Burning Grass Pellets as a Biofuel is Economical, Energy-Efficient,
|Jerry Cherney, the E.V. Baker Professor of Agriculture, sits in front of one of three pellet stoves at Cornell’s Mt. Pleasant Research Farm, where he tests different pellets made from grasses as an alternative fuel. Nicola Kountoupes /University Photography|
This alternative fuel easily could be produced and pelleted by farmers and burned in modified stoves built to burn wood pellets or corn, said Jerry Cherney, the E.V. Baker Professor of Agriculture. Burning grass pellets hasn’t caught on in the United States, however, Cherney said, primarily because Washington, D.C., agencies have made no effort to support the technology with subsidies or research dollars.
"Burning grass pellets makes sense; after all, it takes 70 days to grow a crop of grass for pellets, but it takes 70 million years to make fossil fuels," said Cherney, who noted that a grass-for-fuel crop could help supplement farmers’ incomes. Cherney presented the case for grass biofuel at a U.S. Department of Agriculture-sponsored conference, Greenhouse Gases and Carbon Sequestration in Agriculture and Forestry, held March 21-24 in Baltimore.
"Grass pellets have great potential as a low-tech, small-scale, renewable energy system that can be locally produced, locally processed and locally consumed, while having a positive impact on rural communities," Cherney told those at the conference.
The downside? "Unfortunately grass has no political lobby, which makes the startup of any new alternative energy industry problematic," Cherney said. He noted that a pellet-fuel industry was successfully established in Europe by providing subsidies to the industry. And even though the ratio of the amount of energy needed to produce grass pellets to the amount of energy they produce is much more favorable than for other biomass crops, the lack of government support prevents the industry from going forward, he said.
Cherney has made a comparison of wood pellets with various mixes of grasses and the BTUs (British Thermal Units) produced per pound. He has found that grass pellets can be burned without emissions problems, and they have 96 percent of the BTUs of wood pellets. He also noted that grass produces more ash than wood — meaning more frequent cleaning of stoves. Currently, he is testing the burning of pellets made from grasses, such as timothy and orchardgrass, as well as weeds, such as goldenrod, in pellet stoves at Cornell’s Mt. Pleasant Research Farm. This demonstration project is funded by Cornell’s Agricultural Experiment Station.
Cherney pointed out that grass biofuel pellets are much better for the environment because they emit up to 90 percent less greenhouse gases than do oil, coal and natural gas. Furthermore, he said, grass is perennial, does not require fertilization and can be grown on marginal farmland.
"Any mixture of grasses can be used, cut in mid- to late summer, left in the field to leach out minerals, then baled and pelleted. Drying of the hay is not required for pelleting, making the cost of processing less than with wood pelleting," Cherney said. "The bottom line is that pelletized grass has the potential to be a major affordable, unsubsidized fuel source capable of meeting home and small business heating requirements at less cost than all available alternatives."
Biomass Energy Comparison
Various materials tested by: Agricultural Utilization Research Institute, Waseca, Minnesota
|Alfalfa (leaf and stem)
||12.25%||6934 – 7729||7.94% – 9.06%||0.195% – 0.22%|
||6.02%||7786 – 8501||2.48% – 2.67%||0.02% – 0.02%|
| Corn Gluten
||12.06%||7199 – 8097||3.78% – 4.30%||0.33% – 0.375%|
| Corn (Shell) 54.5 lb/bu
||13.43%||6924 – 8100||1.13% – 1.23%||0.11% – 0.13%|
| Corn (High Oil) 56.2 lb/bu
||12.49%||7398 – 8480||1.17% – 1.34%||0.095% – 0.11 %|
| Corn (Waxy) 56.6 lb/bu
||13.09%||7073 – 8113||1.26% – 1.44%||0.12% – 0.135%|
| Corn Cob
||7.12%||7369 – 7911||2.16% – 2.32%||0.04% – 0.04%|
| Corn Stalks
||9.14%||7057 – 7768||6.18% – 7.64%||0.035% – 0.04%|
| Dried Distillers Grain w/solubles
||9.27%||8459 – 9422||4.13% – 4.16%||0.4% – 0.45%|
| Dried Distillers Grain w/o
||13.35%||8473 – 9848||1.96% – 2.24%||0.34% – 0.4%|
| Hardwood Pellets
||7.08%||7955 – 8573||0.34% – 0.36%||0.01% – 0.01%|
||12.49%||7143 – 8242||3.17% – 3.58%||0.135% – 0.16%|
||10.25%||8783 – 10230||5.19% – 6.22%||0.29% – 0.33%|
| Straw – Wheat
||8.26%||6839 – 7375||10.40% – 11.33%||0.07% – 0.075%|
| Straw – Oat
||6.91%||7153 – 7626||7.90% – 8.49%||0.05% – 0.055%|
| Sugar Beet Pulp
||9.70%||6597 – 7345||3.80% – 4.31%||0.14% – 0.16%|
| Sunflower Hulls
||8.65%||8474 – 9654||2.86% – 3.13%||0.14% – 0.15%|
| Wheat Middlings
||12.58%||7228 – 8415||5.18% – 6.00%||0.15% – 0.17%|
||10.38%||7159 – 8063||2.08% – 2.28%||0.2% – 0.22%|
1. Moisture: ASTM D3173;
2. Ash: ASTM D3174;
3. Btu/lb: ASTM D1989;
4. Sulfur: ASTM D4293
This is The Reality of Wood Pellet Fuel
Cordwood, wood pellets, wood chips, waste paper, along with dozens of other agricultural by-products capable of being used for energy, are all examples of biomass fuel. The most compelling principle of biomass is that it is renewable. Given proper forest and agricultural management, biomass is virtually limitless, and has proven to be price stable. The environmental benefit of the fuel is that it turns readily available waste products into clean and efficient energy.
