Page 258 - Biosystems Engineering

236 Cha pte r Se v e n

capturing SO in coal combustors. The lack of availability of low-cost
x
lime is the limiting step for the commercialization of this technology.
The carbonyl groups present in bio-oils can react with ammonia,
urea, or other −NH -containing materials to form imide and amide
2
bonds. Slow-release fertilizers containing up to 10 mass% of nitrogen
can be obtained. These fertilizers have lower leachability and contrib-
ute to good soil conditioning due to the formation of humic type
materials (Robson 2000; Czernik and Bridgwater 2004).
The presence of phenolic groups and terpenoids makes crude bio-oils
very attractive in the production of wood preservatives replacing creo-
sote (Freel and Graham 2002). Some terpenoid and phenols are known
to act as insecticides and fungicides. Biocarbo (http://www.biocarbo
.com), in association with Vallourec & Mannesmann Tubes (V&M) in
Brazil, produces glues and a sealing material from decanted tars.

Chemicals Obtained from Crude Bio-Oil Fractions
Products of better quality, with better performance could be obtained
if the bio-oils were refined and separated into fractions in which the
functional groups of interest are concentrated. Adding water to bio-
oils results in the formation of a viscous oily phase rich in lignin-
derived compounds and an aqueous phase rich in carbohydrate-
derived compounds. The aqueous phase is used commercially in
effective meat browning agents. Low-molecular-weight aldehydes
(especially hydroxyacetaldehyde) and phenolic compounds are effec-
tive meat-browning agents and responsible for the smoky flavor.
Many food-flavoring compositions have been patented and commer-
cialized by the Red Arrow Products Co. (Underwood and Graham
1991; Underwood 1990; Czernik and Bridgwater 2004).
Environmentally friendly road deicers (Oehr et al. 1993; Oehr
1995; Czernik and Bridgwater 2004) can be obtained from the reaction
of volatile organic acids (mostly acids such as formic, acetic, and pro-
pionic) abundant in water-soluble fractions with calcium salts. The
technology used to obtain these products is very similar to the one used
by the old wood-distillation industry to remove the acids before dis-
tilling the resulting water phase to produce methanol spirits (Klar
and Rule 1925; Czernik and Bridgwarter 2004). The resulting liquid
residue after the removal of methanol is an oily phase rich in sugars.
A water-insoluble fraction is rich in oligomers sometimes called
pyrolytic lignin. Pyrolytic lignin has been used as a phenol replacement
for the production of phenol–formaldehydes resins (Himmelblau 1991;
Chum and Kreibich 1993; Roy et al. 2000; Giroux et al. 2001). Thirty to 50
mass% of phenol can be replaced by pyrolytic lignin in novalak and
resole formulations. Pyrolytic lignin is less reactive than phenols but
shows lower toxicity and is cheaper (Czernik and Bridgwater 2004).
The U.S. National Renewable Energy Laboratory (NREL) has pat-
ented a separation method to produce resins from the phenols and
furans present in bio-oils (family C). The method developed by NREL