In this review, we summarize the knowledge of the production and properties of charcoal that has been accumulated over the past 38 millenia. The manipulation of pressure, moisture content, and gas flow enables biomass carbonization with fixed-carbon yields that approachor attainthe theoretical limit after reaction times of a few tens of minutes. Much of the heat needed to carbonize the feed is released by vigorous, exothermic secondary reactions that reduce the formation of unwanted tars by augmenting the charcoal yield in a well-designed carbonizer. As a renewable fuel, charcoal has many attractive features:  it contains virtually no sulfur or mercury and is low in nitrogen and ash; it is highly reactive yet easy to store and handle. Carbonized charcoal can be a good adsorbent with a large surface area and a semimetal with an electrical resistivity comparable to that of graphite. Recent advances in knowledge about the production and properties of charcoal presage its expanded use as a renewable fuel, red...

/pdf/the-art-science-and-technology-of-charcoal-production-2yxzbuvb7k.pdf

The Art, Science, and Technology of Charcoal Production†

Impact of pyrolysis temperature and manure source on physicochemical characteristics of biochar.

The removal of crop residues for bio-energy production reduces the formation of soil organic carbon (SOC) and therefore can have negative impacts on soil fertility. Pyrolysis (thermoconversion of biomass under anaerobic conditions) generates liquid or gaseous fuels and a char (biochar) recalcitrant against decomposition. Biochar can be used to increase SOC and cycle nutrients back into agricultural fields. In this case, crop residues can be used as a potential energy source as well as to sequester carbon (C) and improve soil quality. To evaluate the agronomic potential of biochar, we analyzed biochar produced from poultry litter, peanut hulls, and pine chips produced at 400°C and 500°C with or without steam activation. The C content of the biochar ranged from 40% in the poultry litter (PL) biochar to 78% in the pine chip (PC) biochar. The total and Mehlich I extractable nutrient concentrations in the biochar were strongly influenced by feedstock. Feedstock nutrients (P, K, Ca, Mg) were concentrated in the biochar and were significantly higher in the biochars produced at 500°C. A large proportion of N was conserved in the biochar, ranging from 27.4% in the PL biochar to 89.6% in the PC biochar. The amount of N conserved was inversely proportional to the feedstock N concentration. The cation exchange capacity was significantly higher in biochar produced at lower temperature. The results indicate that, depending on feedstock, some biochars have potential to serve as nutrient sources as well as sequester C.

Effect of Low-Temperature Pyrolysis Conditions on Biochar for Agricultural Use

We investigated the behavior of biochars in arable and forest soil in a greenhouse experiment in order to prove that these amendments can increase carbon storage in soils. Two qualities of biochar were produced by hydrothermal pyrolysis from 13C labeled glucose (0% N) and yeast (5% N), respectively. We quantified respiratory losses of soil and biochar carbon and calculated mean residence times of the biochars using the isotopic label. Extraction of phospholipid fatty acids from soil at the beginning and after 4 months of incubation was used to quantify changes in microbial biomass and to identify microbial groups utilizing the biochars. Mean residence times varied between 4 and 29 years, depending on soil type and quality of biochar. Yeast-derived biochar promoted fungi in the soil, while glucose-derived biochar was utilized by Gram-negative bacteria. Our results suggest that residence times of biochar in soils can be manipulated with the aim to “design” the best possible biochar for a given soil type.

Effect of biochar amendment on soil carbon balance and soil microbial activity

Combustion and gasification rates of lignocellulosic chars

A half century ago, Rosalind Franklin identified two distinct families of organic materials:  those that become graphitic during carbonization at high temperatures and those that do not. According ...

Do All Carbonized Charcoals Have the Same Chemical Structure? 1. Implications of Thermogravimetry−Mass Spectrometry Measurements

Charcoals produced by a modern, efficient method were studied in the kinetic regime, at oxygen partial pressures of 0.2 and 1 bar by thermogravimetric experiments and their reaction kinetic modeling. The charcoals were ground to an average particle size of 5−13 μm. A partial removal of minerals from the feedstock (corncobs) by an acid-washing procedure resulted in ca. 6 times higher specific surface area in the charcoal. Despite the increased surface area, this sample evidenced a much lower reactivity. A model based on three reactions gave an adequate description over a wide range of experimental conditions. Thirty-eight experiments on four charcoal samples were evaluated. The experiments differed in their temperature programs, in the ambient gas composition, and in the grinding of the samples. Characteristics of the combustion process were determined including activation energy values characteristic for the temperature dependence of the burnoff, formal reaction orders characterizing the dependence on the...

