Now for something completely different. We are going from the cells up to large scale
stuff. This is actually a pair of presentations.
I’m going to do the first part and Matt Smith, one of the doctoral students in Natural Resources,
is going to handle the second part. So, we are looking first at…Well, why don’t
we get into. Let me check my arrows here. Must be that
one. Yes! Ok. So conferencing with New England
Dairy folks in the recent past, among the things they are concerned about were reducing
costs and obviously there is a range of things that you have to spend money on. Energy, bedding,
things like that. So this project carves out the bedding part and the energy part. To bring
some experimental knowledge to figuring out how we might be able to do this a little bit
better. So, in a nutshell, the project is this one slide. I’m going to cover in the
next few minutes the woodlands, wood shavings part. I’m going to get it from the stump to
the shed, which is the title of my little part. And then Matt is going to take over
and turn the shavings over to the dairy herd, let them use it and then cycle back through
on what to do with the compost, how to recover energy and then get it back on to the farm
fields to sort of close the loop. If we were really closing the loop, we’d take the compost
and put it back in the woods, but that is a little hard to do. So, what we wanted to
do first is get some idea of what we were spending at the University. We have dairy
operations, including the Organic Dairy Farm, and we buy lots of Eastern White Pine woodshavings,
that’s the EWP. We buy it by the van load. It’s available. It’s very good material for
bedding. At one time, it used to be relatively inexpensive. You go back far enough, sawmills
used to give away their sawdust, right? Well, those days are gone, right? You have to buy
it now. And shavings are a lot and we have this new biomass industry out there that is
beginning to suck up some of the lower grade material. Your competing for what you are
out buying. So, that’s what the University has found in their own operations. So, it
looked like we were spending somewhere between, I’ll do the math here quickly, 18-21 dollars/cubic
yard or about $2000 for 100 cubic yards and it would have to be trucked in from a long
ways, so a big part of that cost is the transportation. Gee, well, maybe, if we produced it locally,
we could eliminate that transportation cost. Plus, other margins that might be built into
other productions. We’re showing from our accounting system that we’re spending $75-85
thousand per year for animal bedding. That’s a lot of money. The question is can we do
it ourselves cheaper than buying it off farm. And if we can do it, maybe the dairy farmers
of New England can do it as well. So, what are the systems that have to be in place and
what do they cost to operate? And does that set up a circumstances that makes it economically
feasible for our private operation agriculture to actually do this versus an experimental
operation where we can afford to make mistakes. Because, we are supposed to make mistakes,
that’s what experiments are about. Dairy farms can’t. Research makes the mistakes for the
farmers and this sorts out whether this system will or will not work. So, we’ll walk you
through a few of the things we thought about and a little bit of our initial preliminary
data to get a sense of where we are heading. We are operating mostly on the Organic Dairy.
Almost exclusively on the Organic Dairy Farm and the associated woodlands located in Lee,
NH. Many of you have probably visited that farm and know where it is and how it operates.
There’s a woodlot associated with that farm. And we acquired a wood shaving machine. And
you can see that it is not an inexpensive piece of equipment, $60,000. And it’s the
bluish item here in the middle. We are using only soft woods. We are using mostly pine
and hemlock. And the dimensions are somewhere between four and eight feet long. They can
be between two and twenty four inches in diameter. We don’t want to get them too small and we
don’t want to get them too large. Get them to large and they won’t fit into the shaving
machine. So, there’s a lot of things to go into. Figuring out what we should be measuring.
And so here’s a list of 25 things and probably looked at more closely, there’d be even more.
