Exploring the potential of sugarcane straw biochar: Insights into N2O emissions and microbial functional genes

• Published in: Biomass & bioenergy 2024-03, Vol.182, p.107070, Article 107070
• Main Authors: Gabetto, Fernanda Palmeira, Tenelli, Sarah, Netto-Ferreira, Julia Barra, Gonzaga, Leandro Carolino, Isidório, Maria Andresa Santos, Carvalho, João Luís Nunes
• Format: Article
• Language: English
• Subjects: Bioenergy; Black carbon; GHG emission; Marker genes; Straw removal; X-ray photoelectron spectroscopy
• ISSN: 0961-9534; 1873-2909
• DOI: 10.1016/j.biombioe.2024.107070

Sugarcane straw has been considered a promising cost-effective feedstock for bioenergy production through pyrolysis. Straw-based biochar is a by-product from biomass pyrolysis that has the potential to mitigate nitrous oxide (N2O) emissions. However, the understanding of how biochar influences N2O emissions remains limited. This study assessed the effects of sugarcane straw-based biochar on soil N2O emissions and its interaction with functional genes associated with N2O production and consumption in tropical conditions. A greenhouse experiment was conducted for 60 days to evaluate the following treatments: control (CTR), N fertilizer (NF), NF + 15 Mg ha−1 straw (NF + S); NF + 5 Mg ha−1 biochar (NF + B5); and NF + 10 Mg ha−1 biochar (NF + B10). Results showed that N2O emissions were 73 % higher in the NF + S than in the biochar treatments. However, biochar treatments did not reduce N2O emissions compared to NF. Soil N–NH4+ availability was reduced under NF + S but was greater in biochar treatments at initial sampling time-points. High soil C content was observed in the NF + B10. Although NF + S increased sugarcane biomass, it registered the highest N2O-yield scaled emission. N2O-yield scaled emissions in NF + B5 and NF + B10 were 63 % and 62 % lower than in NF + S. The NF + S increased the abundance of AOB-amoA genes, suggesting that nitrification was the major N2O-producing pathway. Conversely, biochar effects on soil N2O emissions were not correlated with nitrification or denitrification genes. Thus, converting sugarcane straw into biochar is feasible strategy to reduce N2O emissions and increase soil C sequestration in tropical soil. [Display omitted] •Straw coverage increased soil N2O emissions.•Soils under biochar application emitted 73 % less N2O than straw-covered soils.•High N2O emissions were driven by AOB-amoA genes.•Conversion of straw into biochar is a good strategy to mitigate soil GHG emissions.