Question

Suggest the alternative types of fuels to be used to save fossil fuels

Answer 1

Well, the rising use of fossil fuels may cause the shortage of fossils fuels in future, There are various other types of fuels that can be used as alternative of them and mostly these are renewable fuels or energy source. 
The one of the best fuel is the solar energy . Sun rays can be converted in to useful energy( i.e electrical ) which can then be used as fuels .
 Similarly BIodiesel obtained from oils are the most advanced alternatives to the diesel as source of fuel,
Also, the wind energy can also be used in this regard. Moreover biomass and geothermal energy can also be used for fuels 

Answer 2

Fossil fuels like Coal, petrol and Natural gas are getting exhausted due to the human activities.
There is a need to conserve the fossil fuels and also  we need to switch  over to other alternative fuels like :

---> Bio fuel can be derived directly from  plants or indirectly from agricultural and domestic waste
----> Bio mass --Derived from plants material ....
----> Bio Ethanol--- alcohol made by fermentation of molasses of sugar cane. Ethanol an be used as a fuel in vehicles.. Brazil country uses Bio ---Ethanol as a fuel for vehicles..
---> Bio Diesel---Produced from oils or fats using Transesterification...
---> Hydrogen Compressed natural gas mixture --- HCNG is a mixture of compressed natural gas with 4- 9% of H2 by energy.

--->Bio Gas --- is methane produced by process of anaerobic  digestion of organic material by anaerobes.