mattyoga

Using Woodchips for Solids Mineralisation, Nitrate Reduction & Filtering

50 posts in this topic

Thanks Gary,

I was thinking of trying a woodchip exchangeable insert in a laundry basket. Water trickles through woodchips, so woodchips have air around them, then simply lift out basket tip on compost pile or worm bin and restock.

Possible issues:

If not free draining enough, then anaerobic and associated gases.

Tanin staining of water. Not really an issue, my earthan beds do that already in winter.

Chemical residues on woodchips. Will have to wash and age them a bit first.

Getting the mix of chips right will be the challenge. Not too course or fine With a good range of sizes. May need to be partly broken down to strip nitrates...

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Hi mt

Thanks Gary,

I was thinking of trying a woodchip exchangeable insert in a laundry basket. Water trickles through woodchips, so woodchips have air around them, then simply lift out basket tip on compost pile or worm bin and restock.
 

Did you read this

 

With all this talk of woodchips, I thaught I'd post this alternative use of it,

 

“EVALUATION OF TIMBERFISH’S PROPRIETARY SYSTEM FOR PRODUCING FISH USING WOOD CHIPS AT THE CONSERVATION FUNDâ€

http://timberfishtech.com/sites/timberfishtech.com/files/pdf/FWI%20Timberfish%20Final%20Report%20-%207%2026%202011.pdf

 

Cheers

 

 

cheers

crsublette likes this

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Wow thanks Ande, that was a great read, and shows good practical use of woodchips. I'm wondering if plants would grow in the woodchip trickle filter? And also if whether you have an mbbr in the system, whether the nitrates would rise. Ie do woodchip filters draw down nitrates as well as ammonia. The paper didn't really focus on how much nitrogen was immobilised compared to being gassed off through denitrification, though hypothesised the anaerobic denitrification was low.

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Hi Matt,

 

Filtration that produces a value-added by-product in the form of wood chips that have been inoculated with nitrogen is a very useful thing.  

 

We're only working with the tip of the iceberg here.  

 

Wood chips that are pasteurised (and subsequently inoculated with the appropriate spores) can be used as substrate for growing fungi.....and then used for growing soil.  Or the wood chips can be dried and used for fuel.

 

Gary

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This gives a figure of 

 

60 mg of nitrogen per litre of mix per week for a 'lousy' potting mix, though maybe a good filter material!

 

http://archive.agric.wa.gov.au/objtwr/imported_assets/content/hort/flor/cp/fn2007_pottingfertfinal2_areid.pdf?noicon

 

reminds me of the stuff VelaCreations was doing on fungal filters.....

Edited by mattyoga (see edit history)

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...Altough this suggests that if the filter is kept aerobic, then nitrates will increase.  I'm struggling to find a way of sequestering the nitrate.  Wheres a chemo/microbiologist when you need one!

 

http://www.chesapeake.org/stac/presentations/63_Ruane%20E%20et%20al_2011_On%20farm%20treatment%20of%20dairy%20soiled%20water%20using%20aerobic%20woodchip%20filters.pdf

 

Looks like woodchip filter can certainly be used to trap solids, and also as a biofilter medium, though not sure how to go about stripping nitrates out, other than by plant usage rather than sequestering/stabilising it for later usage.

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This suggest that Nitrate can only be 

 

immobilized by being used in microorganisms

used in plants

or denitrified

 

http://nmsp.cals.cornell.edu/publications/factsheets/factsheet2.pdf

 

So I could only hope to lower it by one of these methods, and only uptake by plants offers the potential for long term stabilization.  Unless you can utilize a system where the microbes grown (NO3 immobilised) are routinely dispersed to soil growing areas where they are then mineralised for plant use.  Would this reduce nitrate leaching into groundwater or would they all just die and get mineralised and converted back to nitrate straight away? If so I may as well just water the garden with my fish water direct!  

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Hi Matt,

 

If the end result of using a wood chip filter is that you end up with degraded wood chips (AKA potting soil), that's got to be a useful outcome, does it not?

 

Gary

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You're right Gary. What i'm stuggling with is the undesatnding of the mass flow behind it - Ultimately if I could derive a composted product that contained humates then I would have succseeded in stabilising some nitrigen and carbon.  Though I've not found any references that explain how this process happens and whether nitrates can be converted to humates.

