Reduce nitrogen in atmosphere'

Professor J.W. Erisman of VU University, Amsterdam. - ENERGY RESEARCH CENTRE OF THE NETHERLANDS

JAN WILLEM ERISMAN is currently the Extraordinary Professor of Integrated Nitrogen Studies at the Energy research Centre of the Netherlands, VU University, Amsterdam. He has a background in environmental research, especially the atmosphere biospheric exchange of gases and aerosols related to acidification and eutrophication and climate change. Recently, his work has focussed on optimising food and energy production while minimising the environmental impacts of increased reactive nitrogen production. He has also been involved in research on clean fossil fuels, hydrogen production from fossil fuels, hydrogen storage and concepts for a hydrogen economy as well as carbon dioxide (CO2) capture technologies.

Erisman was recently in New Delhi to attend the 5th International Nitrogen Conference. At the conference venue, he shared his views on the impacts of nitrogen on climate change with Frontline. Excerpts:

How does the correlation between the time trends of nitrogen (N2) emission and CO2 emission over the years come about?

That is mainly because the drivers for both are the same. In the combustion sources, CO2 as well as NOx [oxides of nitrogen] are formed. That is a one-to-one relationship actually. But also in fertilizer production we use fossil fuels methane is converted into CO2. Since the drivers, the sources, are similar, the emissions are also similar.

Nitrogen has a net negative forcing on the climate as against the positive forcing by CO2. How do you see the evolution of these competing forcings in the long term and the net impact on global warming given that fertilizer production and consumption are only likely to increase?

I think in the long term it will change. Because of human health, we will try to reduce the influence of [aerosol] particle loads in the atmosphere [arising from NOx emissions], and if you reduce the particle loads, you of course increase the radiation effect. [Aerosol] particles and CO2 sequestration are the two which have a negative effect on the radiative balance. If you decrease particles by decreasing the emissions of NOx and of ammonia, that will have a clear effect on radiative balance, resulting in an increase in warming.

Is health the only issue or are there other issues involved that call for reducing particulate emission?

There are other issues as well, like [the impact of] deposition on the ecosystem, for example. But looking at the past, human health is the best driver for environmental policies actually. The human health-particulate relationship will come into play in [determining] policies, whereas ecosystem surfaces, like deposition of nitrogen on forests and biodiversity issues, have less attention. It's lower on the priorities.

The immediate impact of increasing nitrogen in the atmosphere is the increase in biomass, but according to you in the long term this will result in the depletion of biomass. Is my understanding correct?

No. I said that only in the context of ozone. What I said was that because of nitrogen emission, especially NOx, ozone is formed and ozone affects the biomass. I think there will be an increase in biomass production especially in natural areas.

In that sense the carbon sequestration effect of nitrogen through biomass formation will increase. But, if there is going to be a net positive impact on climate change, will it not lead to an increase in the use of fertilizers?

I don't hope so because if you only focus on climate change, they have a positive effect. But if you look at all the other environmental impacts, especially biodiversity reduction, that is a negative impact. So, because of the negative impacts on the environment, ecosystem surfaces and biodiversity, you should reduce nitrogen in the atmosphere.

So what are the key issues in the management of nitrogen in the atmosphere?

Basically, it is increasing the nitrogen use efficiency. We can make a major change in that. The second priority is reduction in NOx emissions from industry, for which catalysts are available now. The third is human waste treatment.

Are these considerations region-dependent or universal?

For nitrogen in agriculture, nitrogen management is the same everywhere: optimisation of the use of nutrients combined with water so that there is minimum loss of nitrogen. But how to do it, that is different in different areas.

R. Ramachandran