I read recently that 50% of a loaf of bread's carbon dioxide (CO2) footprint was due to the amount of fertiliser used in producing the wheat needed to make the loaf. It’s not surprising when you realise that 1% of global energy generated each year is used by a single chemical process – the Haber-Bosch cycle - the energy intensive chemical reaction that fixes atmospheric nitrogen into ammonia, which can then be made into ammonium or nitrate fertilisers.

N2 (g) + 3H2 (g) ⇌ 2NH3 (g)

Added to the fact that an estimated 40% of the available land mass is used to produce food and most of that is used to grow grains that feed cattle, chickens, pigs and other livestock, it’s no wonder that the biggest hidden energy costs in farming is the production of fertilisers.

In addition recent studies have concluded that excess fertiliser addition to crops can cause a ‘belching’ of gaseous nitrous oxide (N2O) from the overloaded microbes found in the soil. This effect has been found to be exponential, and could be putting up to 5% excess N2O into our atmosphere. Nitrous oxide is a potent greenhouse gas as is 200-300 times more effective in trapping heat than CO2. Who knew the humble loaf could do so much damage?

Farm to Fork, Education is the Key

Plenty of work is concentrated in reducing the energy consumption required for the Harber-Bosch cycle, with new heavy metal catalysts being developed by chemists. Further routes of ammonia production are being investigated by academics across the globe. But these new synthetic routes might be decades away from scale-up and delivery and therefore are not going to help achieve a CO2 reduction in the short term.

Pressure is therefore being turned to consumers and farmers. Consumers are being asked to consider food miles, buy more local crops and consider seasonal vegetables.  Farmers are being driven to use less fertiliser on each crop by understanding the growth cycles of their crops and delving into deeper understanding of the biology of the crop. By adding fertiliser at the correct time, farmers can not only increase total yield of crop but affect crop ‘nutritional components’ such as increasing final protein content in wheat.

Real-time measurement and precision application


Crop sprayer in field

What is required is a real-time measurement and application system which detects nitrate levels in soil and targets the areas with low nitrogen concentrations, ensuring only these areas have fertiliser added. However, currently these mapping systems are time consuming and bulky. The development of a fully integrated real-time sensing and application technique would allow farmers to cover each crop with a unique application of fertiliser as required by the soil and crops. This would require a robust sensing technology, in depth software algorithms all tied in with a dispensing system with capability to accurately dose and we have discussed previously why one does not exists today.

At Cambridge Consultants we work on integrated sensing systems that range from a targeted crop spraying system that deliver precise amounts of additive to miniaturisation of medical diagnostic equipment. We regularly integrate our wide range of expertise including world class optics, robust mechanical engineering, data analytics and communications, and fluid dynamics to create breakthrough products and innovations. In-soil nitrate sensing is one of the areas which we are investigating internally, where we believe we can have a positive impact on the hidden CO2 burden of agriculture.

Stuart Gilby
Principal Chemist

Working in our Applied Science group, Stuart develops chemistry solutions for new product developments.