In choosing a science fair project, try to pick something that you have a basic understanding about. You want to test the relationship between two factors, known in scientific terms as the independent variable and the dependent variable. You basically think the availability of one variable influences the other, such as the amount of sunlight plants receive has an impact on how much they grow.
Other ideas worthy of consideration would be the effect of temperature on water dissolving sugar; the effect of mass on force generated; the effect of acceleration on force generated; the effect of density on bouyancy. All these ideas demonstrate the relationship between the two factors called the independent variable and the dependent variable. Virtually anything that you think causes something else is testable in the form of an experiment and would make a great science fair project.
Will turning plants into a biofuel using enzyme works? What areas can I research about it?
I would suggest always doing a project that allows you to collect measurable data that can be shown in graphic format. Some projects may require this but if yours does not then I would include it anyway because a graph is easy to read and makes a project board look nice. Some ideas I have are as follows:
1. What type of lunch meat grows mold faster? (Or sub any specific type of thing for the lunch meat like fruit, veggies, etc)
2. How the pH level of the soil relates to plant growth? (I found that one on-line if you look below)
3. How walking (a finite amount of time per day) affects your blood pressure.
I think all of these would produce great graphs and you could take nice pictures for each of these. I hope this helps!