Which is more important for biofuels – soil or crops?

As a scientist on Earth, I was pleased to see this soil. I shouldn’t have been surprised. Farmers have known this for centuries.

Soil texture and soil microbes are key. This is what the farmer does when he reaches his hand down, scoops some soil into his hands, looks at it, smells it and sighs.

This is especially important if you’re trying to capture carbon from the atmosphere and put it into plants that produce biofuels to either run cars or power power plants.

Biofuel is a fuel derived from a living material called biomass (usually plant matter). Examples of biofuels include, but are not limited to, biodiesel, ethanol, and vegetable oils. Biofuels can be classified into three different types based on the source of the biomass. Since biofuel is obtained from existing plant growth, it is considered a renewable source of energy.

Ethanol is the most common biofuel in North America, with most gasoline containing up to 10% ethanol. This fuel is referred to as E10, where the number indicates the percentage of ethanol in the fuel. Flex-fuel vehicles are capable of running up to E85. The remaining 15% of the fuel should be gasoline since ethanol is difficult to ignite in engines.

Most of the carbon in the soil is in the form of organic matter. The composition of this substance is determined by plants, microbes and soil. However, scientists do not fully understand how variation in plant inputs, the structure of soil microbial communities, and the physical and chemical properties of soils interact to influence the chemical composition of soil organic matter.

Researchers at PNNL, led by Kirsten Hofmockel, addressed this knowledge gap by combining microbial properties with detailed soil chemistry from two longstanding bioenergy research experiments. They found that soil texture was more important than crop type in soil microbial community composition and soil organic matter chemistry.

Plants take carbon from the air, build cells, and then release some of the carbon into the soil through roots and root exudates. Some have suggested that growing biofuel crops on marginal soils, which generally have a low carbon content, may be a way to remove carbon from the atmosphere and store it underground. But this turned out to be incorrect.

Scientists must understand the controls of how soil organic matter builds up to identify successful strategies that improve soil health and increase carbon storage, especially for potential biofuel crops.

In the PNNL studies, researchers describe the effect of crops and location on fungal and bacterial community structure, potential enzyme activity, soil carbon chemistry, and soil carbon and nitrogen concentrations in two long-running biofuel field trials.

The two sites had corn and grass crops. One of the sites was predominantly sandy loam soil, while the other had predominantly sandy loam soil. The research found that yield had less influence on soil microbial community structure and the chemistry of organic matter than soil type.

Soil type was particularly influential on the fungal community structure and the chemical composition of the relatively stable carbon. After eight years of no-till management, clay loam soils still contain twice as much total carbon and nitrogen as sandy loam soils, with no significant response to biofuel cultivation.

The figure below, from Christopher Kasanke, Qian Chao, Sheryl Bell, Alison Thompson and Kirsten Hofmukle (2020) shows the sharp differences in soil effects. Note that the soil made the difference in both crops in terms of carbon and nitrogen retention. The key to the figure is – total carbon (a) and total nitrogen (b) in sandy corn (light blue), sandy grass (dark blue), placer maize (light red), and placer grass (dark red) significantly (circle). Small aggregates (triangular) generated using an optimized moisture sieving approach. The plotted values ​​represent the average percentage C or N per gram of dry soil.

Lower panels are micrographs of micro-aggregations in sandy (c) and alluvial (d) soils, showing how micro-structure can affect things like soil and nutrient retention. In sandy soils, there is very little micro porosity to hold.

The researchers concluded that this is likely the result of enhanced bacterial activity in the soil. So initial site selection is critical for plant-microbe interactions and greatly influences the long-term potential for carbon storage in topsoil under biofuel production.

Alternatively, deep-rooted perennials used in biofuel production may provide a means to capture carbon deep in the soil. The ability of biofuel farming systems to sequester carbon depends on how carbon from plant and microbial sources interacts with soil minerals. Microbes Different in soil depth. Deep-rooted plants provide an opportunity to increase carbon input and reduce carbon return to the atmosphere. But it all depends on soil chemistry. Our research continues to dig deeper into the soil profile to understand the most promising soil factors for carbon sequestration.”

Biofuels and fossil fuels (coal, oil, and natural gas) are both derived from organic matter, but they differ in how the organic matter died out recently. Fossil fuels come from organic materials that have been dead for millions of years, while biofuels come from organic materials that have recently died.

From a climate change perspective, using biofuels in an engine still releases the same amount of carbon dioxide as fossil fuels. However, since it is derived from modern biomass that has absorbed carbon dioxide2 As it grows, CO2 Its release in combustion causes no net increase in atmospheric carbon, bringing biofuels close to carbon neutral, regardless of the costs of CO2 and nitrous oxide for agricultural equipment, fertilizer production, transportation, and biomass conversion.

On the contrary, fossil fuels release carbon dioxide2 that have been stored for eons. Burning it increases the amount of carbon dioxide in the carbon cycle, especially in the atmosphere and oceans.

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