News | MnDRIVE Environment

Hog Manure Revisited

With funding from a MnDRIVE Environment Demonstration Grant, UMN researcher Roger Ruan makes the most of manure.

by Reed Grumann

Where others see waste, Bioproducts and Biosystems Engineering professor Roger Ruan sees opportunity—in this case, repurposing wastewater from livestock operations to extract economic value and address a potential environmental threat from one of Minnesota’s largest industries: hog farming.

Minnesota is the second largest pork producer in the country, with a headcount of nearly 9 million pigs and hogs. Like any livestock industry, pork producers need solutions for treating manure. There’s inherent value in animal waste as a source of biogas, bedding, and even building materials. But before it is reused, it must be properly treated. One popular treatment choice, and the focus of Ruan’s research, is anaerobic digestion.

Anaerobic digestion involves the controlled growth of microbes in an oxygen-free environment. Large tanks similar to those you might see at your local brewpub can convert food and agricultural waste into valuable byproducts that are safe for the environment. Typical anaerobic digestion systems, however, are unsuitable for hog manure, which contains higher levels of nitrogen and organic materials when compared to other animal waste. “Even after traditional anaerobic digestion, hog waste still contains high levels of nitrogen and other nutrients,” says Ruan, which can leach into water systems and cause eutrophication and kill fish, prompt unwanted and overwhelming vegetative growth, and even pollute our drinking water.

From an environmental perspective, such high concentrations of protein and nutrients are a problem. But from a biosystems lens, they’re an opportunity. “We developed a systematic approach for manure wastewater from pigs while treating it at the same time,” says Ruan. His system expands the scope of anaerobic digestion from treatment to resource recovery, aiming not only to prepare hog manure for proper disposal but also to extract and process the excess nutrients into valuable byproducts.

The first issues Ruan’s system addresses are low carbon levels and excess ammonia. When cycled through the digestion process, the protein-rich contents of hog waste are converted into ammonia, which inhibits certain microbes from further digesting the manure. “We add cellulosic biomass, hydrolyze and apply a small vacuum to strip away the ammonia gas,” says Ruan, which is then absorbed with sulfuric acid to produce ammonium sulfate, a valuable fertilizer.

Adding biomass and removing ammonia from the digestion system also balance the carbon-nitrogen ratio, making the manure slurry an ideal growth medium for methane biogas production, and the remaining wastewater can be used for algae cultivation. Algae extract CO2 and organic carbon, nitrogen, and phosphorus as it grows, further reducing the concentration of nutrients in the hog manure. Algae can also effectively remove heavy metals and other hazardous materials. “So, the algae can be grown, harvested, and used as animal feed because it often has very high levels of lipids and protein,” says Ruan, “If levels of heavy metals are high, we can then prioritize the algae to produce biofuel.”

After the algae is removed, the remaining manure wastewater can further be used to grow hydroponic vegetables like tomatoes, lettuce, and microgreens. These vegetables absorb much of the remaining nutrients from the wastewater while effectively reusing manure wastewater at yet another step of Ruan’s system. Ruan also conditions the wastewater in between different processes and removes any leftover particulate matter using biochar, a carbon-dense material similar to charcoal. After this, the wastewater is safe to be disposed of.

“These kinds of processes are actually very successful in treating the wastewater,” says Ruan. “We produce ammonium sulfate fertilizer and methane biogas. We can grow algae for animal feed or biofuel production. We can grow vegetables. We can process solids to use for agricultural byproducts or biochar. And, we can use biogas and biochar as fuels to generate electricity.” There is clear economic value in bioproducts generated by Ruan’s system. The only remaining challenge is scaling his design for mainstream use.

The current system has only been showcased on a small scale in laboratory and greenhouse settings. Using the Demonstration Grant and other funding supports, Ruan hopes to expand his system, showing that it can be used on a larger scale and identifying areas where automation could reduce costs. “When it’s small scale, you still need human labor to monitor, control, and harvest… In the future, we could use robotics, sensors, and big data control systems.” By increasing the capacity and reducing labor costs, Ruan envisions a design viable in rural and urban agricultural operations within the next decade.

With MnDRIVE Environment’s support, says Ruan, “We were able to optimize each step of the process. Now it seems to function quite well.” He hopes that the results of his Demonstration Grant will inspire new partnerships with private sector companies ranging from urban hydroponic centers to rural agricultural settings.