/pdf/combustion-kinetics-of-corncob-charcoal-and-partially-18nrnz9m0s.pdf

Combustion Kinetics of Corncob Charcoal and Partially Demineralized Corncob Charcoal in the Kinetic Regime

A high-yield activated carbon is produced from macadamia nut shell charcoal by (i) carbonization of the charcoal at 1173 K, (ii) air oxidation of the carbonized charcoal in boiling water (AOBW) at 503−553 K, and (iii) activation (a second carbonization) of the oxygenated carbon. In step ii, air is bubbled through a sparger to maintain a relatively high concentration of dissolved oxygen in the water, and the boiling water serves to control the temperature of the carbon during its gasification by the dissolved oxygen. Carbon dioxide is observed to be the only gaseous product of the oxidation chemistry. The oxidation results and the properties of the activated carbons from AOBW are similar to those obtained by controlled atmospheric air oxidation. However, the rate of CO2 formation is observed to increase with time to a plateau for AOBW, whereas the gasification rate decreases with time for atmospheric air oxidation. Multiple cycles, involving AOBW followed by activation, efficiently increase the specific su...

Activated Carbon from Macadamia Nut Shell by Air Oxidation in Boiling Water

Porous, fluorescent zirconia particles of nearly 380 nm diameter were prepared without template molecules
or labeling dyes. The porous structure is the result of aggregation-induced particle formation. The inherent
fluorescence is assigned to coordinatively unsaturated Zr4+ ions at the sol–gel derived ZrO2 surface. After
physico-chemical characterization of the native zirconia particles carboxyl and/or amine bearing drug molecules
(D,L-a-difluoromethylornithine – DFMO, ursolic acid – UA and doxorubicin – DOX) were adsorbed
onto their surface, and the products were analyzed with Fourier-transform infrared spectroscopy (FTIR),
thermogravimetry (TG), small-angle X-ray scattering (SAXS), fluorimetry and zeta potential vs. pH measurements.
We have found that DOX complexes coordinatively unsaturated Zr4+ ions without dislocating them,
while carboxyl-bearing drugs interact with basic surface Zr–OH sites eliminating some of the carbonate
species. The adsorption of UA at the zirconia surface shifts considerably the isoelectric point of the surface
and thus provides kinetic stability to the particles at physiological pH. An in vivo biodistribution study in
two healthy dogs performed by SPECT/CT detection after 99mTc labeling of the nanocarriers has shown
the possibility of drug delivery application.

Inherently fluorescent and porous zirconiacolloids : preparation, characterization and drugadsorption studies

In this work the torrefaction of two typical Hungarian biomass materials, wheat straw and black locust wood was studied. Three different torrefaction temperatures were applied: 225, 250 and 300°C with one hour isothermal period. The untreated and torrefied biomass materials were characterized by thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) techniques. The alkali ion contents of the samples were determined by ICP-OES technique. It was found that the thermal treatment at 225°C for 1 hour modifies the thermal decomposition mechanism of the cellulose content of the sample, indicating chemical changes in the cellulose structure. At 250°C the hemicellulose content of the analyzed biomass materials partially decomposes. Furthermore, the most labile lignin groups (terminal CH2OH) also start to decompose. At 300°C torrefaction temperature the major part of hemicellulose and cellulose decomposes. The degree of the cellulose decomposition highly correlates with the alkali ion content of the samples.

Emma Jakab

Papers

Do All Carbonized Charcoals Have the Same Chemical Structure? 1. Implications of Thermogravimetry−Mass Spectrometry Measurements

Combustion Kinetics of Corncob Charcoal and Partially Demineralized Corncob Charcoal in the Kinetic Regime

Activated Carbon from Macadamia Nut Shell by Air Oxidation in Boiling Water

Inherently fluorescent and porous zirconiacolloids : preparation, characterization and drugadsorption studies

Thermal decomposition of black locust and wheat straw under torrefaction