Biomass is fuel that comes from our local forests.
The main differences between these three fuels are moisture content, percentage of bark, and the amount of processing each one goes through.
Wood Pellets
Most of our customers rely on premium wood pellets as their biomass fuel because it is the driest, most flexible, easiest to manage and most energy dense biomass option. Pellets have a moisture content of between 5% and 8%.
Wood pellets flow like water, moving easily from a bulk delivery truck into a storage bag, bin or silo and on into the boiler. Bulk delivery of wood pellets is now available in most areas of New England.
Wood pellet systems are more flexible and fit more easily into buildings at less cost.
Precision Dry Wood Chips (PDCs)
Precision Dry Wood Chips (PDCs) are another locally produced biomass fuel that can be burned as cleanly as wood pellets in boilers that are designed for them, which are fairly common among European biomass boiler manufacturers.
PDCs are green bole wood chips that have been screened so that none are much bigger than an old-fashioned matchbook. Then they are dried down so their moisture content is less than 30%. Our mid to larger clients are turning to PDCs because they cost 35% less than wood pellets. In installations with moderate to heavy fuel use, the extra costs of a PDC-burning boiler system are minimal compared to the future fuel savings involved.
PDCs are produced in our Peterborough manufacturing facility and delivered by our blower trucks.
Green Wood Chips
These are trees, cut down, chipped up and delivered. As fresh-cut wood, green chips contain up to 50% moisture (the typical range is between 35% and 50%) so they are typically burned in very large boiler systems specifically designed for wet chips.
Some green chip boiler systems can burn whole tree chips but we tend to not recommend this; the better the fuel, the cleaner the burn. Other green chip boilers burn only bole wood: main tree trunks only.
The higher percentage of moisture in green chips results in fewer BTUs being realized per ton. Bark is also typically higher with whole tree chips which means more ash accumulation. Green wood chips are quite inexpensive to buy but the infrastructure investment required to burn them can be quite costly so only the largest fuel users can cost-justify a green wood chip boiler system.
Biomass Fuel Comparisons
Delivery Access
Wood Pellets
- The biomass fuel with the most flexibility is the wood pellet. They are the most compact fuel and are easy to transfer from truck to silo to boiler using pneumatic systems and flexible augers.
- Silos can be 80' from the delivery truck, enabling pellet systems to be the most adaptable to existing boiler room situations.
PDCs
- At sites with limited land and access to the boiler room, PDCs have proved to be the best fuel choice because they are blown into a silo through a 5” diameter pipe. The PDC delivery truck can be 50’ away from a silo and requires minimal maneuvering space.
Green Wood Chips
- Green chips are delivered by live floor truck which requires a great deal of space for backing up and turning around, not to mention the construction of pits into which chips are literally “dropped off”.
Storage
Wood Pellets
- The most popular storage option for wood pellets is a 12’ diameter x 26’ high steel agricultural silo with a 28-ton capacity (the net equivalent of 3,360 gallons of #2 fuel oil).
- Silos can be 100' from the boiler.
PDCs
- The most popular storage option for PDCs is a 19’ diameter x 20’ tall cylindrical steel silo that can contain as much as 42 tons of PDCs (the net equivalent of 3,930 gallons of #2 fuel oil).
- Silo must be within 30' of the boiler, typically sitting adjacent to each other with an exterior wall between them.
Green Wood Chips
- A very typical storage system for green wood chips is a covered, in-ground concrete bunker that can contain a pile of chips that would be 24’ wide x 16’ long x 12’ deep. This would contain 47 tons of green chips (the net equivalent of 3,670 gallons of #2 fuel oil).
Material Handling
Wood Pellets
- Pellets flow easily like water or are easily blown, allowing for most flexible system design.
PDCs
- Rigid augers are required to move the PDCs from silo to boiler which makes system design less flexible than for pellet systems.
Green Wood Chips
- Requires dedicated personnel to monitor the quality and processing of the green chips.
- Heavier material handling systems are required.
Cost / Economics
Wood Pellets
- Usually best fuel for light commercial and residential applications.
- Most expensive biofuel.
PDCs
- Usually best for small to mid-sized systems.
- 35% less expensive than wood pellets.
Green Wood Chips
- Least costly of the three fuels to purchase, but green chip boiler systems require a higher initial investment and higher levels of monitoring and maintenance.