Next generation tech needed for soil carbon scale-up
Creating carbon credits from soil is a messy business beset by challenges. But practitioners are confident that a combination of innovative technology and quality protocols will help unleash a market with transformative potential, writes Steven Gilmore.
A critical assessment of the soil carbon market can paint a doubtful picture. Models used to estimate sequestration miss the complexity of how and under what conditions soil stores carbon. Testing and sampling is problematically expensive, making projects hard to scale. Protocol standards vary widely in quality and precision. Credit prices remain low.
“A mess” is how Freya Chay, a program associate at non-profit CarbonPlan, described the market recently.
And yet there are organisations that have proved it is possible to create and sell quality credits. Credits that represent not only sequestered carbon, but an improvement in farming practices and an income boost for growers.
US-based Indo Ag issued its first soil carbon credits in June through the Climate Action Reserve (CAR) registry. CAR has one of the more rigorous protocols, according to CarbonPlan, which analyses climate solutions. “And it's hard,” says Chris Harbourt, IndigoAg’s chief strategy officer. “It is a heck of a protocol.”
What we proved to everyone this past summer is that it's not only possible, but we achieved it. We issued 19,000 tonnes of carbon credits and put real dollars back in the pockets of farmers.”
But choosing the strictest protocols is vital to create confidence that a tonne of carbon purchased is a tonne of carbon sequestered.
In 2021, CarbonPlan analysed and scored 17 different soil carbon protocols on rigour, additionality, durability, and safeguards. Each protocol received a rating between one and five. The most common score was one. Although CAR was one of the most rigorous protocols – and the only one to require permanence of 100 years – CarbonPlan judged it weak on additionality and safeguards. Some firms in the market are arguing for even weaker protocols to make the process easier.
“What we proved to everyone this past summer is that it's not only possible, but we achieved it,” says Harbourt. “We issued 19,000 tonnes of carbon credits and put real dollars back in the pockets of farmers.”
The focus in the US industry, says Harbourt, has shifted from wondering whether projects with rigorous protocols are possible, to how to scale them up.
Here, technological innovation will be a key part of the solution. US-headquartered Boomitra is tackling soil carbon sequestration at scale, and has projects in Africa, Latin America and India.
CEO Aadith Moorthy says the firm now has millions of acres under project, collectively able to remove millions of tonnes of Co2. “We plan to be at the gigatonne scale by the end of the decade,” he says.
Boomitra starts with physical soil sample data to calibrate its measurement system. But in measuring sequestration from improved farming practices, the firm uses satellite data from across the electromagnetic spectrum to assess how much carbon is in the soil. Scanning 1.5 million acres of a project in Northern Mexico at 10m2 resolution allows a degree of measurement across that would be impossible with direct sampling, Moorthy says.
“If you did 10 metre level soil sampling, maybe the cost of sampling is 10 times more than the cost of the carbon credit,” he says. “What people do as standard today is every 40 acres or so. That level of soil sampling is already more than 50% of the carbon credit [cost].”
We plan to be at the gigatonne scale by the end of the decade
Scale is crucial to generate a sufficient flow of credits cost-effectively and to meaningfully lower emissions. But there is scepticism that a satellite-only approach to measuring sequestration is viable.
Moorthy argues that at scale, the volume of precision measurements means uncertainty is very low. All measurement and modelling techniques come with errors and uncertainty, but many practitioners say robust physical sampling remains key.
CarbonPlan only awards its highest score on rigour to protocols that use direct sampling as the basis for issuing soil carbon credits.
The problem is that laboratory soil sampling is “pretty cost-ineffective,” says Kelly Gillespie, vice president of digital ecosystem services at Bayer, which launched a carbon programme for US farmers in 2020.
On the hunt for tech solutions, the firm held a Grants4Tech challenge on soil carbon measurement earlier this year. Canadian finalist ChrysaLab has developed a portable probe for real-time measurement, which would avoid the time and logistical costs of shipping samples to a lab.
Dutch firm SoilCASTOR uses cutting-edge spectroscopy, beaming light from a scanner no larger than a computer mouse and analysing the reflecting frequencies to determine soil carbon content. “We are fast and furious evaluating a tonne of different kinds of technology to see how accurate and how fast they can measure soil carbon,” says Gillespie.
Calibrating carbon models
Satellites, although not a silver bullet solution, likely have a key role to play. Not only can they help determine if certain crops have been grown, but their measurements can help improve and calibrate carbon models.
One of Bayer’s finalists was German firm Constellr, which is developing the potential for thermal infrared microsatellites. Harbourt also expects to see firms leverage a combination of ground and satellite data in the future as new techniques become available.
Like Bayer, IndioAg is on the hunt for innovative technology around soil sampling, from ground penetrating radar to remote sensing. But improving the quality of aerial survey data will not shed the need to drill further down into what is happening in the dirt.
Studies indicate that common improvement practices like no-till farming increase carbon storage near the surface, but can lead to less carbon stored further down. Gillespie suspects that physical sampling below the current 30cm standard is on the horizon. “We're going to have to get to a place where we're measuring deeper, and we're going to understand how much of that surface carbon is actually sinking deeper into the soil,” she says.
We’re already in a climate crisis. If we waited for all the technology to be perfect and all the financial markets to be in place…I don’t think we have that kind of luxury.
Expanding best-practice soil carbon credit projects in emerging markets highlights the importance of better measurement and modelling. IndioAg was able to draw on years of academic data to back up its sequestration estimates for project crops in the US. But Harbourt notes that some crops – even within the US – simply do not have the necessary data. “That gets very challenging as you go internationally,” he says.
In entering new countries, some organisations choose locations and crops that are similar to US analogues with an established database. But the fact that most of the existing soil carbon models were built and calibrated in the US remains a problem for scaling operations globally, says Gillespie.
No new market avoids growing pains and there is no reason to sacrifice precision and reliability in a rush to ramp-up projects. Investors need to reward adherence to the best protocols, and protocol standards have to improve as new techniques and innovations come online. Existing tools and measurements will yield errors, but the energy transition has demonstrated how quickly technology can improve when deployed at scale.
“We’re already in a climate crisis,” says Gillespie. “If we waited for all the technology to be perfect and all the financial markets to be in place…I don’t think we have that kind of luxury.”