This is a breakdown by source of yearly nitrous oxide (N2O) emissions from human activities and processes, expressed as weight in teragrams. The sources of human nitrous oxide emissions are
The synthetic fertilizer used for agricultural processes contains a lot of nitrogen. The nitrogen in the soil causes a lot of direct N2O emissions, at 2.5 teragrams per year or around 30% of total human emissions. Excess fertilizer causes even higher relative emissions. There are many technical solutions to reduce emissions while keeping, or even increasing, agricultural yields. Many such solutions focus on providing the right amount of fertilizer at the right time.
We have included aquaculture emissions, which comprise 0.1 teragrams, to fertilizer emissions. A large part of aquaculture emissions comes from the fertilizers used to make aquaculture feed.
When manure is left on the field or managed in dry processes, it emits considerable amounts of nitrous oxide, at 1.5 teragrams or almost 20% of total human emissions. Manure can be managed by wet processes, which reduces the nitrous oxide emissions but increases methane emissions. Some technical solutions focus on modifying the animal feed to reduce nitrogen in the manure, thereby reducing nitrous oxide emissions.
The combustion of fossil fuels in, for example, power plants, cars and airplanes is a well-known cause of CO2 emissions, but it also emits nitrous oxide (N2O). Any advances to reducing fossil fuel dependency will thus also reduce nitrous oxide emissions.
The largest part of industrial emissions happen in the production of fertilizer, nylon and similar products. Technologies are available to reduce emissions in these processes.
Burning biomass like crops, grasses and trees releases nitrous oxide. Biomass is burned, for example, for heating, cooking and clearing fields. Also, forest fires – whether naturally or intentionally lit – emit nitrous oxide. Emissions from biomass burned naturally are included in the yearly human emissions because of the difficulty in separating the numbers.
The roughly 0.3 teragrams of nitrous oxide emissions from waste come from, for example, wastewater treatment and landfill.
There are a lot of indirect sources of nitrous oxide emissions. The largest part, at roughly 1.4 teragrams per year, comes from indirect nitrogen deposition from agricultural practices and fossil fuel combustion. Deforestation, the rising CO2 levels and the changing climate each have multiple processes that increase and reduce nitrous oxide emissions, with an average net effect of around 0.2 teragrams per year, but with relatively high yearly fluctuations that are visible in the chart.www.nature.com: A comprehensive quantification of global nitrous oxide sources and sinks, Tian, H. et al.
The unit teragram describes the average weight of atmospheric nitrous oxide per year.Wikipedia: Teragram
The two agricultural sources, fertilizer and manure, have the largest emissions, and those from fertilizers are growing the fastest due to their increasing usage worldwide. Fossil fuel and industry emissions have remained rather stable due to technical solutions for emissions reduction. The largest part of the indirect emissions are also from agricultural processes and fossil fuel combustion. Large fluctuations of indirect emissions come mostly from climatic responses that, over the years, have a low net effect. Biomass and waste are still significant sources, together accounting for more than 10% of total emissions.
There is a very long delay in the data. This is because this data is produced periodically by a global research project where scientists contribute to a mutually agreed knowledge base. It takes a lot of time and effort to generate trustworthy data that we can be confident in.Global Carbon Project: Nitrous Oxide Budget
The Global Carbon Project has a Global Nitrous Oxide Budget besides its Global Carbon Budget. It uses inventories, models, atmospheric inversions and more to build up the inventory.
Global Nitrous Oxide Budget 2020Credits: A comprehensive quantification of global nitrous oxide sources and sinks by Hanqin Tian, Rongting Xu, Josep G. Canadell, Rona L. Thompson, Wilfried Winiwarter, Parvadha Suntharalingam, Eric A. Davidson, Philippe Ciais, Robert B. Jackson, Greet Janssens-Maenhout, Michael J. Prather, Pierre Regnier, Naiqing Pan, Shufen Pan, Glen Peters, Hao Shi, Francesco N. Tubiello, Sönke Zaehle, Feng Zhou, Almut Arneth, Gianna Battaglia, Sarah Berthet, Laurent Bopp, Alexander F. Bouwman, Erik T. Buitenhuis, Jinfeng Chang, Martyn P. Chipperfield, Shree R.S. Dangal, Edward Dlugokencky, James Elkins, Bradley D. Eyre, Bojie Fu, Bradley Hall, Akihiko Ito, Fortunat Joos, Paul B. Krummel, Angela Landolfi, Goulven G. Laruelle, Ronny Lauerwald, Wei Li, Sebastian Lienert, Taylor Maavara, Michael MacLeod, Dylan B. Millet, Stefan Olin, Prabir K. Patra, Ronald G. Prinn, Peter A. Raymond, Daniel J. Ruiz, Guido R. van der Werf, Nicolas Vuichard, Junjie Wang, Ray Weiss, Kelley C. Wells, Chris Wilson, Jia Yang, and Yuanzhi Yao (2020), Nature, DOI:10.1038/s41586-020-2780-0Delay: ~ 6 years