# Question: How much ethanol can you get from yeast slurry?

You may have seen DB in the news recently “saving the world” with Brewtroleum

Can someone explain to me, as I’d love to know, how you get 30,000 litres of ethanol from 58,000 litres of yeast slurry?

The way I understand it, there would be beer left in this slurry, lets be generous and say 50% is beer. Lets assume it is high gravity beer, pre dilution, so maybe 8% abv.

50% of 58,000 litres x 8%abv = 2,320 litres of 100% ethanol.
100% of 58,000 litres x 8%abv = 4,640 litres ethanol.

How do you get 30,000 litres of ethanol?

Maybe I’m wrong, and have misinterpreted the information they have presented, or totally misunderstand the process. I’d love to think this isn’t another marketing stunt.

If they can extract this much ethanol, how cost effective is it? and will this be an ongoing process to save the world?

The media haven’t presented more than the original press release, with a celebrity (haha, Green MP), and line of cars waiting to get this gas. Were all the cars driven by DB employees?

## 5 thoughts on “Question: How much ethanol can you get from yeast slurry?”

1. Dan Capper says:

I’m also highly skeptical of this being practical whatsoever. It’s 100% a marketing stunt. Aside from the small volume that you’d get back, the energy expended to filter out the muck and then distill the “beer” would be a significant proportion of – if not more than – the energy remaining in the extracted ethanol.

2. Zane says:

The line of cars was because they offered a free fill (up to \$50) to the first bunch of cars to turn up… I too am interested in how they are getting ethanol from spent yeast?

3. Aaron says:

It’s simple. All you have to do is add a bunch of fermentable sugar, water, and leave it. Viola! The yeast slurry has magically turned into ethanol! And, as a bonus, you get more yeast slurry to make more ethanol!
/sarcasm

4. sheppy says:

Given that its commercial beer I’d say there never was any drinkable beer in the first place!

5. I think I found the answer in the press release / media coverage

“O’Donnell said he would like to see Brewtroleum become a permanent fixture at petrol stations, with the first batch expected to last just six weeks.

“It’s a case of testing consumer demand and assessing the feasibility of ongoing production and logistics”, he said.”

So it will run out in 6 weeks, and they will say it isn’t economically viable.

Aaron – Yes adding sugar to the yeast will make ethanol, but they weren’t implying that were they?

NZH even said “In what is claimed to be a world first” http://www.nzherald.co.nz/business/news/article.cfm?c_id=3&objectid=11476245

..it does take much to even find this link http://www.probrewer.com/ethanol-from-yeast-538/ to Sierra Nevada from 2009, let alone the comment from this link which suggest AB and Coors did it even earlier.

I wish the reporters would take the time to investigate a story or even spend 5 minutes with Google to actually add some value to the press releases they are cutting and pasting