Backyard Aquaponics
A place to discuss aquaponics

What sort of mass of beer waste is produced per litre of beer, and how many kg of fish will it produce?

The ultimate aim would be to figure out the golden ratio i.e. volume of beer brewed per mass of fish. Then this can be extended to the area required to grow e.g. hops & barley, minus the area saved by growing space-efficient fish, fruit & veg in aquaponics. It should be possible to figure out a (crude) total footprint that is sustainable in an ongoing way. I'd like to do something similar for other feeds such as duckweed and soldier fly larvae.

If it equals, say, a tenth of a hectare of barley to make 200 litres of beer which yields enough protein to grow 20 kg of fish + 100 kg veggies per year, then that's great. However, if it takes ten hectares of barley to produce a 20 kilolitres of beer and this only produces enough waste to feed 1kg of fish and 5kg of veggies, you're going to be having a lot of beer-only meals!!!

Please note I have no idea what any of the actual figures are - those numbers are all pulled out of the air.

The beer waste of an average batch is about 10-14lbs of grain (dry, it would be much more once saturated and swollen with water)

I end up with about 55 12oz bottles of beer, and a batch can cost $25-$35US... the spent grains are always discarded..feeding them to fish would be great !

The process of Malting barley is such a PIA, it is not reasonably possible to grow your own.. I'm just trying to use a waste material .. if I brew 1-2 batches of beer per month, will the waste be enough to raise 50 tilapia ??

I'm brewing on Wed, so I'll be collecting the spent grains to test on the fish, l'll keep you posted on what happens ..

Has anyone tried to feed their tilapia brewers grains ??

Depends if you are a AG (All-Grain) Brewer or not.

I tend to use already Liquid Malted Barley plus additions of Grain up to around 1.5 kg per brew to give it an edge.

So for me it would equate to

1.5kg of Grain per 20lt of Finished Beer

If you were an AG Brewer then you could use any ratio from 2kg to 10kg depending on what you are brewing. Then you would also need to calculate the percentage of different grains to grow depending on style of beer.

Here is a leaked Coopers Ratio-

For their Pale Ale here are the figures

46000L Capacity
4600kg Pale (Grain)
40kg Crystal
200kg of Wheat

To scale that down to an average brew of 23lt you would need

2.3kg of Pale
0.02kg of Crystal
0.1kg of Wheat

Totaling 2.42kg of Grain


In my opinion it would take up way too much space and time to grow your own Grain. Growing your own hops is fine though.

Cheers & Beers
Dave

I wasn't suggesting we grow our own grain - but in terms of the "broader footprint" of our urban food production system, it'd be good to know how much farmland needs to be taken up elsewhere to support it.

So... 2.4kg from 23 litres of beer.

There seems to be a good bit of info here:
http://www.fao.org/ag/aga/agap/frg/afris/Data/468.HTM

protein content seems to be relatively high (25-30%) but digestibility may be an issue.

If we were to assume that the fish would simply chow down the spent grain, we would have to accept that they would have a lower Feed Conversion Ratio (FCR) than with high-protein, highly digestible fishmeal based feed. Let's say their new FCR=4 (anyone?)

So your 2.4kg of spent grains could theoretically produce, say, one fish 500-600g in weight.

In other words you have to drink 23 litres of beer per fish you eat.

In terms of land area, 2.4 kg = approx 1/400th of a tonne, and based on a very conservative 1 tonne/ha, that's 25 square metres of farm land required to produce 23 litres of beer and one fish per year. If you want 50 fish, the grain will take up something in the ball-park of 1250 sq. m (roughly a third of an acre) of farmland, and you will have to produce / drink 1150 litres of beer...

But then you'll be growing veggies too.

I have 5 acre's and from rough calcs it will take me about 1 Year to drink 1150L of Beer at 1.2 18L kegs a week.

Ok.. I have a plan of action..
I'm going to let leonard the largemouth go in the pond, and put 5 tilapia in his tank (60 gallon) and feed them from the 8 lbs of spent grain I have on hand, that way I won't kill the lot if it doesn't work..

How much protine would be left in the grain after use? I would think most of the nutrients would be spent.

Good question?

I plan to go the other way and try the yeast cake as food with maybe some spent grain as binder and maybe and egg or two.
I've got a lager going at the moment when it ferments out I may give the experiment a go. I may even go as far as try and build some sort of press for making pellets ( an excuse to use my wood working tools)

H.

lol - I hear a Tim Allen grunt between the lines there. I love my tablesaw too, but could not figure out anything AP to do with it.

Seriously though no need to make round pellets, just bake in sheets and then break into pieces. The fish don't care what shape they are.

Yeah, I hear you. I'm actually hopeing to get something the consistancy of pasta dough, then run it through a pasta roller, say a fettucini which can be broken down into smaller pieces once dry or baked.

H.

Bump. I am an all grain brewer as well and brew 10gal (38L?) every two weeks.. typically I start with 20-35lbs of dry malted grain and the spent grain go on the compost pile. How have these experiments been working, especially with the tilapia?

I'm pretty sure the mashing process removes sugars, rather than proteins. You don't really want protein in your beer.

so are you guys just talking about throwing some dried mash grains into the tank or is it necessary to process with other additives prior to feeding? just dried crushed mash is ok? i have mucho beer mash as well. ive been feeding it to red wigglers and they luv it lots. i basically lay down a thick layer of newspaper on ground. wet it down good. and then i take an incubator/breeder box of red wigglers in coco and spread that out over the paper and then cover that with dried beer mash mixed with cardboard/brown paper. Just hedgerows on the ground. worms like crazy. no effort other than watering.(well..you need shade cover too) i planned to automize with misters via pvc on valve. for now i just hit it with a hose every few days. the paper on bottom layer acts as moisture retainer and refuge incase i get lazy. so far been workin real good.

i have more mash though than i can use so id like to participate in working out a DIY mash feed with those with more knowledge about feed and nutrietns. I am currently setting up my tilapia hatchery now.

any input for mash based feed ingredients for tilapia production appreciated.

I threw a bit of the spent grain from last weeks brew into the trout tank and they ate it but the second bit I threw in was met with slow acceptance and mostly sank to the bottom.

They probley thought the booze bus was around the corner