Beyond Scrubbing: Reducing Sulfate Stress from Wastewater at Minnesota Power’s Last Coal-burning Power Plant

When Minnesota Power ceases coal operations at its last coal-fired power plant, the company must also manage the sulfate-laden wastewater in its retention pond. However, current sulfate-treatment technologies are expensive and energy-intensive. With help from a MnDRIVE Environment Demonstration Grant, University of Minnesota researchers have partnered with Minnesota Power to develop an integrated biological treatment system that can contribute to life-cycle management options of wastewater.

By Isaac Conrad

Beginning energy production in 1958, Minnesota Power’s Boswell Energy Center quickly became a bedrock for communities and industries across Northern Minnesota. Sawmills, pit mines, and the small towns they supported, relied on the energy produced at the coal-fired power plant. As the climate crisis intensifies, Minnesota Power is looking toward renewable energy and other options to meet the Northland’s energy needs. As a result, the utility will cease coal-fired operations at the Boswell Energy Center power plant by 2035. Minnesota Power is looking for additional options to manage sulfate-containing wastewater, some of which have already been implemented.

Current technologies designed to remove sulfate from wastewater have a hefty price tag. According to Chan Lan Chun, research lead at the Natural Resources Research Institute and the UMD Department of Civil Engineering, “If we want to protect freshwater resources from difficult-to-manage pollutants like sulfate, we need an alternative sulfate-treatment system.”

Sulfate enters the environment from natural and human-made sources. In the case of Minnesota Power, when coal is burned, it generates sulfur-containing gas that can lead to acid rain if released into the atmosphere. To prevent this outcome, Minnesota Power traps that gas in water using a process known as wet scrubbing. The sulfur-laden water is then stored in a retention pond on site. This pond water must be treated before it is released into the Mississippi River or managed via evaporative processes at the plant.

No matter its origins, excess sulfate serves as a biogeochemical stressor that poses a threat to freshwater plants and animals. How? “Naturally occurring microbes convert sulfate to sulfide,” explains Chun. “Every organism needs a food source and a breathing source. In our case, humans eat Cheetos and breathe oxygen. In the process, we gain energy. Sulfate-reducing microbes use carbon substrates or hydrogen as a food source and sulfate as a breathing source.” The byproduct, sulfide, is a form of sulfur toxic to plants like manoomin because it can suppress photosynthesis, damage plant cells, and stunt growth. As a result, companies generating sulfate-rich wastewater must decrease the amount of sulfate in the discharge to limits that regulators deem safe enough to avoid sulfide contamination.

Illustration by Alvina Salim and Issac Conrad

Existing sulfate treatment technologies, like reverse osmosis and ultrafiltration membranes, are available but expensive. They also produce a salty brine solution as a byproduct. However, managing brine waste is also energy-intensive. Chun and her collaborators believe their biological sulfate treatment system can be part of the solution reducing both cost and energy consumption when the system becomes mature on an industrial scale.

To address the problem, Chun and her collaborators have partnered with Minnesota Power, Minnesota Department of Health, and Yawkey Minerals Management LLC to develop a new technology to neutralize sulfate wastewater using microbes already present in the surrounding ecosystem. Chun, along with Nathan Johnson from the Department of Civil Engineering at the University of Minnesota Duluth and Lee Penn from the Department of Chemistry at the University of Minnesota Twin Cities, have conducted key aspects of the project. The system has many moving parts, but it can be understood as three major steps.

First, sulfate-rich water flows into the bioreactor and interacts with microbes. During this interaction, the microbes convert sulfate to sulfide. Next, the sulfide-rich water flows through columns with iron mineral particles that bind with the sulfide and form solid waste. Finally, once the solid waste forms, the treated water can leave through the other end of the system, separate from the stable solid waste.

Using microbes that come directly from the pond and surrounding soil makes this biological sulfate treatment system unique. Successfully removing sulfate from the water requires less energy because the microbes do most of the work as they “breathe.” As long as Chun’s team provides the microbes with a food source (organic carbon, hydrogen or both), they can survive in the bioreactor by “breathing” sulfate and reducing it to sulfide.

Chun’s team isn’t the first group to study biological sulfate reduction, but funding from MnDRIVE Environment allowed the team to test the technology at a pilot scale on-site. Chun shares that “Our system is 150 gallons; bigger than I am. I could dive in there (but will not for safety)!”

She is cautiously optimistic about the scalability of this system. “We treat about 0.1 gallons of water per minute. A next step pilot test (that would prove the process works at larger scales) is about 5 gallons per minute, so we are not there yet.” Also, not every industrial application requires the same level of sulfate removal. The level of sulfate removal depends on water reuse goals and the discharge point, so the team can manipulate different parameters to help clients reach their respective targets.

