A study from the university’s agricultural and biological engineering researchers found that turning cellulosic feedstocks like corn stover and switchgrass into pellets means ethanol producers can use existing transportation and handling equipment designed for corn grains.
But, while denser pellets would also mean cheaper transport and storage, the pellet-producing process is so inefficient at present, the benefits from cheaper transport and logistic are effectively lost.
The key issue appears to be that during the pellet-making process, nearly half of the biomass material can be lost.
Klein Ileleji, an associate professor of agricultural and biological engineering, said: “There needs to be research focused on increasing the efficiencies and reducing the losses in densifying bales into pellets or briquettes since the potential economic gain in transportation and storage will make a huge impact in reducing the logistics cost.”
Complexities
The study, which received funding from Duke Energy and was published in the current issue of the journal
Applied Engineering in Agriculture, highlights the logistical complexities for ethanol producers switching from corn to cellulosic feedstocks.
The findings were that bales of unprocessed biomass were cheaper to transport at small ethanol production facilities, while pellets would prove more cost effective at larger ethanol plants, defined as 100 million gallons of production capacity each year. This was because the larger plants would require feedstocks from a wider radius around them, making transport a bigger factor.
Transport costs would be lower for large plants if pellet plants were located close to growing fields, the report said.
Storage costs for bales were significantly higher than for grain and pellets no matter what the size of the production plant. Storage costs for a 60 million gallon per year plant would be three times higher for bales than pellets, but 85% of the costs would be for new bale-handling equipment.
The report concluded that the cost of converting corn stover and switchgrass into pellets outweighed the transportation and storage savings.
“Without solving the logistical issues, commercial production of second-generation biofuels will not take place,” said the Purdue University associate professor.
The study did not compare costs of converting baled or densified cellulosic biomass into ethanol, but Prof Ileleji plans to look at the issue next.
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