Toward carbon mitigation resiliency in the agriculture sector: An integrated LCA-GHG protocol-IPCC guidelines framework for biofertilizer application in paddy field.

The agriculture sector contributes 22 % of global greenhouse gas emissions, with fertilizers accounting for 10.6 % of that portion. To reduce this, biofertilizers can be employed due to their lower emissions throughout production and application. Past studies have quantified either the upstream or downstream emissions of biofertilizers, yet the direct and indirect emissions from a life cycle perspective remain unclear. Additionally, most studies did not consider local conditions such as soil organic carbon and soil nitrogen content, leading to inaccuracies in the calculated greenhouse gas (GHG) emissions. This study solves this gap by developing a new integrated methodology using the life cycle assessment, IPCC guidelines, and GHG protocol to quantify the life cycle greenhouse gases of a paddy biofertilizer product from Malaysia. Most GHG emissions are derived from Scope 3 emissions, contributing to 16.69 t COeq/ha/yr or 87.33 % of the life cycle GHG emissions. Of this figure, methane alone contributes 84.48 % of all Scope 3 GHG emissions. Scope 1 emissions contribute to 2.08 t COeq/ha/yr or 10.84 %, and Scope 2 emissions amount to 0.35 t COeq/ha/yr or 1.83 % of the life cycle GHG emissions. Since the fertilizer ratios contain 70 % chemical fertilizer and 30 % biofertilizer, the upstream emissions of biofertilizers only contribute to 5.43 % of the total Scope 1 emissions, equal to 0.69 % of the life cycle GHG emissions. The sensitivity analysis revealed that fluctuations in total organic carbon content significantly impact on GHG emissions, potentially causing fluctuations of 100 t COeq/yr. A scenario analysis suggests that a nationwide phase-out of chemical fertilizers could lead to a maximum reduction of 10.12 % in agricultural GHG emissions by 2030. This study contributes to the United Nations Sustainable Development Goal (UN SDG) 13 by providing a comprehensive assessment of biofertilizer life cycle GHG emissions, highlighting their potential to reduce GHG emissions and supporting the development of low-carbon national policies.