Scottish Nitrogen Balance Sheet 2020

Introduction

Why is nitrogen important?

Nitrogen is a basic building block of life. It is present everywhere across the economy and environment, forms a constituent of a wide range of materials and processes, and is especially important as a fertiliser in relation to growing and producing food.

This ubiquity means that the effective and efficient use of nitrogen is an important consideration, with far reaching consequences. Losses of nitrogen into the environment can have harmful effects on, for example, climate change, air quality, water quality and biodiversity. Optimal use of nitrogen inputs to the economy, as well as re-using and recycling any nitrogen in waste products, are key pathways for minimising such losses, whilst also maximising the benefits associated with vital processes such as food production.

What is a Nitrogen Balance Sheet?

A Nitrogen Balance Sheet, sometimes also called a Nitrogen Budget, is a way to understand and keep track of the flows of nitrogen across different parts of the economy and environment, as well as to and from other countries or regions. It then allows these flows to be analysed in a joined-up way. Summary calculations can be made of how efficiently nitrogen is currently being used and national metrics of Nitrogen Use Efficiency (NUE) are some of the key outputs from the new Scottish Nitrogen Balance Sheet (these are set out in section Nitrogen Use Efficiency of this report).

However, it is important to appreciate that the full Scottish Nitrogen Balance Sheet (SNBS) is a far richer and more complex data source than can ever be expressed in any given set of simple summary metrics. The full initial SNBS dataset has been published alongside this report and can provide the basis for a wide range of further analyses and outputs, depending on users’ interests.

Through The Climate Change (Nitrogen Balance Sheet) (Scotland) Regulations 2022, Scotland has committed to establishing a statutory whole-economy Nitrogen Balance Sheet, with regular formal review.

Scotland is, to our knowledge at the time of writing, the only country in the world to have enshrined in law a regularly updated, cross-economy and cross-environment Nitrogen Balance Sheet. Many other countries have carried out occasional research-focussed balance sheets, as evidenced in the European Nitrogen Assessment^[1] which includes a UK nitrogen budget. However, these studies differ considerably in the flows and systems included and the methods applied in the calculations, which makes comparisons difficult.

What is the Scottish Nitrogen Balance Sheet used for?

The main statutory purpose of the SNBS is to support progress to Scotland’s national greenhouse gas emissions reduction targets. This is because one form of nitrogen - nitrous oxide (N₂O) - is an important greenhouse gas. Identifying opportunities for improving how efficiently nitrogen is used across key parts of the economy will, therefore, help with tackling climate change.

However, the fact that nitrogen - in all of its many forms - is basically everywhere in the economy and environment means that the evidence base provided by the SNBS also has the potential to support a range of wider policy applications. These include the development and monitoring of air quality policies (NO_x and ammonia (NH₃) being important air quality pollutants) and the identification of further opportunities to promote environmental efficiency in the production of food, natural fibres and more. As noted above, the new SNBS dataset may also assist stakeholders outside of the Scottish Government in generating their own analyses and outputs.