Building a grass-based bio-energy industry will require advances on three fronts: (1) creating demand through price competitiveness and heating appliance compatibility, (2) developing reliable, cost-effective densified fuel production and (3) making it worthwhile for grassland owners to produce sustainable bio-energy crops. These can be thought of as three legs of a stool, all of which must be present for the stool to stand. This brief essay focuses on the second item: developing reliable, cost-effective densified fuel production.
Although there are special systems such as those manufactured by Reka that can burn undensified fuel, densification into pellets and/or briquettes is going to be necessary for widespread adoption. Densification facilities, whether they be mobile or stationary, have to be designed for optimum production and minimum cost. People who know how to do this well can be found in the dairy and livestock feed mills that serve New York and the Northeast.
An opportunity may exist to work with one or more of these mills to test grass pellet production under real-world conditions and establish the economics. Such a research effort could be a model of public-private partnership. The ideal candidate for such a project would be a mill that has some amount of surplus pelletizing capacity. Depending on their configuration, some mills produce both pelletized feed and bulk mixtures. If the demand for bulk mixtures increases relative to pelletized feed, such a surplus capacity can occur.
The research may cause feed mills to add grass fuel pellets to their product lines or it may open the door for new entrepreneurs. In the future, densified grass fuel could be delivered in bulk to on-site storage at the points of use with the same delivery vehicles that are currently used for feed deliveries. Another approach could be the interchangeable container method, as described by Tony Nekut in the February 13 posting.
If no feed mill can be identified that would agree to participate in a funded research project as described above, another alternative would be to fund a dedicated test-bed facility. It would be economical, however, to use existing equipment located in a feed mill if possible.
I am hopeful that this is one of several issues that participants will discuss at the HeatNE Conference in Manchester, NH on April 14-15. Grass energy will have a higher visibility at this year’s conference than in the past. I encourage you to attend.
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Community Biomass Energy has received a grant to design and prototype a container-based system for delivering and dispensing bulk biomass fuels. The initial focus will be on baled grasses. The grant, which is funded by USDA and administered by the New York Farm Viability Institute, provides consulting support for the project through SUNY Cobleskill.
We have been involved in two NYSERDA funded projects to install state-of-the-art biomass fired heating systems. The first project at the Cayuga Nature Center was completed in 2009; the second, at the Town of Danby highway department garage, will be completed this year. Experience with these projects has revealed issues related to receiving, storing, and handling bulk solid fuels that could hinder their expanded utilization. Both of these mid-scale projects require roughly 50 tons of fuel annually, about two semi-trailer loads. In both cases, the fuel is delivered into a bulk storage building and then transferred as needed with a front end loader to the boiler feeding system. In both cases, this material handling solution is acceptable because there is adequate space, and loaders and operators are available. In many potential applications, this solution is not viable due to lack of space, equipment, or personnel.
The present project aims to address these material handling issues by developing an integrated, bulk fuel delivery and metering system based on the concept of standardized, interchangeable containers. The design goal is 10 tons of fuel per container. At 20 pounds per cubic foot, a bulk density characteristic of tight bales and minimally compressed wood chips, the container volume will be about 40 cubic yards, a typical volume for commonly available large roll-offs. Fuel delivery will amount to exchanging an empty container for a full one. The system will interface with the heating system and transfer fuel from the container to the combustor as needed. Automated fuel supplier notification of nearly empty containers could be included as an added feature.
Some key advantages of this system will be: 1) minimized capital costs for consumer; 2) minimized responsibilities for consumer; 3) common shared fuel processing for all consumers; 4) minimal additional fuel densification; 5) multi-fuel capability.
This project is still in the conceptual stage, but the hope is to move it forward quickly so a prototype is tested and ready for use within 1 year maximum. Here is a list of tasks: 1) research what, if anything, is already developed and available; 2) design system; 3) perform comparative economic analysis of system vs. alternatives; 4) build and test prototype.
At the time our proposal was written, we suggested that the Danby project could serve as a test bed. Although this option remains available, it may not be the ideal venue because the project will likely be completed before the prototype is available and because ample space, manpower, and equipment are available to implement a more typical solution with larger on-site fuel storage and walking floor semi-trailer fuel delivery. If anyone reading this can suggest another potential test bed venue (a rural propane or fuel oil heated school, for example) or would like to partner with us on this project, please contact Tony Nekut (email@example.com).
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R&D of a mobile grass pellet mill
Hudson Valley Grass Energy has developed a fully mobile mill capable of producing two tons of grass pellets per hour. Implementing this mobile unit is the central goal of our company, although we are also working to further research and marketing of grass pellets. Intensive field R&D over the last year and a half has brought the mill, which sits on a 25-foot trailer, to operation today. This article will share with you a few significant improvements that were realized throughout our journey.
Material transport and storage, some of you may already be familiar with the fact that ground hay does not flow and has serious bridging problems. We’ve tackled this issue by applying constant mechanical agitation using augers. Augers transport raw material between all of the components on our trailer. We spent months building an effective mixing bin that would act as a buffer between the hammer and pellet mills. I believe that it was our fifth iteration that finally worked. This buffer zone compensates for the variable output of the hammer mill and is key in ensuring a constant feed rate to the pellet mill.
Feed rate, many mill operators will attest to the fact that pellet mills need a constant feed rate to run at optimal efficiency. However, we noticed that even with the feed rate constant our mill responds differently to each raw material. This was problematic in that some batches handled fine while others overloaded the mill or wouldn’t pellet at all. This makes sense considering that grasses vary so much in physical composition. Therefore, in addition to keeping a feed rate in the mill constant, it is also vital to be able to adjust this rate to make up for varying material density and composition. Ultimately our method has become to start feeding the material in slowly then ramp up the rate until the die warms up and reaches its “sweet spot”.
Steam, adding steam to our operation has also helped us to pelletize a range of material characteristics. With steam you can accept hays that are otherwise too dry or require higher temperatures to activate their natural binders (which is often a problem with switchgrass). Additionally, steam is beneficial to the die because it reduces wear and helps it to reach and maintain optimal temperature. Pellets produced with steam often are higher quality with less fines and greater hardness.
Please visit our newly updated website at http://www.hvge.org!
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