Abstract
The application of biochar (the by-product of biomass pyrolysis), as a soil amendment has been accepted as a sustainable solution to improve soil quality. The current study aims to establish a decision support tool for characterizing, ranking, and selecting biochars of different origins for soil improvement, thereby contributing to the development of a systematic approach, which lacks in the existing literature.The development of a Multi-Criteria Decision Support Approach applying a banded and weighted rating and scoring system allowed the selection and ranking of various biochars suitable for improving sandy soils before application. First, 14 selected, different biochar products (produced from industrial by-products, herbaceous, wood-based and manure-based feedstocks) were characterized with several physicochemical, biological and ecotoxicological methods taking into account both the technological and the environmental efficiency aspects of biochar utilization. Then, a system for the assessment and ranking of biochars for acidic, and calcareous neutral sandy soil improvement was developed, which could be flexibly adapted to different soil problems as well. Based on their performance in the tests, scores from (−5) to (+5) were assigned to each biochar. As a result, the grain husks and paper fiber sludge biochar was ranked as the most suitable for both acidic and neutral calcareous sandy soil improvement, with 55 and 43 scores, respectively (from the maximum 100). The applicability of this innovative multicriteria scoring-ranking system, as a tool for potential biochar users, was verified in microcosms and field-scale experiments, demonstrating the positive influence of this biochar on the acidic sandy soil.
Highlights
Biochar, the solid product of organic material pyrolysis is a highly heterogeneous material with chemical composition and physical properties that vary depending on feedstock and pyrolysis conditions [1, 2]
Based on XRF measurements performed on several biochar products and on literature data we found that the limit value was mostly exceeded in case of the following toxic metals: Co, Cu, Cr, Ni, Zn
3 Results and discussion 3.1 Results of biochar characterization The biochars were tested with a wide range of methods taking into account both the technological and the environmental efficiency aspects
Summary
The solid product of organic material pyrolysis is a highly heterogeneous material with chemical composition and physical properties that vary depending on feedstock and pyrolysis conditions [1, 2]. Many studies have shown that biochar applied to soil positively influences soil physico-chemical properties and improves soil functions, such as water and nutrient holding capacity [3,4,5,6,7], enhances resilience to drought and certain diseases and contributes to climate change mitigation by building soil carbon sinks [8]. The fact that the raw materials (feedstocks) and the biochar product may contain high concentrations of organic and inorganic contaminants imposes the environmental and human risk assessment to provide information for a safe biochar application [2, 5, 11] Connected to this topic, there are gaps in the ecotoxicity assessment of biochars, several studies have been performed on this issue [5, 9, 11].
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