1/2 Keg Fermenter ?

I picked up two 15 gallon kegs very cheaply from a home brewer who was selling off equipment. Can I use these as primary or secondary fermenters if the the batch size is 5 gallons or is there too much space in the keg? (potential spoilage)

Thanks in advance for your help.

why not just brew two batches in a day and fill 'em up? it would take a big chunk of your day but it would be worth it to have ten gallons instead of five.

I'm building a kegerator with 4 taps to dispense 4 styles of beer so I want to keep each batch to 5 gallons. Do you think a 15 gallon primary or secondary fermenter is going to be OK?

im shure it would work, what are you gonna use for the top of the keg? you should check out those brewer hardware sankey to fermenter adapter's. they look pretty nice ive been thinkin about picken one up. i have a 9 gallon demijohn that ive brewed 5 gallon batches in and it worked fine. i dont see how their would be that big of a problem with the bigger 15 gallon keg except for the air thats inside before the onset of fermentation. if you have co2 for your kegs you could alwase purge a nice layer over the beer then stick on the air lock. im no pro so dont take my opinion for fact.

Since you've got the fermentation space, I'd go with PaloAlto and make a single 10gal batch (really no extra work, provided you've got a burner that can fuel the boil). Extra kegs are relatively cheap, so you fill two, put one in the kegerator and leave the other to condition even more in the keg. It will only get better!

why not just stick with traditional bucket or glass fermenters if you're looking to do 5 gallon batches? use the kegs for an all-grain set up (HLT, MLT, or boil kettle). using a keg as a boiling kettle will allow you to do full boils.