Sustainable forest initiatives, wood manufacturing by-products and other forms of forest agricultural management provide cost effective pellet fuel manufacturers with low cost materials by retrieving biomass materials from these programs. The majority of North America’s forest is second-growth and requires periodic treatment in order to address forest health and fire mitigation. A tremendous amount of unusable material remains on the forest floor after such treatment; material rejected by high-end wood product manufacturers but a perfect resource for commercial pellet manufacturers.
By engineering waste such as cornstalks, straw, wastepaper, wooden shipping pallets, residual forest waste, even animal waste, pellets can utilize millions of tons of waste and put them to work.
The benefits of pellet fuel
Pellet manufacturers take by-products (like wood waste) and refine them into pencil sized pellets that are uniform in size, shape, moisture, density and energy content. Why not simply burn raw biomass? First, the moisture content of pellets is substantially lower (4% to 8% water, compared to 20% to 60% for raw biomass). Less moisture means higher BTU value and easier handling especially in freezing situations with green raw biomass materials. Second, the density of pellet fuel is substantially higher than raw biomass (40 lbs. per cubic foot vs. 10-25 lbs. per cubic foot in raw material form). More fuel can be transported in a given truck space, and more energy can be stored at your site. Third, pellets are more easily and predictably handled. Their uniform shape and size allows for a smaller and simpler feed system that reduces costs. This high density and uniform shape can be stored in standard silos, transported in rail cars and delivered in truck containers. Pellets pose none of the explosion risks or environmental pollution from spills as nonrenewable fossil fuels do.
The remarkable consistency and burn efficiency of pellet fuel produces a fraction of the particulate emissions of raw biomass. Pellet burners feature the lowest particulate matter emissions of all solid fuel burners.
When you heat with biomass, carbon dioxide is released into the atmosphere. Trees absorb this carbon dioxide in equal amounts as they grow, so burning pellets does not increase the amount of this greenhouse gas in the atmosphere.
Arsenic, carbon monoxide, sulfur and the greenhouse gas carbon dioxide are just a few of the air and water pollutants resulting from the use of all nonrenewable fossil fuels as a heat and an energy source. Even if the supply of nonrenewable fossil fuel was unlimited, the economic and associated environmental costs of transporting and burning ever-increasing amounts of nonrenewable fossil fuels are simply unsustainable. In fact, since pellets can burn more efficiently (system efficiency averages at 80%) than other fuels, emissions from pellet burners meet even the most stringent EPA requirements.
Any remaining ash in the burn chamber, when removed, is of little consequence. Once the ash is emptied periodically, it can actually double as a fertilizer. Finally, pellet store poses no soil or water contamination risks. A spill can be cleaned with a shovel … not a hazardous waste crew.
Combustion systems & changeover
Though pellet fuel installations have a reputation in some circles as ‘alternative’ choices, their functional components are virtually identical to those of the more conventional oil, coal or gas systems. The European example offers a glimpse of what future opportunities hold. They include a pellet storage container, a burner, an automated feeder to supply that burner, a boiler, exhaust system and chimney. There is no need for extensive permits or containment because there is no volatile oil or gas. Any storage can take place above or below ground, making maintenance and filling easier and further reducing costs of installation and upkeep.
A heating system producing approximately 500,000 BTU/hr (that of a small school’s system, for instance) currently burning oil, coal or natural gas, in many instances can be changed to burn pellets with retrofits made only to the burner, plus the addition of a combustion conveying system and a storage container. In such a system, the existing boiler and heat delivery structures remain unchanged. Solid fuel systems such as those burning coal or wood chips are more easily retrofitted to burn pellets through simple feed and air supply adjustments. A pelletized, refined fuel will always burn cleaner than the virgin material form.
The pellet fuels burn process holds emissions far below those of nonrenewable fossil fuels. Future research in commercial pellet burning systems are employing various technologies which are promising even further increases in efficiencies.
©2017 Make Your Own Pellets, LLC | (last updated 3-4-2017)