Frequently Asked Questions (FAQs)
(The questions sometimes change, and so do the answers as we learn more about the process)
- Pellet stoves
- Other appliances
- Pellets & Pelleting
- Grass production
- Grass biofuel history
- General questions
- Rarely asked questions
How frequently does the ash pan need to be dumped in a pellet stove?
This depends on the stove, the ash pan capacity, and the rate of pellet feeding. With a medium feed setting using grass pellets that are 4-5% ash content, ash would probably need to be removed every couple of days. Some stoves, such as the Country Flame Harvester Corn stove, require ash to be removed daily, regardless of the type of pellet or if corn is the fuel used.
Which pellet stove works best for burning grass pellets?
At the current time, the Harman corn stove, the Harman P68 stove, and the Quadrafire stove appear capable of handling grass pellets at least up to 5% ash content, without any modifications to the stove.
Why is low ash content generally more desirable when burning biomass pellets?
Low ash content may actually increase the chances of problems due to chunks of melted ash (“clinkers”), because low ash grass tends to have ash with a lower melting point. High ash increases the chances of buildup on the burn pot surfaces, restricting air flow and influencing the removal of ash from the burn chamber. High ash content also means more frequent dumping of the ash pan.
Who is manufacturing pellet stoves specifically to burn grass?
No company is doing this, but several are attempting to modify their stoves to better manage non-wood fuels.
Can I burn grass pellets in my pellet stove?
Most likely not. Average pellet stoves with a standard burn pot are not designed to cope with high ash content. In general, corn stoves have more potential to handle grass pellets because they are designed to deal with a somewhat messy residue. With the escalating corn grain price, interest in corn stoves has plumetted.
Can I recycle the ash as fertilizer?
Yes. Ash from herbaceous plants, like wood ash, is highly alkaline. It can be used as a liming agent to increase soil pH. It also contains some essential plant nutrients, but would be considered a very weak fertilizer source. It would provide almost no nitrogen.
Does burning cause pollution?
It can. That is why some research and development on pellet stoves and boilers is desirable. Since any particulate matter from burning biomass is likely to be very alkaline like the ash residue, this small amount of material should not contribute to acid rain problems, it might help alleviate them.
Who is burning grass pellets in stoves or boilers at this time?
There are several demonstrations currently running in New York State, as well as a few in Vermont and Pennsylvania.
How much routine maintenance is required to burn grass in pellet stoves?
Routine (weekly) maintenance is recommended for burning any type of pelleted material (including wood pellets) in any pellet stove. Aside from dumping ash at necessary intervals, the heat exchanger and burn pot area will need cleaning at least once a week. The flue pipes should be inspected for buildup.
Can pellet boilers burn grass pellets?
A few. The Danish Reka pellet boiler (10-60 kW sizes), The Harman PB100 pellet boiler, and the LEI Bioburner (model 100 and 500 versions) have successfully burned grass pellets. The major advantage of boilers over stoves is that they provide hot water and central hot water heating. Most commercially available pellet boilers are designed to burn wood pellets and possibly corn grain. Large commercial-scale boilers are capable of burning grass biomass.
What is a gasifier?
Thermal decomposition of organic matter in an oxygen deficient atmosphere at controlled temperatures produces combustible gases. Solids remaining from this process are ignited to provide the heat for driving off moisture and also driving off the volatile gases. Gases can be collected and used to power a turbine or internal combustion engine to generate electricity. Heat can also be used as an energy source from this process.
Is pelleting required for biomass burned in a gasifier?
Some form of densification is necessary, loose material will not work effectively. It is possible that briquetting and/or cubing would work in lieu of the more expensive pelleting process.
Can large hay or straw bales be burned without any densification (pelleting, cubing, etc.)?
Some large heating units have been tried in North America, using whole bales for fuel, with variable success. Whole bales have been used in Europe to power large boiler operations.
Why is it so difficult to pellet over-wintered switchgrass?
Grass left out in the field over winter, most of the inflorescence (head) component is lost, and some of the leaves. Grass is leached free of all soluble components, and is also very low in protein content. Soluble components and proteins are helpful as binding agents for pelleting. Lignin is also a good binding agent, but lignin content of grasses is much lower than wood. As a result the overwintered grass strongly resists pelleting.
Are there other markets for grass pellets, in addition to energy?
Yes. Straw pellets are currently being used for horse bedding in some markets. Not only are they considered higher quality bedding than sawdust or shavings, but they can be less expensive. Any mature grass hay should make pellets suitable for bedding. Grass pellets are also being used as a soil mulch.
What does it cost to start up a pelleting business with commercial-sized equipment?
Quite a lot. A gross estimate for the purchase and set up of all the equipment necessary to start up a pelleting business might cost around 0,000 for used equipment. Production costs for pelleting have been as low as /ton of hay, with large scale equipment, but the initial investment would be several million dollars.
Can I purchase a small-scale pelleting unit for personal use?
