| Liquid biofuels are promising alternatives in future application since they can be used as transportation fuels to replace traditional petroleum fuels. Crude bio-oil which is derived from biomass fast pyrolysis has several inferior properties such as high water and oxygen content, low heating value, high viscosity and strong acidity. Therefore it should be upgraded in supercritical fluids system to be high quality biofuel. Based on bio-oil upgrading technology in supercritical medium, a novel path is researched to convert bio-oil to oxygenated liquid fuel which is fit for internal combustion engine and it has a good application prospect.Relying on the support of National Basic Programs, experimental study on emissions of upgrading bio-oil upon gasoline engine system was investigated in this work. The most efficient pathway of crude bio-oil production and subsequent upgrading in supercritical ethanol was evaluated using life cycle assessment. Moreover, the environmental life cycle assessments of bioethanol and biodiesel were conducted.Based on the chemical composition analysis data of upgraded bio-fuel,3groups of typical model oil were prepared to represent the bio-fuel. On one single-cylinder and four-stroke gasoline engine, a series of combustion tests of model oil, model oil-gasoline blends were conducted. The results showed that HC and CO emissions using model oil obtained an obvious decrease of33.4%and60.9%. It was achieved that upgraded bio-fuel had a bright application prospect on gasoline engines from the test results.As potential alternative vehicle fuel, upgraded bio-oil presents more excellent performance than traditional gasoline and diesel with0.295MJ/MJ non-renewalbe energy consumption and25.05g eq.CO2/MJ greenhouse gas emission by life cycle assessment. Upgrading step is the crucial unit which accounts for37.97%of total energy consumption and40.91%of GHG emission. The results suggested crude bio-oil upgrading processing and bio-oil production process were the most important units in the overall conversion pathway and had greater influence on both environmental aspects such as net non-renewable energy and GHG emission.Meanwhile upgraded pyrolysis bio-oil was compared with bioethanol and biodiesel. In contrast to conventional biomass-based liquid fuel bioethanol, a reduction of54.6%in net non-renewable energy and a reduction of63.7%in GHG emission were obtained, to biodiesel the two parameters were41.0%and51.8%respectively and to lignocellulosic bioethanol were28.0%and54.6%. |
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