Small scale FOOD/Kitchen Waste
On – Site Treatment Units (Reactors)
A. Review
Prepared by A. Brazas, July 2014
1
8th
July, 2014
I think that everyone involved in Food Waste Recycling business should have
understanding what there are ...
2
2) LIQUID Food DIGESTORS / Wet BIOREACTORS/ BIO-LIQUEFACTION
machines – water adding and biological liquefaction process...
3
Please, look „Regarding the Environmental Efficacy of Food Waste Disposers. Summary
prepared by: Michael Gitter, P.E. Se...
4
3) COMPOSTERS / DECOMPOSERS – real composting machines: biological
(aerobic digestion - composting) process occure, and ...
5
 Autothermal Thermophilic Aerobic Digestion (ATAD) process it
is well known technology, which is widely used for sewage...
6
ECO-Wiz®
Dry System work with a microbial additive that is specially
designed and produced.
This additive contains a pow...
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Food/kitchen Waste On-site Composters, Bio-liquefactors, Disposers, Dewaterers, Dehydrators, ATAD systems. A Review, A. Brazas, Jyly 2014

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Presented information about Food/kitchen Waste On-site Composters (composting machines), Bio-liquefaction machines, Disposers (Grinders/Shredders), Dewaterers, Dehydrators-dryers, ATAD machines, and information about Compost Bio-stability and Maturity.

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Food/kitchen Waste On-site Composters, Bio-liquefactors, Disposers, Dewaterers, Dehydrators, ATAD systems. A Review, A. Brazas, Jyly 2014

