Abstract
The heating of biomass under low-oxygen conditions generates three co-products, bio-oil, biogas, and biochar. Bio-oil can be stabilized and used as fuel oil or be further refined for various applications and biogas can be used as an energy source during the low-oxygen heating process. Biochar can be used to sequester carbon in soil and has the potential to increase crop yields when it is used to improve yield-limiting soil properties. Complex bio-physical interactions have made it challenging to answer the question of where biochar should be applied for the maximum agronomic and economic benefits. We address this challenge by developing an extensive informatics workflow for processing and analyzing crop yield response data as well as a large spatial-scale modeling platform. We use a probabilistic graphical model to study the relationships between soil and biochar variables and predict the probability and magnitude of crop yield response to biochar application. Our results show an average increase in crop yields ranging from 4.7% to 6.4% depending on the biochar feedstock and application rate. Expected yield increases of at least 6.1% and 8.8% are necessary to cover 25% and 10% of US cropland with biochar. We find that biochar application to crop area with an expected yield increase of at least 5.3%–5.9% would result in carbon sequestration offsetting 0.57%–0.67% of US greenhouse gas emissions. Applying biochar to corn area is the most profitable from a revenue perspective when compared to soybeans and wheat because additional revenues accrued by farmers are not enough to cover the costs of biochar applications in many regions of the United States.
Highlights
Biochar is a carbon rich soil amendment produced from biomass by a thermochemical process, pyrolysis, or gasification [1]
The model predicts that the biochar application rate has a diminishing marginal effect on the yield response, i.e. the yield effect is higher with low biochar application rates and flattens out at higher application rates
In contrast to other researchers [11, 18, 20] who found the greatest effect of biochar on coarse texture soils, we did not find a significant correlation between response ratio (RR) and sand content
Summary
Biochar is a carbon rich soil amendment produced from biomass by a thermochemical process, pyrolysis, or gasification [1]. The alkalinity of biochar, its high internal porosity [10], and capacity to absorb cations, i.e., a cation exchange capacity (CEC), can increase soil nutrient and water holding capacity [11–13] without compromising soil conservation goals [5]. This can lead to increases in crop yields in less fertile and degraded soils which often coincide with high rural poverty [2, 5]. The ability of biochar to sequester carbon and alleviate soil limitations on crop yields depends on the biochar’s properties, which are influenced by properties of the feedstock used to produce the biochar and by the production technology (pyrolysis/gasification technologies) [8, 14]
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