Frank G. A. Verheijen

Toward the Standardization of Biochar Analysis: The COST Action TD1107 Interlaboratory Comparison

Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and many other applications. However, analytical methods for its physical and chemical characterization are yet far from being specifically adapted, optimized, and standardized. Therefore, COST Action TD1107 conducted an interlaboratory comparison in which 22 laboratories from 12 countries analyzed three different types of biochar for 38 physical-chemical parameters (macro- and microelements, heavy metals, polycyclic aromatic hydrocarbons, pH, electrical conductivity, and specific surface area) with their preferential methods. The data were evaluated in detail using professional interlaboratory testing software. Whereas intralaboratory repeatability was generally good or at least acceptable, interlaboratory reproducibility was mostly not (20% < mean reproducibility standard deviation < 460%). This paper contributes to better comparability of biochar data published already and provides recommendations to improve and harmonize specific methods for biochar analysis in the future.

Reductions in soil surface albedo as a function of biochar application rate: implications for global radiative forcing

Biochar can be defined as pyrolysed (charred) biomass produced for application to soils with the aim of mitigating global climate change while improving soil functions. Sustainable biochar application to soils has been estimated to reduce global greenhouse gas emissions by 71‐130 Pg CO2-Ce over 100 years, indicating an important potential to mitigate climate change. However, these estimates ignored changes in soil surface reflection by the application of dark-coloured biochar. Through a laboratory experiment we show a strong tendency for soil surface albedo to decrease as a power decay function with increasing biochar application rate, depending on soil moisture content, biochar application method and land use. Surface application of biochar resulted in strong reductions in soil surface albedo even at relatively low application rates. As a first assessment of the implications for climate change mitigation of these biochar‐albedo relationships, we applied a first order global energy balance model to compare negative radiative forcings (from avoided CO2 emissions) with positive radiative forcings (from reduced soil surface albedos). For a global-scale biochar application equivalent to 120 t ha 1 , we obtained reductions in negative radiative forcings of 5 and 11% for croplands and 11 and 23% for grasslands, when incorporating biochar into the topsoil or applying it to the soil surface, respectively. For a lower global biochar application rate (equivalent to 10 t ha 1 ), these reductions amounted to 13 and 44% for croplands and 28 and 94% for grasslands. Thus, our findings revealed the importance of including changes in soil surface albedo in studies assessing the net climate change mitigation potential of biochar, and we discuss the urgent need for field studies and more detailed spatiotemporal modelling.

A comment on ‘Biochar and its effects on plant productivity and nutrient cycling: a meta-analysis': on the importance of accurate reporting in supporting a fast-moving research field with policy implications

S IMON JEFFERY * , FRANK G .A . VERHE I J EN † , ANA CATAR INA BASTOS † and MARIJN VAN DER VELDE‡ *Soil Biology and Soil Biological Quality Group, Wageningen University, Postbus 47, 6700AA Wageningen, The Netherlands, †Centre for Environmental and Marine Studies (CESAM), University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal, ‡International Institute for Applied Systems Analysis (IIASA), Ecosystems Services and Management Program, Schlossplatz 1, A-2361 Laxenburg, Austria

Sustainability, certification, and regulation of biochar

Biochar has a relatively long half-life in soil and can fundamentally alter soil properties, processes, and ecosystem services. The prospect of global-scale biochar application to soils highlights the importance of a sophisticated and rigorous certification procedure. The objective of this work was to discuss the concept of integrating biochar properties with environmental and socioeconomic factors, in a sustainable biochar certification procedure that optimizes complementarity and compatibility between these factors over relevant time periods. Biochar effects and behavior should also be modelled at temporal scales similar to its expected functional lifetime in soils. Finally, when existing soil data are insufficient, soil sampling and analysis procedures need to be described as part of a biochar certification procedure.

Concise overview of European soil erosion research and evaluation

Abstract Soil loss by erosion is a major threat to European soil resources. It is linked to most other threats to soils and is estimated to incur substantial costs to society. To monitor and evaluate soil erosion comprehensively, measurements and modelled estimates of soil loss by erosion need to integrate water, wind and tillage erosion, as these are common throughout Europe. Tolerable rates of soil erosion (thresholds) in Europe can be set equal to estimated soil formation rates, that is, ~1 t ha−1 yr−1, but defining this threshold will require further research in the context of soil functions. There is a strong need for improving the knowledge base of current erosion rates, especially to develop and validate reliable erosion prediction models. This should include depositional environments (e.g. flood plains) where greater erosion rates than those on hill slopes may be tolerable, depending on the consequent effects on all relevant ecosystem goods and services provided by soil. Moreover, in considering erosion at catchment (watershed) level, the distance between erosion sites and areas of deposition should be taken into account.

