Fuel emissions: The difference between diesel and biodiesel exhaust

A growing concern over the environmental effects of diesel and diminishing natural resources has lead to the development of biodiesel. Biodiesel has promising potential as eventually replacing most of the diesel used in automobiles. Currently, a significant amount of air pollution is contributed by pollutants from car exhaust and fuel emissions. This then leads to the question of how does exhaust and emissions from biodiesel differ from diesel. Would using biodiesel improve fuel emissions or will this new fuel have no substantial affect on the environment?

Petroleum diesel has many combustion products such as: carbon dioxide, carbon monoxide, nitrogen oxides, sulphur dioxide, polycyclic aromatic hydrocarbons, and particles of soot, dust, smoke, and aerosols (particulate matter). Carbon dioxide contributes to global warming by acting as a "greenhouse gas" and keeps heat from escaping into the atmosphere. Nitrogen oxides lead to formation of ozone along with hydrocarbons and accounts for the ground level smog present in major cities. Hydrocarbons are also suspected of being carcinogenic and particulate matter can lead to complications in health and the respiratory system [1]. Long term diesel emission is harming the environment, so if biodiesel does produce a significantly lower amount of air pollution then the incentive for everyday use is even stronger.
The definition of biodiesel is the mono alkyl esters of the fatty acids derived from vegetable oils (1). Alcohol and a catalyst are mixed with vegetable oil producing glycerin and methyl esters, the biodiesel component, through transesterification [2]. This process is necessary in order to lower the viscosity of the oil and increase fuel efficiency (1). It is also important to remember that there are multiple types of biodiesel based on the type of oil used. Palm seed, soybean, and peanut oil are all commonly used for biodiesel [3]. Different types of oil may lead to slightly different emission results.
Based on current research the most popular and most successful way of collecting and analyzing car exhaust and emissions is by using a dilution tunnel for the initial collection [3]. A dilution tunnel is a large tube or tunnel that provides space where the gases from car exhaust can mix and become diluted enough for later analysis. In order to determine the differences between petroleum and biodiesel emission, car exhaust will