Evaluating the performance of humanure as a potting mix for lettuce (Lactuca sativa) seedlings

Composting human feces (“humanure”) is a simple, affordable method for recycling waste, producing a material similar to commercial potting mixes. This novel approach contrasts with more common practices like biosolids application and wastewater irrigation, offering new opportunities for fecal reuse in horticulture and home gardening. This study evaluated the suitability of humanure as a potting mix for lettuce (Lactuca sativa) seedlings in an emergence experiment. Four humanure blends from small-scale composting systems were compared to two garden soils and a commercial potting mix as a control. Emergence speed and total emergence were combined into an emergence index (EI), and seedling size was measured after 25 days. Three of the four humanure blends performed comparably to the control, with EIs over 77.4 and leaf growth above 2.36 cm. The fourth blend, with a lower pH, had good emergence (EI = 53.4) but stunted growth (<0.84 cm). These results highlight the variability in homemade compost quality and the importance of proper management. Garden soils performed poorly in terms of emergence (EI = 12.2 and 7.6), with insufficient seedlings for statistical analysis on growth. This study demonstrates that small-scale composting of human feces can produce high-quality compost suitable for use as a potting mix. It also underscores the need for improved guidelines and regulations for the production and use of humanure beyond traditional sewage applications.