Cambridge Research Shows Potential for 80%
Reduction in Carbon Emissions From Fertilizers by 2050
ByUNIVERSITY
OF CAMBRIDGE
Researchers at the University of Cambridge have measured how much
carbon is produced by fertilizers from the beginning to the end of
their life cycle. This is important, as fertilizers are responsible
for around five percent of all greenhouse gas emissions. This is the
first time anyone has accurately measured this. They discovered that
by the year 2050, it could be possible to reduce carbon emissions from
fertilizers to only one-fifth of what they are now.
Researchers have calculated the carbon footprint for the full life
cycle of fertilizers, which are responsible for approximately five
percent of total greenhouse gas emissions – the first time this has
been accurately quantified – and found that carbon emissions could be
reduced to one-fifth of current levels by 2050.
The researchers, from the University of Cambridge, found that
two-thirds of emissions from fertilizers take place after they are
spread on fields, with one-third of emissions coming from production
processes.
Although nitrogen-based fertilizers are already known to be a major
source of greenhouse gas emissions, this is the first time that their
overall contribution, from production to deployment, has been fully
quantified. Their analysis found that manure and synthetic fertilizers
emit the equivalent of 2.6 gigatonnes of carbon per year – more
than global
aviation and shipping combined.
“Our work gives us a good idea of what’s technically possible, and
where interventions would be meaningful – it’s important that we aim
interventions at what matters the most, in order to make fast and
meaningful progress in reducing emissions.” — André
Cabrera Serrenho
Carbon emissions from fertilizers urgently need to be reduced;
however, this must be balanced against the need for global food
security. Earlier research has estimated that 48% of the global
population is fed with crops grown with synthetic fertilizers, and the
world’s population is expected to grow by 20% by 2050.
The Cambridge researchers say that a combination of scalable
technological and policy solutions is needed to reduce fertilizer
emissions while maintaining food security. However, they estimate that
if such solutions could be implemented at scale, the emissions from
manure and synthetic fertilizers could be reduced by as much as 80%,
to one-fifth of current levels, without a loss of productivity. Their
results were reported on February 9 in the journal Nature
Food.
“Incredibly, we don’t actually know how many chemicals we produce
globally, where they end up, where and how they accumulate, how many
emissions they produce, and how much waste they generate,” said
co-author Dr. André Cabrera Serrenho from Cambridge’s Department of
Engineering.
Serrenho and his co-author Yunhu Gao undertook a project to accurately
measure the total impacts of fertilizers, one of the two main products
of the petrochemical industry. Of all the products made by the
petrochemical industry, the vast majority – as much as 74% – are
either plastics or fertilizers.
“In order to reduce emissions, it’s important for us to identify and
prioritize any interventions we can make to make fertilizers less
harmful to the environment,” said Serrenho. “But if we’re going to do
that, we first need to have a clear picture of the whole lifecycle of
these products. It sounds obvious, but we actually know very little
about these things.”
The researchers mapped the global flows of manure and synthetic
fertilizers and their emissions for 2019, along all stages of the
lifecycle, by reconciling the production and consumption of nitrogen
fertilizers and regional emission factors across nine world regions.
After completing their analysis, the researchers found that, unlike
many other products, the majority of emissions for fertilizers occur
not during production, but during their use.
“It was surprising that this was the major source of emissions,” said
Serrenho. “But only after quantifying all emissions, at every point of
the lifecycle, can we then start looking at different mitigation
methods to reduce emissions without a loss of productivity.”
The researchers listed and quantified the maximum theoretical impact
of different mitigation methods – most of these are already known, but
their maximum potential effect had not been quantified.
Emissions from the production of synthetic fertilizers are mostly from
ammonia synthesis, partly due to chemical reactions used in the
production process. The most effective mitigation at the production
stage would be for the industry to decarbonize heating and hydrogen
production. Additionally, fertilizers could be mixed with chemicals
called nitrification inhibitors, which prevent bacteria from forming nitrous
oxide. However, these chemicals are likely to make fertilizers
more expensive.
“If we’re going to make fertilizers more expensive, then there needs
to be some sort of financial incentive to farmers and to fertilizer
companies,” said Serrenho. “Farming is an incredibly tough business as
it is, and farmers aren’t currently rewarded for producing lower
emissions.”
The single most effective way to reduce fertilizer-associated
emissions, however, would be to reduce the amount of fertilizers that
we use. “We’re incredibly inefficient in our use of fertilizers,” said
Serrenho. “We’re using far more than we need, which is economically
inefficient and that’s down to farming practices. If we used
fertilizer more efficiently, we would need substantially less
fertilizer, which would reduce emissions without affecting crop
productivity.”
The researchers also looked at the mix of fertilizers used around the
world, which varies by region. The researchers say that replacing some
of the fertilizers with the highest emissions, such as urea, with
ammonium nitrate worldwide could further reduce emissions by between
20% and 30%. However, this would only be beneficial after
decarbonizing the fertilizer industry.
“There are no perfect solutions,” said Serrenho. “We need to rethink
how we produce food, and what sorts of economic incentives work best.
Perhaps that means paying farmers to produce fewer emissions, perhaps
that means paying more for food. We need to find the right mix of
financial, technological, and policy solutions to reduce emissions
while keeping the world fed.”
Serrenho and Gao estimate that by implementing all the mitigations
they analyzed, emissions from the fertilizer sector could be reduced
by as much as 80% by 2050.
“Our work gives us a good idea of what’s technically possible, what’s
big, and where interventions would be meaningful – it’s important that
we aim interventions at what matters the most, in order to make fast
and meaningful progress in reducing emissions,” said Serrenho.
Reference: “Greenhouse gas emissions from nitrogen fertilizers could
be reduced by up to one-fifth of current levels by 2050 with combined
interventions” by Yunhu Gao and André Cabrera Serrenho, 9 February
2023, Nature
Food.
DOI: 10.1038/s43016-023-00698-w
The research was part of the C-THRU
project, led by Professor Jonathan Cullen, where researchers from
four UK and US Universities are working to bring clarity to the
emissions from the global petrochemical supply chain.