“I don’t claim that biological sulfate treatment is the silver bullet. But we are contributing to a suite of technologies. Our system can combine with others to achieve sulfate removal to very low levels, resulting in less energy and waste,” says Chun. Right now, there is no system like it on the market, but Chun’s team aims to fill that gap, and several industry partners have expressed interest in the project.

For Chun, the collaboration at the heart of the project is the key to its success. Her team works closely with diverse stakeholders through sharing the findings and listening. “[But] the biggest stakeholders are the freshwater ecosystems we are seeking to protect from sulfate. They provide clean water; they grow manoomin and fish. We all value clean water. It’s a special resource in Minnesota.” Through careful collaboration, the project team has managed partnerships with stakeholders as large as Minnesota Power and as small as the microbes in the bioreactor to protect clean water and healthy ecosystems that benfits all Minnesotans.

Notes from the Field: A Student Perspective on Science Communication as Climate Action

By Isaac Conrad

Countries in the Global South, like Morocco, will be among the most severly impacted by a warming planet, despite bearing little responsibility for the emissions contributing to the global climate crisis. Yet Morocco has emerged as a leader in climate policy and action using an often overlooked strategy: science communication. In 2022, I had the opportunity to spend the summer traveling in Morocco as part of the Undergraduate Research Study Abroad program through the University of Minnesota Duluth, where my research focused on attitudes toward climate change and the role of science communication in mobilizing public support for climate policy.

Around four in the morning, calls to prayer echo throughout Rabat, Morocco, waking me for the day. Lights begin to flicker across the skyline; some pray in their homes, while others trickle down the winding streets to the nearest mosque. As I become accustomed to these calls, I begin to find beauty in the chorus of voices waking the city. Moroccans wake together, pray together, and take on the day — together. This philosophy extends to all parts of Moroccan life. From cooking to childcare, Moroccans look out for each other, and their response to the climate crisis is no different.

Despite contributing little to global greenhouse gas emissions, Morocco has faced, and will continue to face, serious climate impacts. Every week, another headline warn of the latest “historic” heat wave; As many international scholars have projected, Morocco is confronting severe droughts, decimated crop populations, and an influx of climate refugees. In the face of these challenges, Morocco has taken a multi-pronged approach in addressing climate change.

Initiatives like Clean Beaches, the Noor Solar Facility, and Qualit’air have earned Morocco a top ranking in the Climate Change Performance Index – an international framework used to evaluate nations’ climate protection efforts. Morocco is ranked 8th on the index, and the US is ranked 55th; the first three spots are left open because no nation has done enough to combat the climate crisis. For each initiative, argues Mina Lalaoui Kamal, a Regional Advisor Morocco’s Ministry of Environment, science communication has played a key role in Morocco’s success.

Mina and I meet two days into my stay in Morocco. I hop into a blue taxi, and not knowing French or Arabic, I ask the driver to take me to Hotel Oscar, where I am meeting Mina. The taxi driver just stares at me blankly. Luckily, a Moroccan fluent in English is watching our interaction; she laughs at me, translates, and sends me on my way. When I arrive, Mina greets me with a smile and traditional Moroccan mint tea. For the next two hours, we discuss her Fulbright experiences, the Ministry of Environment’s policies, and Morocco’s use of science communication.

As an Environmental Advisor, Mina is responsible for various projects; she coordinated Morocco’s 2015 plastic bag ban, aided desalination efforts around the Moroccan coast, and implemented waste recycling plants in major cities. Mina is quick to point out that science communication has played a big role in her success, and emphasizes that her efforts are multifaceted. Often, she relies on interpersonal conversations with stakeholders to develop an understanding of the science and necessary policy solutions, but she also deploys larger scale communication campaigns for broader reach.

“Youth are our future leaders, and whether they know it or not, they have influence on their communities right now,” Mina shares. As such, young people are the target audience of many of the science communication programs in Morocco. Eco-schools is one program that sets Morocco apart from other nations. Participating schools shape curriculum around the environment, and they aim to teach the next generation about the role they play in the environment stewardship. Nearly one million students have graduated from eco-schools. Another program has similar goals as the Science Communication Lab at the University of Minnesota. Young Reporters for the Environment aims to foster a generation of reporters who can investigate topics related to the environment and communicate science and solutions with the broader public. Both programs result in greater scientific literacy as well as a greater understanding of Moroccans’ place in the broader climate crisis.

