Soil carbon sequestration for a sustainable food value chain

The term "carbon farming," which refers to nature-based solutions, describes land management practices that decrease greenhouse gas (GHG) emissions from agricultural operations and increase the amount of CO2 that plants remove from the atmosphere and store in the soil as soil organic carbon (SOC), preferably permanently.

Carbon credits are carbon offsets that account for removing or avoiding carbon dioxide-equivalents (CO2-e). Governments, businesses, and people who can't cut emissions buy these credits to reach carbon neutrality or net-zero emissions. In the context of carbon farming, carbon credits are an extra way for farmers to make money.

Also, carbon farming improves the health of the soil naturally by sticking to some of the best ways to manage land in agriculture. This leads to highly productive land that is more resilient to climate change. For example, the soil will be better at storing water and need less synthetic fertilizer to generate higher yields

In the Paris Agreement, 196 countries agreed to keep global warming below 2 degrees Celsius, ideally 1.5 degrees Celsius, compared to levels before the industrial revolution. To achieve that, we must decrease our global CO2 emissions by almost half by 2030 and to "net zero" by 2050. However, our emissions are still rising by double digits.

Our mission is to promote sustainable agriculture, which can meet the world's food demands today and into the future. To do this, we give farmers advice that helps them get the most out of their farming inputs, like nitrogen fertilizer, which makes it easier for carbon to be stored in the soil. So, our plan to help carbon farming can help farmers make more money by selling the carbon they have managed to store.

This is the next step that makes sense for us to take to grow our business and give our current and future clients the tools they need to get to carbon neutrality as quickly as possible. We got money from the European Space Agency and the German Aerospace Agency to do a feasibility study. This will let us talk to the people with a stake in carbon farming to find out about their problems and test our technological solutions so they can use them.

Agriculture can contribute by lowering its carbon footprint and compensating for carbon that either agriculture or any other business cannot immediately lower. This natural way to store carbon is very appealing because it won't affect our ability to grow food, which is much more important.

Soil has more carbon (2,500 billion tons) than the atmosphere and all plant life combined. Good agricultural practices help the soil to hold onto that carbon. We have lost about 133 billion tons of carbon (488 billion tons of CO2-e) because of industrial agriculture, but we can get it back without overusing the soil's ability to store carbon.

So, there is a huge chance to put carbon back into the soil, which we can do by using regenerative farming practices. This makes the soil better at holding on to carbon and stronger against climate change.

In the soil carbon cycle, nitrogen is crucial. How much carbon an agricultural system can store depends on what kind of nitrogen is used. Consider starting a fire to burn some wood; to do so, you'll need a match. Nitrogen is like putting a match to the carbon in the soil because without it, it would have stayed in the soil for a very long time. The air contains oxygen, which serves as an accelerator. The fuel that is burned and released into the air is soil carbon. If these three factors come into play, the soil carbon gets released.

We do not need nitrogen to grow crops, but nitrogen comes in different forms that impact the carbon cycle. Some of those forms are not good for storing carbon in the soil. For example, growing legumes and storing nitrogen in that form is stable and beneficial for crops, but using liquid nitrogen fertilizer, which may leach or volatilize nitrogen from the soil, is a very inefficient use of nitrogen.

Regenerative agriculture, according to the Rodale Institute, has the potential to offset more than 100% of our annual emissions. Other conservative estimates, however, suggested that regenerative agriculture could contribute to offset up to 13% (0.56 - 1.15 t of C per hectare per year) of our annual emissions. Therefore, agriculture can certainly contribute to the fight against climate change, but the exact amount is something we still need to understand better.

The fact that most of the study mainly depends on models rather than a significant amount of geographically diverse field data on Soil carbon change over time contributes to some of this uncertainty. Due to the local climatic conditions, soil quality, and agricultural practices, agricultural areas also have a wide range of potential to trap carbon.

However, we believe this is the best course of action (nature-based carbon sequestration) because it is the most efficient and cost-effective alternative we presently have for satisfying our food demands while offsetting our carbon emissions.

There are additional options than soil carbon sequestration for carbon offsetting. Like turning waste into carbon and storing it in the ground, direct air capture, forest-based carbon sequestration, etc.

Due to the rise in forest fires, forest-based carbon sequestration is becoming increasingly fragile. In addition, there isn't enough space for us to grow new forests because more trees are being cut down for food production. Our options for storing carbon in forests are thus limited. On the other hand, direct air capture or comparable options are effective but still expensive, which probably will decrease in the future. Carbon farming is, therefore, now the greatest choice since it is affordable and can be put into practice without requiring a significant initial investment.

The best method for calculating the quantity of soil carbon in a field is to test the soil for its organic carbon content, which may be done by taking soil samples and analyzing them in a lab. The soil carbon stored in the first 30 cm of soil, or the first meter of soil may be estimated using these carbon measures. Every five years, we should conduct soil tests to monitor changes in the soil organic carbon (SOC). The increase in SOC shows that soil is effectively sequestering and storing carbon, increasing the soil carbon pool. The delta change in carbon stock may be transformed into carbon credits, which can subsequently be exchanged for carbon offsetting.

Modeling the change in carbon stock caused by adopting certain regenerative farming practices is another cost-effective strategy. While this method does not need soil sampling, it does call for regional tailoring, which may be achieved by conducting field experiments to identify the factors. For instance, provided that the agricultural practices include increased crop rotation, cover cropping, and no-till farming, we can estimate that in Germany, where the annual precipitation is more than 800 mm, the loamy soil may store roughly 1 ton of carbon a year. Satellite images could then monitor these farming practices and generate carbon credit. It's important to note that the USA will likely benefit from this technique since they already have the necessary factors. We still need to develop models for reliable soil carbon stock assessment for other parts of the world.

Some are attempting to assess carbon stock using satellite imagery, which does not require soil sampling in the operational setting, as regional tailoring is the bottleneck in the modeling technique. However, this method necessitates an enormous number of soil sample tests in order to calibrate satellite data, which is a downside because it requires high upfront costs to build the models.

After considering all of the above, we conclude that the current best course of action is to rely on soil sampling while using strategic soil sampling approaches to minimize the number of soil samples required. Then, create a high-resolution soil carbon map for the whole farm using these soil samples to calibrate satellite data for a specific farm. Any other choice would be like "trying to run before we even learn to walk."

All these methods fall under the umbrella term "MRV" (Measurement, Reporting, and Verification), which refers to the standards or protocols used by independent verifiers to generate carbon credits.

Measurement, reporting, and verification, or MRV for short, are fundamental methodologies (also known as standards or protocols) to monitor the farm's progress and determine if carbon credits can be generated.

MRV protocols vary from one carbon program to another. The service providers often determine which protocols to use. However, most protocols try to establish a baseline measurement that reflects how the farm is managed before introducing practices that sequester soil carbon. For this process, historical data from the farmers is needed, often from the last three to five years. In addition, soil samples are gathered and examined in order to determine the baseline soil carbon stock, and sometimes models are used to run some projects.

Typically, carbon farming projects last for at least ten years. Therefore it's critical to monitor any changes to the farm's practices (such as cover crops), which may be done through reporting. Farm management software designed for carbon farming is typically used for data collecting on the farm and preparing reports.

The verification procedure usually happens within 3-5 years from the start, determining if the information on practice change satisfies the requirements for the issue of carbon credits. An independent auditor often performs verification in order to assess the validity of the carbon farming data and determine how many carbon credits (CO2-e) will be generated as a result of the practice changes.

Different verification agencies will have rules to certify the information's validity. Verra and Gold Standard are two of the top independent carbon-certifying organizations.