combustion -- the process of burning
e: The combustion in the forest generated great damage.

prototype -- the first form that a new design of a car, machine etc has, or a model of it used to test the design before it is produced
e: No matter how many prototype we make, we just can not get it right.

diesel -- a type of heavy oil used instead of petrol in engines, especially in trucks, buses, and trains:
e: The steam locomotives were superseded by diesel units.

engine -- the part of a vehicle that produces power to make it move
e: There must be something wrong with the engine of my car.

biomass -- plant and animal matter used to provide power or energy
e: Liquid fuels are made from biomass.

feedstock -- the raw material that is required for some industrial process
e: People use corn as feedstock to produce ethanol.

oxygen-- a gas that has no color or smell, is present in air, and is necessary for most animals and plants to live.
e: She died from lack of oxygen.

obstacle-- something that makes it difficult to achieve somethingCOLLOCATIONS
e: Lack of education is an obstacle of success.

alternative -- an alternative idea, plan etc is different from the one you have and can be used instead
e: Please find alternative means of transport.

regulatory -- a regulatory authority has the official power to control an activity and to make sure that it is done in a satisfactory way
e: New drugs have been approved by the regulatory authority

emission -- a gas or other substance that is sent into the air
e: The emission of using ethanol is less than oil.

liquid –a substance that is not a solid or a gas, for example water or milk:
e: Water is a liquid.

scale -- the size or level of something, or the amount that something is happening
e: There are many scale between low level and high level.

enthusiast -- someone who is very interested in a particular activity or subject
e: He is a movie enthusiast.

mainstream -- the most usual ideas or methods, or the people who have these ideas or methods
e: The of mainstream is how to protect environment.