Generally speaking, petroleum is a mixture of compounds known as hydrocarbons. These compounds contain carbon and hydrogen in the ratio of CnH2n+2 for alkanes, the most well-advertised probably being octane (C8H20). In terms of length, one can distinguish between the liquid portion (that which we call oil) with between 5 and 42 carbons, and the gaseous portion (that which we call natural gas) like LPG (liquefied petroleum gas).
Now, I'm not so certain about what you meant about your second question, but I'm supposing that you're talking about biogas. Biogas is an alternative energy source employed mostly on the rural (correct me if I'm wrong) level. This utilizes the fact that as organic matter decomposes in the absence of oxygen, a various mix of vapors are produced with methane being the top component. Methane, being an odorless and flammable gas, can then be piped to individuals for use.
No, petroleum is a fossil fuel.
Petroleum is cheaper.
An alternative fuel is any variety of fuel which is not diesel or petroleum-based.
Petroleum is a hydrocarbon mixture, containing a variety of chemicals made out of carbon and hydrogen.
Machinery and equipment. computers, chemicals, petroleum and petroleum products, textiles and clothing
The raw feedstock for a lot of polymers is indeed petroleum.
petroleum if there's plastic in it
crude liquid chemicals and petroleum
Petroleum, agriculture, chemicals, minerals and ores.
crude liquid chemicals and petroleum
L. A. Waddams has written: 'Chemicals from petroleum'
Petroleum is good, as it can be cracked and polymerised into other use full chemicals, it is bad because drilling from the ground is expensive.