Section 4 Vegetation and Soils (BEIS) Emissions: CO, NO, and VOC

Biogenic emissions are emissions that come from natural sources. They need to be accounted for in photochemical grid models, as most types are widespread and ubiquitous contributors to background air chemistry. In the NEI, only the emissions from vegetation and soils are included. Other relevant sources not included in the NEI are volcanic emissions (geogenic), lightning oxides of nitrogen (NOx), and sea salt. Biogenic emissions from vegetation and soils are computed using a model that utilizes spatial information on vegetation, land use and environmental conditions of temperature and solar radiation. The model inputs are typically horizontally allocated (gridded) data, and the outputs are gridded biogenic emissions, which can then be speciated and utilized as input to photochemical grid models.

In the 2023 NEI, biogenic emissions are included in the nonpoint data category, in the EIS sector “Biogenics – Vegetation and Soil.” Table 4.1 lists the three source classification codes (SCCs) used in the 2023 NEI that comprise this sector. These three SCCs have distinct pollutants: SCC 2701220000 and 2801700200 have only NOX emissions, and SCC 2701200000 has emissions for carbon monoxide (CO), volatile organic compounds (VOC) and three VOC hazardous air pollutants (HAPs): formaldehyde, acetaldehyde and methanol. Note that there is a fertilizer adjustment for soils on agricultural lands in the SCC 2801700200. In the 2020 NEI, all the soil nitric oxide emissions were included in one SCC, 2701220000.

Table 4.1: SCCs for biogenic sources

SCC	SCC Level Two	SCC Level Three	SCC Level Four	2020NEI	2023NEI
2701200000	Biogenic	Vegetation	Total	BEIS4 VOC	BEIS4 VOC
2701220000	Biogenic	Vegetation/Agriculture	Total	All BEIS4 soil NO	BEIS4 soil NO non-ag lands
2801700200	Agriculture Production - Crops	Fertilizer Application	Total: Biogenic		BEIS4 soil NO ag lands