Recently, Southern Scientific co-founder Michael Murphy discussed the future of carbon sequestration in agriculture with MTU Ag Scientist and Farmer James McCarthy. Here is a compendium of the discussion in a question-and-answer format.
Carbon sequestration is the taking of carbon dioxide from the atmosphere and bringing it down into the ground through the plants, firstly, to increase the plant volume mass and secondly, to increase carbon in the soil. This process improves the soil nutrient by increasing the organic matter content of the soil.
For example, in grass fields, carbon is taken from the atmosphere. Most of the structure of the grass is carbon from the air when you take out the water. So, when the cattle come along and eat the grass, they’re taking away carbon that should be staying in the soil.
Some of the carbon will go into the soil and be present in the roots. And also, the animal life and insect life such as worms and beetles in the soil. And they’ll also make up the living biomass and then eventually the dead biomass.
For carbon sequestration, there might be a scheme by the E.U. to pay farmers, but are there other benefits for farmers in maintaining the carbon in the soil and enhancing the carbon cycle?
Absolutely! When you do the grassland management required for carbon sequestration (i.e. you have your soil fertility in good order and all of the nutrients present to enable optimum carbon sequestration by increasing soil organic carbon), you also improve the quality of the soil.
This means, for example, increasing its cation exchange capacity so you hold nutrients. You’re more likely to accumulate nitrogen, which means you will have a higher standard of nitrogen present. And that actually increases the fertility and thereby increases the yield.
So, there’s a double benefit for farmers when they do the hard work of actually increasing the fertility of each soil by tuning up all of the trace elements.
The reason why we’re now sampling to a depth of 30cms is so we can assess the profile of carbon in the soil. Previously, we would have just done the topsoil of ten centimetres or four inches for P, K and lime. But now we want to actually take a further measurement so that farmers will know the carbon content of their soil, which will form the time zero or reference value for their soil.
Once you take the sample in your field, we will test it in the laboratory for carbon. And we will give you back a report with the carbon percentage in your soil on a profile basis across your farm.
You won’t sequester carbon with mediocre soil; you have to have high soil fertility. And for that reason, you need to adjust and tune the soil fertility. In other words, you need to do your basic phosphorus, potassium and your lime, but you also need to do the trace elements, which we call the soil health check.
To measure carbon, we need to go to 30 centimetres, which is one foot. And the reason for that is that if carbon sequestration becomes monetized by subsidies or incentivized by the national government in Europe, people will know precisely how much carbon they have.
So, when they measure the carbon on time equal to zero or the year one, they will have a reference value. And then, in five or ten years, they will know the accumulated carbon sequestration.
Your carbon tonnage is quite variable, depending on the soil type. But if the grassland management is at its optimum, one could achieve more than 0.6 tonnes of carbon per hectare per year and possibly up to 1.3. This is seen in studies in different parts of the world on carbon sequestration. Of course, farmers would be paid for that carbon by somebody emitting it at the other end in another industry or by an E.U. scheme.
Not operating in Ireland at the moment or indeed in most parts of Europe. But in the U.S., for example, several companies have been paying farmers to sequester carbon into their tillage, land their arable land. That carbon creates a unit credit, usually one tonne. It’s about $30 per tonne. And that carbon, once verified and certified after a number of years, becomes a tradeable entity. Traders are then purchasing that carbon. Companies like Microsoft are buying up these certificates.
So, a farmer could hold the carbon in the ground and give the certificate to a trader. And that carbon than would be sold in the open market. But it will need to be certified by taking a soil test on day one and then taking it sometime later to show that the carbon in the soil has increased.
There are companies in the U.S., such as, for example, Indigo, who are verifying the quantity of carbon to authenticate this certificate so that it can be traded confidently. This carbon credit is then set off against these companies’ carbon emissions to attain their zero carbon emissions to address climate change.
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