 

Theres two themes in this thread at present

1. using wood chip filters to capture and mineralise solid wastes out of the fish/plant loop

2. using wood filters in the loop as a fines filter and possibly a method of reducing nitrates

 

Point 1 seems fairly straight forward - just dump solid rich water from a RFF into a pile of wood chips and wack some worms in  (there'll probably turn up to the party anyhow!)

 

Point 2 - Ultimately you're right, it will result in composted wood chips, I'm just not sure if it will help reduce nitrates or fines for that matter.   Guess it might just be a case of try it and see....There is definitely enough citations showing the use of woodchips as biofilters and mechanical filters, so as long as they stay aerobic they should not do any harm.

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Thanks Swede, Funnily enough I've been trying to source Vetiver just as a green mulch crop for my fruit trees, though its hard to find here.

 

If I could grow more plants hydroponically I'd grow stuff to eat.  My issue is lack of space for hyrdo growing and excess nitrates due to more fish than plants...and I've got 10m3 of woodchips to play with!

 

However, it may be good to plant around the fruit trees and mop up any excess nitrates going into the ground from the excess AP water I water them with!

TheDictator likes this

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Why not use vertiver grass grow hydroponicaly harvest and compost for soil garden. Keep wood chips for mulch.

 

Why not do both?  Use the tree mulch to capture the solids and the nitrogen (and other nutrients) to grow the vetiver grass.

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The only drawback I can see with the woodchips is the buildup of tannins or tannic acid. I don't currently know the numbers as to whether it is a real issue or not.

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I don't think they should be an issue - I've not found it to be an issue with Earthan beds, and the timberfish example that Ande posted was also ok.

 

I'm going to try a pilot setup in my system run pretty much as a dutch bucket with woodchips in and stick a tomato in there to see what happens :)  Only issue is its the wrong time of year for toms - will have to use  a winter gross feeder like broccoli...  The dutch bucket appeals as if I have a bucket within bucket insert I can just take the whole lot out, tip it on the compost heap and start again :)

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Hi Ravnis

The only drawback I can see with the woodchips is the buildup of tannins or tannic acid. I don't currently know the numbers as to whether it is a real issue or not.

I think light tannins "dis cooloration" can be good to some exctent, for surtan species as a anti-stressor

Tannic acids may be a different matter, I would avoid oak/walnut/cherry woodchips

 

cheers

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"Implementing Fungal Cultivation in Bio-Filtration Systems - The Past, Present and Future of Mycofiltration" by Alex Taylor and Paul Stamets has some useful information about the use of wood chips in filtration.....particularly once it's been inoculated by mycrozial fungi.

Edited by Gary Donaldson
Broken link fixed (see edit history)

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I wonder how luke boshier experiments did in the long run, he  and velacreations were working on something like that.

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Yeah I read that post recently - seemed to be working ok, though the thread died.  Would be awesome to get more yield in the form of oyster mushies....

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So I've done some experimentation

 

1)  woodchips in dutch buckets with low solid loading rates.... toms did not go very happy, though eggplant did for some reason.  So plants can grow in them, though I think the media can just get too wet for them - course chips better.

 

2) woodchips in shopping basket as fines filter in RAS.  worked ok, though fungus knat or some other little flying thing would breed up and come out into the RAS water causing lots of dead small gnats in the water.  Did clear the water up quite well.

 

3) woochips/coir mix as filter from min tank to plant loop - got clogged up and wood overflow - coir bogs down the hydro conductivity too much.  

 

I plan to try replacing my minerailisation tank with a 100L wood chip filter.  To this end I wanted to see what sort of ratios were required to get the sweet spot of 30:1 CN ratio.   Here are my figures:

 

wood chips CN ratio = 400:1

fish poo CN ratio = 10:1

hence need 20x more fish poo than wood chips to get CN of 30:1 average.  i.e 1 kg of woodchips will take 20kg of fish poo to get to a CN ratio of 30:1.  and 20kg of fish poo would take about 60kg of fish food (assuming they poop out 33% of what they eat).  I would probably err on the side of caution and half those figure, though it does show that 10kg of woodchips could handle a fair amount of fish solids IF well mixed.  bottom line a 100L wood chip filter should be able to handle at least 3 months of fish feed before I change it.  I like that kind of low maintenance intervention.

 

I've got some oyster mushroom spawns running now, so will start to experiement with that soon.  I think a myco filter will be far more effective at removing fines.

ande likes this

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could also make BIOCHAR out of the wood chips with Top-lit updraft kiln (TLUD)

 

high resale value as well 

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