ISU researchers have received $190,000 in grants from the Iowa Biotechnology Byproducts Consortium to turn erstwhile compost into a bio-oil that could be used for boiler fuel and potentially transportation fuel.
First, the manure needs to be dried so it can be burned. The manure is mixed with corn stalks and put in a big drum, using small blower to keep the air circulating and an auger to turn the mixture once a day. Within about five days, bacteria and fungi working to decompose the mix have naturally raised the temperature to about 150 degrees Fahrenheit. Within another 20 days or so the moisture content is down from 60 percent to about 20 percent, a process the researchers have dubbed bio-drying.
The mixture is then rapidly heated in a fluidised bed reactor with no oxygen, a process called fast pyrolysis. The process thermochemically breaks the molecular bonds in the mixture, producing charcoal that can be used to enrich soil and an evaporate that is condensed into the bio-oil.
Preliminary tests indicate every kilogram of dried mixture produces 0.2 to 0.5 kilograms of bio-oil depending on the operating conditions. The energy content of dry manure is 12 to 18 gigajoules per ton (0.9 tonnes).