The Renewable Energy Center:
Promoting, Educating, Facilitating and Consulting Native Grasses for Energy
Working with farmers, land owners, businesses, schools and consumers to promote, educate and facilitate native grasses for energy. Offering guidance on grass energy crops, feedstock supply, CHP systems, pellet fuels and appliances, the manufacturing and sourcing of grass pellets, slugs and briquettes as a sustainable locally grown clean fuel for heating and electrical generation.
Energy from Plants:
While the sun provides 10,000 times
the energy consumed on this planet each year, the challenge has been capturing, storing, and distributing this energy into a usable fuel.
Grass energy - perennial grasses, and particularly Switchgrass, prairie corde grass, hay and other grasses collect and store that energy more efficiently than any other system yet devised. This is nature at its best. Grass energy crops are an integral component of the country's renewable energy solution.
The use of these particular plants as a source of energy allows for a truly closed-loop, sustainable system. Warm season native grasses are harvested using conventional equipment Co fired by the bale at Electrical Generating Plants or turned into a solid fuel.
This solid fuel can be used to heat our homes, schools, public buildings, greenhouses, hospitals, and universities, or to help power our communities, all while doing so in an environmentally friendly manner.
Biomass crop conversion into liquid fuels is now in the test production stages. Grass Farms maybe providing our nation with a sizeable fraction of its transportation fuels by the year 2020
Native Prairie Grasses as Fuel:
Prairie once covered hundreds of millions of acres in North America, an ecosystem which supported millions of grazing bison and countless other wildlife species dependent on the resiliency and vast production potential of the plants that grew there. Big Bluestem, Indiangrass, Little Bluestem, Eastern Gammagrass, Switchgrass, and hundreds of other plant species including other grasses and wildflowers existed for thousands of years slowly forming deep, carbon rich soils, which were later transformed into one of the most productive agricultural areas in the world. This same grass ecosystem has the potential to yield millions of tons of biomass annually that can be transformed into many forms of usable energy such as electricity, heat, liquid fuels, and biogas in a very environmentally sustainable system.
Switchgrass, just one of these native grasses, has been shown to convert at 80-84% efficiency
in some pellet stoves and can have a BTU value 8,000 to 8,900 BTU/lb
, which is very comparable to wood pellets. One study completed in Canada has shown the energy profit ratio of 14.5 including production and harvesting costs, which means it takes one BTU of fossil energy to produce 14.5 BTU’s
of useable biomass energy. This represents one of the most favorable energy profit ratios that exist today in renewable, biomass fuels.
Switchgrass roots sequester carbon and organic matter throughout the soil. The production of native grasses can help to reduce air pollution by reducing greenhouse gas emissions when combusted in place of fossil fuels. As a perennial, the plant sequesters carbon from the atmosphere each year to grow roots and new above ground vegetation. Harvesting and combustion of this biomass is simply recycling the carbon into the atmosphere where the process can start all over again. In fact, carefully managed fields with low fossil fuel inputs have the potential to become “carbon negative”
by storing carbon that is not harvested (decaying roots, etc.) in the soil where it can reside for many years.
The best available technology today utilizes highly controlled combustion parameters and emission technology to ensure that the burning of biomass is as clean and efficient as possible. Pelletized switchgrass has been burned and the particulate matter has been analyzed in a study in Canada to show that it reduces greenhouse gas emissions by 88%, 93%, and 89%
compared to electricity, oil, and natural gas respectively.
Biomass heating systems are currently a very viable option for homes, schools, and other facilities. Homes, schools, hospitals, institutional buildings, and other facilities, like greenhouses and offices, can save significant money using biomass systems. Collectively, biomass-fired systems can become part of the support structure for local economies through revenue generation, jobs, and energy savings.
The development of viable grassland agricultural opens new options that will give producers and landowners an alternative they have previously not had. Perennial grass crops will do best growing on fertile ground, but can also flourish on marginal land that may not have produced positive cash flow prior to growing grass. The local or eventual widespread production of native grasses as a crop for energy use has the potential to increase revenues for producers and decrease costs for consumers. The money spent on the grass fuel is cycled back into the local economy as local production and local consumption become more widespread and accepted.
