Data on Cleanup Efforts/Bioremediation

I wanted to take a deeper look into use of bacteria to cleanup oil spills because there are many commercialized genetically modified strains. They are being used more commonly now and it would be best to see if this method would indeed work as well as it is intended to. But there are actually lots of limiting factors that influence the breakdown down of oils.

Based on data from a study I have a chart showing the effectiveness of degradation of oil field waste using bacteria.

From "Ground Water Monitoring and Remediation."

The chart shows varying amounts of initial percentage of petroleum in different pits with the red bar representing the final percentage left after 30 days. Basically the end results or the results of the chart shows that even with varying degrees of petroleum contamination the final result shows an almost full degradation. This all happens within about 30 days or less. But this was done in probably optimal conditions with an aerobic setting and adequate nutrients for the bacteria.

According to the U.S. Geological Services cleaning up the existing contamination in just the United States alone could cost as much as $1 trillion dollars! Bioremediation helps lower the costs by,  

Treating contamination in place as most of the cost associated with traditional cleanup technologies is associated with physically removing and disposing of contaminated soils. Because engineered bioremediation can be carried out in place by delivering nutrients to contaminated soils, it does not incur removal-disposal costs. 
Harnessing natural processes: At some sites, natural microbial processes can remove or contain contaminants without human intervention. In these cases where intrinsic bioremediation (natural attenuation) is appropriate, substantial cost savings can be realized.
Reducing environmental stress: Because bioremediation methods minimize site disturbance compared with conventional cleanup technologies, post-cleanup costs can be substantially reduced.

Limitations!

Oil spills can happen anywhere, from arctic to tropical marine, from soil to water, and that is why
the physical and chemical environment of oil spill can vary significantly from one to other. 

Many factors have been proved to influence microbial degradation of petroleum, including physical status of oil spill, temperature, oxygen, nutrients, soil type and characteristics, and vegetation etc. Generally, there are two kinds of oil spills: Oil spill in water and oil spill in soil. The biggest different between them is the degree of spread.

One of the biggest limitation is due to anaerobic conditions the rate of breakdown is greatly reduced but is still possible.

Temperature

The temperature affects the physical status of petroleum as higher temperatures will result in higher viscosity, the volatilization of toxic alkanes is reduced, and their water solubility increased, delaying the rate of biodegradations. The second effect is on microbial activity. Higher temperature usually resulted in better activity of enzymes and therefore increased rate of metabolism. 

Nutrients 

Microorganisms require nitrogen and phosphorus for decomposition of hydrocarbons and
incorporation into biomass, therefore the availability of these nutrients are important for bioremediation. The addition of nutrients like biostimulants will improve the degradation of petroleum pollutants in both soil and water.

Costs!

I've looked through a few bioremediation companies and they all incur that "their method" is the best and some even have recorded data and papers recording their work. Some even have apparently their own genetically modified version of the pseudomonas bacteria strain. As for cost wise I was going to email them and ask but it's kind difficult as it depends on the area, and the widespreadness of the situation for them to be able to quote me. But as mentioned before bioremediation is a lot more cost effective when compared with most solutions.

The conclusion based on my opinion on varying effectiveness, cost, difficulty, and the disturbance and harm to the environment is that bioremediation is most likely the best solution. As the convenience of being able to apply it to many different environments and also not causing harm to the environment.