Abstract
The current study aimed at evaluating an untreated pig manure, firstly for its suitability for soil amendment in combination with an agricultural/bio-solid biochar, and secondly for its potential to be used for adsorption of hazardous species, replacing expensive activated carbons. Column soil leaching experiments were designed to simulate field conditions, and physical, chemical and mineralogical analyses were performed for raw materials and/or leachates. For activated carbon production, the manure was gasified by steam or carbon dioxide at high temperatures. Biochars were analyzed for organic and mineral matter, structural characteristics and organic functional groups. Activation by steam or carbon dioxide greatly enhanced specific surface area, reaching values of 231.4 and 233.3 m2/g, respectively. Application of manure to the soil promoted leaching of nitrates and phosphates and raised COD values of water extracts. Biochar addition retained these ions and reduced COD values up to 10 times at the end of the three-month period. The concentrations of heavy metals in the leachates were low and, in the presence of biochar in soil blends, they were significantly reduced by 50–70%. The manure presents a significant potential for adsorption of various pollutants or improvement of soil amendment if carefully managed.
Highlights
The ash content of manure was high, whereas its carbon, hydrogen and oxygen contents were lower among the other materials
The amounts of sulfur and nitrogen of manure and bio-solid samples were significant, revealing gaseous emissions during thermal treatment, and increased capacity for plant nutrition when applied to soils for amelioration
When manure biochar was activated with either steam or carbon dioxide at high temperatures, the yield was lower with respect to pyrolysis only and the drop was greater in the presence of steam
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Animal wastes such as manure, a low-value byproduct of livestock feedlots, are readily available in large quantities in most countries around the world, including those of South. In Greece, where animal breeding activity is highly developed, about 41 Mm3 of animal wastes is produced annually [1] and stocked outside animal processing industries or in rural areas, causing environmental pollution. Traditional land application is no longer a viable solution. EU directives 1991/31/EC and 1991/676/EC imposed a reduction in the quantity of biodegradable wastes going to landfill
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