Ammonium bicarbonate fits well into a circular economy. Fearing the volatilisation of ammonia, European countries have banned this nitrogen fertiliser, but the ammonia emission is easy to limit. Reassessment of ammonium bicarbonate as a fertiliser is therefore justified, according to research reported in the latest issue of the Plant nutrition courier.
Treat flue gases with ammonia, and carbon dioxide emissions will drop significantly. According to experts, this is a promising approach to reducing emissions of this greenhouse gas. The reaction of ammonia with carbon dioxide produces ammonium bicarbonate, which can be sold as a fertiliser in agriculture and horticulture. Due to its lower cost price, this fertiliser can compete well with urea and other nitrogen fertilisers. Ammonium bicarbonate can also be extracted from air from animal housings and from liquid digestate, a residual product from the fermentation of, for example, animal manure or vegetable waste. A lot of research is being done worldwide into the (re)use of ammonium bicarbonate, which is produced when capturing carbon dioxide using ammonia from flue gas from power plants.
Scientists see a clean role for ammonium bicarbonate as a fertiliser. In this way, the captured carbon dioxide is fixed in crops or agricultural land. However, European regulations are hampering the contribution of ammonium bicarbonate to shaping the circular economy.
Ban
Ammonium bicarbonate can decompose into ammonia, carbon dioxide and water. It is a potential source of ammonia volatilisation, more than other ammonium-containing fertilisers, urea and animal manure. Most European countries have therefore agreed at some point to ban the use of ammonium carbonates as fertiliser. The agreement was made within the framework of the so-called Gothenburg Protocol, which prescribes measures to reduce ammonia emissions and other forms of air pollution. According to an analysis in the latest issue of the popular science magazine Plant nutrition courier, the ban on the use of ammonium carbonates as fertiliser is in conflict with the principles of the Gothenburg Protocol. The parties involved have agreed that emission-reducing measures should not constitute a means of arbitrary or unjustifiable discrimination or a disguised restriction on international competition and trade. Anyone who bans ammonium carbonates as a fertiliser and at the same time permits other fertilisers under certain conditions that can also release ammonia, is making an unjustified distinction. The Gothenburg Protocol does not show that the environmental benefits of ammonium bicarbonate were taken into account in the decision. Emission-reducing techniques such as fertiliser coating and incorporating the fertiliser granules into the soil are also not mentioned in the Protocol. Incidentally, no agreements have been made about the production of this fertiliser.
Stabilisation
The Plant nutrition courier analysed the Protocol in the context of the renewed interest in ammonium bicarbonate. Research groups in Japan, the United States and Great Britain, for example, are developing refined methods to extract ammonium bicarbonate from air from animal housings, residual products from fermentation processes and flue gas. Scientists worldwide are also working successfully on stabilising ammonium bicarbonate. The risk of ammonia emission is therefore drastically reduced. Incidentally, research into stabilising this ammonium fertiliser has old papers. Ninety years ago, German inventors patented the coating of granular ammonium bicarbonate. Nowadays, patent applications mainly come from China. Crops there still get part of their nitrogen requirement in the form of inexpensive ammonium bicarbonate, despite the strong advance of the more stable urea with its much higher nitrogen content.
The digital magazine Plant nutrition courier published six times a year about cutting-edge research into plant nutrition and fertilisers.