Greenhouse gas emissions from soil after lime application – evidence from literature search and laboratory experiments

Lime (CaCO₃) is used during sugar production for purification, thereby releasing carbon dioxide (CO₂) within a closed vessel. This CO₂ is then re-bonded into CaCO₃ and is brought to arable fields as sugar factory lime (SFL) to mitigate soil acidification. In this context, sugar factories currently face challenges in accounting for their greenhouse gas emissions because of current policy strategies and standard values. In this study, we (i) clarified that lime-derived CO₂ in sugar factories has no climate impact because it is not released to the atmosphere, and that liming soils is a common Scope 3 agronomic measure. Moreover, we (ii) ran a literature study on existing data of CO₂ emissions from arable soils after lime application and found that site and management factors highly drive emission rates. Thus, to model CO₂ emissions accurately, we need a broad set dataset from experiments. As a result, reducing the current IPCC standard emission factor to about 50% appears to be a reasonable approximation. Further (iii), we ran a laboratory incubation testing different SFL applications on the functioning of nitrous oxide reductase. We found that SFL improved the capacity of acidic soils to reduce nitrous oxide to N₂ comparably to synthetic CaCO₃.