Silage / Moist mass as building material - what will happen??

Hi,

We have mastered making silage by building wooden boxes, plastic lining them, treading them solid with grass, then putting another plastic lining on top with water or soil to keep it weighed down.  

We have just hit both Spring and Wwoofer season in New Zealand, and making silage is a key item on our list.

We would also like to in corporate our silage bins into another use, however, and it seems that a wall of silage would be most similar to an earthship - a very thick solid mass, but one that can be moist.

We are in a very temperate climate near the sea.  Our winter temperature is average 2C min and 11C max, with a record lowest of -4.  Our summer average is 11C min and 22C max, with a record highest of about 30C.  

Two possible uses for it are firstly
- the side and back of a greenhouse that will retain a minimum temperature of 15C at night to grow our sensitive tropicals and capsicums etc.  If it is warmed in the day - how much heat will be thrown out at night?  (We would have a rocket stove/thermal mass backup)
- all four sides of a mushroom-growing house that we want to keep at about 15-20C year round.  We can easily add heat in winter, but would such a building keep at 20C on the occasional 30C summer day?

We would need to have walls that we could access to fill and empty with silage - we could have ones that  we can dismantle and rebuild the outer side.  I am yet to work out how to do the roof - maybe just conventional rockwool batts inside a plyboard frame on a slope?

Would love any advice you can give on how this might work out.

Howdy Annie, I had to read your post twice as where I come from, in the corn growing states of the USA, silage is ground up corn stalks that we feed to animals.

But it sounds like you are "composting " grass in boxes which creates heat and you want to use the heat to warm a greenhouse?

I don''t think that is what they want to do, they want to physically use them as a building material, but I do not think that is the best usage. i grew up on a farm and could barely hold my hand in the silage pile in the dead of winter it was so hot. I always thought it was stpid for us farmers to be heating our houses with oil when we had huge feed piles outside our barns we did NOT want to get hot.

Other then the hassle of messing with pipe while digging out the winter feed for livestock, I cannot see any reason why a farmer could not heat a structure AND provide feed to their livestock.

Now I say this in regards to horizontal silage bunkers and not bags of silage know as Baleage to may people.

sorry - to be more clear - our primary purpose is to have a store of silage as stock food.  While we can pasture all year round here, we need to supplement feed for 2-3 months of most winters and summers, but it would be good to have extra store on hand.  It lasts for up to 3 years so we could rotate it round.  We could also full the walls with woodchip at other times to maintain the mass.  We get regular loads dumped by our local tree remover.

Many people in NZ make silage from corn stalks, but often it is also just made with grass or hay - which is also called "haylage".

My analysis is that if you want to conserve on building material making the silage boxes in you case the south wall of the greenhouse would be a reasonable experiment. If it does heat up as Travis suggests, it probably would not be a problem in your coastal climate where some day may get reduced solar gain do to fog or cloud cover.
When you have recorded the temperature cycle of the silage you could determine if or when you might want to use it for tempering the mushroom growing.

maybe you could try double box walls, as you are taking boxes from one side the other 1/2 wall remains until you have rebuilt the first side with fresh boxes.

As time goes by and you see the fluctuations in temp and seasons and silage supply you may be able to plan out how to use the inner walls as thermal mass to help regulate temps inside (I can only guess the wet grass etc has some weight.)

It does seem like a fair amount of manipulation however you do it, and probably wise to have backup walls for that cold snap that has you using more than just 1/2 of your supply, or that year when you get caught with other chores and the silage either doesn't get made or you don't have time to stack it, or whatever.

My guess is that if you have an idea(s), just start playing with it with no great expectations and then take time to sit down and look at your walls, your movements, the effects on your systems, how you feed, etc. The idea is to make less work and have the elements of your design take care of each other as much as possible.

If you wanted to have feed for your livestock, and provide heat for your building, you could forgo the packing in boxes, have a horizontal bunker, and then as the horizontal bunker is filled, run pex pipe through the pile. That heated water would then be pumped to your building.

This is how Jean Pain type compost heating works.

It would be a pain to dig out the feed and not mess up teh pex tubing, but for emergency feed it would not be that bad.