Evaluating the environmental and agronomic implications of bone char and biochar applications to loamy sand based on sorption data

Azeez et al. Environmental Systems Research https://doi.org/10.1186/s40068-024-00379-y Environmental Systems Research (2024) 13:49 Open Access RESEARCH Evaluating the environmental and agronomic implications of bone char and biochar applications to loamy sand based on sorption data Jamiu Oladipupo Azeez1,2 , Ganiyu Olawale Bankole1* , Adeoba Courage Aghorunse1 , Toyin Blessing Odelana3 and Oladele Abdulahi Oguntade3 Abstract Background The widely adopted use of charred biomass for agronomic and environmental purposes; and the reported positive and deleterious effects necessitated the need for this study to ascertain the potential causes of the erratic results surrounding the use of charred biomass in agriculture and the environment. A batch sorption experiment was carried out to determine the sorptive and desorptive capacity of bone char and biochar on nitrate, ammonium, phosphate and sulphate concentrations in a loamy sand soil. The potential agronomic and environmental implications of the sorption data were also discussed. Results The results indicated that bone char is richer in nutrient composition than biochar, with 70% more ability to sorb nutrients. The bone char and biochar sorption isotherms conformed to the H-curve isotherm type. Bone char and biochar have multiple layers of adsorption sites. Nutrient adsorption maxima, binding energy, and maximum buffering capacities of the soil were increased with the addition of bone char and biochar. The unamended soil was observed to retain as low as 6% of added nitrate to as much as 58% of added phosphate, while bone char retained 56% of added sulphate, 47% of phosphate, 76% nitrate and 64% of ammonium. Generally, bone char retained 60.6% of the added nutrients, while biochar retained 40.7% of the nutrients. The addition of bone char led to a 45.8% increase in the nutrient retention ability of the soil and a 36.1% increase with the addition of biochar. Conclusion The nutrient sorption characteristics of biochar should be studied prior to its use as a soil nutrient amendment. It was concluded that bone char or biochar is a potential soil nutrient immobilizer; hence, applications for agronomic purposes should take cognizance of the native soil fertility so as to appropriately add fertilizer input before use. Keywords Bone char, Biochar, Soil nutrients, Sorption isotherms, Adsorption, Desorption, Immobilization *Correspondence: Ganiyu Olawale Bankole 1 Department of Soil Science and Land Management, Federal University of Agriculture, P.M.B. 2240, Abeokuta, Ogun state, Nigeria 2 Crop Research Program, Institute of Food Security Environmental Resources and Agricultural Research, P.M.B. 2240, Abeokuta, Ogun state, Nigeria 3 Department of Crop Production, College of Agricultural Sciences, Olabisi Onabanjo University, Ayetoro, Ogun state, Nigeria © The Author(s) 2024. 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To view a copy of this licence, visit http:// creativecommons.org/licenses/by-nc-nd/4.0/. Azeez et al. Environmental Systems Research (2024) 13:49 Background The recycling of organic wastes in the raw or processed forms is a world-wide popular practice. This is partly because of the need to reduce and reuse waste materials and to eventually ensure environmental sustainability. The use of processed organic wastes in agriculture has been advocated by scientist and is popularly being adopted, particularly by organic agriculture practitioners basically because of its relative affordability and also due to its environmental friendliness (Piccirillo 2023). Animal bones, wood shavings, and sawdust are major waste generated from animal-meat and forestry enterprises, particularly in tropical Africa where animal meats are processed almost manually and where timbers are sawed and smoothed using crude equipment. One of the alternative ways of using animal bones is the incineration of the bones and the resulting ash used as bone meal in the poultry industry. This is the common practice in subSaharan Africa, but the current use of the bone as a feed material in the production of bone char is gaining popularity (Amalina et al. 2022). Wood shavings and saw dust are relatively more abundant and constitute environmental nuisance in saw mills in south western Nigeria and other sub-Saharan African countries. This menace has necessitated the need to look for alternative use of the waste. This has resulted into the conversion of the saw dust and wood shavings into ashes and their subsequent application as liming materials, this, however is known to contribute to the carbon-dioxide pool in the atmosphere and hence, contributing to global warming. The agronomic use of biochar made from wood shavings has wide acceptance in Africa but little is known of bone char. The agronomic importance of the application of charred organic materials from either plant or animal origins is enormous. Several works have reported the improvement in the soil’s ability to supply nutrients and the overall improvement in soil physical, microbiological, and chemical properties (El-naggar et al. 2019; Irfan 2017; Tomczyk et al. 2020; Gu 2021). Application of biochar has also been reported to increase the yield of crops grown in the soils to which the biochar has been applied (Li et al. 2018; Azeem et al. 2021). The use of biochar in environmental studies in the developed countries are well documented in literatures (Hassan and Carr 2021; Talaiekhozani et al. 2021) but not much of such studies have been done or reported in the sub-Saharan African countries, this is majorly due to the wide popularity and the use of biochar amongst agronomists but less by the local environmentalists. Biochars properties have been documented to be dependent on the types of feedstock and the pyrolysis temperature (Rashid et al. 2019). The structural and elemental assessment of biochars has earlier been reported to assists in anticipating their specific ecological impact (Li et al. 2016). Page 2 of 15 Usually the fibrous structures of the wood shavings or sawdust and the hard texture of bone were retaine (...truncated)