We need to know how well the machine operates. We need to know about all of the other equipment
that needs to be brought in. We have to compare it to what we are spending, because if it
turns out to be cheaper to buy someone else’s bedding, that’s a good answer. We have to
take care of the purchase of the shaving machine. What the interest rates might be if we had
to borrow money to do that. How many years it’ll take to pay off that loan. How many
years the machine is going to last. And what’s it worth at the end. Is it just scrap metal
or is it actually something we might be able to sell off and roll over as you might any
other of your farm equipment. How much power does it take, is required. What the drying
process is and things like that. And then, when we get done with all the variable things
that go into it, we’ll have some idea of how many hours we can operate the machine. How
many hours it takes to load. How many tons or cords of wood we can use. What we are spending
on labor. What we are spending on fuel, maintenance. We discovered among other things, I’m sure
you aren’t surprised, the machine does breakdown. It does take time to get it going again. We
found it is easy to jam the machine if you didn’t load the logs carefully, among other
things. Anyway, I’ll go quickly through the steps here. Chainsaw and skidder to fell the
wood in the University Woodlands, which are right next to the farm, so it was fairly easy
job to do the harvesting operation and then transport the wood to the staging area next
to the wood shaving machine. For our initial experiment, we harvest approximately 50 cords
of eastern white pine and 10 cords of hemlock. The cost was about $78 per cord to get the
stuff to the landing area. Now that is a little high. Part of that cost has to do with some
road repair that we had to do. So, that cost is being charged against those first few loads
of pine. As we go further and bring more wood, the road cost will be amortized across more
volume and that cost should go down. Our preliminary calculations suggest that we were pick up
the wood from a little over two acres. We probably can sustain this. You can see that
we’ve cleared out pretty well. We’ve got fairly expensive stands of fairly low quality white
pines, so we are feeling pretty good about it. One of things we did do, when we did get
an occasional good log. Back up a little bit here…this one looks like it has a little
promise to it. If we had a saw log, a couple truck loads worth, we were able to trade that.
So we aren’t shaving the number one saw logs, we are sending those off to the sawmill. We
are hanging on to the number 3 saw logs, because there isn’t much difference between a number
3 saw log and a piece of pulp wood. So, we trade the good stuff, for the not so good
stuff. Ratio was about 1.25 to 1. So we got more pulp wood than we got saw logs and we
recognized we had to share the cost of trucking that in, because somebody else did the harvesting
of the pulp wood elsewhere and they had to bring it to us. That’s one of the other things,
even though you are sharing the cost, you are still paying the cost of “delivered wood”.
That’s one of the things that brings that $78 number up higher than it should be. But,
we did gain some biomass as a result, so in normal operations, a dairy farm could sell
off those saw logs and recover from someone else. That might be possible. There’s always
plenty of low-grade wood that people much rather haul a shorter distance to somebody’s
farm than a four hour round trip to Jay, Maine or something. Given the cost of diesel and
everything else. So, shaving the wood from the woodpile, which we don’t have…well,
back here we have a woodpile…and we have a woodpile. From the woodpile. Small piece
of equipment, grapple onto three or four logs, bring them over to…is this the little arrow?
Yup, here it is…we built a little deck here, which allowed us to shave off the bark. Shaving
goes much better without the bark. And we also found that by letting the logs sit for
a little while, the bark shuffs off a lot easier. So, we cleaned off a good bit of the
bark. And then, it’s lifted up and loaded into the hopper, which is the red piece right
here. And then that hopper moves back and forth against the shaving head that is underneath
and the chips/shavings come out the other end. Matt, did you bring the bag? Ok. Visual
aid will be coming around. I’d say you could open it up and put your hand it in it, but
we might litter all around in here, so whatever you’d like to do. So, what we figured out
in going through this process and we are relatively rookies at this and Matt and a couple of work-studies
did the actual labor here. I think they still consider themselves rookies at it. So, we
didn’t put through a whole lot of material to get started. Among other things, there
was a warranty repair that needed to be done by the manufacturer, so we shut down for that,
plus we are competing for the use of some of the equipment, like this loader here, with
the farm. So, we didn’t put through as much wood as we expected, but we seem to be operating
at about 12 cubic yards to the hour. So, when we are actually up moving, running along,
the shavings are coming off that shaver pretty well. And, working through the cost, what
we have so far, to produce the green shavings, just what it takes to get it through the shaver
into the wagon, the van, that we have, we figure it is about $6 a cubic yard without
counting the machine cost. That’ll be paid for the wood shaver and the amortization and
all of the things we have to deal with the capital costs for that equipment. That’s obviously
going to add to the $6, but just the quick run through the labor, the wood, the fuel
for the machine is about $6 per cubic yard. So, once we get the rest of that figured out,
we’ll have a pretty good idea. Somewhere above $6, but we think below $18, will be the final
answer that you can actually do this on the farm for less than the purchase price of wood
shavings. And we hope to get a detailed cost analyst done a little bit later. So. Building
this, I guess, spreadsheet on steroids is the best way to describe it. It’s fairly complicated,
which would look at the situation of whether a dairy operation can afford to buy a wood
shaving machine to actually do their own production. Of course, one of the other issues is to have
a forest attached to the farm. Where you’d have to have some sort of wood supply or somebody
has to bring the wood to the wood shaving machine. We were able to go a little over
a couple acres. That says one acre, but I guess it was closer to two. Well, we harvested
one acre? [Off screen: Yup] But, we could have harvested two. So, we are also as part
of that experiment, we need to measure in fairly excruciating detail how much volume
we actually got out of here. You know, the quick scaling thing, foresters might do? I’m
a forester, so I know how that’s done. That just gives you a really rough idea, but we
want to have good production numbers of how many cubic yards of shavings we are getting
out the other end. We have to have a much more detailed analysis of how much wood in
these stems, as we shave them up. So, we have to do a bit more experimentation and verify
that things work and then we’ll turn it loose on the public and see what they think. We
are also interested in looking at the eastern white pine versus the eastern hemlock. We’ve
got lots of pine, but we also have a lot of hemlock and a lot of that is in jeopardy right
now with the woolly adelgid and so it is a good question, what do we do with that stuff?
