Agriculture: Trade in the climate saver Humus

The build-up of humus in agriculture helps to store more CO2 – as a step against climate change. In order to reward farmers for this, special “humus certificates” are sold. But that is controversial.

Humus, the top layer of soil, is a valuable commodity: it nourishes the plants, stores water and absorbs carbon from the atmosphere through photosynthesis. Together with the oceans, the soil is the largest CO2 store. The Thünen Institute certifies that the top meter of agricultural soil in Germany alone stores around 2.5 billion tons of organically bound carbon.

The following applies: An increase in humus of 0.1 percent per hectare corresponds to around five to six tons of bound CO2 – under optimal conditions. But “carbon farming” in agriculture requires sophisticated management, great expertise and often a change in operating procedures.

For a better “carbon footprint”

How should farmers be rewarded for this service? For example with humus certificates: companies pay a certain amount per tonne of stored CO2, of which the farmer receives a share. In this way, the companies can improve their “CO2 footprint” in the public image, the farmer is rewarded with more fertile soil and additional operating income.

But that is exactly what is causing criticism: humus build-up is to be advocated, but “the compensation of greenhouse gas emissions from other sectors through humus build-up via CO2 emission certificates is (…) rejected,” says a joint position paper by NABU, BUND, WWF and more than 20 others organizations. Humus can also be broken down again through incorrect management, so CO2 storage is not sustainable.

And: It is an unfair system because not every soil has the prerequisites for a significant build-up of humus. Since agriculture itself emits a total of around 106 million tons of CO2 equivalents every year, such compensation should not be sold to other sectors.

Certificates according to the TÜV-tested method

For the farmers Christoph Uhl and Herbert Ullrich from Unter Schneidheim, carbon farming has become a new mainstay. They are contractual partners of the CarboCert company near Lindau on Lake Constance, which trades in humus certificates. Uhl and Ullrich currently store around 1125 tons of CO2 annually on their 250 hectares of arable land and earn 30 euros per ton. Regional companies can then purchase this storage capacity in the form of certificates from CarboCert, they pay 50 euros per ton.

The rest covers CarboCert’s costs: Every three to four years, GPS-controlled, it takes soil samples from the same places on the fields, whose humus content is analyzed in the laboratory. If the humus content has increased, the amount of stored CO2 can be verified or calculated from the difference. CarboCert has secured TÜV approval for this process.

There is no panacea for building humus

Being paid for more fertile soil and at the same time for CO2 storage – that sounds good for every farmer at first. But: There is no manual for hummus formation. Every company, every floor is different. Uhl and Ullrich work according to the methods of regenerative agriculture, which they are constantly developing. The cornerstones: Diverse crop rotations and very specific undersown crops, which as a plant community imitate a “meadow type” on the field.

Cultivation in the ridge system, i.e. on small hills, provides light and warmth and stimulates root growth. This in turn promotes vital soil life, which is ultimately supposed to metabolize the carbon. In addition, compost tea and microorganisms are used. A positive side effect: mineral or commercial fertilizers are superfluous in this system, soil life and plants feed each other.

Arable farmers at an advantage

Christoph Uhl and Herbert Ullrich are pure farmers. They have a clear advantage over grassland farms: German fields currently have a humus content of around three to five percent. In the case of grassland, it can be 20 percent or more. The development potential on fields is therefore significantly higher. It is true that humus cannot be built up indefinitely on the field, but with an arable area of ​​11.7 million hectares in Germany, the CO2 storage potential is large. “Carbon farming” as an effective tool against climate change is therefore obvious.

For this to happen, however, agriculture must be sustainable. Vital soil life, an optimal interaction of plants and microorganisms – that cannot be built up with cultivation that is one-sidedly aimed at optimizing the yield. In order to motivate farmers for climate-friendly arable farming, you have to offer them compensation for the higher effort and lower yield. Whether this is better done with humus certificates or possible new funding models is still a matter of debate.