Tapping latent bioenergy
One of Shulin Chen’s major research aims is to give industry incentives to implement environmentally beneficial waste processing technology and similar processes.
For instance, his work on improving anaerobic digester technology could vastly reduce the pollution from agricultural waste, such as manure, and produce a source of renewable energy. Chen is also developing an innovative process that may reduce the waste from potato processing by turning it into an environmentally safe value-added product for industry.
A sustainable energy source
In a recent study, Chen’s group found that eastern Washington has an annual supply of 4.3 million tons of unused dry biomass (a combination of remnants from harvested crops, residue from crop processing, animal waste, and municipal solid waste).
Tapping the latent energy in that biomass—for instance, burning the methane produced when the anaerobic bacteria in a digester break down organic waste—could produce enough electricity to supply 15 to 40 percent of eastern Washington’s yearly residential consumption. However, selling methane for fuel by itself is not enough to make anaerobic digesters profitable, especially in places like eastern Washington, where electric power is relatively inexpensive.
So, with the help of a grant from the U.S. Department of Agriculture, Chen is working on developing more efficient anaerobic digesters, while researching ways to make the byproducts more profitable.
For instance, the fibrous organic material that remains after digestion may be sold as a soil conditioner similar to peat moss, and a precipitated solid called struvite, which is rich in nitrogen and phosphorus, could be used as a slow-release fertilizer.
“It is not a question of if it can be done,” Chen says. “The technology is there. It’s a matter of reducing the associated costs.”
Reducing pollution at a profit
Another project of Chen’s that combines economic and environmental value involves an innovative fermentation and separation process that could reduce the amount and environmental impact of waste from potato processing. This process may also turn potatoes that are unsuitable for grocery shelves or French fries into a profit for growers.
The process uses both cull potatoes and the wastewater generated during potato processing. Generally, wastewater is distributed on land for irrigation, but must be monitored closely in case the starch, protein, nitrogen, and phosphate it contains reach levels that pollute the soil.
Chen has found that using a certain strain of the fungus Rhizopus oryzae to ferment potatoes utilizes the starch and protein, making the wastewater safer to use afterward.
It also yields lactic acid (a common food additive), and a significant amount of fungal biomass composed mostly of chitin.
Chen estimates that the cull potatoes produced in Washington state alone could be converted to approximately 94.5 million pounds of lactic acid using his process: a value of approximately $47 million. And when it comes to producing chitin, a little goes a long way—pure chitin currently fetches a wholesale price of $4,500 per pound.
Research in this area could be implemented in processing plants across the United States as ongoing improvements make the process more cost-effective.
More on Shulin Chen's environmental research
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