What is any energy resource that can be used in place of fossil fuels called

I think those are usually called "alternative fuels", or
"alternative energy sources".  Those are things like
wind, solar, hydro, geothermal, tidal, nuclear etc.

I don't like that description at all.  It makes it sound as if
there's something about them that's not quite right, and
that we don't really take them seriously.

The only thing that makes them "alternative" is that we're
just now discovering them, for the first time since we left
the caves. 

Up until now, we've always been happy to burn the stuff
that's cheap and easy to get from a hole in the ground. 
But we're just now starting to notice that it's poisoning
the air we breathe, and plus, so many people have been
using it for so long that now, it's becoming harder to get. 

So we're starting to look around now and see what else
we can use to do the job.

Acetic acid  /əˈsiːtɪk/, systematically named  ethanoic acid  /ˌɛθəˈnoʊɪk/, is a colourless liquid  organic compound  with the  chemical formula  ch3cooh (also written as ch3co2h or c2h4o2). when undiluted, it is sometimes called  glacial acetic acid.  vinegar  is no less than 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water. acetic acid has a distinctive sour taste and pungent smell. in addition to household vinegar, it is mainly produced as a precursor to  polyvinyl acetate  and  cellulose acetate. it is classified as a  weak acid  since it only partially  dissociates  in solution, but concentrated acetic acid is corrosive and can attack the skin.acetic acidnamespreferred iupac nameacetic acidsystematic iupac nameethanoic acidother namesvinegar (when dilute); hydrogen acetate; methanecarboxylic acid[1][2]identifierscas number64-19-7  3d model (jsmol)interactive image3dmetb00009 reference506007chebichebi: 15366  chemblchembl539  chemspider171  drugbankdb03166  echa infocard100.000.528ec number200-580-7e numbere260  (preservatives)gmelin reference1380iuphar/bps1058keggd00010  meshacetic+acidpubchem  cid176rtecs numberaf1225000uniiq40q9n063p  un number2789inchiinchi=1s/c2h4o2/c1-2(3)4/h1h3,(h,3,4)  key:   qtbsbxvteameqo-uhfffaoysa-n  smilescc(o)=o