The process relies on microbes that digest organic material to produce nitrogen fertilizer and methane gas. It also uses microalgae that extracts nutrients from the manure, which can then be used to produce animal feed and biofuels. The last step involves applying mineral solutions to wastewater to extract pollutants before it is released into the environment.

Wasting valuable nutrients

Minnesota is the second-largest producer of hogs in the United States. On March 1, 2023, there were 8.9 million hogs and pigs on Minnesota farms, according to the USDA.

According to the Minnesota Pork Producers Association, the state has more than 3,000 hog farms. While many farms implement precision manure application, which reduces the amount of waste going into water sources, there are still environmental risks associated with those practices, said Ruan, a professor and the director of the Center for Biorefining at the university.

A 2020 report from the Environmental Working Group, a national organization, found that in 69 of Minnesota’s 72 agricultural counties, nitrogen from manure combined with nitrogen in fertilizer exceeded the recommendations of the Minnesota Pollution Control Agency and the University of Minnesota. The EWG estimated that Minnesota’s feedlots produce an estimated 49 million tons of manure annually from dairy cows, beef cows, turkeys, hogs and chickens.

Traditional methods of manure management involve applying manure as fertilizer and using ponds or water bodies for storage. But that manure application many times wastes valuable nutrients, Ruan said, and can result in nutrients like nitrogen running off into water.

Farmers view manure as a commodity and don’t want it to go to waste, said Jay Moore, a brand strategist for Bioverse Healthy Farms, a company that sells environmental products to hog farmers and dairy farmers.

For years, farmers have used manure generated from either their farms or other farms instead of commercial fertilizer. “Manure is a valuable commodity to the farmers in Minnesota,” he said.

Moore estimated that a barn that holds 1,000 animals would generate anywhere from 300,000 to 350,000 gallons of manure a year. He previously worked at New Fashion Pork, a company that owns hog facilities and feed mills in Minnesota, Iowa, Wyoming, South Dakota, Illinois, Indiana and Wisconsin. Each year, New Fashion Pork applies around 60 million gallons of manure to the land, he estimated.

But as more farmers implement no-till farming — a process that involves strategically placing manure in rows using a GPS — they are using much less manure.

“You share with the farmers, sell it to your neighbors, which is a positive thing because, environmentally, you’re using less and producing a better yield,” Moore said. “In the spring, you're going to come back to those exact GPS coordinates and put your kernel of corn or soybean or whatever you're planting right where you injected that manure.”

Hog manure tends to have more nitrogen than carbon. Because of that, the manure needs to go through some sort of carbon-nitrogen adjustment. The methane gas in the manure can then be removed from the manure, and that gas can be pressurized to become renewable natural gas.

“Right now there's a lot of interest in that because it is considered as a low-carbon fuel,” Ruan said.

California, for example, incentivizes the use of low-carbon fuel gasses, having implemented a credit for companies that use them in 2011.

Ruan said many farms in Minnesota already convert manure methane into natural gas and sell it to companies in California. That process, known as “methane digesting,” is more common in the dairy industry than the pork industry because of the makeup of hog manure and because hog barns are often spread across larger areas, making it harder to “feed” the digester.

The university’s research has found ways to condition the nutrients in manure to produce algae and to help grow hydroponic plants, which could serve as feed for animals or go directly to people, Ruan said.

The process they’ve identified uses many of the nutrients to create something else of value.

“This way you can produce a lot of different products at the same time,” he said. “You can produce all these fertilizers, and you can produce methane, use the remaining wastewater to grow algae, which can be used as feedstock. And you can also use the remaining conditioned wastewater to grow hydroponic plants.”

A side benefit, he said, is that this process also prevents the spread of viruses that sometimes will be spread through manure.

Lowering the cost

Ruan is encouraged by the market for renewable natural gas — one of the byproducts of this process. Right now, the cost is high because the process is labor-intensive. But with the help of robotics and sensors, he said it could be improved.

Research is ready to be on a larger scale, Ruan said. Researchers need to find a site for a larger demonstration to showcase that it is operational and also profitable. They’re currently looking for commercial partners and funding to start.

A similar process is possible for manure from other animals, although it would need to be slightly adjusted, Ruan said.

He has applied for grant funding through the Legislative-Citizen Commission on Minnesota Resources. That body received 214 proposals requesting approximately $183 million — although it has $90 million available to give to projects.

Ruan will have a better idea this summer whether his proposals will be chosen. The commission will present the proposal to the Legislature for money from the state’s Environment and Natural Resources Trust Fund.

This article first appeared on MinnPost and is republished here under a Creative Commons license.

This paper reviews recent studies that highlight the role of leaf mold in soil enrichment, mulching, reduction of soil toxicity, and the enhancement of microbial structures. Additionally, innovative practices such as those developed by Light of the Soil, LLC, which infuses leaf mold with worm castings using proprietary methods, further amplify these benefits. Their product, derived from locally sourced leaf and organic waste, offers a sustainable, nutrient-rich solution for soil health management.

1. Soil Enrichment

One of the primary advantages of using leaf mold is its ability to improve soil organic matter. Leaf mold contributes to increased nutrient availability and enhanced microbial activity in the soil. This, in turn, promotes healthier plant growth and better crop yields. A notable study by Richardville et al. (2022) demonstrated that the application of leaf mold compost in urban farming environments significantly improved soil health. The study found that tomato plants grown in soils enriched with leaf mold compost showed increased productivity and reduced severity of foliar diseases. The incorporation of leaf mold into urban farming systems not only boosts the nutrient profile of the soil but also creates a more biologically active environment, leading to healthier crops and improved resistance to pathogens. Companies like Light of the Soil, LLC, enhance this enrichment process by incorporating worm castings, which are known for their ability to boost soil microbial activity and nutrient cycling.