Do we let it die? Or do we have a reasonably economic, low use for that low-grade material
and can we go out and capture that and still make good shavings for the dairy herd. And
right now, other things they are working on, various methods to dry the bedding. Getting
a kiln is a fairly expensive thing. We also have to think about future stands, because
if you don’t have a massive woodlot. The University has 2000 acres all together nearby that farm.
Other people won’t have that access. What size forest do they need? What’s the composition
of the forest that you need in order to do this on a sustainable basis? So those are
questions that remain to be answered. Our timber harvesting is done by our Woodlands
Manager, Steve Eisenhaure, and some other folks who have been participating. University
employees at the Organic Dairy Farm and other students or employees at the College of Life
Sciences and Agriculture. And we thank them. We have questions? We have one question. I
can answer one question and then I’ll hand it over to Matt and let Matt fill in the rest
of the story. Now that we’ve got the chips, what do we do with the chips? [From the Audience]
Matt may have to answer it anyway, Ted, what is the dry matter of the shavings as they
came off the lot and sat for six months or I’m assuming you don’t shave them fresh, I
know that some sat there for a while? [Matt] So the six month logs came out at 30% and
then we tried drying them with the solar dryer and got them down to 20%, but oddly enough
the whole outer shell that was out in the sun for six hours got down to 9% moisture
content. So, we are thinking we’ll just stir the pile around and that’ll be the most effective
low cost method, but we’re hoping to get a group of engineering students to really try
out different drying methods that are low cost, so that’s going to be this upcoming
summer. [Audience member] So what is the target? Like if you were purchasing shavings at UNH?
[Matt] Kiln-dried is the best. We purchase it at 9-10%, but the regional equilibrium
is at 12%, so really we are shooting for 12%, which is what we are currently using at the
Organic Dairy right now. [pause]
[Matt appears] So, this is the second half of my dissertation work is pretty much what
happens to the bedding after we shave it. And so, Ted got us through the first two steps
of the process of actually cutting down the trees and then processing the logs and shavings.
And, so, after that the shavings go into UNH’s bed pack system. As of now, we are purchasing
700 cubic yards a year for that particular farm and we are processing another 3000 for
the other farm systems, the Equine Facility and the Fairchild Dairy. So, I’ll go through
each one of these steps right here. So, some background on the composting heat recovery
facility is that it was donated by a private donor with supplemental funding from the New
Hampshire AES. And the primary goal of this heat recovery compost facility is to produce
heat, find the best way to extract the heat from the compost and also find the best way
to use the heat. And so, as of right now, the heat on the farm is being used to warm
water, it is pretty much a pre-boiler, that goes into the milk house and there is a supplemental
boiler in there as well that bumps the water another 70 degrees, but we are pretty much
saving cost on warming water. And the cool thing is this only the fourth facility in
the world using this technology. Two of them right now are in Vermont and there is another
one in New York and there are people thinking of building one in Boston. And so, there aren’t
too many, so we are kind of breaking the ground here. Testing technology. There are a few
little kinks that we are working out. And the system that actually develops this technology
is in Vermont and it’s called, Agrolab Technologies. And the cool thing is that this technology
is actually developed out of the aerospace industry and someone came up with the idea,
“Hey, we could use this for composting.” I’ll explain how the technology works in the upcoming
slides. The UNH facility is called an aerated static pile heat recovery compost facility.
I say there are only four of these in the world, but truthfully there are many more,
they just aren’t using the heat recovery unit. The way an aerated static pile system works
is you pretty much load the compost into the facility and then you don’t turn it after
that. Unlike a lot of other composting operations where you are turning it to aerate it. In
this situation you are actually using a fan system to supply the microbes with oxygen.
