By strategically planting perennial grass in corn and soybean fields, we can effectively address the unintended environmental impacts of growing these dominant row crops. These impacts include soil erosion, fertilizer runoff, and greenhouse gas emissions.
However, it’s crucial that converting portions of farmland back to prairie makes financial sense for farmers. That’s why a dedicated research team, led by landscape ecologist Lisa Schulte Moore from Iowa State University, has spent the last six years studying how to efficiently turn harvested grass into a lucrative source of renewable natural gas.
“We’re looking at existing markets where there is already a demand, using existing infrastructure to reduce costs of the energy transition, and creating wins in multiple categories. We want wins for farmers, wins for businesses, wins for municipalities, and wins for society,” said Schulte Moore, professor of natural resource ecology and management and director of the Consortium for Cultivating Human And Naturally reGenerative Enterprises (C-CHANGE). “We can have great conversations about what could be, but unless it benefits everyone along these supply chains, it won’t happen.”
Schulte-Moore’s research group recently published peer-reviewed articles modeling the economic feasibility of grass-to-gas production in various settings. Their analysis sheds light on the potential benefits of this system.
“To replace natural gas with resources that revitalize sustainable agriculture, we have to be able to quantify how much energy we can produce and show it can be cost effective and environmentally friendly,” said associate professor of mechanical engineering Mark Mba-Wright, co-author of the studies.
The research is supported by a $10 million federal grant in 2020, another $10 million in federal backing in 2022, and approximately $650,000 from the Walton Family Foundation. The focus of the work is to optimize and expand the use of anaerobic digesters. These digesters aid in producing biogas through the natural process of organic matter biodegrading without oxygen.
The captured biogas can then be processed into a versatile fuel that can substitute for petroleum-based natural gas, power electrical generators, and even produce fertilizer.
The research published in BioEnergy Research details how a network of up to 10 digesters in and around Ames could effectively meet the city’s heat and power demands. A variety of feedstock supplies, including livestock manure, biofuel byproducts, food waste, and grassy biomass, could be utilized.
The focus on producing renewable natural gas was found to be the most economically viable, with the potential to provide clean energy production incentives to ensure competitive pricing. Understanding how digester supply chains could serve municipal needs can help city leaders explore new possibilities.
“We wanted to consider the seasonality of the supply and demand over a year to give a mayor, for instance, scenarios to look at and strategize around,” he said.
A recent study in Global Change Biology Bioenergy investigated the potential economic and environmental impact of installing two new digesters to process grassy biomass in the Grand River Basin in northwest Missouri and southwest Iowa. The study’s findings suggest that over a 20-year period, these digesters could generate over $400 million in profit under optimal conditions.
Additionally, the production of 45 million gigajoules of renewable natural gas would result in a carbon footprint 83% lower than that of natural gas derived from fossil fuels, equivalent to about 12.5 billion kilowatt hours. Furthermore, the emissions from this process are projected to be lower than those from corn-based ethanol or soybean-based biodiesel. This research underscores the potential of utilizing grassy biomass as a valuable and sustainable resource for renewable energy production.
“This is dotting our ‘i’s and crossing our ‘t’s to confirm the benefits are what we’d expect. We’re providing a road map to help build infrastructure, which will, in turn, reduce future costs,” he said.
The study’s findings present lucrative opportunities that hinge on current carbon credit initiatives such as the California Low Carbon Fuel Standard and the federal Renewable Fuel Standard. To maximize returns, it is imperative to engage in high-yield grass and prairie restoration on underproductive farmland.
The researchers aimed to maintain a high level of realism in both studies by considering all associated costs, including capital expenses. As methodologies advance and new research findings emerge, the accuracy of these studies will only improve in the coming years, according to Schulte Moore.
“In the future, we will refine our models by plugging in data our research teams have collected right here in Iowa,” she said.
Journal reference:
- Olumide Olafasakin, Ellen M. Audia, Mark Mba-Wright, John C. Tyndall, Lisa A. Schulte. Techno-economic and life cycle analysis of renewable natural gas derived from anaerobic digestion of grassy biomass: A US Corn Belt watershed case study. BioEnergy Research, 2024; DOI: 10.1111/gcbb.13164