Negative emission farming

Abstract

In comparison with levels in 2000, global carbon dioxide (CO2) has increased by 43.5 ppm to 414.4 ppm during 2020, an increase of 12%. Indeed, concentration of atmospheric CO2 now is higher than at any time during the past 3.6 million years (Stein 2021). Similarly, the global average concentration of methane (CH4) for December of 2020 was 1,892.3 ppb, representing an increase of about 119 ppb (6%) since 2000 (Stein 2021). Despite the shutdown caused by the COVID-19 pandemic, the increase in atmospheric concentration of CO2 during 2020 may be among the largest for the entire period since the records started. There has also been notable increase in atmospheric concentration of nitrous oxide (N2O), primarily due to the use of nitrogenous fertilizers (WMO 2020). Thus, there is a strong need to identify sources and sinks of these gases, especially those of CH4 and N2O, which are 28 and 285 times more potent, respectively, in trapping heat than is CO2 (IPCC 2007). While known sources include fossil fuel combustion, land use conversion, biomass burning, rice paddies, cattle production, etc., the role of soil processes has not been given the emphasis that is deserves. Whereas science-based and sustainable use of soils of agro-ecosystems and other managed land uses can be a sink for CO2 and CH4, soils prone to degradation by diverse processes (e.g., decline in soil structure, compaction, anaerobiosis, erosion/deposition) can be sources of CH4 through methanogenesis and of N2O through nitrification and denitrification. The impact of soil degradation, difficult and challenging to quantify as it may be, …