Wood chips are small, uniform pieces of wood created as a byproduct of processes like sawmilling, forestry operations, and routine tree maintenance. Derived from logging residues, branches, or unsaleable wood materials, this material was once considered waste but is now a valuable commodity. Its consistent size, physical structure, and chemical composition allow for versatile use across sectors, from backyard gardening to industrial manufacturing and energy production.
Uses in Landscaping and Horticulture
Wood chips are widely employed as an organic mulch, providing a protective layer over the soil surface in garden beds and along pathways. This application is highly effective for moisture management, reducing water evaporation caused by sun exposure and wind. By insulating the ground, the mulch helps the soil remain moist for longer periods, reducing the need for frequent irrigation.
The insulation provided by wood chips also serves to moderate soil temperature. They keep the soil cooler in summer and warmer in colder months, preventing temperature extremes that can stress plant roots. This stable environment encourages healthier root growth and better plant establishment.
A thick application of wood chips is an effective, non-chemical method of weed suppression. The dense layer blocks sunlight, preventing weed seeds from germinating. As the chips slowly decompose, they add organic matter to the soil, improving its structure and encouraging earthworms.
Wood chips also offer a clean, natural aesthetic when spread around trees and flower beds, enhancing the visual appeal of a landscape. For pathways and playgrounds, they provide a soft, resilient surface that is both durable and eco-friendly.
Wood Chips as a Renewable Energy Source
Wood chips are a significant source of woody biomass used to generate heat and electricity through combustion. They are a readily available fuel source for residential wood chip boilers and industrial or municipal power plants. The uniform size of the chips, typically 10 mm to 45 mm, allows them to be fed automatically and efficiently into specialized heating systems.
This biomass is considered a renewable energy source because the trees used to produce the chips can be replanted and sustainably harvested. Wood fuel is often described as carbon neutral because the carbon dioxide released during combustion is roughly equivalent to the amount the tree absorbed during its growth. This creates a closed carbon cycle, resulting in minimal net carbon emissions compared to fossil fuels.
Large-scale facilities utilize wood chips by burning them in industrial boilers to create steam, which drives turbines to generate electricity. This process offers a sustainable alternative to coal and natural gas for heating and power generation in district heating systems. The high energy properties of wood chips mean that one ton can provide approximately 4,100 kWh of energy.
Industrial Material and Manufacturing Input
Beyond energy, wood chips serve as a foundational raw material in manufacturing, particularly for pulp and composite wood products. They are the primary feedstock for producing wood pulp, the fibrous material used to make paper and paperboard. In the pulping process, wood chips are treated mechanically or chemically to separate cellulose fibers from the binding lignin.
For chemical pulping, wood chips are cooked with agents to dissolve the lignin, resulting in a high-strength pulp used for items like shipping containers. Mechanical pulping involves grinding the chips to separate the fibers, often used for products like newsprint. The quality of the wood chips directly influences the strength and quality of the final paper product.
Wood chips are also reformed and bonded to create various composite materials. Products like particleboard, medium-density fiberboard (MDF), and oriented strand board (OSB) rely on wood chips or fibers as their main component. The chips are mixed with adhesives and subjected to heat and pressure to create engineered wood panels that offer structural stability and efficient material usage.
Environmental and Specialized Applications
Wood chips have unique roles in environmental management, notably as a filtration medium for contaminated water runoff. They are utilized in denitrifying woodchip bioreactors, where the carbon serves as a food source for microbes. These microbes consume nitrates and convert them into harmless nitrogen gas, effectively cleaning agricultural runoff before it enters waterways.
Wood chips are also used in animal husbandry as livestock bedding, providing a soft, cushioned surface and high absorbency to control moisture and odors. Used bedding can then be composted, creating a nutrient-rich soil amendment. For culinary applications, specific types of wood chips, such as hickory or cherry, are heated to generate smoke that penetrates meats and cheeses, enhancing flavor profiles.