Summery of the Final EU-COST and ANS Biochar Symposium 2015

End of September 2015, the Joint International EU-COST and ANS e.V. Biochar Symposium was hosted Hochschule Geisenheim University which was visited by roughly 190 researchers, practitioners and stakeholders from Europe and overseas.

Biochar is a recalcitrant form of biogenic carbon that can be used to sequester ("lock up") atmospheric CO2 that has formerly been fixed by photosynthesis into biomass as carbon (C), with the general idea to use this "recycled atmospheric carbon" for beneficial environmental and agricultural purposes. Biochar can be produced by modern clean pyrolysis techniques from a range of biogenic feedstock materials such as greenwaste, greenhouse residue, grape and fruit tree wood and prunings, wood-chip sievings, grain husks, paper fiber sludge, nut shells, digestate and so on; it may be called "charcoal" if the feedstock is pure wood. In modern pyrolysis techniques the generated heat and oil can be used to substitute fossil fuels. Another technique, hydrothermal carbonization, was also touched as a conference subject, mainly for P recycling from waste streams such as sludge.

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Johannisberg castle overlooking vineyards and the Rhine valley

The young research area (a so-called "emerging field") is rooted in research on fertile anthropogenic dark earths found e.g. in the Amazon basin (Terra preta do Indio). These soils contain considerable amounts of biochar, have higher soil organic matter contents (besides biochar), nutrient stocks and soil pH values and are generally much more fertile than adjacent SOM-poor acidic soils. Hence roughly 10 years ago the idea to sequester former atmospheric CO2, via photosynthesis plus pyrolysis, in the more stable form of biochar, and use biochar to eventually enhance soil fertility sparked research activities and evoked pioneer enthusiasm around the world. Of course, things turned out to be not as easy as initially anticipated; also, unexpected findings emerged.

Hence, in 2015, scientists and stakeholders met at Geisenheim to consolidate what has been learned, identify mechanisms of biochar action, and lay out the pathways for future promising research and development. The Geisenheim Biochar Symposium was jointly organized by the EU COST Action TD1107, "Biochar for sustainable environmental management" (COST = cooperation in science and technology, an EU funding program for inter-European knowledge exchange and transfer), and by the non-profit Organization ANS e.V. (Arbeitskreis für die Nutzung von Sekundärrohstoffen und Klimaschutz). Prof. C. Kammann, newly appointed work group leader for "climate change research in special crops" took the opportunity to invite these organizations to Geisenheim, since she is a steering committee member of the EU COST Action "biochar", manages the short-term scientific mission funds of the COST Action, and chairs the ANS working group "biochar".

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Evening walk in the vineyards with outdoor wine tasting

The conference was regarded as a great success according to the participants' feedback, and Geisenheim was perceived as a special and beautiful location for such a meeting; even the weather was brilliant (which was the hardest thing to organize, stated Prof. Hans-Reiner Schultz, President of Geisenheim University, when he opened the conference on Monday 28th).

The conference was structured into two more basic-research oriented days and one stakeholder- and practitioner day, and hosted 10 topical sessions. All in all, roughly 50 oral and 50 poster contributions offered new insights; session leaders and keynote speakers summarized latest biochar knowledge and understanding and will wrap it up for a final EU COST publication.

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Sunset over the Rheingau valley

A key feature to biochar use is its stability against degradation, however there are also fears that biochar addition to soils may trigger faster degradation of soil endogenous organic matter (called "positive priming"). These issues were addressed by session 1 on "carbon persistence", led by Prof. Saran Sohi from the UK Biochar Research Centre. In his keynote lecture, Prof. Yakov Kuzyakov (Göttingen University, Germany) demonstrated, using sophisticated 14C labeling-tracing techniques, that even after 9 years of incubation under controlled conditions only small amounts of biochar (maximum 6%) had been degraded, and most of it during the first months. During the "carbon stability" session the question was tackled if the addition of biochar may lead to an accelerated degradation of endogenous soil organic carbon (which was not the case, particularly if studies were longer-lasting); or if greenhouse gas emissions (CO2, N2O) can be predicted by the physico-chemical properties of different carbon amendments (which was the case). Finally, detailed stable isotope studies from Australian subtropical grassland and an Italian forest crop plantation demonstrated that the role of plants is often overlooked in biochar research, but may be crucial: On one hand, the Italian research group showed that the biochar itself may be mineralized faster in the presence of plant roots than in bare soil. The Australian research group, on the other hand, found considerable "negative priming" in the presence of biochar, i.e. they showed that plants (ryegrass), via root biomass and root exudates, were able to increase the soil organic carbon content significantly faster/stronger when the soil was amended with biochar than without. From a global perspective it is this "C return on investment" that may be more important than the C sequestration within the biochar itself. The topic of biochar-C persistence was also highlighted in a memorable plenary opening lecture on the second day by Dr. Johannes Lehmann, Cornell University, New York (USA). He demonstrated how biochar mineralization may be overestimated with short-term experimental approaches, and "how much stability" is really needed to implement C-negative biochar strategies.

