Carbon emissions from fertilizers could be reduced by as much as 80% by
2050

Date:
February 9, 2023
Source:
University of Cambridge
Summary:
Researchers have calculated the carbon footprint for the full life
cycle of fertilisers, 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.


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FULL STORY ========================================================================== Researchers have calculated the carbon footprint for the full life
cycle of fertilisers, 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 fertilisers take place after they are spread on fields,
with one third of emissions coming from production processes.

Although nitrogen-based fertilisers 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 fertilisers
emit the equivalent of 2.6 gigatonnes of carbon per year -- more than
global aviation and shipping combined.

Carbon emissions from fertilisers 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 are fed with
crops grown with synthetic fertilisers, and the world's population is
expected to grow by 20% until 2050.

The Cambridge researchers say that a combination of scalable technological
and policy solutions are needed to reduce fertiliser emissions while maintaining food security. However, they estimate that if such solutions
could be implemented at scale, the emissions from manure and synthetic fertilisers could be reduced by as much as 80%, to one-fifth of current
levels, without a loss of productivity. Their results are reported 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 Andre' 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 fertilisers, 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 fertilisers.

"In order to reduce emissions, it's important for us to identify and
prioritise any interventions we can make to make fertilisers 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 fertilisers and their emissions for 2019, along all stages of
the lifecycle, by reconciling the production and consumption of nitrogen fertilisers 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 fertilisers 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 fertilisers 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 decarbonise heating and hydrogen
production. Additionally, fertilisers could be mixed with chemicals
called nitrification inhibitors, which prevent bacteria from forming
nitrous oxide. However, these chemicals are likely to make fertilisers
more expensive.

"If we're going to make fertilisers more expensive, then there needs
to be some sort of financial incentive to farmers and to fertiliser
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 fertiliser-associated emissions, however, would be to reduce the amount of fertilisers that we use. "We're incredibly inefficient in our use of fertilisers," said Serrenho. "We're
using far more than we need, which is economically inefficient and that's
down to farming practices. If we used fertiliser more efficiently, we
would need substantially less fertiliser, which would reduce emissions
without affecting crop productivity." The researchers also looked at
the mix of fertilisers used around the world, which varies by region. The researchers say that replacing some of the fertilisers 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 decarbonising the fertiliser 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 analysed, emissions from the fertiliser 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.

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.

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========================================================================== Story Source: Materials provided by University_of_Cambridge. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Gao, Y., Cabrera Serrenho, A. Greenhouse gas emissions from nitrogen
fertilizers could be reduced by up to one-fifth of current
levels by 2050 with combined interventions. Nat Food, 2023 DOI:
10.1038/s43016-023- 00698-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/02/230209114736.htm

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