Rasse Daniel P, Budai Alice, O'Toole Adam, Ma Xingzhu, Rumpel Cornelia, Abiven Samuel
Department of Soil Quality and Climate Change, Norwegian Institute of Bioeconomy Research, Ås, Norway.
Department of Environmental Sciences, Norwegian University of Life Sciences, Ås, Norway.
PLoS One. 2017 Sep 5;12(9):e0184383. doi: 10.1371/journal.pone.0184383. eCollection 2017.
Evaluating biochars for their persistence in soil under field conditions is an important step towards their implementation for carbon sequestration. Current evaluations might be biased because the vast majority of studies are short-term laboratory incubations of biochars produced in laboratory-scale pyrolyzers. Here our objective was to investigate the stability of a biochar produced with a medium-scale pyrolyzer, first through laboratory characterization and stability tests and then through field experiment. We also aimed at relating properties of this medium-scale biochar to that of a laboratory-made biochar with the same feedstock. Biochars were made of Miscanthus biomass for isotopic C-tracing purposes and produced at temperatures between 600 and 700°C. The aromaticity and degree of condensation of aromatic rings of the medium-scale biochar was high, as was its resistance to chemical oxidation. In a 90-day laboratory incubation, cumulative mineralization was 0.1% for the medium-scale biochar vs. 45% for the Miscanthus feedstock, pointing to the absence of labile C pool in the biochar. These stability results were very close to those obtained for biochar produced at laboratory-scale, suggesting that upscaling from laboratory to medium-scale pyrolyzers had little effect on biochar stability. In the field, the medium-scale biochar applied at up to 25 t C ha-1 decomposed at an estimated 0.8% per year. In conclusion, our biochar scored high on stability indices in the laboratory and displayed a mean residence time > 100 years in the field, which is the threshold for permanent removal in C sequestration projects.
评估生物炭在田间条件下在土壤中的持久性是将其用于碳固存的重要一步。目前的评估可能存在偏差，因为绝大多数研究都是对实验室规模热解器生产的生物炭进行的短期实验室培养。我们的目标是首先通过实验室表征和稳定性测试，然后通过田间试验，研究中试规模热解器生产的生物炭的稳定性。我们还旨在将这种中试规模生物炭的性质与相同原料的实验室制备生物炭的性质联系起来。为了进行同位素碳追踪，生物炭由芒草生物质制成，在600至700°C的温度下生产。中试规模生物炭的芳香性和芳环缩合程度较高，其抗化学氧化能力也较强。在为期90天的实验室培养中，中试规模生物炭的累积矿化率为0.1%，而芒草原料的累积矿化率为45%，这表明生物炭中不存在不稳定碳库。这些稳定性结果与实验室规模生产的生物炭所获得的结果非常接近，表明从实验室规模热解器扩大到中试规模热解器对生物炭稳定性影响不大。在田间，施用量高达25吨碳/公顷的中试规模生物炭估计每年分解0.8%。总之，我们的生物炭在实验室稳定性指标上得分很高，在田间的平均停留时间>100年，这是碳固存项目中永久去除的阈值。