Part of my assignment in Morocco included surveying Moroccan citizens for their climate change opinions, beliefs, and risk perceptions and comparing those results to the US population. Result demonstrate that Moroccans are both more aware and more worried about climate change than US citizens. In Morocco, 80% of survey respondents regularly discuss climate change, but only 35% of Americans answered the same. This level of climate awareness is reflected in Morocco’s climate policy, and it can be seen as a message for other nations as well.

If Morocco taught me anything about science communication, it’s that our language needs to be more accessible and centered on the individual experience of climate change. Climate communication campaigns in Morocco have targeted youth because they shape our collective future, and in order to be successful, these campaigns have used language that is accessible to not only younger audiences, but to all audiences. In Morocco, this meant connecting climate change to the weekly heatwaves, record droughts, and climate refugees. For Minnesota, that means we start better articulating the role of climate change in topics that hit closer to home — like toxic algae blooms on Lake Superior, intense “derecho” storm events across southern Minnesota, or chronic wasting disease in deer populations.

If a nation among the least responsible for climate change is leading the international climate policy scene, perhaps that nation’s strategies can be adapted to another nation as well. Science communication has played a key role in Morocco’s climate response; from the peaks of the Atlas Mountains to the valleys of the Sahara Desert, Moroccan citizens are mobilizing to confront climate change. The success of science communication in Morocco suggests that programs focused on science communication — not unlike the Science Communication Lab — play a key role in shaping a nation’s response to climate change.

So, fellow science communicators, let’s get to work telling captivating stories that connect climate impacts to Minnesotans and Minnesotans to climate solutions.

Isaac Conrad is a writing intern in the University of Minnesota Science Communication Lab.

Forever Chemicals, Hemp, and Nanotech: An Unconventional Approach to PFAS Remediation

By Adara Taylor

PFAS compounds, commonly known as forever chemicals, have been found almost everywhere, from samples of human blood to snow and ice on the peak of Mount Everest. A threat to human health and the environment, the verdict is out on who will bear the burden of cleanup–and how.

Enter hemp, a modern hero of phytoremediation—the use of plants to remove contaminants from soil, water, and air. Pollutants, including some PFAS chemicals, cling to water molecules as they’re drawn up stem and leaf tissue, which can later be harvested and moved to a designated waste site. “[But] hemp doesn’t take up all PFAS compounds equally well,” says Haynes, “It tends to take up the smaller molecules—the ones that are happier being in water.”

To capture larger PFAS molecules, Haynes and her graduate students Cheng-Hsin Huang and Riley Lewis set out to construct synthetic nanoparticles that act as a sponge for stubborn, water-avoiding forever chemicals. A solution of nanoparticles sprinkled over contaminated soil, for example, would help mobilize reluctant forever chemicals for uptake by hemp tissue.

“My group has been building nanoparticles that can be used for various applications in plants. We’d also been building nanoparticles for a biomedical application where we were purposefully loading them up with perfluorinated molecules, so it seemed really interesting to ask whether we could essentially hide [PFAS] inside nanoparticles so that plants can take them up?”

The issue of PFAS contamination hits close to home in Minnesota where 3M, one of the earliest manufacturers of PFAS, recently settled for $850 million to help address the damage caused by PFAS leaching from waste sites into local wells and aquifers.

Partnering with Minnesota-based Ecolab, Haynes and her team are looking at two distinctly different nanomaterials carbon dots (CDs) and silica-based particles. Carbon dots are appealing because large quantities can be produced quickly while still being cheap and sustainable. Silica-based particles are another sustainable choice, and chemists have a better understanding of their structure. “Silica nanoparticles have the same chemical composition as sand or glass, but we make them really small, and they look like wiffle balls.” The challenge is to make these tiny wiffle ball-like particles appealing to PFAS so the particles are sucked into the empty cavity at the center. Even if these materials are effective, however, there’s still a need to address the breakdown of indestructible PFAS toxins being held at long-term waste facilities.

Haynes’ research of PFAS remediation began in partnership with collaborators at the Connecticut Agricultural Experiment Station (CAES) and members of the Aroostook band of the Micmac Nation in Maine. The Airforce returned an abandoned–and highly contaminated–Air Force Base to Micmac jurisdiction after firefighting foam drenched the soil with dangerous levels of forever chemicals.

In 2019, the Aroostook band began planting industrial hemp in an attempt to restore the parcel of land where concentrations of forever chemicals reached levels deemed unsafe by federal standards. When collaborating researchers saw a significant (if modest) decrease in soil concentrations of forever chemicals where hemp had been planted, the effort sparked interest and collaborations, like the partnership with Haynes, to find accessible, industry-friendly ways of remediating environments polluted by forever chemicals.

