A question I’ve been asked many times is “can you use lawn clippings to make grass pellets for a pellet stove?”. While making lawn grass pellets is fairly simple to do even using a cheap Chinese imported flat die pellet mill as seen in the video below, it’s actually not a great idea.
While lawn grass pellets (besides being green) obviously look similar to wood pellets, they perform very differently in a pellet stove or boiler. By burning grass pellets made from lawn clippings you could even cause significant damage to your pellet stove or boiler.
The Process of Making Lawn Grass Pellets
First, let’s look at the process of using a pellet mill to turn lawn clippings into grass pellets. As seen in the video above you can get a cheap Chinese flat die pellet with a small single phase motor and quite easily produce grass pellets. In fact, lawn grass clippings is a very easy material to run through the pellet mill. It flows very well and can produce pellets to a good density with a nice surface shine.
In the video above this particular pellet mill owner is showing how he prepares his raw material. He shows how he adjusts the moisture content of the grass clippings and evaluates pellet quality. Even with a very small pellet mill as shown in the video above you can get a reasonable productivity per hour with lawn grass pellets. You will also find videos on YouTube of homemade and DIY pellet mills processing lawn clippings into grass pellets.
But whats Wrong with Burning Grass Pellets from Lawning Clippings?
Let’s presume you have purchased a cheap pellet mill and it’s all gone well. After a few hours, you now have a good amount of ‘quality’ grass pellets. You wish to use these grass pellets made from your lawn clippings in your pellet stove or boiler. However, this is where the issues really begin.
Grass Pellets and Ash Content
Grass pellets will produce around 5-7% ash when produced from lawn clippings, compared to say premium grade wood pellets at between 0.5-1% ash. Now depending on your brand and design of pellet stove or boiler, you may be able to burn grass pellets successfully. Some pellet stoves have a forced auger feed which will push the ash buildup out of the burn pot.
However, most pellet stoves use a basic drop down burn pot design that relies on the combustion fan blowing the ash out of the burn pot. The fan speed will be set up for wood pellets (1% ash), so it simply cannot deal with the ash volume from burning grass pellets.
Grass Pellets and Clinker Formations
The second issue associated with burning grass pellets is clinker formations. This is where the ash gets very hot and fuses together to form a sticky mass. Again, most pellet stoves are not going to be able to deal with clinkers.
Finally, let’s presume your stove/boiler can even deal with the ash and clinker issues, well there is a final issue and the most serious. Grass pellets during combustion produce a lot of chloride which is a high temperature corrosive. So while grass pellets may appear a cheap fuel option they can actually destroy your pellet stove in just a few years of use. The high percentage of chloride increases corrosion damage to the pellet stove significantly.
Why Making Quality Fuel Pellets is not Simple
People often see a video of making grass pellets and think that making wood pellets is also that simple. They then go ahead and purchase a cheap Chinese pellet mill. After trying to operate the pellet mill for the first time and experiencing blocked pellet mill die, they quickly learn that making wood pellets is not that simple. Issues with the die blocking, a low productivity per hour and poor pellet quality are just a few of the issues that I try to help people avoid.
Before you even consider purchasing any equipment I would encourage you to read my post on how to make wood pellets. The general principles apply to making pellets from any biomass material.
Conclusions on Grass Pellets made from Lawn Clippings
So when it comes down to it, is burning grass pellets made from lawn clippings really worth it? While a cheaper alternative to wood pellets they could seriously damage your pellet stove or boiler. Even if you are within the warranty period of the pellet stove. The manufacturer will be able to tell that you have not been using approved wood pellets to cause that type of damage. With many pellet stoves, using anything other than premium wood pellets will void its warranty. While grass pellets made from lawn clippings is not a viable alternative to wood pellets, fuel pellets made from hemp actually have a lot of potential.