Large woodchipper (Europe Chippers model C1175). This type of machine is used to chip large pieces of wood

Woodchips are a medium-sized solid material made by cutting, or chipping, larger pieces of wood. Woodchips may be used as a biomass solid fuel. They may also be used as an organic mulch in gardening, landscaping, restoration ecology and mushroom cultivation. According to the different chemical and mechanical properties of the masses, the wood logs are mostly peeled, and the bark chips and the woodchips processed in different processes.

Woodchips are made in the process of woodchipping with a woodchipper.

Woodchips as raw material[link]

Woodchips are used primarily as a raw material for technical wood processing. In industry, processing of bark chips is often separated after peeling the logs due to different chemical properties.

Woodchips Sources[link]

• Waste wood and residuals from construction, agriculture, landscaping, logging, and sawmills.
• Locally grown and harvested fuel crops

Possible Methods of Woodchip Conveyance[link]

• Pneumatic
• Conveyor belt
• Hopper with direct chute
• Batch system (manual conveyance)^[1][2]

As mulch[link]

Woodchips are frequently the byproduct of pruning of trees. When used as a mulch or Woodchip Mulch at least three inches thick, they conserve soil moisture, moderate soil temperature and suppress weed growth. In climates conducive to growing trees woodchips are readily produced, and may even be available for no additional cost beyond transport.

As Playground surfacing[link]

Woodchips can be reprocessed into an extremely effective playground surfacing material, or impact-attenuation surface. When used as a Playground surfacing (soft fall, cushion fall or play chip as it is sometimes known), woodchips can be very effective in lessening the impact of falls from playground equipment. When spread to depths of one foot (30 centimeters) playground woodchip can be effective at reducing impacts in falls up to 11 feet (3 meters). Playground woodchip is also an environmentally friendly alternative to rubber type playground surfaces.

As fuel[link]

Traditional use of woodchips is as a solid fuel for heating in buildings or in energy plants for generating electric power from renewable energy.

The newer fuel systems for heating use either woodchips or wood pellets. The advantage of woodchips is cost, the advantage of wood pellets is the controlled fuel value. The use of woodchips in automated heating systems, is based on a robust technology.

In a number of cases, coal power plants have been converted to run on woodchips. This is fairly straightforward to do, since they both use an identical steam turbine heat engine, and the cost of woodchip fuel is comparable to coal.

Solid biomass is an attractive fuel for addressing the concerns of the energy crisis and climate change, since the fuel is affordable, widely available, and is carbon neutral and sustainable as long as the crops are allowed to regrow. In most cases, biomass is not carbon neutral as wood is not regrown and the efficiency of biomass operations produce more pollutants than the processes they replace. Compared to coal and nuclear fuels, woodchip biomass does not have waste disposal issues, since wood ash can be used directly as a mineral-rich plant [[fertilizer].

Certain techniques for burning woodchips result in the production of biochar - effectively charcoal - which can be either utilised as charcoal, or returned to the soil. This latter method can result in an effectively carbon-negative system, as well as acting as a very effective soil conditioner, enhancing water and nutrient retention in poor soils.

Automated Handling of Solid Fuel[link]

Unlike the smooth, uniform shape of manufactured wood pellets, woodchip sizes vary and are often mixed with twigs and sawdust. This mixture has a higher probability of jamming in small feed mechanisms. Thus, sooner or later, one or more jams is likely to occur. This reduces the reliability of the system, as well as increasing maintenance costs. Despite what some pellet stove manufacturers may say, researchers who are experienced with woodchips, say they are not compatible with the 2 inch (5 cm) auger used in pellet stoves.^[1]

Micro Combined heat and power[link]

Wood is occasionally used to power engines, such as steam engines, Stirling engines, and Otto engines running on woodgas. As of 2008, these systems are rare, but as technology and the need for it develops, it is likely to be more common in the future. For the time being, wood can be increasingly used for heating applications. This will reduce the demand for heating oil, and thereby allow a greater percentage of fuel oil to be used for applications such as internal combustion engines, which are less compatible with wood based fuel and other solid biomass fuels. Heating applications generally do not require refined or processed fuels, which are almost always more expensive.

