Have biomass...what to do with it

[Yule log]

My friend at work owns a horse farm. They have 15 or so horses that produce a couple spreader loads of waste a day. The manure is mixed with sawdust. She is getting tired of getting stuck in her pastures to get rid of the waste. I told her she was also most likely impacting alfalfa yields thanks to constant compaction. She asked me how she could use the waste to get off the grid by generating her own electricity. Her electric bill is $500 month for the large barn and their house (heat pump). I told her generating electricity might be a stretch due to the power needed to run a generator.

I looked into steam production and electricity generation on a small scale but the few choices I saw were very expensive. High pressure steam boilers can be costly and dangerous if you don't know what you're doing. Even if you know what you're doing, try finding an affordable steam turbine. I thought a roots style supercharger might work backwards but $5K is a lot to spend on something that might not work at all. I then did some research on some Stirling engine companies but that option was cost prohibitive. Next, I considered gasification to run an IC engine based on the FEMA gasifier plans. Looks doable but her biomass is loose so I think there might be bridging problems. She could probably pelletize it but that is another step and more cost. Last of all, I thought of using a Goliath boiler http://www.newhorizoncorp.com/offer.php?id=17 to burn the stuff as is to produce heat for the house and her DHW.

Are there any ideas out there that would help her accomplish her goal or is heat for her home the only option. Btw, it sounds like the Goliath would run $14K.

 

[JustWood]

Horse manure is usually very dry and if it is out of barn stalls it should burn in an OWB. My dad burns green sawdust and cutoffs mixed together (enough sawdust that he has to shovel it in his OWB) from my pallet shop in his OWB. Its usually wet enough that it leaves a damp spot on the concrete floor by his boiler. I think that sawdust that has been stored for a while before being used as bedding would be drier than green from my pallet shop.

 

[renewablejohn]

Yule Log

Similar project to what I am doing but on a smaller scale. For a start horse manure we have used in the past both from woodshavings and chopped straw. we normally dry the woodchip/chit/straw for a week in a polytunnel then put it through a straw chopper and into a silo. Moisture content should be no more than 20% to 30% otherwise it may combust. The easy route which we use is to have a woodchip boiler capable of using thermal oil, a steam evaporator which turns the thermal oil into steam (much safer than a wet steam system although still very dangerous at 150PSI) and then a traditional compound steam engine and generator to get your electricity.Remember electric to heat produced could be in the order of 4:1 so 6kw of electric will require 24kw of waste heat to be used.Turbines are only more efficient from 500kw upwards. The harder route, compress your dried waste into briquettes and use a gasifier to run a normal diesel generator (look up vedbil on the internet for a step by step construction manual of a suitable gasifier. Unfortunately I have not found anybody yet who offers an off the shelf solution its a case of having to do it yourself.

 

[Yule log]

Cool information, thank you.

 

[Gooserider]

I'm not sure that burning is the optimum approach... There was just a recent thread on here with pointers to a website in VT where they discuss using the output of large dairy farms to produce "cow-power" electricity. Rather than burning the product - (I notice that several of the proposed OWB regulations being pushed by various groups explicitly forbid burning manure as fuel BTW) they put it into an anerobic digester tank which produces large amounts of methane gas. They feed the methane to a gas-engine powered generator, which produces large amounts of electricity, and waste heat which is used for heating buildings, producing hot water to clean equipment, etc. The remaining solids are dried and reused as bedding material instead of wood chips. The liquids were used as fertilizer.

The operations cited were large, on the order of 500-1,000 cows, I don't know how it would scale to a smaller farm, but it would seem possible, and might be less of a problem than trying to come up with a clean energy efficient way of producing electric via direct combustion.

Gooserider

 

[renewablejohn]

Gooserider

Thats the problem it does not scale easily with 500 cows being around the critical mass to make the project viable on a commercial basis.

 

[Gooserider]

Gooserider

Thats the problem it does not scale easily with 500 cows being around the critical mass to make the project viable on a commercial basis.

That makes sense, but does it have to be done at a "commercial" scale? It sounded like the OP was mostly looking for a way to deal with the biomass in an ecologically reasonable manner that didn't involve getting stuck in the pasture, with a desired bonus of supplemental heat / power generation... It would sound to me like even if the operation was on a much smaller scale, the potential would exist to make a significant dent in the electric bill.

I'm not saying that it is the optimum solution, just something to consider as I hadn't seen anyone mention any approaches that didn't involve burning the product, and IMHO all avenues should be explored.

Another approach I've seen is simply to build large compost piles out of the material, plus possibly other things, with pipes running through them - the composting bio-process generates a great deal of heat, why not see about tapping it without necessarily having to burn anything?

Gooserider

 

[Redox]

Yule Log

Similar project to what I am doing but on a smaller scale. For a start horse manure we have used in the past both from woodshavings and chopped straw. we normally dry the woodchip/chit/straw for a week in a polytunnel then put it through a straw chopper and into a silo. Moisture content should be no more than 20% to 30% otherwise it may combust. The easy route which we use is to have a woodchip boiler capable of using thermal oil, a steam evaporator which turns the thermal oil into steam (much safer than a wet steam system although still very dangerous at 150PSI) and then a traditional compound steam engine and generator to get your electricity.Remember electric to heat produced could be in the order of 4:1 so 6kw of electric will require 24kw of waste heat to be used.Turbines are only more efficient from 500kw upwards. The harder route, compress your dried waste into briquettes and use a gasifier to run a normal diesel generator (look up vedbil on the internet for a step by step construction manual of a suitable gasifier. Unfortunately I have not found anybody yet who offers an off the shelf solution its a case of having to do it yourself.

How's your project going? It sounds like you have all the pieces AND the motivation! No, I haven't found anything off the shelf yet. I have to wonder how a silo full of $#@& is going to go over with the neighbors and environmental people? Might as well be trying to build an unlicensed nuclear reactor. You guys are probably on the cutting edge, though. Good luck and keep us posted!

Chris

 

[renewablejohn]

Project is going fine however the credit crunch has travelled over the pond and made it difficult to finance any sort of project even at good rates of return. We have tried every high street bank and none of them are interested. I think it is because they do not have the money to lend in the first place. Secured the contract to supply 4800 MWh to a green energy power company and have suppliers contracted for 3000 tonnes out of the 3500 tonnes of woodchip I require.

 

[kenny chaos]

BIG diff between cow and horse manure for methane production.