Acceleration of Biochar Surface Oxidation during Composting?

Abstract

Biochar composting experiments were performed to determine whether composting is a suitable method to accelerate biochar surface oxidation for increasing its reactivity. To assess the results, surface properties of Terra Preta (Brazil) and ancient charcoal pit (Northern Italy) biochars were additionally investigated. Calculation of O/C ratios by energy-dispersive X-ray spectroscopy demonstrated the anticipated increasing values from fresh biochars (0.13) to composted biochars (0.40), and finally charcoal pit biochars (0.54) and ancient Terra Preta biochars (0.64). By means of Fourier transformation infrared microscopy, formation of carboxylic and phenolic groups on biochars surface could be detected. Carboxylic acids of three composted biochars increased up to 14%, whereas one composted biochar showed a 21% lower proportion of carboxylic acids compared to the corresponding fresh biochar. Phenolic groups increased by 23% for the last mentioned biochar, and on all other biochars phenolic groups decreased up to 22%. Results showed that biochar surface oxidation can be accelerated through composting but still far away from ancient biochars.

Effect of Wood Biochar in Manure‐Applied Sand Columns on Leachate Quality

“…These values were found to be as follows: 83.06% C, 7.4% H, 0.48% N, 6.03% ash, and 0.26% O. Surface area was determined using a Quantachrome Autosorb‐1‐MP instrument as described in Zhou et al (2015). Briefly, sample material was weighed and placed in a 12‐mm sample cell, outgassed, reweighed, and dosed with known quantities of ultrahigh purity N 2 gas.…”

Changes in heavy metal mobility and availability from contaminated wetland soil remediated with combined biochar-compost

“…The binding effect of these functional groups with hydrogen ion in soil led to the increase in soil pH. It has been found that compost could promote the formation of oxygen-containing functional groups in biochar surface on account of the complicated interaction of oxidation and sorption (Khan et al, 2016;Wiedner et al, 2015). Therefore, the specific change of soil pH resulting from the proportion changes between biochar and compost in this study might be explained as follow: when the biochar percentage is low, the interaction between biochar and compost is weak and less due to low biochar amount and high compost content and the weak acidity of compost (pH ¼ 6.23) ( Table 2), so the soil pH increases slightly; as the biochar percentage rises gradually and reaches to 20% and 40%, the higher soil pH is obtained, which might be attribute to the fact that 20% and 40% biochar addition could effectively promote the interaction between biochar and compost.…”

The effect of biochar with biogas digestate or mineral fertilizer on fertility, aggregation and organic carbon content of a sandy soil: Results of a temperate field experiment

“…The biochar was produced from green cuttings in a Pyreg™ reactor at around 650°C (Doerth, Germany, http://www.pyreg.de) ( Wiedner et al., , ). Biochar additions varied, with treatments receiving a single application of biochar in 2012 at a rate of 40 Mg ha −1 (B40) or 1 Mg ha −1 for three consecutive years, resulting in a total application of 3 Mg ha −1 (B3) over the duration of the experiment.…”