Greenhouse gas emissions from biogas production from manure in Norwegian agriculture

Manure management in Norway is a source of emissions to air of greenhouse gases (GHGs), specifically methane (CH4) and nitrous oxide (N2O), in addition to other nitrogen species such as ammonia (NH3), nitric oxide (NO) and nitrogen (in the form of N2). The volume of emissions of these GHGs and nitrogen species will depend on a number of factors such as type of animal, carbon and nitrogen content in fodder, manure management system, climate, time of spreading of manure and cultivation practices. All of these parameters need to be taken into consideration when building a model to calculate emissions of methane, nitrous oxide ammonia and potentially other nitrogen
species.

A revised excel model for calculating methane emissions from manure management practices in Norway was developed in 2019 with minor updates in 2020. The model built on the previously used model, as well as current international research focused on methane emissions from use of manure in
anaerobic digestion. The model allows emissions of methane to be calculated for all farm-based manure management systems (MMS), including (i) storage of manure which is to be spread to land, (ii) potential manure treatment by anaerobic digestion (with some pre-storage of manure and storage of
digestate) and (iii) grazing on pasture land.

The calculation of methane emissions is divided into 9 steps, which correlate to storage prior to either (i) spreading of manure onto land, or (ii) anaerobic digestion and digestate treatment and storage.

In the revised model, the IPCC Tier 2 method has been applied for all animal categories, allowing for use of updated national MCF for liquid manure and the specific MMS distribution for each animal category in Norway, and results in a more consistent approach to estimation of CH4 emissions from manure management systems, as well as better reflects the national manure management practices applied.

This report describes updated methodology implemented in the tool. A description of the values of the different variables used in the estimates and the resulting emissions will be found in the annual Norwegian submission to UNFCCC (National Inventory Report (NIR) and CRF-tables, 2020 version in
preparation).