So, everything is kept aerobic and that’s crucial, because if things go anaerobic, it
doesn’t produce as much heat. So, since we are trying to recover heat, we constantly
need to supply oxygen to the microbes. And pretty much a larger microbial population
means more heat and so this whole project has pretty much turned into a microbio type
study in terms of how can we feed the microbes, how can we keep them happy, how can we prevent
ourselves from killing them, which happens at 160 degrees or higher. Which we’ve done
a few times. So, really it is providing a favorable microbial environment. And so this
slide right here really provides info on how the big picture works. So, we load compost
into the building. And I’m going to describe each one of these steps in great detail, but
this is the basic flow diagram. So, we load compost into our building. And cast into our
concrete are our aeration lines. It is just standard PVC pipe with holes drilled in it
and it is connected to a giant fan system. And so we suck air down through the compost
into this aeration system. All that heated compost vapor, and right now it is about 130
degrees because it is winter time, but typically we can get up to the 150s. All that hot air
flows into this giant heat exchange unit right here. Within this heat exchange unit are these
stainless steel rods. So, when you blow hot compost vapor on one end, it warms the rods
up along their whole length and half the rods are actually contained in a 300 gallon tank
of water. So when you are blasting that hot contaminated compost air on this half, you
are heating up this clean water on this side. And this clean water at UNH right now is about
110 degrees. It has been dropping recently because it is so cold and we have some old
compost batches in there, but ultimately this 110 degree water goes over to the milk cows,
where we bump up the temperature another 60 degrees and then that serves the entire farm’s
hot water needs, so the basic idea instead of warming up 50 degree well water on this
end, we’re only having to warm it up another 60 degrees more, as opposed to 100 degrees.
So, all that is the cost savings right there. So before we load a compost bay. So this is
the inside of our facility, we have to unload a batch of material. It takes about an hour
– 2 hours to unload a composting bay and each composting bay is about 100 tons of material.
And you can see the aeration lines cast into the concrete, four feet apart. Then we also
have to have cover plates over the aeration lines before we load and we also have to put
wood chips on top, because you don’t want to suck compost down into the system, because
it breaks the stands. You have to be very careful about this particular spot, because
if you don’t do it correctly, the whole pile will go anaerobic. And actually the first
composting bay, this one right here, that we loaded, that happened, because we didn’t
have the loading method down the way we do it now. Pretty much we loaded the whole facility
with wood chips across, but when we were backing up the manure spreader to load, the manure
spreader wheels are actually pushing the wood chips aside and manure was dropping down into
the aeration holes. And so we had an entire bay that was loaded and if you’ve seen hard
manure, it is like cement, so no air was getting to it. So now we load the facility in blocks,
eight feet at a time, pile it up higher and it is working beautifully. We are getting
amazing compost temperatures. And so when we load a monthly batch, it is about 215 cubic
yards or a 100 tons per bay. So, we load two bays per batch and so one side of the bay
serves as a control and the other side of the bay serves as a treatment. So, right now
we’ve loaded six batches. The first four batches are really like trial and error. What is the
best compost recipe? What is the best way to load it? And now, batch five and six, we
are starting to do the replicated trials. Which is really exciting. I’ll get to that
in a second. It’s about 12 hours of labor to unload and load a batch. And this time
is continually dropping. It was at 15-18 hours before, because we have feed stocks all over
the place, but now all of our feed stocks are in one location. So now when we are mixing,
we are not driving around as much, so we are streamlining this whole process right here.
And so, heat production. The heat is produced by the microbes, as I said. We have compost
that is done aerobically. There is heat production just from the metabolic activity. An important
point is that the aeration that removes the heat is much higher than the heat required
for the microbes and so if you aren’t pulling enough heat from the system, the microbes
can actually die, because they get too hot. And actually this happened before Christmas
time, we were getting temperatures up in the 170s, because we were following the standard
recommendations for heat removal, but we developed a really hot batch and so we had to turn on
the aeration system. And of course, that was right before I had to go on vacation, so my
parents were at the compost facility over Christmas, watching pile temperatures and
making sure things didn’t go too crazy. Because you don’t want the biological oxidation to
go to chemical, because when that happens you can get spontaneous combustion. Although
it is quite rare, you don’t want to be the person that burns down the compost facility.
Another thing, just on compost vapor, there’s minimal to no methane. There are little pockets
of it, but we are producing a lot of ammonia and if we are doing things right, our ammonia
production will be massive, because that’s what you get when you have high heat compost.
