Research explores win–win ability of grass-powered power production

The unexpected economic effects of growing the strong row crops, such as soil erosion, manure runoff, and greenhouse gas emissions, are addressed by carefully planting perennial grass throughout corn and soybean fields.

However, farmers must understand that returning some of their farmland to the prairie makes economic sense, so a research team led by landscape ecologist Lisa Schulte Moore from Iowa State University has spent the past six years researching how to turn gathered grass into profitable alternative natural gas.

We “review existing markets where there is already a demand,”” we’re using existing equipment to lower the cost of the power transition and make wins in various categories.” We want wins for farmers, wins for businesses, wins for municipalities, and wins for society, according to Schulte Moore, director of the Consortium for Cultivating Human and Naturally Regenerative Enterprises (C-CHANGE ).

” We can have wonderful discussions about what might be, but it wo n’t happen without the benefit of everyone along these supply chains.”

A pair of recently published articles by Schulte-Moore’s research team modeled the financial feasibility of grass-to-gas creation in various settings and from varying perspectives, evaluation that helps flesh out the system’s win–win potential.

We must be able to quantify how much energy we can produce and demonstrate that it can be both economically and environmentally friendly, according to associate professor of mechanical engineering Mark Mba-Wright, co-author of the studies.

City-based scenarios

The focus of the ongoing research is to increase and improve the use of anaerobic digesters. Anaerobic digestion, a natural process by which organic matter biodegrades naturally without oxygen, releases biogas. Captured in tank-like digesters, biogas can be processed into a fuel that easily swaps in for petroleum-based natural gas. Additionally, it can run electrical generators and produce fertilizer.

The Iowa State researchers studied how a network of digesters in and around Ames could meet the city’s heat and power needs in a study that was published in BioEnergy Research. Livestock manure, biofuel byproducts, food waste and wastewater would join grassy biomass as the feedstock supplies for up to 10 digesters. Whether the network was primarily designed to produce natural gas or power determined the locations, size, and number of facilities.

The analysis determined that renewable natural gas was the most economically feasible area of study, with a levelized cost that was roughly twice the average price of conventional natural gas in the past. Promoting clean energy production might help to increase pricing. Regardless, seeing how digester supply chains would work to serve municipal needs helps city leaders envision possibilities, Mba-Wright said.

” 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.

Researchers have had anaerobic digestion discussions with Iowa’s municipal wastewater officials in a number of cities, and their responses have generally been curious, according to Schulte Moore, co-director of the Bioeconomy Institute and 2021 MacArthur Fellow.

” They need to provide a service to their customers 24 hours a day. But they work on 15- to 30-year planning horizons, so they’re also thinking about the future”, she said.

A grass-to-gas road map

In the Grand River Basin, northwest Missouri and southwest Iowa, a second study, published in GCB Bioenergy, was used to simulate the economic and environmental effects of two simulated digesters that would process grassy biomass.

Over their expected 20-year lifespan, the digesters would produce a combined profit of more than$ 400 million under the best conditions, based on the researchers ‘ analysis. The 45 million gigajoules of renewable natural gas produced over the course of two decades, or roughly 12.5 billion kilowatt hours, would have a carbon footprint 83 % lower than the fossil fuel-derived gas. Emissions also project to be lower than those from corn-based ethanol or soybean-based biodiesel.

It’s important to plan how well dairy manure-fed anaerobic digesters that are currently producing renewable natural gas would perform, according to Mba-Wright.

” 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.

Existing carbon credit programs, such as the California Low Carbon Fuel Standard and the federal Renewable Fuel Standard, are used to evaluate the study’s profitable scenarios. On some of the farmland that is least productive, high-yield grass and prairie restoration is also required for the most important outcomes.

In both studies, researchers aimed to be as accurate as possible while taking into account all known costs, including capital expenses. However, according to Schulte Moore, as methods evolve and new research findings emerge, they’ll be even more accurate in the coming years.

” We will refine our models in the future by incorporating data that our research teams have gathered right here in Iowa,” she said.