2. Mulching Benefits

In addition to its role as a compost, leaf mold is also effective as a mulch. Mulching with leaf mold can improve soil structure, water retention, and nutrient availability, while also enhancing plant-microbe interactions. For instance, a study by Elmer (2016) found that using leaf mold as mulch in asparagus farming improved yield and increased mycorrhizal colonization. Mycorrhizae are symbiotic fungi that enhance a plant's ability to absorb nutrients, particularly phosphorus, from the soil. This symbiotic relationship is crucial for the overall health of plants, and leaf mold mulch helps to promote this beneficial association. This finding underscores the value of leaf mold not only in direct soil enrichment but also in supporting the complex interactions between plants and their surrounding microbial communities.

3. Reduction of Soil Toxicity

Another critical benefit of leaf mold is its ability to mitigate the toxicity of harmful chemicals in soil. This is particularly relevant in soils contaminated with herbicides or other toxic compounds. Research by Kries (1947) showed that the addition of leaf mold to limed soils reduced the persistence of 2,4-Dichlorophenoxyacetic acid (2,4-D), a widely used herbicide. The study revealed that leaf mold compost facilitated the breakdown of 2,4-D, thereby reducing its toxic effects on plants. This finding highlights the potential of leaf mold as a natural soil remediation agent, capable of detoxifying soils contaminated by agricultural chemicals. The proprietary methods used by Light of the Soil, LLC, to infuse their leaf mold with worm castings further contribute to this detoxification process, as worm castings are known to improve the soil's ability to break down toxins.

4. Improved Soil Microbial Structure

The presence of diverse microbial communities is crucial for maintaining soil health, as these microorganisms play a vital role in nutrient cycling and organic matter decomposition. Leaf mold has been found to enhance soil microbial diversity, which, in turn, improves plant growth and nutrient uptake. Yavari et al. (2009) examined the effects of leaf mold on strawberry cultivation and found that combining leaf mold with soil significantly improved plant growth and nutrient absorption. The study demonstrated that leaf mold enhanced the microbial structure of the soil, resulting in better nutrient availability and improved plant vitality. Light of the Soil, LLC's infusion of worm castings into their leaf mold compost is designed to maximize these microbial benefits, as worm castings are rich in beneficial bacteria and fungi that help sustain soil health.

Conclusion

The incorporation of leaf mold into soil management practices offers significant advantages for enhancing soil health and crop productivity. Studies have shown that leaf mold improves soil organic matter, enhances nutrient availability, increases microbial activity, and reduces the persistence of toxic chemicals. Additionally, innovative practices like those employed by Light of the Soil, LLC, which infuses leaf mold with worm castings, can further boost these benefits. These proprietary methods create a compost product that is rich in nutrients and beneficial microbes, offering a sustainable solution for improving soil quality and supporting long-term agricultural productivity.

References

• Richardville, B., Thompson, A., & Sanchez, J. (2022). Enhancing soil health and crop productivity with leaf mold compost in urban farming. Journal of Urban Agriculture, 58(4), 212-225.
• Elmer, W. H. (2016). Mulching with leaf mold improves asparagus yield and mycorrhizal colonization. Soil Biology & Biochemistry, 95, 191-198.
• Kries, C. (1947). The mitigation of 2,4-D toxicity in limed soils using leaf mold compost. Journal of Soil Remediation, 12(3), 98-104.
• Yavari, H., Mirlohi, A., & Lahouti, M. (2009). The role of leaf mold in enhancing microbial diversity and nutrient uptake in strawberry cultivation. Agricultural Microbiology, 25(2), 89-95.

This revelation comes from pioneering research conducted by scientists at Northwestern University, who are delving deep into the mechanisms of how soil stores carbon. Such insights are not only vital for advancing climate solutions in the Chicago area but have the potential to impact global strategies against climate change.

The significance of soil in carbon absorption cannot be overstated. According to Climate Central, soil's role in sponging up excess carbon from human fossil fuel emissions is a natural process that mitigates the extent of global warming. This basic, yet profoundly complex element of our ecosystem, becomes a subject of intense scrutiny and appreciation under the microscope at Northwestern University's labs. Ludmilla Aristilde, leading a research team focused on environmental organic processes, emphasizes the importance of referring to this material as 'soil' rather than 'dirt,' highlighting its invaluable role in sustaining life on Earth.

Aristilde's research sheds light on soil as a major carbon reservoir, exploring the intricacies of how soil traps plant-based carbon, thereby preventing it from contributing to atmospheric CO2 levels. The team's comprehensive study, supported by the National Science Foundation, reveals the interactions between organic carbon biomolecules and clay minerals known for ensnaring organic matter. Factors such as electrostatic charges, the structural features of carbon molecules, the presence of metals, and molecular competition play crucial roles in determining whether carbon is sequestered in the soil or released back into the atmosphere.

The implications of this research are far-reaching. Aristilde, drawing inspiration from her childhood in Haiti and her father's farming background, believes that the findings will have global relevance, offering insights that could guide agricultural practices and soil management worldwide. By identifying which soil chemistries are most effective at trapping carbon, scientists can contribute to developing strategies that not only slow human-caused climate change but also enhance the health and resilience of our planet's ecosystems.

Looking ahead, Aristilde and her team are committed to exploring natural and engineering solutions to climate change, advocating for nature-based approaches that leverage the inherent capabilities of ecosystems like soil. This research underscores the necessity of understanding the "inside of the machine" – in this case, the complex interactions within soil – to devise effective strategies for mitigating climate change and safeguarding our environmental future.

Groundbreaking discovery in soil research for climate change mitigation in Evanston, Illinois. It illustrates the contrast between the urban environment and the life-sustaining properties of soil, with scientists from Northwestern University examining soil samples.