But the cool thing is is that ammonia can be scrubbed out really easily with a biofilter.
We are going to be installing one of those next year. And so here’s a picture before
Christmas of the temperatures getting up into the 170s and they were going well beyond that.
So the goal is to get to 160 for pathogen kill, but truthfully you don’t want to get
that hot. You want to maintain it in the 130-150 range. Ideally, 140 and extend that period
for a longer period of time. When you start going up to the 160s and beyond, you can get
a boom and bust cycle. And sometimes, when you go to a bust, it doesn’t go back up and
so we are really refining this. Just to try to keep it in that 140-150 range for a longer
period of time. Because then we’ll get more heat recovery over a longer period. Because
right now, the farm doesn’t have enough biomass to pull off loading two bays every single
month. If this were a true composting facility and we had a lot of biomass, we would only
keep that material in there for four weeks, opposed to 120 days, and then I would want
those high temperatures for that four week period. And then, I’d just cure the compost
afterwards outside, but because we have to keep it in there longer, if you go up into
the 160s-170s, then you’ll have a cold pile in there, not helping you during the winter
time. And here is just some preliminary data. This is a typical curve that we are getting
at the facility now. Where it takes about a week to get up into the 160s. True composting
operations will often be able to get up into the 160s in three days, but since we are doing
heat recovery, that’s dependent on the water molecules and pulling the energy out of there.
We load more wet batches than you typically would load and that’s a recommendation from
the company, because you get better heat recovery initially from it. And so it takes a little
bit longer to get up there. But as you can see, we are maintaining pretty high temperatures.
And these temperature curves right here, we take them once a week. We take 64 measurements
per pile. So we take one foot below the surface, three feet and five feet below. So we are
measuring up the wazoo in the piles. And then we have temperature probes in the aeration
lines themselves and the concrete. So we are tracking all the heat recovery from this entire
system. And so here’s a picture, I’m not actually…can you turn the light down…it’s kind of hard
to see, but here’s our heat recovery unit right here. And you can kind of see this part
right here is just a giant 24 foot culvert pipe. Inside that pipe is isobars. And isobars
actually run through the pipe and into this bulk storage tank of water. And you can actually
see the pipe right there, the isobars coming through. So, when you blast composting from
this end, it warms up this end right here. Like I said, we were getting up to 110 degrees.
When we refine the system, we expect to get up into the 130s and maintain it at 130. And
it is the first facility utilizing this technology. So, it is about $10,000 per year in energy
savings that the first facility has seen. We haven’t calculated how much we are saving,
because as I said we just started using it this past summer. So our cost savings haven’t
been calculated yet, but we are expecting it to be around $5000. We’ll have that number
probably in a year’s time. The payback of this system, the first few facilities that
have done this have seen a 4-8 year payback. Our facility cost a lot more, because we built
a research facility. I’ll get into that in a second. With regard to payback period, a
lot of people always ask, “Oh, what’s the payback? What’s the payback of this?” But,
the truth is with this kind of facility there are so many variables involved that it is
hard to just spit out a payback period, so what we are doing instead is providing everyone
all of our cost information, in specific detail. So people can develop their own payback period,
because we already had tractors, we had a mixer, we had all those things. But a farmer
starting from scratch who needed a payloader or a screener, the payback period would be
much higher than that. So some of the accomplishments so far, helped design the facility. This facility
truly is designed for research with split replicates. And so there is more cost in the
design process because of that. Like I said, we are doing this massive Cooperative Extension
report on how this facility was built, cost structure down to the box of nails, for instance.
It is that detailed. So people could replicate this facility, but also make it even better.
And we discussed how to make it better than the one we have. And how to do it more cheaply.
We’ve also developed a standard recipe on the first four batches. And just for reference,
to produce the hottest mix, we found 30:1 CN ratio, 65% moisture content and a bulk
density, like the pellets per cubic yard, you want a really fluffy mix to pull the air
through the compost. The most recent batch we loaded, two weeks ago, it was a winter
batch, it was 1600 and that was because we had a thaw and all of the materials we loaded
in there were chuck full of water and so that is a frozen block right now. So winter composting,
in our current system, has been a very big challenge, so we are trying to figure that
out, but, you know, the spring, summer and fall compostings worked beautifully. And some
of the research objectives to complete, we need to determine the optimal aeration intensity.
