The Engineering Mindset Part 5: Complex or Complicated? Practical principles or prescriptive targets

Chris and Penny Hamlin explain how an approach focused on direction and principles, rather than numerical targets and specific policies, fosters new opportunities and solutions, providing a framework everyone can use to guide their actions

ONE OF the fundamental differences in approach in a complex system is the need to focus on direction rather than destination.

In essence this means that rather than setting prescriptive targets as you would in an ordered or complicated system, you must focus on principles.

Adopting principles that signify the intent in absolute terms gives clarity of purpose – keep the carbon in the product, get the nitrogen into the crops.

In this article we’ll elaborate on this, once again with reference to the C-THRU research project investigating the mitigation of greenhouse gas emissions from the petrochemicals industry.

C-THRU principle 1: Ensure the nitrogen reaches the crops

In this multidisciplinary, transnational project, a team focused on the issues and mitigation options related to greenhouse gas (GHG) emissions from nitrogen fertilisers.

The issue

Crops require nitrogen to grow. There are four main sources – natural atmospheric deposition, biological nitrogen fixation, manure, and synthetic nitrogen fertilisers. The first two are insufficient on their own to generate enough nitrogen for the current global crop demand. This means we must use manure and/or synthetic nitrogen fertilisers to fill the gap. Current data shows that around half of the food that the world’s population is dependent on is reliant on using fertilisers (natural or synthetic). However, their production and use bring associated environmental concerns – soil acidification, water sources polluted with fertiliser run-off (eutrophication), energy use, and GHG emissions.

Focusing on the emissions, manure and synthetic nitrogen fertilisers are responsible for around 5% of global GHG emissions currently. With the world population set to grow around 20% over the next 25 years, we are faced with the conundrum of how to feed everyone while at the same time reducing GHG emissions to avert climate change impacts. How do you reduce fertiliser-associated emissions without risking food security?

Previous studies had tended to have a narrow focus, concentrating on one aspect only – emissions from production or use. While these are informative, from a complex systems approach these do not fully describe the bigger picture and potentially miss opportunities for action. The team sought to map the emissions across both phases and use this to explore the impact of different mitigation options.

Annually, 108m t of the nitrogen used on crops is sourced from synthetic fertilisers. This results in total GHG emissions of 1.3 Gt CO2e – a third from production processes and a surprising two-thirds from use on farms. Around 67% of emissions from the use of fertilisers are down to direct (55%) or indirect (12%) release of N2O.

Around 55m t of nitrogen from manure is applied to crops every year, generating some 1.27 Gt CO2e – similar levels to synthetic sources. This means that per unit of nitrogen, manure emits 1.9 times more GHG than synthetic equivalents – predominantly due to additional emissions from manure storage and mobilisation. Unless these manure management emissions can be significantly reduced then manure will remain a higher emitter of GHG than synthetic fertilisers on an equivalent basis.

If it was a simple substitution decision then, to reduce overall GHG emissions, we would increase synthetic fertiliser use and reduce manure application. But manure (together with a significant proportion of its associated emissions) is an unavoidable byproduct of animal farming. It is better to use it for a meaningful benefit, ideally reducing GHG emissions and virgin hydrocarbon extraction by lowering the need for additional synthetic fertiliser production.

Ensure the nitrogen reaches the crops

Having understood the scale of the emissions problem, the team looked at numerous different mitigation approaches and combinations of actions.

One stark observation is that on average only 42% of the nitrogen in the fertilisers actually gets into the crops. While this statistic is highly variable by region and depends on the types of soil, climate, farming practices, and crops, it is still disturbing. With nitrogen inputs considerably higher than the nitrogen requirements of the crops, there are significant losses to the environment. Research suggests that increasing the efficiency of nitrogen use globally to around 67% by 2050 would reduce overall nitrogen demand by 48%. This would directly reduce demand for synthetic fertiliser by an order of magnitude and indirectly reduce emissions associated with production and resource extraction.

There are a mix of different approaches available to achieve the efficiency levels required such as irrigation improvements, plant breeding changes to increase the efficiency of nitrogen uptake, and more knowledgeable application of fertilisers at the right rates, quantities, and places. These measures will naturally vary by region and require tailoring to the soil and climate conditions as well as crop types. The team estimated that if the combination of mitigation options they identified with high technology-readiness were deployed, then emissions from synthetic nitrogen fertilisers could be reduced up to 84%.

Establishing the principle of making sure that nitrogen reaches the crops opens up more effective and creative solutions. It also allows room for different approaches in different regions and contexts – another essential characteristic of a complex system.