Talk:Bokashi anaerobic digestion: Difference between revisions

Bran mix[edit source]

Latest comment: 15 years ago2 comments2 people in discussion

What is the bran mix in the photo? Can we make our own, or just use dry leaves? --Chriswaterguy 17:10, 10 December 2008 (UTC)Reply[reply]

I don't know about dry leaves, I think you need the microorganism thingys. But it seems like you can make your own: http://au.youtube.com/watch?v=96fSXccQx9Q (of course this is probably not very likely if you live in an apartment, but maybe a friend on a farm/large block can help you). --pfctdayelise 00:32, 11 December 2008 (UTC)Reply[reply]

The bran mix appears to be an innoculant containing dormant micro-detritivores. See wikipedia:Bokashi composting#Bokashi composting. I accomplish something similar by shoveling old compost on top of fresh leaves, brush, kitchen scraps, etc. in my outdoor compost. A pile of untreated fresh leaves and brush takes longer to break down, because microorganisms have to penetrate the pile before they can eat it. Getting through a few feet of material is probably a long journey for something that is too small for humans to see. Airborne spores will do the trick naturally, but more slowly. I'd guess a bucket of finished backyard compost would make a great bokashi starter, just as it makes a great backyard compost innoculant, although I have not tried any indoor composting methods. My house is on a small lot but I found enough room to handle all my leaves, the leaves from three of my neighbors, my hedge trimmings, the ten Christmas trees I saved from landfill last month, etc. --Teratornis 15:13, 7 February 2011 (PST)

Life cycle analysis needed[edit source]

The article says bokashi "is also a powerful carbon sink, since the method produces no greenhouse gases and can be scaled to sequester large amounts of carbon."

• What does "powerful" mean? It seems the maximum carbon sequestration could not exceed the carbon content of the feedstock (food scraps, etc.). The carbon content of food waste produced by the average resident of a country like the US will typically be a small fraction of that person's carbon footprint. For example, simply burning all of one's food waste would provide nowhere close to the amount of house heat consumed in winter by the average person on my street. A life cycle analysis^W is necessary to determine the overall carbon impact of a particular implementation of bokashi or any other composting method. This is not to say composting is not a good idea. Between composting and recycling, I hardly produce any household waste now (just a small bag every two or three months of non-compostables and non-recyclables). That would reduce trash hauling and landfill space problems if everybody did likewise.
  • I have not yet found a rigorous LCA comparison between composting and biochar^W for carbon sequestration, other than claims that biochar can lock away up to half of feedstock carbon in soil for centuries to millennia. How recalcitrant is the carbon content of compost from say a tonne of leaves, compared to the biochar from a tonne of leaves?
• All composting methods emit greenhouse gases, although they have the potential to not be net emitters. All the emitted carbon was recently captured from the atmosphere by plants, and thus is part of the non-accumulating natural carbon cycle.^W The carbon released by my decaying pile of leaves will be taken up by the trees in the following season as they grow new leaves. Controlled aerobic composting methods (e.g. bokashi, vermicomposting, backyard composting) have a significant advantage over landfilling the waste as the aerobic methods do not produce the same amount of fugitive methane i.e. landfill gas.^W Some landfill sites capture some of their landfill gas and burn it as fuel, or simply flare it. Burning the methane is much better than letting it reach the atmosphere because methane is a highly potent (although fairly short-lived) greenhouse gas. Domestic composting also eliminates fuel consumption from hauling the waste to a central facility. To say bokashi "produces no greenhouse gases" is not completely true; a more precise wording would be bokashi produces very little or no cumulative greenhouse gases. (Global warming is a problem because man's burning of fossil fuels and clearing of forests adds large volumes of extra carbon to the carbon cycle, which cannot be removed quickly by natural carbon sinks which are normally in rough balance with natural carbon emissions. Unless humans augment the natural carbon sinks with artificial carbon sinks, such as biochar schemes, our carbon emissions will hang around in the atmosphere for thousands of years to come.)

--Teratornis 15:43, 7 February 2011 (PST)

point taken, i just adjusted the wording of my original statement --Brunov25 19:22, 7 February 2011 (PST)

Thanks. Sorry about the wall of text there. But it's mostly true I think. I googled and found the Internal Journal of Life Cycle Assessment which has some papers evaluating compost schemes. I'll read them eventually. There are a lot of non-rigorous claims floating around about various aspects of green lifestyle, and it's good to quantify things when possible. --Teratornis 22:08, 7 February 2011 (PST)

Notes of caution[edit source]

I am tagging this page as containing information that should be taken with caution. There is certainly not a scientific consensus on the effectiveness of this process, I will return at some point and add some of the (rather few in number) studies in the scientific literature which both supports and denies the efficacy of Bokashi to this article. As a general point, anaerobic conditions are generally supportive of more harmful pathogenic microbes than aerobic ones, hence for effective breakdown, aerobic conditions are normally advised. Even where anaerobic digesters are used, they need to be monitored and managed carefully. The idea that you could have an anaerobic digester on a kitchen surface which is effective enough to safely digest meat fragments is a myth, as far as I am concerned. I am happy to debate this though, if you know of proof that this thing works, let's hear about it. Joeturner 13:24, 7 February 2013 (PST)

hi Joe: I don't recall seeing any claims that meat gets digested with kitchen counter bokashi. All that is/should be claimed is that meat is fermented sufficiently as to not smell putrid until it gets processed outside the kitchen (in compost or buried in soil) --Brunov25 20:17, 7 February 2013 (PST)

