Spent grain

By September 23, 2014Spent grain

A conversation about spent grain on a wastewater blog? Yup. This is another area that I have a lot of background in. We all know spent grain can & should go to cattle. What else is there to know besides that?

Spent grain is heavy, duh. Handling options vary quite a bit depending on the size of the brewery.

Brew pubs & nanos:

Large trash cans usually work fine. Don’t go with cheapo trash cans, Rubbermaid Brute cans work best. The plastic is thicker and more durable; thinner cans will split, crack, and the handles will rip off. Do line the trash cans with plastic bags. Helps keep things cleaner.

Other options to consider would be an IBC container with the top cut off. A forkliftable plastic bin also works.

Small production breweries:

Volumes are going up. Demands are going up. This means you have less time to deal with this. Hopefully you have an automatic grainout in your lauter tun. If you are in the planning stages, this is usually a ‘trap door’ in the lauter that the grain will fall through. The grain could go in to a forkliftable bin, but again automation is better. The grain could drop in to a spent grain bin below the lauter and be pumped or augered in to an outdoor tank or trailer. Progressive cavity pumps work well in this application, especially for long distances. Augers are just fine for shorter distances. At Deschutes we used progressive cavity pumps and would plumb in compressed air just after the pump to help keep the grain moving. The air would be used on demand if the line felt like it was starting to plug.

I recently received a note from PowerFlo regarding their PD pump with a stainless steel stator.  Here is their webpage for this pump.

I like spent grain silos. They’re not necessarily required, but they are on the list of very ‘nice to have’ when looking at what to spend money on. They should be sized to hold 1.5 truck loads, at least. What kind of truck and how big is it? Bear in mind that truck size can change overnight. Oversize your silo, too big is better than too small.

The other option is no silo and grain out right in to a trailer. This works, but it’s a pain for everyone involved. The truck driver arrives at your site, unhooks his trailer then hooks up to the full trailer. He tells the brewers to stop graining out (or he forgets). He moves the full trailer, unhooks, hooks back up the empty trailer and parks it in place. He tells the brewers its OK to grain out (if he remembers).  Then he unhooks from the empty trailer and reconnects to the full trailer.  Pain in the butt.

Large production breweries:

Again, automation is key. Your brewhouse manufacturer will probably design your spent grain handling system for you. Make sure you have the ability to ‘pig’ the grain out line. Basically put a ball in the line and push it through to clean the pipe. An ‘ice pig’ works good, that way you don’t need to retrieve the ball.

Composting:

I have not done this.  But like any compost system, maintaining the proper C/N ratio and moisture level will be important.  What about rodents and other pests, drainage, wind, odors…  I’ve read about this being used with success with some small farm breweries.  If you would like to chime in we would love to have your imput here.

Storage and hauling:

Storing trash cans full of grain is no fun. Make sure your farmer hauls the material away the day they’re filled if it’s in trash cans. Otherwise it starts to stink, can spill, people can tip it over, takes of space, unsanitary…

A spent grain silo can be built of mild steel. Painted on the outside, unpainted on the inside. A trailer can be steel or aluminum. In all cases, spent grain is a mess. It splashes, drips, stinks and dries like glue. A drain is needed below your outdoor storage location. Ideally this area would be covered to keep out stormwater and the drain would be piped in to your side stream wastewater system. Install a low curb around the area to keep storm water out.  Understand a stainless spent grain silo is always better, but pretty much no one does that.  

Again, ideally a spent grain silo would be designed to drive under it. Another option is for the truck to back under the silo. Do install bumpers near the tank legs in case the truck driver backs the trailer in to a tank leg. Not good. Install reflectors on these bumpers that are easy to see for drivers. You could also put the spent grain silo on the ground and auger the grain in to the trailer.

You need some sort of dispensing device to get the grain out of the silo. A slide gate is easy in concept, but it delivers grain really fast and splashes a lot. A rotary valve dispenser works and can deliver very accurate quantities, but it’s expensive.

Level detection:

3 words. Guided wave radar. Sensor mounts on the top of the tank, stainless steel cable extends through the tank and mounts near the bottom of the cone. This device has a 4-20 mA output and give you accurate level detection in a solid medium with no interference from dust, steam, crud. This works great. It can even work in your malt silos.

The other option is climbing to the top of the tank and looking in. Not as easy as it sounds, steam can make it impossible to see. Snow and ice make it more dangerous than it already is. There are good views up there though.

An overflowing spent grain silo sucks. Talk about a mess. Don’t risk it.

Safety: Spent grain is hot, heavy, and of course a source of curiosity for ne’er-do-wells. You don’t want people climbing your silo, drinking the sticky goo, or playing in the area. Keep it clean and safe.

What about the value of spent grain? When dealing with small volumes, a farmer will be happy to get whatever you have for free. Maybe you’ll get a few cuts of beef out of the deal?

For larger breweries, volumes start to become significant. You have material to get rid of, but a better way to think of it is you have material to sell. In most locations hauling the grain is certainly worth the trouble of hauling it. The value of spent grain is based largely on the percent moisture. The drier it is, the more valuable it is. Efficient lautering is the key to low moisture spent grain. 80% moisture is too high, it drips on the road, sloshes in the trailer, and makes a large slumpy pile at the farm. 70% moisture makes a nice tall pile like gravel, and it stores longer. Another way of looking at it is:

  • 50,000 lbs of 80% moisture grain delivers 10,000 lbs of dry product equivalent
  • 50,000 lbs of 70% moisture grain delivers 15,000 lbs of dry product equivalent
  • 50% more dry product equivalent per truck!
  • 2 dry product truck loads = 3 wet product truck loads

That being said, 70% moisture is pretty tough to do. Very large brewers will run the grain through a belt press to get it. If your brewery is well run and efficient, you should be able to get in the 75-79% moisture range or lower.

What about the farmer/hauler? This stuff is heavy, even though he’s not one of your employees you still don’t want him to get hurt handling these things. For a long time, a farmer we used hauled these heavy trash cans up a ramp in to the back of his pickup. Eventually he installed a lift gate. Eventually his pickup became a work vehicle only since it kept getting splashed with spent grain. A lift gate is good.

For larger volumes, I like to work with a feed broker such as Wilber Ellis. They buy the grain from you and hire a local trucking company to haul the grain.  The advantage here is an easy contract. You can set up the contract to pay the brewery 50% of whatever he sells the material for. Or even 60%. He sells 50,000 lbs of grain for $500, he owes the brewery $250. Easy. He gets $250 for hauling, marketing, and absorbing all risk.

If the farmer is doing the hauling for his own stock, setting the value of the grain is a little trickier. You could set a fixed rate, based on what is the question. Also if the fixed rate is too high you can drive him out of business- obviously not what you want to do. If the fixed rate is too low you are missing out on revenue, but it’s probably the better option. For feedlots you would base it off protein and density. For dairies set it based on other competitive feeds such as corn, soybeans, alfalfa, cottonseeds; also on the price of a gallon of milk. Sound like a lot of work.

What other ideas do you have? What has worked for you? Have any questions? Let me know and I will incorporate them in to this post.

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