Central Boiler Maxim and burning sludge pellets

[Deerdell]

Hello all,

First time posting on this forum, I’ve been on heating help for a little while and have been lurking on here. I’ve been watching for a good used outdoor wood boiler for a while, but have changed my tune towards a pellet boiler to heat my old Wisconsin farm house.

I work at the local waste water plant where we dry the sludge, and are looking into getting a pellet mill to pelletize the final product. We give away all the sludge, so I could have an unlimited supply of pellets. I also farm, so corn is always an easy option when the price is right.

Now I see for sale locally is a pair of central boiler maxim 255pe corn/pellet boilers for $4500 a piece. Not sure how old they are at this point, but they both look very clean, have the WiFi controller, and the listing mentions it might have an ash auger system that isn’t installed.

So I guess I’m looking for opinions on these boilers, anything to watch out for or problem spots I should look close at? Buying two used boilers for less than the price of one new boiler doesn’t seem like a terrible idea. Also, does anyone have any opinions or experience burning something like municipal sludge? From the searches I’ve done, it seems to get brought up once in a while but not sure anyone ever follows through with it. If I don’t buy these boilers, I’d like to find a good used indoor pellet stove to experiment with the sludge pellets in the shop.

 

[JRHAWK9]

Can't help ya with your questions, however, where in south central WI are you? We are in Lake Delton.

 

[Deerdell]

It turns out that burning the sludge is simply not legal without proper permits, not surprising I suppose. So no free heat for me. The tinkerer in me still finds the idea interesting when there’s alot of sludge going to the landfill.

However, I am still curious about the Maxim boilers. I’ve been watching for hood used outdoor wood stoves, but I’m getting the idea with a job, a farm, and kids that I don’t have time to cut all that wood. So what’s the opinion on outdoor pellet boilers?

 

[brenndatomu]

So no free heat for me. The tinkerer in me still finds the idea interesting when there’s alot of sludge going to the landfill.

You guys flare off any digester gas?
I'd love to compress that excess into 100 gallon LP tanks and use that in a modded (if needed) NG or LP furnace...but I'm sure it's the same thing...permits, liability, etc , etc.

 

[Deerdell]

Our plant is 100% aerobic, so no gas is being collected. Before this job I serviced milking equipment in dairy farms, and one farm had digesters and turbines. That’s something that fascinated me. Takes a lot of volume to be cost effective. However, a previous employee from when I farmed said in Central America and Africa where he had worked had small systems all over that didn’t cost an arm and a leg. Probably had less government bureaucracy to wade through tho..

 

[brenndatomu]

We have one of the larger dairy farms in Ohio near here and they were supposedly building a digester/turbines last year, but I've seen no progress so I dunno what happened with that then...they milk 3000 cows in this location (they have another too) so plenty of "fuel"

 

[Deerdell]

There was a group of 3 dairies here that put in digesters together, one of them went boom. I don’t remember any of the details, but I was mad I didn’t get to go see the aftermath.

 

[brenndatomu]

This one nearby went boom recently...power went out and they had no backup power...really?!

Three hospitalized after explosion at Quasar Energy's Wooster facility

The official cause of the explosion in the biosolid processing facility isn't known but is not related to severe storms, said a fire official.

www.the-daily-record.com

 

[Deerdell]

We have a backup generator that can run our whole plant. There was one weekend where the power just flickered and never went out. The automatic transfer switch got stuck in the middle somehow. Generator was running, but not connected and the line power was there and not connected. The plant smelled bad for a week after all the aerators and mixing stopped for about 8 hours, things go sour fast.

 

[brenndatomu]

Yup, the bugs die fast and things recover slow!

 

[Highbeam]

“my” plant dries out sludge into class A bio solids that come out like crumbles for chicken feed. Not really pellets but not dirt. Lots of hair and other fun stuff. We cook it hot to get it dry and kill the bugs. People fertilize their gardens with it and I can send dump truck loads to your house for free.

Are you saying this stuff burns? In a pellet stove?

My pumpkins sure grow well with it!