Comparison to other Fuels[link]

Woodchips are less expensive than wood pellets. Also, woodchips are theoretically more energy efficient than pellets, because less energy is required for manufacturing, processing, and transportation; however, this assumes that they are consumed in an appropriately designed burner, and as of 2008, these are mostly only available in large systems designed for commercial/institutional use. In contrast to the lack of residential systems, commercial heating installations have been very successful in terms of performance, cost, reliability, and efficiency.

Woodchips are also less expensive than cordwood, because the harvesting is faster and more highly automated. Also there is a greater supply, partly because all parts of a tree can be chipped, whereas small limbs and branches can require too much labor to be worth converting to cord wood. Woodchips are similar to wood pellet, in that the movement and handling is more amenable to automation than cord wood, particularly for smaller systems. Cordwood generally needs to be "seasoned" or "dry" before it can be burned cleanly and efficiently. On the other hand, woodchip systems are typically designed to cleanly and efficiently burn "green chips" with very high moisture content of 43-47% (wet basis).^[1] (see gasification and woodgas)

Environmental Issues[link]

If woodchips are harvested through sustainable forestry practices, then this is considered a source of renewable energy. On the other hand, it is clear that some harvesting practices, such as clearcutting large areas, are often highly damaging to forest ecosystems.

Theoretically, whole-tree chip harvesting does not have as high a solar energy efficiency, as compared to short rotation coppice; however, it can be an energy-efficient and low-cost method of harvesting. In some cases this practice may be controversial when whole-tree harvesting may often associated with clear cutting, and perhaps other questionable forestry practices.

Woodchips for waste processing[link]

Bark chips, not woodchips, are used as a bulking agent in industrial composting of municipal biodegradeable waste, particularly biosolids.

Woodchip biomass does not have the waste disposal issues of coal and nuclear power, since wood ash can be used directly as a mineral-rich plant fertilizer.

Forest Fire Prevention[link]

Woodchip harvesting can be used in concert with creating man made firebreaks, which are used as barriers to the spread of wildfire. Undergrowth coppice is ideal for chipping, and larger trees may be left in place to shade the forest floor and reduce the rate of fuel accumulation.

Market Products, Supply and Demand[link]

Currently, domestic or residential sized systems are not available in products for sale on the general market. Homemade devices have been produced, that are small-scale, clean-burning, and efficient for woodchip fuels. Much of the research activity to date, has consisted of small budget projects that are self-funded. The majority of funding for energy research has been for liquid biofuels.

Woodchip prices in the United States[link]

"Wood chip costs usually depend on such factors as the distance from the point of delivery, the type of material (such as bark, sawmill residue or whole-tree chips), demand by other markets and how the wood fuel is transported. Chips delivered directly to the (powerplant) station by truck are less expensive than those delivered ... and shipped by railcar. The range of prices is typically between $18 to $30 per (wet)-ton delivered."^[3]

In 2006, prices were $15 and $30 per wet-ton in the northeast.^[4]

In the 20 years leading up to 2008, prices have fluctuated between $60–70/oven-dry metric ton (odmt) in the southern states, and between $60/odmt and $160/odmt in the Northwest.^[5]

European Perspective[link]

In several well wooded European countries (e.g. Austria, Finland, Germany, Sweden) wood chips are becoming an alternative fuel for family homes and larger buildings due to the abundant availability of wood chips, which result in low fuel costs. The European Union is promoting wood chips for energy production in the EU Forest action plan 2007-2011.^[6]

See also[link]

• Renewable heat
• Woodchipping in Australia‎
• Sedore (wood chip burning) Stoves

References[link]

1. ^ ^{a b c} VTHR Green wood Chip Furnace^{[unreliable source?]}
2. ^ US Dept. of Energy report,... Fuel Handling Equipment
3. ^ Woodchip price factors for a power Generating Station in Burlington, VT, US
4. ^ Vermont Heat Research - An Experimental Wood Chip Furnace
5. ^ First quarter wood chip costs up almost 50% in western US, but pulpmills in the US South experienced only small upward price adjustments
6. ^ [1]

External links[link]

Look up woodchips in Wiktionary, the free dictionary.

Wikimedia Commons has media related to: Woodchips

• Commercial Heating Installations
• Vermont Heat Research - An Experimental (inverted downdraft) Woodchip Furnace