Relatively small-scale, used pelleting equipment can be found for sale on the web. It is probably not economically or functionally feasible to set up a small-scale pelleting unit for occasional grass pelleting on an individual farm.
What would be the price of hay sold as biomass for pelleting?
This will be influenced by market supply and demand of biomass vs. fossil fuels, but it is unlikely to be economically feasible without some form of carbon crediting. The actual energy value of hay is probably less than /ton. Mulch hay for mushrooms sells for over 0/ton.
What is the energy value of grass pellets compared to wood or corn?
There is a range in BTU values for different types of wood and grass biomass materials. On average grass might be around 8,000 BTU/lb, premium wood pellets around 8,400 BTU/lb, and corn grain around 10,000 BTU/lb.
How do grass pellets compare economically to fossil fuels?
As of now, we do not have any economic comparisons of cool-season grass pellet systems with fossil fuels. REAP-Canada has made some comparisons of switchgrass with fossil fuels and estimated that switchgrass may be economically with all but natural gas.
Can I mix low quality hay with wood residues and pellet them together?
It may be possible but not a good idea. Pellet dye specifications will be different for grass and wood. It would be much simpler to blend different lots of pellets to achieve any desired ash content, just as multiple feeds for cattle are blended. It would be easy to develop a pricing scheme that valued the ash content and composition of the fuel.
Can I use my lawn clippings for pelleted energy?
No, this is not feasible. Reason No. 1: Even if you have a very large lawn, the number of pounds of grass biomass in clippings is not significant. Reason No. 2: Immature, generally over-fertilized grass leaves produce lawn clippings that will be very high in ash content, over 10%. The clippings will be high in undesirable elements like N, K and Cl. Better to minimize lawn fertilization and mulch mow to recycle these nutrients back into your lawn.
What species are acceptable for grass pellet biofuel?
All grass species and mixtures. Legumes may not work quite as well but also may be acceptable. Grass crop selection should match the soil type, for maximum sustainability and productivity. (see Biomass Species Selector Tool).
Do grass stands need to be fertilized for biofuel production?
No. Mixed grass stands cut once a year with regrowth left in the field to provide soil organic matter as well as wildlife cover should persist indefinitely. A shift in species composition or an increase in weed population is not of great consequence; all have similar BTU/lb. Of course, higher yields will be obtained with some form of nitrogen fertilizer application.
What yield per acre can I expect?
Yield potential is primarily a function of soil type and fertilization (see Species Selector for potential yields in NYS). Soil with the lowest production potential without added fertilizer might yield less than one ton/acre of hay. Good soils with added fertilizer can yield as high as 6 tons/acre. Very little material is lost between baling and pelleting, so one ton of hay will yield slightly less than one ton of pellets (some hay moisture is lost during pelleting).
What changes to the farm operation are required for grass biofuel production?
Almost none. The necessary equipment is generally available on the farm. Planting an improved species is an option, but the current species in a mixed meadow will work. Harvest in mid to late summer can be accomplished at off-peak labor times.
How many acres of grass would it take to heat my home?
Wild guess, with a good yield of grass it might take 2 acres to heat a 2,000 sq. ft. detached home for the winter in NYS. Keep in mind that grass yield can vary by up to 10-fold.
Will grass bioenergy solve the energy crisis and the greenhouse gas crisis?
No, but... Every BTU produced locally is one less that we need to rely on from foreign sources. And each BTU of grass bioenergy comes with at least 90% less production of greenhouse gases compared to fossil fuels. Grass bioenergy can provide some local energy security. Heating 5.5% of residential homes in NYS with biomass could offset 100% of the greenhouse gas production attributed to agriculture in the state.
Why is it recommended to overwinter switchgrass in the field before harvesting?
Ash content and composition of fuel is critical for many pellet appliances. Overwintering switchgrass lowers ash content by leaching of the forage and loss of plant components that are higher in ash (inflorescence and leaves). This produces a fuel with characteristics more like wood, but will also result in yield loss of 20% up to 50%. Warm-season grasses (switchgrass, indiangrass, big bluestem etc.) start growth late in the spring and do not mature until later in the season. There is little opportunity to cut these grasses in the fall, allow them to leach, and then bale in a dry state. There is generally ample opportunity to harvest last year’s growth the following spring before new growth resumes. Pelleting this material may be problematic.
Is it reasonable to overwinter cool-season grasses prior to harvest?
Probably not. Reed canarygrass has been successfully overwintered in Sweden. However, overwintered reed canarygrass in NY during the winter of 2003-04 resulted in 100% loss of harvestable yield. Overwintered reed canarygrass in Iowa also was not very successful. Since cool-season grasses mature early in the summer it is possible to cut them and allow for leaching during the summer, with time left to bale a dry product.
How old is the “new” concept of grass heating in the US?
