Fossil fuels take millions of years to be formed which includes the formation of coal, petroleum and natural gas.
When dead vegetation and animals get buried deep inside the earth under high temperature and pressure for millions of years, resulting in the compression of organic materials thus it leads to the formation of fossil fuels.
As these required conditions cannot be provided in a laboratory hence fossil fuels cannot be created in the laboratory.
As fossil fuels are present in limited quantity hence they are regarded as non-renewable resources. And reckless use of fossil fuels will gradually lead to their depletion.