Carbon storage in soils could be an environmental solution
We are told that healthy soils retain huge amounts of carbon from the atmosphere. Scientists find that this is not always the case. A new one survey dampens hopes of carbon capture by soils.
Does hemp absorb carbon?
It has been scientifically proven that industrial hemp absorbs more CO2 per hectare than any forestry or cash crop and therefore constitutes the ideal carbon sink. Additionally, CO2 is permanently bound in the fiber which is used for everything from textiles to paper and as a building material.
The rapid growth of hemp makes it one of the fastest CO2-biomass conversion tools available, more efficient than agroforestry. It is possible to grow up to two crops per year, which doubles the absorption of CO2.
Although regenerative agriculture does not have a universal definition, the term is often used to describe practices aimed at promoting soil health by restoring soil organic carbon. The world's soils store many times more carbon than the atmosphere, acting as a natural "carbon sink". But globally, soil carbon stocks have declined due to factors such as the conversion of native landscapes to cropland and overgrazing. One of the goals of regeneration practices is to use some of the carbon that plants have taken up from the atmosphere to help restore soil carbon.
4D imaging reveals the mechanisms of protection and release of clay and carbon
After'Elon Musk announcement, carbon is becoming an extraordinary climate challenge and hemp could play a fundamental role.
Carbon cultivation is a centerpiece of climate strategy, but new research complicates common assumptions about how it can work.
In November, a group of more than 150 former officials and advisers to President Biden convened published a list of recommendations intended to help his administration "get started" on the climate crisis. Among the proposals, the most important is the creation of a federal "carbon bank", which would pay growers to adopt conservation practices such as cover crops and no-till in their fields.
How can hemp capture carbon in soils in theory?
Soil absorbs about 20% of anthropogenic carbon emissions annually, and clay is one of the main carbon capture materials. Although sorption to clay is widely believed to strongly retard microbial decomposition of soil organic matter, increased degradation of organic carbon associated with clay has been observed under certain conditions. The conditions under which clay influences microbial decomposition remain uncertain because the mechanisms of clay-organic carbon interactions are not fully understood.
This study reveals the spatiotemporal dynamics of carbon sorption and release in model clay aggregates and the role of enzymatic decomposition by directly imagining a transparent smectite clay on a microfluidic chip. We demonstrate that the clay-carbon protection is due to the almost irreversible sorption of high molecular weight sugars within clay aggregates and to the exclusion of bacteria from these aggregates. We show that this physically protected carbon can be enzymatically broken down into fragments which are released in solution. In addition, we suggest relevant improvements for soil carbon models.
The basic concept is that these activities help plants to suck carbon from the atmosphere and direct it into the soil, turning farmland into a big sponge capable of absorbing all the greenhouse gases we emit. and which retain heat. A carbon bank would encourage farmers to adopt such practices. Ultimately, the former officials suggested, the federal government could continue to sell these carbon credits to polluting companies looking to offset their own emissions.
But there is still a lot that we don't yet know about carbon retention in soil: how to measure it accurately, how to price it, and what practices actually increase it. This week, the research opened up an additional area of uncertainty: A study of the interactions between carbon, soil, and soil enzymes raises new questions about the actual residence time of captured carbon in soil.
In a recent study, scientists at Princeton University designed a series of experiments that allowed them to observe how carbon molecules stick and peel off clay, a key part of the soil that holds carbon.
Scientists have long known that microbes release some of the carbon in the process of decomposing organic matter in the soil. But the long-held assumption is that clay can thwart this process by binding to carbon and protecting it from microbial activity..
New findings, published Wednesday in Nature Communications, call into question the reliability of this hypothesis
First, lead author Judy Yang incubated carbon molecules, common soil bacteria, and tiny clumps of clay, formally called clay aggregates, in a petri dish. Under the microscope, she discovered that over time, the bacteria were too large to penetrate the clay, and therefore were unable to directly access the carbon stored there. This is the good news - it means microbes have been prevented from breaking down carbon molecules and releasing them into the atmosphere.
