Analysis & Characterisation
The analytical infrastructure for biochar quality and carbon sink certification did not exist when the EBC was first published in 2012. Standard methods developed for coal, soil, or activated carbon were not directly transferable to the biochar matrix — a highly porous, heterogeneous pyrogenic material with unique adsorption behaviour that confounds conventional extraction and measurement techniques. Building a reliable analytical framework was not a secondary task; it was a precondition for everything else.
The institute's role in this began 2013 with organizing the first international biochar inter-laboratory comparison with 24 participating laboratories from 12 countries. The proficiency test was assisted by the EU-COST Action TD1107. The results (Bachmann et al. 2015) revealed the scale of the problem: reproducibility across laboratories was poor for several key parameters, particularly PAH, where biochar's strong adsorption capacity meant that standard soil extraction methods systematically underestimated contamination. The ring trial established which methods worked for the biochar matrix and which did not, directly shaping the analytical protocols codified in the EBC. To this day, only EBC-endorsed laboratories using validated extraction methods are accepted for certification - a direct consequence of this early work.
Contaminant Analytics
The long-standing collaboration with Thomas Bucheli and Isabel Hilber at Agroscope produced the analytical foundation for contaminant control in biochar. Hilber, Bucheli & Schmidt (2012) published the first quantitative PAH determination method validated for the biochar matrix — demonstrating that standard soil methods systematically underestimated PAH content due to biochar's extreme sorption capacity, and establishing toluene Soxhlet extraction as the reference method. This was the prerequisite for all subsequent regulation. The three authors also provided (2015) the comprehensive review of PAHs and polychlorinated aromatic compounds in biochar for the second edition of Biochar for Environmental Management, the field's standard reference text.
A critical question followed: if biochar binds PAHs so strongly, are those PAHs actually available to organisms? Hilber et al. (2017) measured bioavailability and bioaccessibility across 43 real-world biochars including post-pyrolytically treated samples (co-composted, lacto-fermented). The result: PAHs in biochar were overwhelmingly desorption-resistant, and biochars acted as net sinks rather than sources of PAHs in the environment. Exposure only became relevant above total concentrations of 10 mg/kg — well above the EBC threshold of 6 mg/kg. Hilber et al. (2019) extended this to animal systems, incubating biochars in cow ruminal liquid and finding that at higher PAH concentrations (up to 60 mg/kg), more than half of the PAHs were released in the digestive system — the paper that justified the strict EBC-Feed PAH limits.
On the production side, Grafmüller et al. (2024) investigated the formation of polychlorinated dioxins and furans (PCDD/F) and PCBs during the pyrolysis of chlorine-rich feedstocks, establishing the conditions under which dioxin formation can be reliably prevented.
Physical Chemistry
Understanding how biochar interacts with water and dissolved substances at the molecular level requires methods beyond conventional chemical analysis. Conte & Schmidt (2017) introduced Fast Field Cycling NMR relaxometry to biochar science — a technique that measures the dynamics of water molecules within biochar's pore system, revealing how water is retained, moves, and interacts with the pyrogenic carbon surface at timescales invisible to bulk measurements. This line of work was extended in a broader review (Conte et al., 2021) synthesising recent advances in understanding biochar's physical chemistry, including surface interactions, porosity, hydrophobicity transitions, and the role of organic coatings in modifying biochar behaviour after soil application. Both publications contribute to moving biochar characterisation beyond static property lists toward a dynamic understanding of how the material actually functions in its environment.
Permanence Proxies
Predicting how long biochar carbon will persist without waiting centuries is the central analytical challenge for C-sink certification. Hagemann et al. (2025) systematically analysed over 100 biochars, measuring three candidate proxies: the H/Corg molar ratio, hydrogen pyrolysis (HyPy), and the solid electrical conductivity (SEC) measured under standardised compression using the Black Gauß I device developed by the Ithaka Institute and Eurofins. All three correlated strongly with each other and with pyrolysis severity. HyPy-resistant carbon reached over 90% of total carbon in high-temperature biochars. SEC proved to be a fast, inexpensive alternative suitable for routine quality control. A complementary approach uses Random Reflectance, an optical method adapted from coal petrology. Sanei et al. (2025) introduced inertinite quantification — the geologically stable maceral group in coal — as a direct morphological proxy for the persistent carbon fraction in biochar, grounding C-sink certification in methods peer-reviewed in geology for over a century. These proxies now form the analytical backbone of the Global Biochar C-Sink Standard v4.0.
A current frontier is the development of proxies for biochar permanence — methods to predict how long biochar carbon will persist in the environment without waiting centuries for empirical confirmation. Hagemann et al. (2025) systematically analysed over 100 biochars produced across a wide range of temperatures and feedstocks, measuring three candidate proxies: the H/Corg molar ratio (already used in the C-Sink standards), hydrogen pyrolysis (HyPy, which eliminates all non-aromatic and small aromatic species up to seven fused rings), and the solid electrical conductivity (SEC) of the compressed biochar. All three proxies correlated strongly with each other and with pyrolysis severity. HyPy-resistant carbon — the fraction surviving hydropyrolysis at 550°C under hydrogen pressure — reached over 90% of total carbon in high-temperature biochars, confirming it as a robust measure of the geologically persistent carbon pool. SEC, measured under standardised compression using the Black Gauß I device developed by the Ithaka Institute and Eurofins, proved to be a fast, inexpensive proxy that correlates with both HyPy resistance and H/Corg, making it suitable for routine quality control. These three proxies now form the analytical backbone of the persistence modelling in the Global Biochar C-Sink Standard v4.0. The current state of biochar permanence science and its implications for policy and certification are summarised in a policy commentary co-authored with leading international biochar scientists (Schmidt et al. 2025).
The institute does not operate an analytical laboratory. Its role is to develop the methods, validate them through inter-laboratory comparisons and peer-reviewed publication, and codify them into the EBC and C-Sink standards. The routine analysis is performed by EBC-endorsed laboratories; the analytical innovation happens here.