Abundant and Stable Char Residues in Soils: Implications for Soil Fertility and Carbon Sequestration

Abstract

Large-scale soil application of biochar may enhance soil fertility, increasing crop production for the growing human population, while also sequestering atmospheric carbon. But reaching these beneficial outcomes requires an understanding of the relationships among biochar's structure, stability, and contribution to soil fertility. Using quantitative 13 C nuclear magnetic resonance (NMR) spectroscopy, we show that Terra Preta soils (fertile anthropogenic dark earths in Amazonia that were enriched with char >800 years ago) consist predominantly of char residues composed of ∼6 fused aromatic rings substituted by COO − groups that significantly increase the soils' cation-exchange capacity and thus the retention of plant nutrients. We also show that highly productive, grassland-derived soils in the U.S. (Mollisols) contain char (generated by presettlement fires) that is structurally comparable to char in the Terra Preta soils and much more abundant than previously thought (∼40− 50% of organic C). Our findings indicate that these oxidized char residues represent a particularly stable, abundant, and fertilityenhancing form of soil organic matter.

Biochar and forest restoration: a review and meta-analysis of tree growth responses

“…In non-forest systems chars are increasingly recognized as playing a critical role in soil nutrient dynamics as well as constituting a long-term C stock (Spokas 2010). For example, recent results suggest that nearly all the cation exchange capacity of Mollisols, some of the world's most productive agricultural soils, may be attributable to pyrogenic carbon (Mao et al 2012). There is remarkably little information available on the distribution of natural chars, their properties, and their potential role in soil processes and forest productivity, particularly in forest ecosystems with relatively long natural fire return intervals.…”

Gasification biochar as a valuable by-product for carbon sequestration and soil amendment

“…Gasification biochar generally contains a considerable amount of minerals and recalcitrant carbon and is considered an attractive product for soil amendment due to its fertilizer and carbon sequestration potential [3,4]. Carbon sequestration in soil mitigates the effect of climate change [5], and may furthermore help to maintain or even improve the soil fertility. This is of key importance to be able to fulfill the increasing global demand for producing crops for both food and energy [6].…”

Investigation on Prospective Energy Power from Corncob Husk Biomass and its Biochars by Kinetic Parameters and Isoconversional Models

“…where k is defined as the rate constant of reaction whose temperature dependence is expressed by the Arrhenius equation: (2) where Eα is the apparent activation energy (kJ mol ). The rate of transformation from solid-state to volatile product is described by the following expression: 11,12 (3) where α is the conversion degree of the process; k(T) is the time of process; f(α) is the rate constant and the reaction model.…”

“…The organic oxygen in the samples is evolved during the pyrolysis according to the level of hemicelluloses and lignin breakdown. The main wave numbers considered on the FTIR peaks of the biochars for air and nitrogen atmospheres were: CO 2 By the analysis of the generated absorbance is observed how much energy was absorbed in a specific wavelength region. Overall is noted that the pyrolysis atmosphere is an important parameter, because peak intensities are greater under air atmosphere and demonstrate the more oxidized status of the sample, thus leading to more potential safety and storage risks.…”

“…Biochar is a carbon rich solid material produced by thermal decomposition of organic matter, generally biomass wastes. 2 Biochar is also known as a multifunctional material in agro-systems which is employed primarily as a soil conditioner for immobilizing metals, improvement of drought resistance, recovery and fertilization of the soil. 3 Both biomass and biochar can be used to design and fulfill a lifecycle favoring a competitive agricultural based world economy, inside farms and overall agro and energy based industries.…”