Application of bio-oils from lignocellulosic biomass to transportation, heat and power generation-A review

This review will be concentrated on the application of bio-oil produced from the cellulosic biomass among the various liquid biofuels to transport fuels, heat and power generation as substitute. Main application of bio-oil and biocrude from two main thermochemical processes, i.e., pyrolysis and liquefaction include boiler for heat and electricity production, diesel engine or gas turbine for power generation, and diesel engine for transportation fuel. Fast pyrolysis is the most popular process for converting cellulosic biomass to high yield of bio-oil with relatively low cost. For the application of bio-oils to transportation, heat and power generation, physical upgrading methods such as emulsions (bio-oil/diesel or bio-oil/biodiesel) and blends of bio-oil/oxygenated fuel (ethanol, diglyme) were mainly used and tested. The studies on the spray characteristics of emulsions and blends in diesel engine condition are not available in the literature. In most studies on the combustion and emission characteristics of emulsions and blends, CO emission was increased in most fuels and engines tested and HC was increased or comparable to diesel operation. However, NOx and soot emissions were decreased in most case of experiments. In the pressure-swirl nozzle for gas turbine application, preheating and blending techniques were employed to reduce the SMD of spray. In case of blend for the application of heat and power generation, E20 blend was mainly selected in most studies. Most studies related to bio-oil combustion in burners, diesel engines and gas turbines demonstrated the higher HC, CO and soot emissions than the original design fuel. Although the properties of bio-oil/methanol blend were widely investigated, there are no studies available about the application of bio-oil/methanol blend to transportation, heat and power generation in the literature. In addition, more research is required for the combustion of upgraded bio-oils for transportation application. (C) 2014 Elsevier Ltd. All rights reserved.