Warm season grasses are preferred by ground-dwelling wildlife such as rabbits, wild turkeys, pheasants, quail and a variety of songbirds and small mammals. The habitat provided by these native prairie species are three of the basic requirements of grassland wildlife-food, shelter and space. Warm season grasses thrive and provide high quality forage for livestock during hot summer months.
Harvest and Storage:
Native grasses such as Switchgrass, Big Bluestem, and Indiangrass are increasingly being utilized as feedstock for renewable energy projects. As producers plant and manage these grasses for a wide variety of applications, proper harvest management is critical to ensure that the feedstock produced is able to be processed or utilized as intended. Material that is not properly taken care of post harvest may lose value or become unusable for its intended purpose. This is intended to outline some of the details during and after harvest that should be considered to maintain quality of harvested material.
Harvest of native grasses for combustion purposes differs slightly from harvest intended for conversion to liquid fuels or other biomass use. The quality of the biomass material can be improved by weathering the material overwinter to reduce the inorganic fraction of the material by exposing it to precipitation in the field allowing leaching of water soluble components out of the material. This leaching period also allows for nearly complete air drying of the material before harvest.
Generally speaking, delaying harvest until at least the first of February or later will give the material sufficient time to leach and dry before harvest. This means that this opportunity to harvest is generally best when the ground is frozen and free of snow and ice. If fields have high percentages of Big Bluestem and Indiangrass that tends to lodge early in the winter, this material can be cut and left in the field in windrows to be baled at a much later date. This cutting should still be delayed until four to six weeks after a killing frost to allow for adequate translocation of nutrients to the roots systems in order to maintain the grasses future productivity and stand longevity.
A residual stubble height of 8 inches is recommended for a few very important reasons. One important reason is that stubble left at 8 inches
will have less of a tendency to puncture tires during harvest operations. The longer stubble will bend or fold over as the tires pass over them, while short stubble is rigid and can puncture even heavy duty tires. Additionally, maintaining a cutting height of 8 inches will mean that there is less of a chance to pick up rocks or other debris at ground level. Rocks can pose a serious threat to processing and combustion equipment. If raking of windrows is needed at any time, care should be taken to ensure that the rake teeth do not come in contact with the ground which could result in rocks and soil contaminating the material. Leaving crowns at a height of 8 inches will also help to maintain healthy stands as it allows the plants to retain nutrients and energy stores for following year growth.
Bales that are able to be stored inside should be transported directly to storage after harvest to avoid picking up moisture, road dust, or other contaminates. In this way material can be stored for many months without compromising quality. This becomes very important when the material is to be densified before use, as this is process is very sensitive to moisture fluctuations. Bales that must be stored outside should be stored on pallets, dry ground, or gravel pads. If storage is on gravel, care must be taken to inspect for this gravel sticking or frozen to the bale after it is picked up.
Covering these bales with tarps will reduce storage losses greatly. Net wrap sheds water much more effectively than conventional twine and can reduce the surface area that comes in contact with the ground further reducing storage losses. Bales stored uncovered in the open weather can expect significant fluctuations in moisture content and overall quality. Uncovered bales can experience as much as 40% loss
of usable biomass.
Slugs or Briquetting:
To utilize the energy stored in grass, the crop must be harvested and processed into a ‘user-friendly’ format, either on the farm or transported to a facility.
Like wood, grasses can be densified into high energy packed pellet fuel. Conversion of native grasses into pellets using a small scale, mobile pelletizing unit which can convert baled grass into pellets for combustion in homes, offices and other facilities.
These portable units are moved to the farm or the harvest site to perform densification when this process makes sense. Small scale stationary units are also available for the farm when higher production is required.
A less-expensive densification method (higher throughput per hour) is by forming the grass into larger slugs, cubes and briquettes allowing the material to be handled and stored easily, transported economically, and burned efficiently. One advantage to this method is to allow more commercial market sectors to accept and utilize the fuel.