Biochar standardization and legislation harmonization

AbstractIt is a relatively new concept to use biochar as soil amendment and for climate change mitigation. For this reason, the national and supranational legislation in the EU is not yet adequately prepared to regulate both the production and the application of biochar. Driven by this “regulatory gap”, voluntary biochar quality standards have been formed in Europe with the European Biochar Certificate, in the UK with the Biochar Quality Mandate and in the USA with the IBI Standard which is intended to be used internationally. In parallel to this, biochar producers and biochar users in a number of EU countries were partly successful in fitting the new biochar product into the existing national legislation for fertilisers, soil improvers and composts. The intended revision of the EC Regulation 2003/2003 on fertilisers offers the opportunity to regulate the use of biochar at the EU level. This publication summarizes the efforts on biochar standardization which have been carried out by voluntary products sta...

Biochars in soils: towards the required level of scientific understanding

Key priorities in biochar research for future guidance of sustainable policy development have been identified by expert assessment within the COST Action TD1107. The current level of scientific understanding (LOSU) regarding the consequences of biochar application to soil were explored. Five broad thematic areas of biochar research were addressed: soil biodiversity and ecotoxicology, soil organic matter and greenhouse gas (GHG) emissions, soil physical properties, nutrient cycles and crop production, and soil remediation. The highest future research priorities regarding biochar’s effects in soils were: functional redundancy within soil microbial communities, bioavailability of biochar’s contaminants to soil biota, soil organic matter stability, GHG emissions, soil formation, soil hydrology, nutrient cycling due to microbial priming as well as altered rhizosphere ecology, and soil pH buffering capacity. Methodological and other constraints to achieve the required LOSU are discussed and options for efficient progress of biochar research and sustainable application to soil are presented.

Generating crop calendars with Web search data

This paper demonstrates the potential of using Web search volumes for generating crop specific planting and harvesting dates in the USA integrating climatic, social and technological factors affecting crop calendars. Using Google Insights for Search, clear peaks in volume occur at times of planting and harvest at the national level, which were used to derive corn specific planting and harvesting dates at a weekly resolution. Disaggregated to state level, search volumes for corn planting generally are in agreement with planting dates from a global crop calendar dataset. However, harvest dates were less discriminatory at the state level, indicating that peaks in search volume may be blurred by broader searches on harvest as a time of cultural events. The timing of other agricultural activities such as purchase of seed and response to weed and pest infestation was also investigated. These results highlight the future potential of using Web search data to derive planting dates in countries where the data are sparse or unreliable, once sufficient search volumes are realized, as well as the potential for monitoring in real time the response of farmers to climate change over the coming decades. Other potential applications of search volume data of relevance to agronomy are also discussed.

Representativeness of European biochar research: Part I–field experiments

A representativeness survey of existing European Biochar field experiments within the Biochar COST Action TD1107 was conducted to gather key information for setting up future experiments and collaborations, and to minimise duplication of efforts amongst European researchers. Woody feedstock biochar, applied without organic or inorganic fertiliser appears over-represented compared to other categories, especially considering the availability of crop residues, manures, and other organic waste streams and the efforts towards achieving a zero waste economy. Fertile arable soils were also over-represented while shallow unfertile soils were under-represented. Many of the latter are likely in agroforestry or forest plantation land use. The most studied theme was crop production. However, other themes that can provide evidence of mechanisms, as well as potential undesired side-effects, were relatively well represented. Biochar use for soil contamination remediation was the least represented theme; further work is needed to identify which specific contaminants, or mixtures of contaminants, have the potential for remediation by different biochars.

Representativeness of European biochar research: part II – pot and laboratory studies

Biochar research is extensive and there are many pot and laboratory studies carried out in Europe to investigate the mechanistic understanding that govern its impact on soil processes. A survey was conducted in order to find out how representative these studies under controlled experimental conditions are of actual environmental conditions in Europe and biomass availability and conversion technologies. The survey consisted of various key questions related to types of soil and biochar used, experimental conditions and effects of biochar additions on soil chemical, biological and physical properties. This representativeness study showed that soil texture and soil organic carbon contents used by researchers are well reflected in the current biochar research in Europe (through comparison with published literature), but less so for soil pH and soil type. This study provides scope for future work to complement existing research findings, avoiding unnecessary repetitions and highlighting existing research gaps.