I thanks for the quick reply. Do you have evidence of that claim? Surely the whole point of this thing is to produce a safe, effective substance that can be used as garden fertiliser. What other point is there? The processing of animal byproducts is a major concern of many composting regimes around the world, we should not muddy the issue by making claims of this technology, in my opinion. Meat byproducts cannot be processed safely at home, IMO. Joeturner 00:24, 8 February 2013 (PST)

Joe: Are you asking me to provide evidence that microbes in EM, or whey or kombutcha or apple cider vinegar will prevent meat from putrefying in a box inside a kitchen? That is the only claim I make. As far as I can tell, this page does not muddy waters :-) You seem to be looking for a place to debate whether meat byproducts can be processed safely at home. Although, this page does not deal with this topic, it makes me think about all those who have been and continue to make sausages at home for generations. --Brunov25 08:28, 8 February 2013 (PST)

Bruno, I suggest you edit the page, which currently reads as follows: "Bokashi anaerobic digestion is a method of anaerobic digestion to prepare almost ANY kitchen waste (incl. carnivorous waste) for composting (incl. directly into the earth)" I'm not questioning what you think or believe, I'm asking for evidence of what the page claims. Joeturner 08:35, 8 February 2013 (PST)

Joe, I am not making any claims in that line ... I am simply describing a method named "bokashi" for processing kitchen waste (in contrast to putting it in the garbage, or directly into the compost). My municipality now picks up kitchen waste (including of animal origin) at the curbside in order to process it using some sort of patented anaerobic process with the final product sold back to landscapers as finished compost. I still prefer to use bokashi in order to skip the middle man :-) I can see this means a lot to you... what I cannot see is exactly what bothers you. Are you worried about people getting fooled into spending lots of money on bokashi when it might not significantly improve their gardens? Bokashi is $10/kg commercially, and $1/kg when one makes it. A 1 kg bag lasts for about 2 months in my home. --Brunov25 20:43, 8 February 2013 (PST)

Safety[edit source]

Re the question of safety, raised above, if Bokashi is used for animal products. Which aspect of safety do we mean?

• Safe from predators? If it's well broken down before being put into the garden, I'd assume yes.
• Safe for handling with bare hands? I assume no. (Anaerobic digestion implies anaerobic pathogens, which can be nasty). (The original Bokashi might
• Safe for handling with gloves (assuming it's not allowed to dry out, and safe for burying in a hole in the backyard? I assume yes, assuming it's not placed near to the food-producing parts of any plants, and not near the surface.
• Safe to keep in the house? If it's not leaky, and not on a food-preparation surface, and if placing food into it doesn't bring you into direct contact with the anaerobic bacteria, I'd assume yes, but perhaps there isn't as much margin for error as we'd like... that depends partly on just how dangerous those anaerobic bactera are likely to be. Anyway, those criteria mightn't be met, so I'd say it depends.

--Chriswaterguy 20:58, 8 February 2013 (PST)

I don't think there is much evidence that material from a Bokashi is 'well broken down' and hence may not have any meaningful effect on making materials unattractive to vermin.

Handling is an issue, but this is mostly determined by what is exactly going on in the Bokashi reactor. Given there is so little science published on the subject, there is no guarantee that the bran innoculations are actually creating viable communities of anaerobic microbes, therefore it is not possible to state the danger level. If we are assuming that an anaerobic digestion situation has been established, then yes, it is a potential risk, depending on the materials that have been put into it. Anaerobic pathogens could be transfered to humans by hand, from splashing onto the kitchentop, possibly from inhaling spores etc. If the materials used are only vegetable in origin, the risks should be pretty low, but they increase when animal byproducts have been added to the mix.

Safety in the garden should be a negligible risk, but again determined by the contents of the reactor. Generally speaking, if you are using meat byproducts, you'll not want to spread the materials onto anything you are going to eat directly (cabbage leaves, lettice etc), in these scenarios adding it to soil and burying is adds an important barrier to potential infection.

I don't know how people use them in the house, but in my view cultivating any microbes in conditions where they are not being properly monitored (other than perhaps yoghurt) is a very dangerous thing to do. There are deaths and sickness fairly regularly from imperfect canning and bottling operations where the jars have not been properly sterilised and the bugs have been allowed to multiply. Usually, as far as I can tell, this is a problem with potted meats rather than from jam moulds. Joeturner 00:55, 11 February 2013 (PST)

The food waste in a "Bokashi Reactor" is fermented just like cabbage is fermented and turned into sauerkraut. It is anaerobic but the pH is lowered compared to the types of anaerobic situations are you worried about. The lower the pH , the less likely human pathogens will thrive. the EM itself is at ph < 3.6 before the bottle is opened... and it stays that way for weeks (even months) if opened and kept in the fridge. I say this because sometimes I spray EM or equivalent directly on the food waste, bypassing the bran... but adding bran is good because it makes for a better C:N ratio in the finished product.

Ultimately, when we talk about relative risks and likelihoods, without the benefit of proper scientific studies, we have to compare with similar processes. Meat is also routinely fermented for human consumption in low pH mediums with appropriate microbes. We also have access to CDC statistics which can greatly help calm down fears. For those who want to minimize the risks (although we don't yet know if this is significant since no studies have been done on fermented meat safety as a soil amendment), we could recommend not burying fermented food waste containing meat byproducts directly in the food garden... but let's not forget that animals are constantly dying, excreting and shedding parts in garden soil ... it is unavoidable except perhaps in highly controlled hydroponic systems. --Brunov25 12:31, 11 February 2013 (PST)