Pioneers who settled in the Midwestern prairies had no wood and could not afford coal. So they burned “Prairie coal” (buffalo chips) until supplies grew scarce. Then they switched to burning grass, twisted up into packets (the earliest form of densification). The packets were known as “cats”. (Fire on the Hearth, by J.H. Peirce, 1951, Pond-Eckberg Co., Publ.).
What ideas came with the immigrants to allow burning hay on the prairies in the 19th century?
Large brick or stone “Russian” furnaces were fed significant quantities of loose grass 3-4 times daily, the structure radiated sufficient heat for up to 6-8 hours. They were usually centrally-located in the house.
Did Yankee ingenuity build a better mousetrap?
Numerous US patents were granted for hay burning iron stoves in the late 19th century. Metal cylinders over a foot in diameter or magazines were stuffed with grass, and tension was provided to feed the hay directly into the firebox. One packed cylinder could keep a good fire for an hour or two. These stoves were very dangerous to operate. Various devices also were invented for twisting grass into sticks that could be cut to length like stove wood.
How far back is the Cornell connection with grass heating?
The following is part of a letter sent by Daniel W. Oaks to his brother on Dec. 13, 1877 in the Sioux Falls Dakota Territory (Courtesy of H. David Thurston, Cornell Emeritus Professor of Plant Pathology; Daniel Oaks was his great grandfather).
“Now D.B. I would like to tell you about how we got along without wood for fuel instead of working my team to death a hauling wood from 6 to 20 miles all winter to get enough to last. All summer I just take my mower and horses and go down to the Sioux bottom and in two days I can cut and put up enough hay to last me one year. And then not having to cut it. That is the worst of all. I do sympathize with you that have to chop wood. Instead of doing that all you have to do is whenever tired you can go and sit down by the side of a stack of hay and twist and rest all the same time. I would not chop the wood if you would give it to me. I have altered my stove so that I can burn hay better than I can wood.”
If you would like to see the full text of this interesting letter click here.
When was pelleting first used commercially in the US to provide heating fuel?
The first municipal installation using pelleted fuel in the US was in Watertown, S.D. which fired the heating plant for the downtown area in the early 1970’s. They pelleted flax straw for this purpose. The installation operated until the flax grower moved out of town. (Courtesy of Bob Massengill, Pellet Systems Consulting).
Are grass pellets meant to replace wood pellets?
Absolutely not. If both were available for the same price, wood pellets would be preferred as they will burn with less ash, making for easier cleanup of the stove. If the biomass combustion industry continues to expand, however, there will not be enough wood pellets to meet the market. This is the situation in parts of Europe and why wood pellets are currently being imported from North America to Europe (only economical due to subsidies).
Why are you bothering with this? Americans will not choose to cope with the relative inconvenience of a pellet heating system.
Some will. Bioenergy from grasses has quite a litany of environmental benefits, sooner or later an ecological response to energy concerns will have concrete value.
Wouldn’t it be more economical and energy efficient to focus on systems capable of utilizing whole bales without any need for densification?
No doubt large-scale, whole bale systems would be more economical and energy efficient. They are large units that require municipal, company or industry support, and are more constrained by the radius of economical transport of bulky biomass feedstocks.
What would be the best way for the USA to become energy independent?
A serious effort at energy conservation in everyday life by citizens would do far more to improve our energy independence than the sum total of all solid biofuel technologies.
What are the disadvantages of grass pellet fuel?
As with coal or wood stoves, and wood pellet stoves, routine maintenance is required. Pellet handling and ash removal make this less convenient than fossil fuels. Appliances burning grass will be more susceptible to corrosion, and may require additional modification to deal with emissions.
Why do Federal and State governments have no interest in grass pellet biofuel?
Grass has no political lobby. A grass roots effort is not enough.
Where in the US does grass pellet biofuel have the most potential?
The Northeast. For many decades the Northeastern US has been officially labeled as the “Hay & Pasture” Region of the country. Like much of Europe, the temperate humid climate is not so hot for corn, but perfect for grass. A recent published switchgrass study in the northern US by USDA-ARS personnel concluded “Western North Dakota is subject to periodic drought and wide fluctuations in precipitation that would jeopardize the capability of producers to provide a consistent supply of switchgrass biomass for biofuel purposes.” (Agron. J. 97:549. 2005). So although some northern regions are not as well suited as others, grass bioenergy has good potential all across the northern tier of states that have a high winter heating requirement.
Is there any state government with interest in grass biofuel?
New York, Pennsylvania, and Vermont have shown some interest, but increasing availability of fossil fuels from U.S. sources, coupled with increasing conversion of grasslands to high value grain crops, have put grass biofuel on the back burner.
When is a boiler not a boiler?
Strictly speaking, boilers are combustion appliances that are under pressure and produce steam. The US EPA will tell you that they are really “hydronic heaters”, providing hot water heat.
How do you get “low ash” grass?
1. Grow warm-season grasses. 2. Mow grass and allow it to remain in the field through one or more rain events, to leach out soluble minerals.