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Uncertainty prevalent in soil
While initial focus is on
carbon sequestration, other opportunities also exist with immediate
Fatka | Jul 28, 2021
Scientists estimate that agricultural
soils could remove 4-6% of annual United States emissions, but the
current system lacks verification to know if soil carbon credits are
encouraging actions to close in on those targets. Credits for soil
carbon sequestration currently lack comparability and consistency,
which creates uncertainty in soil carbon markets. Efforts are
underway, however, to improve the quality of credits and help
realize the full greenhouse gas mitigation potential of agricultural
In a new report — Agricultural Soil Carbon Credits: Making sense of
protocols for carbon sequestration and net greenhouse gas removals —
Environmental Defense Fund and the Woodwell Climate Research Center
reviewed the 12 published protocols used to generate soil carbon
credits through carbon sequestration in croplands. The protocols
take different approaches to measuring, reporting and verifying net
climate impacts, and to managing the vital issues of additionality,
reversal and permanence. The result is a confusing credit
marketplace where it is difficult to compare credits or guarantee
climate benefits have been achieved, the organizations note.
“As addressing climate change becomes ever more urgent, we’re seeing
a gold rush of investment in soil carbon credits. The stakes for the
climate and farmers are extraordinarily high,” says Emily Oldfield,
lead report author and agricultural soil carbon scientist at EDF.
“Agricultural soils could remove 4-6% of annual U.S. emissions. We
need credible, consistent and cost-effective measurement and
verification to know with confidence that soil carbon credits are
moving us toward that target.”
Public and private sector efforts are underway to improve
measurement technologies and methods and to set unified standards
for high-quality agricultural carbon credits that accurately
represent carbon sequestration and net greenhouse gas removals.
Soil carbon protocols take different approaches to measuring,
reporting and verifying net climate impacts, and to managing the
vital issues of additionality, reversal and permanence. This
variation makes it difficult to ensure climate benefits have been
“Until these variations can be resolved, paying farmers to sequester
soil carbon will remain an uncertain approach to greenhouse gas
mitigation but can still deliver important benefits for climate
resilience, soil health and water quality,” the report notes.
The Senate overwhelmingly passed the Growing Climate Solutions Act
earlier this summer to direct the USDA to set guidelines for
high-quality agricultural carbon credits. The House has introduced
its own version but has not taken up the bill itself. Callie
Eideberg, director of agricultural policy for EDF, says, “USDA must
be ready to swiftly implement the bill when it becomes law to
increase certainty that markets deliver for farmers and the
Related: Landmark Growing Climate Solutions Act clears Senate
Agricultural soils can contribute meaningfully to climate mitigation
and resilience efforts. Once guidelines and standardization between
protocols are in place, the enthusiasm for soil carbon credits can
be channeled productively toward slowing the rate of climate change
and adapting to impacts that are already here. This will benefit
both farmers and the planet, EDF adds.
“Businesses face intense pressure to reduce emissions at the pace
and scale that the science demands,” says Katie Anderson, senior
manager for EDF+Business. "Companies must focus on reducing
emissions from their own operations and supply chains, as well as
investing in high-quality carbon credits. But, it’s crucial that
both soil and forest carbon credits have environmental integrity,
guidelines for use and that they’re integrated into a clear pathway
Soil carbon remains difficult to measure for a variety of reasons.
While scientists understand how soil carbon responds to farm
management changes, scientists can’t currently predict the amount
and longevity of new carbon sequestration on all farms. Detecting
soil carbon changes over time requires a high number of samples,
which are costly to collect and analyze, and may need to be
collected from different soil depths depending on soil type and
conservation practices used.
“There are exciting new research efforts and technological
developments underway that will greatly reduce the cost of verifying
soil carbon credits,” says Jonathan Sanderman, contributing report
author and associate scientist at the Woodwell Climate Research
Center. “Increasing accuracy at scale, while also being able to pass
on most of the value of a carbon credit to the farmer, is critical
to ensuring functioning carbon markets.”
Researchers can advance technology that will make it easier to
measure soil carbon levels over time and more cost-effective to
verify carbon credits.
Beyond just soils
While much of the current attention is focused on soil organic
carbon sequestration, the opportunities to reduce emissions
associated with agricultural activities are equally worthy of
consideration, as their mitigation potential is large, and they have
many advantages over soil organic carbon sequestration as a
mitigation strategy, the report notes.
For instance, reduction of fuel consumption, methane emissions or
fertilizer inputs results in avoided emissions that are permanent
and therefore do not have the risk of reversal. Without the risk of
reversal, there is no need for risk management requirements like
maintaining a GHG offset credit buffer. Avoided emissions are also
immediate, unlike soil organic carbon sequestration, which takes
many years to accumulate to measurable levels.
An important avoided emissions opportunity for farmers is the
reduction of nitrous oxide emissions from soil. Nitrous oxide is a
potent GHG with a global warming potential of 265 over 100 years or
264 over 20 years, the report explains.
Agricultural soils are responsible for 78% of nitrous oxide
emissions in the U.S., representing about 5% of total GHG emissions
on a 100-year time frame. “By optimizing manure and inorganic
fertilizer application, many farmers can save money and reduce
nitrous oxide losses from soils, while also reducing nitrate
leaching and providing water quality benefits,” the report adds.
Capturing biogas, which is usually more than half methane, currently
emitted from manure management systems can provide permanent,
immediate climate benefits, as well as revenue since biogas can be
processed to pipeline-grade methane.
Livestock also produce methane via enteric emissions. The report
states, “Work is underway to develop feed additives or diet changes
to reduce enteric emissions, and protocols to credit those avoided
methane emissions are being considered. However, getting such feed
additives to grazing beef cattle, where most livestock methane
emissions occur, will be a challenge.”
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