Shrub Willow: Building a Better Biofuel

Prof. Larry Smart ’87 converts woody biomass into renewable fuel...


By Yvonne Huang via the Cornell Daily Sun, 1/23/13

The shrub willow, a plant normally planted as ornamental hedges or used in weaving baskets, could now be one of the next mainstream biofuel crops used as a low-impact energy source to replace corn. Since 1998, Prof. Larry Smart ’87, plant genetics and physiology, has helped develop shrub willow as a viable biofuel through breeding programs.

“We’re trying to develop fast-growing willow as a new bioenergy crop that’s highly sustainable, grows well on marginal land and potentially could support job growth and economic development in the rural Northeast,” he said.

Smart currently works at Cornell’s New York State Agricultural Experiment Station in Geneva.

Better Than Corn?

Like all plants, willow is carbon-neutral. When processed, it leaves behind no carbon footprint. Unlike natural gas, which can leave a substantial carbon impact on the environment, biofuels either cause no effects on the environment or in most cases, have a positive effect. Any carbon the biofuel releases was previously absorbed from the air by the plant during photosynthesis.

The shrub willow has often been compared to corn, the current leader in producing biofuel. Willow’s net energy ratio –– a measure of how much fossil fuel energy is put in compared to how much energy is produced –– can be up to ten times that of corn and five times that of gasoline. While willow is a more efficient and viable bioenergy crop, it has so far only been harnessed to produce electricity. According to Smart, researchers are currently working with the New York company Mascoma to make ethanol from willow. Scientists like him are conducting research to convert woody biomass, like the willow, into liquid transportation fuels efficiently and affordably.

An Undemanding Fuel Source

Shrub willow can thrive in areas where other crops cannot such as poorly-drained lands and nutrient depleted soil. These areas are labeled as marginal lands because they have been deemed unfit for producing profitable crops. In the Northeast alone, there are millions of acres of farmland that go unused because they are considered marginal. With the commercialization of the shrub willow, these acres could be used to power local buildings, schools and homes.

Unlike most other biofuel crops such as corn or sugar cane, shrub willow plots are not plowed and replanted after every harvest. Shrub willow only needs to be planted once every 25 to 30 years as it resprouts after every harvest. Root systems develop in the planted soil, preventing erosion and trapping carbon within the soil, which is typically released when plots are plowed. This can improve soil quality substantially by the time the willow goes through its full life cycle.

The willow does not require application of herbicides and pesticides throughout the shrubs’ growing years. Harvesting can be accomplished with ease by adding a willow cutter to the front of a corn harvester every three to four years. Additionally, shrub willow doesn’t need much fertilizer as does corn. According to Smart, this helps prevent fertilizer run-off, which could potentially contaminate nearby lakes and streams.

Willows in the Works

But as is the case with most breeding programs, the shrub willow has potential problems. The shrub willow is a monoculture crop, a cloned plant cut from the same selected parent. Because every crop is genetically similar, the crops are susceptible to diseases and pests. Smart and his team have circumvented this problem by incorporating near relatives of the willow and expanding what they have identified to be the most viable genotype of the willow. By the end of the year, Smart and other collaborating scientists will have completed the genomic map of the shrub willow. This will allow scientists to better understand the plant and help identify other species that can be used to create hardier and more effective shrub willow biofuel.

Smart trusts that his work in new bioenergy sources will favorably affect rural and local areas.

“It really means a lot to me to have my research have a positive impact on society, especially in New York state,” he said. Several local school districts have already benefitted from his research by replacing their natural gas burners with biofuel burners that use willow wood chips.

According to Smart, the shrub willow project could be fully commercialized and ready for a larger-scale expansion within a few years. And as society becomes more aware of the growing need for more alternative fuel options, research into biofuels, like the shrub willow, is becoming increasingly more important.

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