Haynes describes it as a significant part of the remediation process. “Even if this proposal works perfectly, it doesn’t break down the PFAS. It pretty much just says ‘Can we at least know where it is? Can we use a tool to concentrate [PFAS molecules] in one place so that we know where they are so we can do whatever’s next?’ We’re working on just the concentration part of the puzzle, hoping to add to the bigger overall solution.”

Efforts like those made by Haynes, CAES, and the Micmac Nation may not mark the finish line in the global effort to remediate PFAS chemicals, but they may open a path forward for sustainable PFAS removal in Minnesota and beyond. Ecolab, a global player in the water treatment and purification industry, is looking at commercial applications for the technology.

While there may not be a single solution to the global issue of PFAS contamination, nanoparticles could become part of the toolkit for removing forever chemicals from contaminated soil—part of a suite of technologies addressing the problem. “I’m a big believer that there’s not going to be one big winner,” says Haynes.”It’s going to be a conglomeration of chipping away from [many] angles.”

Minnesota’s Fantastic Fungi

By Isaac Conrad

The Iron Range in Northern Minnesota is known for many things–tall pine forests, crystal clear waters, and blue-collar communities. True to its name, the Range is rich in deposits of industrial metals, and for decades, environmental groups, industry, and local communities have debated the fate of mining in the region. Some say mining is necessary to support the working communities there, and others say the health risks for local communities and ecosystems outweigh the temporary economic boost. Either way, this debate is familiar throughout the Northland.

The Soudan Mine, not far from the Boundary Waters Canoe Area, was once a rich source of iron. When it ceased operation in 1962, however, residue from toxic metals lingered in wastewater surrounding the mine. Left untreated, these toxins threatened the ecosystems and natural resources vital to the Northland economy, culture, and identity. University of Minnesota researcher, Cara Santelli, (BTI / Earth and Environmental Science) grew up near Lake Vermillion and the remnants of the Soudan Mine. Today, she is searching for solutions to help clean up the mine’s contaminated wastewater.

Current approaches to treating toxic wastewater are expensive, so Santelli is looking for a cheaper, more natural solution. Periconia, an indigenous fungus, shows promising potential for bioremediation–the cleanup of environmental contaminants via organisms, usually microbes. Growing in the salty, metal-rich waters of the abandoned Soudan, Periconiaproduces manganese oxide. This mineral can effectively eliminate toxic metals by incorporating them into its chemical structure. With funding from the MnDRIVE Environment program and other sources, Santelli and her colleagues hope to capitalize on this unique ability, but first, Periconia needs to grow at an industrial scale.

Brandy Stewart, a postdoctoral researcher in the Santelli Lab, has been tasked with determining the perfect conditions for Periconia to grow. The fungus may be native to the region, but the deep waters of the mine are not the optimal condition for Periconia when used for bioremediation. To overcome this challenge, Stewart built bioreactors to simulate the mine water conditions and test potential strategies for more productive fungal growth.

Preliminary results demonstrate that Periconia can grow quite well in the suboptimal, mine-like conditions–especially in the presence of carpet fibers. Carpet fibers provide a base to which the fungus can attach and anchor. Stewart found that the presence of these carpet fibers dramatically improves the growth and productivity of the fungus; productive Periconia creates a thick biofilm that uses manganese oxide to capture the toxic metals and store them in its hyphae. As shown by x-ray fluorescence images, manganese oxide effectively captures copper, one of the remaining toxic metals in the Soudan Mine.

X-ray fluorescence imagery showing very similar groupings of manganese oxide minerals (left) and copper ions (right) along strands of lab grown Periconia hyphae (tangled, thread-like structures comprising the main body of the fungus). Courtesy of Brandy Stewart.

Although still in experimental stages, Santelli and Stewart hope to build larger bioreactors to scale up their fungal bioremediation system for application in the Soudan. These bioreactors may help prolong the life of current, expensive wastewater treatments, or even serve as a potential replacement if they prove to be effective at capturing metals like copper, cobalt, and nickel. While Periconia will not bring about an end to mining debates in the Northland, it offers promising potential for bioremediation on the Iron Range and beyond.

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Demonstration Grants

The MnDRIVE Advancing Industry, Conserving our Environment initiative is requesting new Demonstration Grant proposals that take proven remediation solutions and scale them up for implementation in our sustainable economy.

Next Demonstration Grant RFP – TBD
Demonstration Grant Application Deadline – TBD
Demonstration Grant Award Announcement – Mid-December

Awards up to $500,000

To view most recent Demonstration Grant RFP – click here

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