Willow biomass crops are being developed as sustainable systems for their ability to produce a suite of ecological and environmental benefits, including their use as a renewable feedstock for the production of heat, electricity, biofuels and/or bioproducts.These systems are relatively new but Native Americans used willows for many applications and Onondaga County was the center of a thriving willow basket industry in the late 1800s and early 1900s. Research on willow biomass crops started at SUNY-ESF in 1986 and is the longest-running program in North America.
Shrub willows have several characteristics that make them appealing for biomass production: high yields that can be obtained in three to four years, ease of propagation from dormant cuttings, a broad underutilized genetic base, ease of breeding for desirable characteristics, the ability to resprout after multiple harvests, and chemical composition and energy content similar to other northern hardwood species.
The willow biomass crop system is built around planting genetically improved varieties on marginal agricultural land and managing the crop using the plant’s ability to resprout after cutting.The willow is planted as 25-cm (~10-inch) cuttings of one-year-old stems.The plants are left to grow for three to four years and are then harvested during the late fall or winter.The willows resprout the following spring and start a new three-to four-year rotation. A single planting can be grown and harvested for approximately 20 to 25 years.
Compared to annual crops, the perennial nature and extensive fine-root system of willow crops reduce soil erosion and non-point source pollution, promote stable nutrient cycling and enhance carbon storage in roots and the soil. Providing an alternative crop for marginal agricultural land will create new income streams and job opportunities in rural communities.
As an energy source, the low inputs required by willow biomass crops and their perennial nature result in a large, positive net energy ratio of 1:55 or more for the biomass that is produced.This means that for every unit of nonrenewable fossil fuel energy used to grow and harvest willow, 55 units of energy is produced (compare to fossil fuels which have ratios of 1:10-80). In addition the system is carbon neutral so willow used to generate energy adds no additional CO2 to the atmosphere.
Willow biomass cropping systems are in their infancy and there is potential for significant advancement through research to improve production techniques and plant varieties through breeding.These increases will further offset dependence on fossil fuels. Additionally, increased deployment of willow provides other environmental benefits as shrub willows can be used as living snow fences, to revegetate and clean up former industrial sites and to stabilize stream banks.