How much heat can we pull from the system without crashing it. So, we are going to be
taking that risk right there. We also want to see if we can do high nitrogen charges,
to see if we can get more heat. We have a giant leachate tank. This entire system produces
about 1500 gallons of this syrupy, brown liquid a week from the aeration system, from the
condensation, and also from the compost leaching in general. Question is, can we put that back
in there and does it justify the cost and the time of doing so with regard to heat production
in the end. We also want to test various compost covers to see if we can actually pull more
heat from the system. We have two of these on there right now. We’ll have results in
probably two months time. We’ll post it on the website to see whether or not it is economical
to put compost covers on for heat recovery. The covers were $300 each, so it’ll be interesting
to see how long it’ll take to pull that money back. I also want to compare various mixing
options. Right now, we are mixing with the manure spreader and it is working beautifully.
But, if we used another type of mixer, would the mix be better? Would it produce more heat?
So, we are going to test that out. Capital costs of the facility, it cost $538,000 to
build our compost facility. $37,000 of that was the heat exchanger. This also included
a mixing pad. So if a non-institutional organization were to do this, it would probably be a little
less, about half as much. But, that’s going with a clear span structure, that’s going
with concrete waste blocks and all of those details are going in that large report we
are going to be publishing in the next few months on how to do this much more cheaply.
And it has all the cost structure. Just for fun, we also put the operating cost. It costs
about $3 to produce every cubic yard of compost and that cost is constantly going down and
that is just the electricity cost for running the fans, and for running the circulation
pump and all that. It is about $3 to produce a cubic yard of compost for us right now.
I’d just like to thank the work-study students and the farm staff for helping me out. It
is a big project and all of the help we’ve had has made it much better. Questions?
[Anita]So, what Matt’s talk was about is another aspect of having an Agricultural Experiment
Station. We, the University, the Agricultural Experiment Station, can explore new ideas,
take the risk that we wouldn’t want individual farmers to take, but looking at new technology,
new approaches, and, in this case, our hope is to drive down the cost of inputs and figure
out optimal ways to do this. That is why Matt is going to work very heavily with Extension
in getting that information to everyone. [Audience member]So, Matt, one of the new
types of dairy barns that have been designed just recently is called a compost bed pack.
And compost bed pack, you basically put down bedding and you till it twice a day to turn
it over. The goal for the compost bed pack is that the temperature should get up to about
150 degrees, which is what you are doing here. So, just thinking outside the box, that compost,
farmers won’t like this, could probably be put back under the cows.
[Matt] It could. After it was done. People were asking about compost and bed packs earlier.
It wouldn’t be good for this system if you were using material after the fact, because
you’ve lost all your heat. Theoretically, you could use the compost material instead
of shavings. But there’s a whole group of people that think that’s fantastic and there’s
another group that’s like, “You are putting this high nitrogen, or potentially high microbial
count, material there.” But, it comes down to, do you heat it enough. Because if you
don’t heat the compost enough, then it is going to be a disaster.
[Audience member]Dr. Brito and I were on a compost bed pack farm just this past Fall
and it was the cleanest barn. The cows were immaculate.
[Anita] Could you add some microbial studies to test out the pile in different place at
the end to see what classes of bacteria are left.
[Matt] Yeah, you certainly could. And actually, if it wasn’t an organic farm, there’s some
companies…because my first research, when I was a Master’s was on ethanol, and they’ve
developed some microbes that go after cellulose like crazy, like some genetically modified
ones, but obviously you can’t bring that on to an organic farm, but there is interesting
potential research for composters bringing in that type of organism inside of a composting
system, especially if you are doing heat recovery. Because, you can go beyond the thermophilic
stage. There is a lot of microbial research that could be done on these systems.
[Audience member] So with the air…what did you call it? Where the air is flowing through,
you put dry materials there to prevent wet materials, smaller materials, getting caught.
What other options are there? Could straw be an option, finer screens? You know, that
seems like it was a bit of a challenge. [Matt] That’s standard in the industry now.
They are actually bole wood chips, they are big chips that you put down.
[Audience member]Oh, I was picturing the shavings we were just looking at.
[Matt]No, there big, chunky material. Actually, some places use screens, but it is more expensive.
If it warps, you can hit it with the payloader. So, people have found the cheapest is just
to use the big chips. [Audience member] So, they are big heavy chips.
[Matt] It’s about a cubic yard for aeration lines. So, every bay takes about four yards
of that material. [Audience member] So, where do you get that?
[Matt]We just buy it from a lumber trucking industry.