LIFE CYCLE ASSESSMENT AND THE NITROGEN CYCLE

Life Cycle Assessment (LCA) is well-established methodology that enables a quantitative environmental analysis of processes or products. A central characteristic of LCA is the holistic focus on products or processes and their functions, considering upstream and downstream activities.

 

In an LCA study all emissions and resource consumption related to a defined product or process are first quantified in a so-called Life Cycle Inventory (LCI). The subsequent step, called Life Cycle Impact Assessment, investigates the potential environmental consequences of the emissions and resource consumption. LCA has found widespread applications in product development in industry, benchmarking and marketing of products, and within policy making to name a few. A framework for LCA has been standardised by the International Organisation for Standardisation (ISO) in the ISO 14040 series.

 

The fertilizer industry applies these LCA principles to address the nitrogen cycle when developing techniques to optimise the use of reactive nitrogen.

 

Nitrogen is vital for life through its role in the atmosphere and as an essential component of all proteins and of DNA. The atmosphere is 78% nitrogen, but under the form of dinitrogen which is chemically inert, not reacting with other elements. Making it available to plants requires large amount of energy to break the chemical bonds of dinitrogen, such as that provided by lightning. Some bacteria are also capable of fixing dinitrogen and a few of these form symbiotic relationships with plants as, for example, leguminous crops (e.g. soybean, alfalfa).

 

Nitrogen is also fixed industrially through the Haber-Bosch process, which is the basis for production of nitrogen fertilizers and now represents more than 60% of the available reactive nitrogen.

 

Without reactive nitrogen, life could simply not exist as we know it, and it is scientifically proven that 40% of the world population exists because of mineral fertilizers.

 

However, when supplied in excess this now reactive nitrogen can also have unwanted impacts on the environment: reactive nitrogen can contribute to smog, acid deposition, climate change, coastal eutrophication and stratospheric ozone depletion. It is estimated that between 85 and 95% of this reactive nitrogen is lost along the food chain, being released in the environment.

 

The fertilizer industry collaborates with the scientific community to develop techniques and practices which minimise the lost of reactive nitrogen while continuing to meet the challenge of feeding the world population, expected to increase by 30% in the coming 20 years.