Activated Biochar

In 2017, the Ithaka Institute launched the Empyrion project — funded by the Swiss Federal Office for the Environment — to answer a straightforward question: can biochar produced from diverse, regional available waste biomass replace fossil coal-based activated carbon in municipal wastewater treatment?

The project produced a systematic series of over 100 activated biochars from different feedstocks, varying pyrolysis temperature and activation conditions. The results demonstrated that wood and woody residue biochars, physically activated at high temperatures, can eliminate organic micropollutants from biologically treated wastewater at efficiencies comparable to commercial fossil-based activated carbon (Hagemann et al. 2020). The work was conducted in collaboration with Agroscope and Eawag (Swiss Federal Institute of Aquatic Science and Technology), with pilot-scale testing in operational wastewater treatment plants.

The significance is both environmental and economic. Switzerland alone exports over 170,000 tonnes of waste timber annually. Processing even a fraction of this through pyrolysis and activation would produce roughly three times the activated carbon needed for the country's advanced wastewater treatment — while sequestering carbon rather than releasing it. The activated biochar pathway turns a waste management problem into a climate-positive water treatment solution.

A companion publication (Hagemann et al., 2018) provided a systematic review linking activated carbon, biochar, and charcoal — three forms of pyrogenic carbon that had been studied in separate scientific communities — establishing the conceptual framework for treating them as a continuum rather than distinct materials.

More recent work addresses per- and polyfluoroalkyl substances (PFAS), the persistent synthetic contaminants now found in soils, water, and food chains worldwide. In our publication led by Cornelissen et al. (2025), we proposed a closed-loop remediation concept: PFAS-contaminated soils are phytoremediated using plants that accumulate PFAS in their biomass; the harvested biomass is pyrolysed, destroying the PFAS molecules at high temperature; and the resulting biochar is returned to the soil as a sorbent and carbon sink. The "virtuous cycle" of phytoremediation, pyrolysis, and biochar application provides a scalable pathway to bring PFAS-contaminated agricultural land back to safe levels for feed and food production.

Complementary research on biochar's interaction with PFAS includes work on sorption mechanisms (Goranov et al. 2024) and the activation of persulfate by biochar and iron for the degradation of organic contaminants (Zhuang et al. 2025) — extending the activated biochar concept from passive sorption to active chemical remediation.