Benefits and limitations of biochar for climate-smart agriculture: a review and case study from China

Abstract

Biochar has gained significant attention in agricultural and environmental research over the last two decades. This comprehensive review evaluates the effects of biochar on soil organic carbon (SOC), emission of non-CO2 greenhouse gases, and crop yield, including related mechanisms and major influencing factors. The impacts of biochar on SOC, methane and nitrous oxide emissions, and crop yield are controlled by biochar and soil properties and management practices. High-temperature biochar produced from lignin-rich feedstocks may decrease methane and nitrous oxide emissions in acidic soils and strengthen long-term carbon sequestration due to its stable aromatic structure. In contrast, low-temperature biochar from manure may increase crop yield in low-fertility soils. Applying biochar to farmlands in China can increase SOC content by 1.9 Pg C and reduce methane and nitrous oxide emissions by 25 and 20 Mt CO2-eq year−1, respectively, while increasing crop yields by 19%. Despite the increasing evidence of the positive effects of biochar, future research needs to explore the potential factors that could weaken or hinder its capacity to address climate change and secure crop production. We conclude that biochar is not a universal solution for global cropland; however, targeted applications in fields, landscapes, or regional scales, especially in low fertility and sandy soils, could realize the benefits of biochar as a climate-smart measure.Highlights The findings of research on biochar's effects on soil C sequestration, GHG mitigation, and crop production were summarized. The factors influencing the impact of biochar on soil functioning were reviewed. The effects of biochar on soil C sequestration and GHG mitigation in farmlands of China were quantified. Graphical Abstract

Effects of Biochar and Arbuscular Mycorrhizal Fungi on Soil Health in Chinese Kale (Brassica oleracea var. alboglabra L.) Cultivation

“…Notably, these values did not exhibit statistical differences from the untreated planting soil (T1 and T8). Our findings largely align with numerous prior studies suggesting that the addition of biochar to soil can enhance organic matter and organic carbon levels through diverse mechanisms, like stable carbon sequestration, reduced decomposition, enhanced microbial activity, improved soil structure, promotion of plant growth, and chemical binding [3,85,86]. However, it is important to highlight that the specific effects of biochar on organic matter and organic carbon levels can vary, influenced by factors such as biochar type, feedstock, and application rate, along with the soil characteristics [87].…”

Sustainable Technological Applications of Green Carbon Materials

“…Biochar is a product of the valorization of feedstocks, like municipal organic waste and agri-industrial residues, through slow pyrolysis [28][29][30][31][32][33][34][35][36][37]. Thermal processes, like pyrolysis and carbonization, convert biomass into a carbon-rich microporous material with a well-developed porous structure, a highly specific surface area, and a high degree of aromatization (Figure 6) [28][29][30][31]. These features can be tuned using different raw materials and the technical characteristics of pyrolysis.…”

“…These features can be tuned using different raw materials and the technical characteristics of pyrolysis. Biochar is added to soil to modify its physical and chemical composition, microbial activity, soil fertility, and pollution load [28][29][30][31][32][33][34][35][36][37]. Carbon nanomaterials have another important role in agricultural practices, namely as nanocarriers for pesticides and fertilizers, allowing the controlled release of active molecules [20].…”

“…These features can be tuned using different raw materials and the technical characteristics of pyrolysis. Biochar is added to soil to modify its physical and chemical composition, microbial activity, soil fertility, and pollution load [28][29][30][31][32][33][34][35][36][37]. Biochar contains inorganic elements that are macronutrients, particularly N, P, and K, and micronutrients to plants; when added to soils, they will improve their fertility, resulting in high crop yields [28,29].…”

Biochar and organic fertilizer drive the bacterial community to improve the productivity and quality of Sophora tonkinensis in cadmium-contaminated soil

“…Biochar can also increase soil enzyme and bacterial activities ( Muhammad et al, 2018 ; Effrey et al, 2019 ; Shen et al, 2019 ; Wan et al, 2023 ; Xiao et al, 2023 ). However, long-term single-use of biochar can also have drawbacks, such as reducing the effectiveness of plant nitrogen ( Bo et al, 2023 ; Wang et al, 2023 ; Zhang C. et al, 2023 ; Zhang N. H. et al, 2023 ; Zhang X. et al, 2023 ; Zhang Z. et al, 2023 ; Zheng K. et al, 2023 ; Li et al, 2024 ). In practice, biochar is commonly used with supplemental nutrients, such as organic fertilizer, to enhance soil quality, mitigate heavy metal stress, and increase crop productivity ( Muhammad et al, 2017 ; Saeed et al, 2021 ).…”