 

[Deerdell]

“my” plant dries out sludge into class A bio solids that come out like crumbles for chicken feed. Not really pellets but not dirt. Lots of hair and other fun stuff. We cook it hot to get it dry and kill the bugs. People fertilize their gardens with it and I can send dump truck loads to your house for free.

Are you saying this stuff burns? In a pellet stove?

My pumpkins sure grow well with it!

Yes ours is the same, comes out like dry dirt. Some larger aggregates, some fines, and a good amount of dust. We have been drying it to over 90% solids because we bag it and it’s shelf life is stable over 90%. We put it in 2300 lb bags, and under 90% solids it will crust and not come out of the bags. So between dust and shelf life, we would like to pelletize it. We ran some through a small pellet mill, it was 92ish% solids, had to spray some water on it, but it made some perfect pellets. The place we tested it had a pellet stove in the office and we tested it, it burnt just fine. Might need to be 50/50 with wood pellets depending on the stove. I expected it to smell like burnt hair, but it didn’t. Didn’t smell like a nice camp fire, more like leaves and brush but not an offensive smell.

We are a long way from seriously looking at a pellet mill, just doing research how to solve the dust and shelf life issues at this point. Unfortunately not permitted to burn it I guess, but I’d like to research the emissions and pollution aspect of it. Also curious if it would eat away and corrode a residential stove in short order.

 

[Highbeam]

Yes ours is the same, comes out like dry dirt. Some larger aggregates, some fines, and a good amount of dust. We have been drying it to over 90% solids because we bag it and it’s shelf life is stable over 90%. We put it in 2300 lb bags, and under 90% solids it will crust and not come out of the bags. So between dust and shelf life, we would like to pelletize it. We ran some through a small pellet mill, it was 92ish% solids, had to spray some water on it, but it made some perfect pellets. The place we tested it had a pellet stove in the office and we tested it, it burnt just fine. Might need to be 50/50 with wood pellets depending on the stove. I expected it to smell like burnt hair, but it didn’t. Didn’t smell like a nice camp fire, more like leaves and brush but not an offensive smell.

We are a long way from seriously looking at a pellet mill, just doing research how to solve the dust and shelf life issues at this point. Unfortunately not permitted to burn it I guess, but I’d like to research the emissions and pollution aspect of it. Also curious if it would eat away and corrode a residential stove in short order.

I’m not too concerned with how permitted we are to burn it but it’s corrosiveness to the stove and flue might matter. Then again, the corn stove people manage.

I’ve spread tons of it with a rotary fertilizer spreader. Definitely need a shower before bed that night!

Getting the butt dust (as we call it) into pellets like a stove expects would take a pellet mill. Rats.

 

[Deerdell]

I’m not too concerned with how permitted we are to burn it but it’s corrosiveness to the stove and flue might matter. Then again, the corn stove people manage.

I’ve spread tons of it with a rotary fertilizer spreader. Definitely need a shower before bed that night!

Getting the butt dust (as we call it) into pellets like a stove expects would take a pellet mill. Rats.

We also spread it with a lime spreader. We give it away, we don’t make enough of it to deal with the extra testing for a license to sell it. Growing up on a dairy farm, my lungs have been abused. If I don’t wear a good respirator that dust knocks me down. Even the respirator isn’t always enough. I’d like to get a cheap old used multi fuel just to play around and see how it works.

 

[Highbeam]

We also spread it with a lime spreader. We give it away, we don’t make enough of it to deal with the extra testing for a license to sell it. Growing up on a dairy farm, my lungs have been abused. If I don’t wear a good respirator that dust knocks me down. Even the respirator isn’t always enough. I’d like to get a cheap old used multi fuel just to play around and see how it works.

We give it away too and even deliver if you can take a dump truck load. What I don’t have is a pellet mill.

 

[Deerdell]

Ya have a tractor, spreader, and bulk delivery truck. Being that I used to dairy farm and I still crop farm, the days we go out to spread is like getting payed to farm. I love it. What kind of dryer do y’all have?

 

[Mr._Graybeard]

I've always wondered how much heat these outdoor pellet boilers lose to the environment. That may be less of an issue with a firewood boiler that can generate hundreds of thousands of BTUs when burning full tilt. Checking the CB literature, the Maxim 255PE is rated at 190K BTU. Considering the relatively limited output, I wouldn't want to see a single BTU bleed into the great outdoors.

