Charcoals
Commercial charcoals and other lignocellulosic charcoals represent the carbonized residues of initial starting plant material that has been subjected to incomplete combustion and/or pyrolysis. The chemical and physical properties of charcoal prepared from lignocellulosic material in the laboratory vary significantly and are dependent on multiple factors, including starting material, temperature, ramping rates, atmosphere, and oxygen mass transfer conditions (1). In this context, we propose a large quantity of synthetic charcoal obtained using reproducible techniques from a single source. Moreover, because it still can be difficult to ensure reproducible results, we produced two large batches of each of two well-homogenized charred materials, one of which is representative of wood charcoal and one of which is representative of grass charcoal (2).
Wood and grass charcoal were produced from well-defined biomass sources under standardized conditions in a pilot scale pyrolyis oven (300 mm diameter, 700 mm length) at the Swiss Federal Laboratories for Materials Testing and Research, Ceramics Division. The temperature programme was as follows: room temperature increased at the rate of 300 degrees K per hour up to 200 °C (no hold), then 50 degrees K per hour up to 450 °C (held for 5 hours). Nitrogen flow rate was 500 litres per hour. The wood originates from Chestnut (Castanea sativa) trees and was made into pieces of established size, charred and homogenized. Rice (Oryza sativa) straw was taken as are a reasonable starting material for grass charcoal, since it was easy to obtain, inexpensive, and high in silica (a major chemical difference between grass and wood). Rice straw originated from Southern Switzerland (Magadino Plain). Production conditions and properties of the charcoals are described in detail in (2,3).
Ordering information
The charcoal standards are well homogenized, stored under standard lab conditions, and can be shipped on request. Subsamples (4 g each) can be ordered from Michael W. I. Schmidt, Univ. Zurich, Dept. Geography, 8057 Zurich, Switzerland (michael.schmidt@geo.uzh.ch).
Cost 40 EUR for each charcoal sample.
References
(1) Mackay D. M., Roberts, P. V. 1982. The dependence of char and carbon yield on lignocellulosic precursor composition. Carbon, 20 (2), 87-94.
(2) Hammes K., Smernik R.J., Skjemstad J.O., Herzog A., Vogt U.F., Schmidt M.W.I. 2006. Synthesis and characterisation of laboratory-charred grass straw (Oryza sativa) and chestnut wood (Castanea sativa) as reference materials for black carbon quantification. Organic Geochemistry 37, 1629-1633.
(3) Hammes K., Smernik R.J., Skjemstad J.O., Schmidt M.W.I. 2008. Characterization and evaluation of reference materials for black carbon analysis using elemental composition, colour, BET surface area and 13C NMR spectroscopy. Applied Geochemistry 23, 2113-2122.