Engineer Online, UK
07-31-06
Where there’s muck there’s bio-oil
Industry Channel: Energy & Utilities
Source: The Engineer Online
Iowa State University is continuing its quest to prove there is no farm waste out
of which they cannot make fuel with their latest project to manufacture bio-oil
from manure and corn stalks.
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).