste up to 29.32 percent of daily volatile-solids loading. The acidification limit is tighter, at 22.22 percent, and therefore governs. At that safe share the blend has a carbon-to-nitrogen ratio of 20.99 and a blended yield of 0.3178 m3 per kg of volatile solids, a gain of 13.5 percent over dung alone at fixed total loading. Translated into household measures, the governing limit becomes one 10-litre bucket of kitchen waste to five buckets of cattle dung, which gives a kitchen share of 21.69 percent and a ratio of 21.07. One bucket to four buckets, at 25.71 percent, exceeds the acidification bound.