Fuel pellets for pellet stoves and boilers are today almost exclusively made from wood. However, hemp may start to replace wood as the prominent source of biomass for fuel pellets for domestic pellet stoves and boilers.
Currently, its the wood industry who have really driven the fuel pellet market. Wood pellets produce a much lower ash content compared to grass, hay or straw pellets. Furthermore, grass, hay and straw pellets can create significant issues with corrosion in the pellet stove or boiler. However, hemp fuel pellets have very similar qualities to wood pellets but are made from a much more sustainable raw material.
What are the Issues with Other Biomass Materials?
Before we discuss the benefits of hemp pellets, we need to address the issues other biomass fuel pellets experience. The pellet fuel market is now developing to include other biomass energy crops such as miscanthus, switchgrass and hemp. All of these biomass materials can be collected and processed in the pellet mill to produce grass pellets which are suitable for fuel-flexible pellet stoves and boilers. However different biomass materials produce different combustion results, we have seen this through our experiments with our biomass pellet boiler.
The Issue of Ash
While miscanthus and switchgrass both have their merits, they also have their issues. The problem with most grasses and straws is during combustion they produce a significantly higher ash content than say premium wood pellets. Many pellet stoves and boilers are designed specifically to burn wood pellets with an ash content below 2%. Therefore using grass pellets can often create issues. With some biomass pellets, the ash content can be as high as 10%. Therefore this either means the ash bin fills up really quickly or in some cases, the pellet stove or boiler can stop working altogether.
The other problem with some biomass fuel pellets made from grasses and straws is clinker formations. Clinkers are where the ash melts and forms together into a clump. Most pellet stoves and boilers have no means to deal with clinkers, as they were specifically designed to run on wood pellets. When the clinker is hot it’s soft and sticky. However, when it cools it’s as hard as glass. Luckily our pellet boiler is very durable and able to deal with such clinkers. However, most pellet stoves are not. And a clinker such as that shown in the image above could do a small pellet stove some serious damage.
Why are Hemp Pellets Different?
Well, hemp pellets, unlike other none woody biomass fuel pellets, produce only around 2% ash content. Therefore hemp pellets can be used in a much larger range of pellet stoves and boilers currently on the market today.
Another advantage is that hemp pellets are no more corrosive to burn than wood pellets. This is not the case with fuel pellets made from straw, miscanthus and switchgrass. Finally, hemp pellets do not produce clinker formations as the ash melting temperature of hemp is similar to wood.
So what’s holding Hemp Pellets back?
The biggest issue with hemp is the current legal restrictions around its growth. Industrial hemp under many laws today is covered under the umbrella of laws restricting the growth of marijuana. While hemp may look very similar to marijuana it is not the same plant. The THC content of industrial hemp is so small it’s said you would have to smoke a whole field of hemp to feel any effect. Even where hemp is currently legal there are restrictions on its growth. In the UK you can only grow hemp if there is a suitable processor to take your crop. But this creates the ‘chicken and egg’ scenario. It’s very hard to grow hemp as there are very few legally registered processors. And they are very few hemp processors because they don’t have a ready supply of industrial hemp.
Is all of the Hemp Plant used to make Fuel Pellets?
No, hemp fuel pellets are only produced from the shiv. Hemp shiv is the woody core of the hemp plant. First, the outer fibre is separated from the hemp plant and goes to make clothing and other products. Large hemp shiv particles can be used in construction in combination with lime. What’s left over are small shiv particles and its these particles that can be processed into hemp pellets.
Conclusions on Hemp Fuel Pellets
While wood pellets are currently where the fuel pellet market is focused, hemp pellets could hold significant market share in the future. As the use of industrial hemp scales up, more hemp shiv and shiv dust will be produced. That’s a particular aspect of hemp fuel pellets I find so appealing. The raw material is a byproduct of a byproduct. It means making fuel pellets from hemp is the most efficient fuel pellet process there is.