Wood pellets are getting pricey. To heat my old farmhouse, my 110K-BTU Harman PB105 boiler can go through four bags of pellets on a chilly Wisconsin day, with high temperatures in the low teens. That's $24 worth of pellets in my area. Extrapolating to 190K BTU might put that consumption rate at seven bags, or $42. We might see two or three dozen days like that, or colder, during an average heating season.

Cheap or free fuel like "sludge pellets" or even corn might change that equation, but I don't see anything in the Maxim literature that suggests it can burn corn or anything other than wood pellets.

 

[Deerdell]

I've always wondered how much heat these outdoor pellet boilers lose to the environment. That may be less of an issue with a firewood boiler that can generate hundreds of thousands of BTUs when burning full tilt. Checking the CB literature, the Maxim 255PE is rated at 190K BTU. Considering the relatively limited output, I wouldn't want to see a single BTU bleed into the great outdoors.

Wood pellets are getting pricey. To heat my old farmhouse, my 110K-BTU Harman PB105 boiler can go through four bags of pellets on a chilly Wisconsin day, with high temperatures in the low teens. That's $24 worth of pellets in my area. Extrapolating to 190K BTU might put that consumption rate at seven bags, or $42. We might see two or three dozen days like that, or colder, during an average heating season.

Cheap or free fuel like "sludge pellets" or even corn might change that equation, but I don't see anything in the Maxim literature that suggests it can burn corn or anything other than wood pellets.

I had the impression the Maxim could burn corn, but it needed to have 2 igniters to do it. In a perfect world, I’d put something like that in a lean too off of the garage. Problem is, I don’t have a garage..

 

[salecker]

There is a lady on another forum i am on and she heats completely with nut shells using pellet stoves.
She had to build a crusher to get the size of the shells down.

 

[EbS-P]

Looks like there is some on going research. Just maybe not in the US.

Combustion Performance of Sludge From a Wastewater Treatment Plant in Fluidized Bed. Factorial Modeling and Optimization of Emissions

The combustion performance of a bio-solid waste from a wastewater treatment plant was studied in terms of efficiency and gaseous emissions, by carrying out experiments in a bubbling fluid bed unit and was compared with that of an agricultural waste. The effects of excess air and fuel feeding...

www.frontiersin.org

 

[Mr._Graybeard]

I had the impression the Maxim could burn corn, but it needed to have 2 igniters to do it. In a perfect world, I’d put something like that in a lean too off of the garage. Problem is, I don’t have a garage..

Could be, I just searched for "corn" in the online CB Maxim pamphlet and came up empty.
FWIW, there are pellet boilers that you can install in your basement.

 

[Deerdell]

Could be, I just searched for "corn" in the online CB Maxim pamphlet and came up empty.
FWIW, there are pellet boilers that you can install in your basement.

The outdoor idea was if I was burning sludge. I would still prefer to have the boiler at ground level so I don’t have to move the pellets down the stairs.

 

[Highbeam]

Ya have a tractor, spreader, and bulk delivery truck. Being that I used to dairy farm and I still crop farm, the days we go out to spread is like getting payed to farm. I love it. What kind of dryer do y’all have?

I do not know much about it other than it’s just about 15 years old and we’re budgeting for replacement. It’s big. Im an engineer so I don’t get to operate it but can certainly get access to fresh, hot, product.

 

[Deerdell]

I do not know much about it other than it’s just about 15 years old and we’re budgeting for replacement. It’s big. Im an engineer so I don’t get to operate it but can certainly get access to fresh, hot, product.

We are a BCR bioscrew that we are happy with. I sure hope it lasts long than 15 years!

 

[sloeffle]

Aren’t these bio solid type products loaded with PFAS and heavy metals ?

Toxic 'forever chemicals' found in Michigan farm's beef | Great Lakes Now

By John Flesher, Associated Press Beef produced at a small Michigan farm was found to contain toxic “forever chemicals” after the cattle were fed crops grown with fertilizer made from contaminated wastewater biosolids, state officials said Friday. A consumption advisory issued by state agencies...

www.greatlakesnow.org