However, in another experiment, Yang introduced protein enzymes released by bacteria and fungi to help them process food, into a modified microscope slide containing clay and carbon molecules. Enzymes are much smaller than bacteria, and for this reason, they were not only able to penetrate the structures of the clay, but also helped release almost all of the carbon molecules inside within hours. Once the carbon is released from the clay aggregates, it becomes accessible again to soil bacteria, which can release it from the soil over time. This process could potentially make soil capture a more temporary carbon sink than expected.
Scientists fear that rising atmospheric carbon levels and higher temperatures are bringing us closer to triggering an irreversible but destructive, carbon-generating feedback loop in the soil cycle.
“Previously, we believed that the carbon bound in the clay could not be released within an observable time frame,” said Yang, a former post-doctoral fellow at Princeton and currently an associate professor at the University of Minnesota. “But we have seen that this release takes place in a few hours. Enzymes can penetrate clay, and they can release carbon protected by the clay. If this happens for this type of enzyme, it probably happens for many others as well. "
To be clear, what happened in Yang's lab is a very simplified simulation of what can happen in the field, stripped of countless variables like other elements of microbial life and soil.
Nonetheless, the study helps shed light on cases where soil has been found to release more carbon than expected under certain conditions, worrying scientists who fear that increases in atmospheric carbon levels and higher temperatures. high brings us closer to triggering an irreversible but destructive and carbon-generating feedback loop in the soil cycle.
New avenues for soil research
This does not mean that soil health is an unworthy cause, or that storage is completely futile. On the contrary, Wednesday's conclusions could suggest new avenues for research on soilssaid Rattan Lal, professor of soil science and director of the Center for Carbon Management and Capture at Ohio State University. This includes efforts to understand how to help clay better retain carbon.
“Maybe the great potential for carbon storage that people are thinking about is not permanent as they expected. "
“There are many mechanisms by which clay aggregates can be broken,” Lal said, highlighting practices like plowing and using fertilizer. "The objective of sustainable management is to minimize activities that break aggregates ”.
President Biden signed an executive order directing the Minister of Agriculture to develop a climate plan
Despite the existing and emerging uncertainty surrounding how effectively soils can act as carbon sinks, the idea of a federal carbon bank is likely to continue to gain momentum under the Biden administration. On Wednesday, the president signed a decree ordering the agriculture minister (yet to be confirmed) to develop a master plan on "how to encourage voluntary adoption of climate-friendly agriculture and forestry practices that result in additional, measurable and verifiable carbon reductions and capture ”within 150 days.
The idea carries a lot of weight because it enjoys bipartisan support, as well as the support of groups of farmers, agribusinesses and other actors who are expected to reap financial benefits.
Carbon storage in soils is often presented as a winning solution by both environmental groups and private companies: A broad coalition of stakeholders, including advocates for non-profit organizations, several of the largest food processing companies of the country and the agricultural lobby, have provided support for regenerative practices. Some states like California have already taken the lead in paying farmers to sequester carbon. And in the absence of a publicly-run national carbon bank, many private companies have sprung up in recent years to fill the void.
The idea carries a lot of weight because it enjoys bipartisan support, as well as the support of farm groups, agribusinesses and other actors who could benefit financially from it. The same cannot be said of others practices that would reduce emissions at source.
"If we start to say that we're going to demand a reduction in the use of fossil fuels, or that we are going to demand an increase in the gasoline consumption of cars, or that we are going to dismantle the coal-fired power plants and install the solar energy, there is a lot of lobbying against these things, ”Mr. Schlesinger said. “Almost no one is unhappy with the reduction in soil carbon. Climate advocates might say, "It helps the climate." Farmers might say, “It makes my soils more fertile. What I mean is that this might all be true, but will it do anything for climate change? "