Wood and possibly even grass pellets are produced in some countries including the USA and Canada.
Here in oz I'm not aware of a fuel pellet supplier.
A small pelletizer would come in handy for my intended steam experiments.
I may look into making one when time permits.
Pelletizers come in a number of types including - gear, disc, drum and screw.
I believe wood (and grass?) can be pelletized without extra bonding agents if the feedstock is heated enough to melt the lignin.
Ideally the pelletizer would be powered by renewable energy.
If it was steam powered then the steam could also be used to heat the feedstock.
I like the idea of a "in field" pelletizer which harvests grass and makes pellets in one operation but I'm not sure how practical this is.
26'th July 07,
To get a feel for the problem of making pellets I made a pellet press.
This is not for making large quantities of pellets - it is for making individual pellets to see if the process works.
The plunger is a machined bolt and the cylinder is a steel rod with a hole drilled through it.
The hole size in 10mm dia.
The compression force comes from a 1850Kg hydraulic car jack I bought for the purpose (au$24).
The jack is welded to a frame made from 50mm square steel tubing with a 3mm wall thickness.
The welds were still hot when I made the first pellet. I grabbed a handful of sawdust off the floor and rammed it into the tube with my fingers. I compacted it as much as possible by ramming the plunger in by hand. The jack then was used to compress it to about 1/3 the volume. I found I could then hammer it out using a bolt to push it through.
The first pellet looked good. This was pressed cold (approx 25 deg C)
I then pressed bamboo leaf, gum leaf and grass. All the pellets looked good with the grass pellet being the best.
If you click on the photo the pellets are labeled.
The grass pellet weighs 3.2 grams. My sums say it has a volume of 2.7 CC and a density of 1.15 g/cc.
To do a reality check I dropped it in water and it sank as expected.
Bulk grass pellets have been reported to weigh about 600kg/m^3 ie a density 0.6 g/cc. So if my pellets in bulk had 50 percent air gaps I'd come pretty close to that figure.
I was planning on making pellets are higher temperatures but these have worked so well I'm not sure I'll bother.
4'th Aug 07.
After weeks of searching I finally found an affordable commercial mill.
Check out the videos.
This PDF has photos of a drum head.
Prairie Grass Pellet Energy
Grass Pellet Production
Pelletisation of Herbaceous Crops