Nutrient dynamics during composting of human excreta, cattle manure, and organic waste affected by biochar

Abstract

Ecological sanitation via thermophilic composting could be a promising solution to the lack of sanitation and limited access to fertilizers, particularly in developing countries. Here, we conducted a 185‐d thermophilic composting experiment with human excreta, and separately with cattle manure, mixed with kitchen scraps, teff [Eragrostis tef (Zuccagni) Trotter] straw, sawdust, and biochar (BC) by using an appropriate‐technology approach. We followed the dynamics of the most important macronutrients (N, P, K), temperature, moisture, pH, electrical conductivity, cation exchange capacity, as well as content of organic matter, organic C, Ca, Mg, and micronutrients throughout the process. Low N (<47%), P (<9%), K (<11%), Ca (<18%), and Mg (<21%) losses and the temperature profile indicated a well‐functioning thermophilic composting process. Compost temperature was >60 °C for 7, 6, 5, and 8 consecutive days for treatments containing human excreta, human excreta amended with BC, cattle manure, and cattle manure amended with BC, respectively, suggesting a final compost product free of pathogens. The compost mixture with cattle manure and BC reached a significantly higher temperature than the same variant without BC, with a maximum value of 65.9 °C on Day 6. For all treatments, final germination index values >100% indicated compost maturity and the absence of phytotoxic substances. Biochar addition reduced losses of organic matter (18−23%), C (33−42%), and N (49−100%) and decreased the amount of extractable NO3− (32−36%) in the final compost. The tested ecological sanitation concept via thermophilic composting is thus a promising strategy to improve access to cheap fertilizer by safe and sustainable sanitation and waste management.

Organic Waste Generation and Its Valorization Potential through Composting in Shashemene, Southern Ethiopia

“…An ecological sanitation model that uses dry toilets, which collect urine, feces, and toilet paper together, using sawdust as an adsorbent material for avoiding smell, was considered. In these dry toilets, all materials are collected together in 20 L buckets, which have a lid and can be stored for several months without odor until they are used for thermophilic composting [56][57][58].…”

“…After peaking, the temperatures will slowly decrease again, reaching an ambient temperature again some weeks to months later. When the compost pile is turned, however, the temperature will shortly increase again to then slowly drop again [36,37,58].…”

“…This study and the composting study by Castro Herrera et al [58] were both conducted as part of the ClimEtSan project, and both used organic waste from Shashemene. Castro Herrera et al [58] additionally used human excreta from ecological sanitation. The study from Castro Herrera et al [58] was conducted during the same period as the present study.…”

“…Castro Herrera et al [58] additionally used human excreta from ecological sanitation. The study from Castro Herrera et al [58] was conducted during the same period as the present study. Following the successful thermophilic composting method of Castro Herrera et al [58], we used the following ratio of organic waste, bulking material (i.e., straw) and human excreta (on a DW basis) for our calculations:…”

Optical sensing of aqueous nitrate anion by a platinum(ii) triimine salt based solid state material

“…The selective and sensitive detection of specific anions for the monitoring and assessment of water quality remains a global environmental and chemical challenge. 1,2 One such example is the nitrate (NO 3 − ) anion; it has widespread use in munitions/explosives manufacturing and chemical fertilizer preparation, 3–5 and an abundance of nitrate found in livestock as well as organic wastes 6 has led to groundwater and food supply contamination and raised public health concerns. Epidemiologic studies have associated continued NO 3 − exposure via ingestion with multiple medical issues that include spontaneous abortions in pregnant women, 7 birth defects of the central nervous system and intrauterine growth restriction in children, 8 and cardiovascular effects 9 and gastric cancer in adults.…”