Castro Herrera, Daniela: Ecological sanitation via thermophilic co-composting of humanure and biochar as an approach to climate-smart agriculture. - Bonn, 2022. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
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author = {{Daniela Castro Herrera}},
title = {Ecological sanitation via thermophilic co-composting of humanure and biochar as an approach to climate-smart agriculture},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2022,
month = jun,

volume = 573,
note = {Lack of basic sanitation and appropriate waste management, limited access to mineral and organic fertilizers, and land degradation are major public health and food security challenges, particularly in developing regions with financial and infrastructural limitations such as in Sub-Saharan Africa. Developing integrated interventions that address these challenges is of great relevance and is becoming more urgent as the effects of climate change increase and as the global population continuously rises. Here, we developed an appropriate-technology ecological sanitation concept via thermophilic composting of human excreta and cattle manure as an approach for climate-smart agriculture. For this, inside traditional wooden compost boxes, we composted human excreta, and separately cattle manure, both with kitchen scraps and teff straw, sawdust and biochar as bulking agents, to produce a compost free of phytotoxicity and pathogens, but rich in nutrients that can be used to improve soil fertility. In order to maximize the benefits of this approach, we particularly aimed at:
(1) Investigating the dynamics of key nutrients and physical and chemical parameters of four composting treatments −human excreta or cattle manure, with and without biochar− to evaluate the feasibility of the appropriate-technology composting process, the type of manure used and the effect of biochar during composting.
(2) Quantifying CO2, CH4, N2O, and NH3 emissions of the different composting treatments to assess their environmental impact and the effect that biochar has on these gas emissions when used as amendment during composting.
(3) Exploring the nutrient dynamics and greenhouse gas emissions of these four types of compost when applied at two different rates (total compost N equaled 170 kg N ha-1, and three times this amount) to a sandy soil at 25°C to evaluate their potential as fertilizers and the role of biochar in increasing C sequestration and reducing nutrient leaching in agricultural soils.
We found that our appropriate-technology thermophilic composting process enabled a well-running and hygienically safe composting not only of cattle manure, but also of human excreta as a hygienically critical waste, as demonstrated by the low nutrient losses, the temperature course, and the relatively low N2O and CH4 emissions. Phosphorus and K delivered by both compost forms showed that the plant demand for P and K based on maize at tropical temperature conditions can be fully covered through human excreta and cattle manure-derived compost application, even at the lower application rate, and could be especially suitable for highly weathered and depleted soils in the tropics with very low P, K and organic matter contents. In contrast, the N provided by all compost treatments was not enough to meet the crop N demand. Our research also demonstrated that compost, especially biochar-compost mixtures, may contribute to carbon sequestration and nutrient retention in agricultural soils and decrease the dependency on synthetic fertilizers, especially on mineral P and K. This work thus demonstrates that the ecological sanitation concept via thermophilic composting with biochar addition is a feasible and climate-smart approach with low requirement for investment and with high potential to increase access to sanitation, soil fertility and food security, and to contribute to climate change mitigation, ecological waste management and sustainable agricultural production.},

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