Managing Grasslands for Biomass and Environmental Services on Underutilized Farmland
Biomass from mixtures of perennial grassland plants can be harvested annually as a source for bioenergy production; a new source of potential income for rural Minnesota. Grassland biomass can be grown on underutilized farmland, land which is not suitable or economical to grow commodity crops. Therefore, grassland biomass can serve as a source of revenue for farmers on land that has been considered marginal. Reestablished native grasslands provide a number of additional environmental services besides biomass for renewable energy.
- Grassland biomass stabilizes soil and prevents wind and water erosion.
- Grassland biomass intercepts nutrients from runoff, therefore protecting natural waters.
- Grassland biomass provides habitat for wildlife.
- Grassland biomass provides resources for pollinators and enemies of crop pests.
Grassland biomass systems can serve the functions of land in the Conservation Reserve Program (CRP), plus provide additional benefits to producers and the environment. With uncertainty about the continuation of the CRP, now is a good time to plan for a market-based approach to fund state and federal goals of protecting soil, water, and providing habitat with perennial cover. A self-sustained grassland bioenergy system can lead to growth and prosperity for rural Minnesota.
State and federal funds have supported UMN research on grassland biomass in experimental plots and farm-scale studies across Minnesota. We have learned how to measure the energy potential of grassland biomass in terms of liquid fuel, direct combustion, and alternative energy production systems, including gasification and anaerobic digestion. We know what traits make a grassland biomass system more suitable for certain energy conversion technologies, and now we are ready to learn how to grow mixtures of plants that maximize those traits for the most economically viable system.
Much progress has been made on measuring the environmental services from small-scale (less than 1% of an acre) grassland plots. There is still uncertainty as to how the results from small-scale plots translate to large-scale fields (more than 20 acres). Some studies are underway to explore how wildlife responds to biomass harvest, but even these studies are limited by size and time.
A better understanding is needed to learn how to quickly establish grassland biomass for specific energy conversion needs. What species should be included to boost biomass yields during the early years of establishment, and what species should emerge during later succession to further improve yields as the stand matures? Also, we need to learn how to identify methods to economically and effectively convert abandoned pastures into high-yielding grassland biomass systems. What agronomic practices should be used to prepare old pasture fields and what species should be added to those fields to improve productivity?
Many logistical and biological challenges relate to the handling and storage of biomass for bioenergy needs. What is the best way to store biomass for the producer: chopped, pelleted, or as whole bales? What form is most efficient for converting to cellulosic ethanol, co-firing with other products for electricity, or for mixing with livestock effluent for anaerobic digestion? These questions can be answered using production-scale research and will help advance a local, sustainable bioenergy industry.
Left: Mowing perennial grassland for biomass production. Right: Loading baled biomass for transport.
Images from YouTube video by Jacob Jungers.
Long-term and large-scale planning
To build upon the foundation of our knowledge in grassland biomass, the next phases should be set up as long-term projects on large-scale fields. For instance, projects that are 40 acres or larger could provide useful information about how grassland biomass systems interact with other components of the environment at a landscape scale. Also, cost-benefit analyses are lacking for large-scale projects. These projects can serve as potential models for producer systems. Long-term monitoring of existing and future projects will allow planners to initiate new, and adapt current projects to maximize grassland biomass production.
Craig Sheaffer, Professor, Department of Agronomy and Plant Genetics
Don Wyse, Professor, Department of Agronomy and Plant Genetics