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  Outdoor wine tasting: history lessons ("How the late vintage (spätlese) was discovered")

The second session dealt with biochar production (lead by Dr. Ondrej Masek) and how this can influence biochar properties and effects in soils. Keynote speaker Dr. Stephen Joseph, teaching in Australia and China, and a biochar material scientist of the first hour, gave interesting practitioner case studies where they had achieved economically viable success on-farm, mainly in land remediation and fertility improvement using biochar-mineral complexes. One interesting strategy of biochar use that he reported was biochar feeding to cows, and biochar-manure transport into the soil using dung beetles, which visibly turned the Australian farmers' degraded lands towards improved fertility in only 3 years (practice ongoing). Stephen Joseph as well as Hans-Peter Schmidt (day 3) impressively demonstrated that using biochar as a nutrient carrier to create "carbon-based fertilizers" may have a largely unexplored potential to improve yields and reduce fertilizer needs (i.e. to improve the nutrient use efficiency, and hence reduce environmental impacts).

Another item in biochar research, highlighted in session 3, is the often-conjured danger of pollution (by e.g. heavy metals or polycyclic aromatic hydrocarbons, PAH), versus the ability of biochar to sorb such compounds, i.e. the potential to serve as a remediation agent. Here, the Norwegian keynote speaker and well-known environmental pollution expert Prof. Gerard Cornelissen tried to balance the "Janus-Face of biochar" to answer how large the dangers really were, compared to the chances. The session, led by Dr. Thomas Bucheli (Agroscope, Switzerland), concluded that the often-anticipated danger is more or less negligible, given that sufficient control over the feedstock and modern pyrolysis techniques are exerted; and that it is rather the chances for soil remediation and waste-water treatment that are recognized via the latest research results, particularly when it is the bioavailable fractions that are investigated, rather than total loads.

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The conference dinner hall: The old church of cloister Johannisberg

Another session, 4, dealt with the chances that biochar or hydrochar (produced via hydrothermal carbonization, another different technique) may offer in horticulture for peat reduction, and also for improving plant resistance against pests and pathogens. The latter is a fascinating underexplored topic of biochar research, at the moment led by an Israeli group around Dr. Ellen Graber (session lead) and Dr. Omer Frenkel (keynote). Here, a lot of promising findings were obtained lately, using small amounts of biochar that increased plant defenses against pathogens.

The sessions that dealt with biochar use in agriculture and animal husbandry (e.g. session 5 led by Prof. G. Cornelissen; keynote Prof. Alessandro Peressotti) revealed that the initial simplistic idea of spreading large amounts of pure, production-fresh biochar onto agricultural lands is neither tremendously yield-improving nor economically viable. Thus, it likely represents a wrong pathway, particularly in temperate fertile soils. Dr. Greet Ruysschaert, Belgium, presented a meta-study on results from 32 European field trials from the early days of biochar research when large amounts of pure biochar were applied. She reported that in 80% of all cases no effect was found, in 6% a negative and in 12% a positive effect, respectively (in 2% the data were not usable). Although it is good news that there is not much to fear when sequestering C in soils, a lack of a return of (pure biochar-C) investment will not generate the desired C sequestration; to date, biochar is too expensive for such a strategy. However, the sessions also revealed that the by far better way forward is to use small doses of biochar in nutrient-rich environments (in silage, animal fodder, manure conditioning), or as a bio-carbon-based carrier for fertilizers, either organic or mineral; and that a tiny dose of under-foot application of biochar-based fertilizers or biochar-composts in the manner of conservation farming may provide much better economic incentives for using biochar, particularly when the biochar production costs on-farm can be lowered. Here, the results presented by Prof. Joseph (Australia, China, South America) and by Hans-Peter Schmidt (Nepal, including reforestation projects) were most impressive, with yield increases by +30 to +300% compared to nutrient-only controls.

The conference sessions also touched the potential of biochar or biochar-blends for reducing non-CO2 greenhouse gas emissions, dominantly nitrous oxide (N2O) which increases globally due to the excessive use of N fertilizers and legumes (to feed 7 billion people). In this session, led by Prof. Claudia Kammann (Geisenheim University), interesting new hypotheses were discussed by keynote lecturer Dr. Nele Ameloot (Belgium) or Dr. Kurt Spokas (USDA, USA) and others for deciphering the mechanisms that cause the often-observed reductions in N2O emissions when biochar is used; this beneficial effect is still not sufficiently understood.

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Animated talking and (scientific) exchange during the conference dinner

During the practitioner day several techncail approaches were discussed to recycle phosphorus from waste streams such as sewage sludge by either pyrolysis or hydrothermal carbonization techniques. Prof. Thomas Appel, Bingen technical University, presented an approach developed together with the Pyreg GmbH to turn nearly all sludge-P into a plant-available form by hygienization of sludge at about 500°C by pyrolysis techniques. Also, non-agricultural uses were discussed, e.g. the use of biochar as a component in building materials in concrete mixtures to reduce the large carbon footprint of concrete production, and substitute sand. Engineer Michele Di Tommaso, Switzerland, reported that using biochar as a substitute for special fibres in fire-proof concrete mixtures for tunnel construction was successfully tested; mixutres were able to withstand high temperatures by allowing water vapor to escape the concrete (tunnel building). Using biochar in concrete mixtures reduced NOx (NO, NO2) air concentrations from cars and vehicles that can reach high levels in e.g. tunnels or inner cities.

Taken together, the overall picture that emerged at the Joint Biochar Symposium in Geisenheim is that of a steady, knowledge-driven "biochar evolution" instead of, as originally anticipated, a "biochar revolution"; but that it nevertheless opens up new pathways for recycling and re-using (fossil) atmospheric carbon dioxide via photosynthesis plus subsequent pyrolysis. The overall consensus was that we cannot afford to dismiss even one good and feasible idea that may be turned into a tool for combatting and mitigating global warming.