Densifying hay and other biomass to heat a home or building can be accomplished by either making pellets and consuming them in a pellet stove, or by making briquettes and consuming them in a standard wood stove or boiler. At this time we have achieved success in making pellets made from hay on our farm and from soybean stalks mixed with hay, and then have burned them in a Quadrafire Santa Fe pellet stove at home over the past two winters. We have also tried to make briquettes in a ZBJ III Briquette Machine for consumption in our wood stove, however are we currently working to overcome challenges with the Briquette Machine’s functionality.
The underlying goal of this work is to understand the production and consumption process, and to identify feasibility for establishing these processes on a community basis, where both dedicated energy crops and agricultural left overs are used to produce densified heating sources and other products that could serve as income and energy sources for local farms and a local community. To support this, I plan in the next year or two to purchase a larger pellet machine capable of supporting several homes, and also will evaluate how communities that move to begin using densified hay as a heat source could generate local jobs, local revenue, and move to a more self-sufficient energy model.
• We can use agricultural waste (stalks) to get multiple products from single crops. Click here to view details describing how using hay for a home heat source fits into the overall concept of Energy Farming where clean energy technologies such as solar, wind, geothermal, & biofuels are farmed from available resources on a given farm or at a desired location.
• Processing and consuming Switchgrass and other grass pellets are environmental friendly and some even consider it carbon negative - meaning that the grass growing in fields remove more carbon from the air that is expelled from equipment used to plant, harvest, and process it.
• As stated at http://www.grassbioenergy.org/:
"It takes 70 days to grow a crop of grass pellet fuel"
"It takes 70 million years to grow a crop of fossil fuel"
• We can provide 100% of our homes winter heating needs with densifying 1 – 2 acres of hay, using Brome grass, Reed Canary Grass, Timothy, and Switchgrass, from our farm.
• Pellets are inexpensive.
• Burning grass is roughly equivalent in BTU output (16,020,000/ton for Switchgrass) to that from wood (all better than oil, propane, gas)
• Less carbon output.
The first chart below shows cost estimates comparing the cost to heat a 2000 sq ft a home with various fuel sources (data gathered 2009 - 2010). The second chart outlines the carbon output for various fuel sources. Notice that burning hay results in nearly the least amount of carbon emissions per million BTU (data gathered 2009 - 2010 and validated September 2011):
The Pelleting and Briquetting process consists of the following steps:
1) Mow hay and let dry to ~12% (the point at which it is to be baled into small square bales)
2) Chop the hay
3) Run the chopped hay through a hammer mill (twice seems to work better)
4) Produce grass pellets with a small pelletizer or briquettes with a briquette machine
5) Lay the pellets out on a screen to dry.
• Pelletizing hay outside of the 12% - 15% moisture range is difficult
• Keeping the die hot enough on the small pellet machine when feedstock is not flowing through. To mitigate, we added a heater as to keep the die hot.
• Amount of ash in pellet stove is greater – here we simply empty the burn pot and ash pan a bit more often. Another option is to buy a pellet stove with an active ash management system.
• Soybean stalks were too dry and had to be mixed with some hay to form a pellet.
• Lignin sticking to inside of the ZBJIII briquette machine tunnel and pitted soft steel inside the tunnel causes blockages. We’re now preparing to have this tunnel bored and then cauberized to harden it up.
The gallery below shows pictures of grass pellets and briquettes that I have produed, along with pictures of all of the equipment involved in harvesting hay for the grass densification process:
Pellet and Hammer Mills