  1. 1. Small scale FOOD/Kitchen Waste On – Site Treatment Units (Reactors) A. Review Prepared by A. Brazas, July 2014
  2. 2. 1 8th July, 2014 I think that everyone involved in Food Waste Recycling business should have understanding what there are differences between: 1) DEHYDRATORS / DRYERS, very often so-called „high-speed composting machines“, but using heaters/boilers for biomass heating(?!)) 2) LIQUID Food DIGESTORS / Wet BIOREACTORS / BIO-LIFUEFACTION machines and Food/kitchen waste DISPOSERS 3) Real COMPOSTERS / DECOMPOSERS - composting machines (BIOSTABILISATORS) and ATAD (Autothermal Thermophilic Aerobic Digestion) machines Small scale FOOD/Kitchen Waste On – Site Treatment Units (reactors): 1) DEHYDRATORS / DRYERS – physical process of heating and dehydration dominate, and biological – composting process presence only as secondary (accessory). Manufacturers and/or equipment name: GAIA corp., EcoVim, Somat, BioGreen360 (dry), and also ERS-machine, Hungry Giant, Oklin International (Green Good), Biomax RTDS (Biomax International Pte Ltd) and many others - who there are advertising its as so-called „high-speed composting machines“. In the Dehydrators / Dryers biological process does not occur in practice (well, it only happens at the very beginning, a couple of hours after load of food waste - then food waste (biomass) become too dry and the composting process is interrupted (optimum moisture content for composting should be 50-60%)). Heating of biomass to > 70 °C (and often at a higher temperature) kill all thermophilic bacteria from exponentially grew (at operating temperature of 40-65 °C) and the resulting destruction of (produced) enzymes... Conclusion - actually in the dehydrators / dryers going on (obviously dominates) only physical drying process. Therefore, a "product" can’t possibly be a bio- stable (biologically degraded - decomposed (rotten)). Also this “product” couldn’t be mature (non-toxic for plans and/or soil microbes. This is by no means the compost. In addition, Dehydrators / Dryers big disadvantage - an expensive operation (due to heating, etc.). Also Dehydrators / Dryers there are expensive, and exist a number of cheaper Food/Kitchen Waste Dewaterers... (?!) The apparatus advantage over the other 2 (4) types of machines - that it is possible to produce feed for animals!
  3. 3. 2 2) LIQUID Food DIGESTORS / Wet BIOREACTORS/ BIO-LIQUEFACTION machines – water adding and biological liquefaction process (very often in anaerobic conditions – microbial hydrolysis / anaerobic fermentation) occure. Manufacturers and/or equipment name: Eco-Save Digestor (Bio Hitech America), EnviroPure (EPW), ECO-Wiz® Wet System, BioGreen360 (wet), Green Key biodigestor, Power Knot, ORCA GreenTM Machine (Totally Green), ecoWater digester (Greentail Invironmental Inc.), Tidy Planet and others. In the liquefied (by adding water) food / kitchen waste bioreactors (liquid digesters)/ Liquefication machines (actually going microbial hydrolysis / anaerobic fermentation machines) the good/kitchen waste is converted into a variety of liquids (grey water) after all spent down the drain! A result an increased loadings of BOD, and TSS to the WWTP, increased loads of organic carbon that reaches water treatment plant, which in turn increases the consumption of oxygen. Also what to buy these expensive machines, if there are various cheap food / kitchen waste Disposers (Macerators, Grinders/Shredders) positioned just under the sink?  DISPOSERS of Food/kitchen waste Manufacturers and/or equipment name: IMC Ltd., InSinkErator, Fowex, EcoFast, Disperator and others, and a dozen of China and South Korea companies. A food/kitchen waste disposal unit is a device, usually electrically powered, installed under a kitchen sink between the sink's drain and the trap which shreds food waste into pieces small enough—generally less than 2 mm —to pass through plumbing. Food/kitchen waste disposers are widely used in North American households, but far less commonly used elsewhere. The most common argument against food waste disposers is that the capacity of WWTPs is not sufficient. Yes, wide using of Food/kitchen waste disposers increased loadings of BOD and TSS to the WWTP. Food/kitchen waste disposal units increase the load of organic carbon that reaches water treatment plant, which in turn increases the consumption of oxygen. A result od disposers using - increased energy consumption for both disposer use and WWTP aeration. The most common conclussion made that in order to allow the use of food/kitchen waste disposers and also food/kitchen waste liquefaction machines - in particular, should be reconstructed wastewater treatment facilities ... Is it true?
  4. 4. 3 Please, look „Regarding the Environmental Efficacy of Food Waste Disposers. Summary prepared by: Michael Gitter, P.E. Senior Environmental Engineer, InSinkErator. Last revised: October 27, 2006“ (remark - and a number of other reports prepared). The main conclusions of this summary report:  Food Waste Disposer (FWD) Life Cycle Analysis show that the FWD/WWTP has the lowest municipality cost (system cost due to disposer cost, which is paid by the homeowner); least air emissions; converts food waste to a recycled resource; is the most convenient system of food waste disposal; is the most likely system for organic source separation; and overall is the most environmentally friendly and sustainable option.  Reduced (food waste) transportation emissions and costs.  As food waste is 60-70% water, the WWTP is a more natural system of Waste processing than hauling the waste to a “solid waste” facility.  The effect of disposers on WWTP processes is very limited.  Additional average pollutant loading due to disposer use is 66 g/person/day BOD, 60 g/person/day TSS, 2.1 g/person/day TKN, 0.3 g/person/day P, and 2.5-5% biosolids.  Up to a 15% disposer market share, the use of disposers in multi-unit dwellings would have a very small impact on sewage treatment systems.  No operational problems are expected for market levels up to 15% in regard to BOD and O&G loadings, or up to 20% market for additional TSS loadings.  At a 15-20% disposer market share, loadings do not result in significant variations in the characteristics of sewage. At a 25% disposer market share, influent BOD would increase 12%, TKN and P would increase 2%. At a 20-35% disposer market share, an increased WWTP system energy consumption is observed due to greater respiration of the active biomass and a larger production of excess biosolids. Beyond a 35-40% disposer market share, additional works must be done at the WWTP. Beyond this figure are increasing impacts, with potentially significant impacts at a 50% market share.  However, this level of market share is unlikely in the near future. European Union (EU) market levels will not exceed 15% in 25-30 years, thus, normal WWTP upgrades will allow for an accommodation of increased disposer loading.  The additional soluble food waste fraction will lead to higher BOD/COD loading within the biological treatment steps, which on one hand will cause a higher oxygen demand, but on the other can serve as a cheap and continuously available carbon source (for nutrient reduction).  The food waste disposer has to be considered an addition rather than a competitor to the current system for the collection of kitchen, food, and garden waste.
  5. 5. 4 3) COMPOSTERS / DECOMPOSERS – real composting machines: biological (aerobic digestion - composting) process occure, and per long time mix of food/kitchen wastes + structural C rich materials become BIO-STABILE. Manufacturers and/or equipment name: JORAform, HotRot, Rocket, Rotoposter, Big Hanna, CITYPOD (Vertal, Inc.), AEL TUBES, Biovator, Eco Values Technology, XACT systems and others. On-site (home) Composting has the smallest environmental impacts, and On-site Composting is the least expensive option for multi-unit residents. Short remarks concerning BIOSTABILITY and MATURITY, and etc. I don't like to be involved into discussions about microbiology of these processes, because I am engineer, and because microbiology isn't a subject of this discussion. For me it is clear that if process of decomposing (decay, rotting) / composting – biostabilisation happen (expired), microorganisms have nothing to eat, and they die (intense biological processes stops held, and bio-waste turned into bio-stabile product COMPOST. Generally it is considered that this is already occurring when the Static Respiration Index (AT4 or BOD4) is < 10 mg O2 / g DM or Dynamic Respiration Index (DRI) < 1000 mg 02/ kg VS / hour. Moisture of compost isn't very important. Whether the compost will be wetter or drier - intensive biological processes will still be ended... Meanwhile, after the dehydration / drying obtained "product" is not a bio-stable. We're just getting him humidity and under favorable temperatures - biological processes begins again be intense.... This is because this "product" is full of food (nutrients) for microbes - because in reality no decay / rotting (decomposing) process happened during dehydration / drying. Composting - a biological decomposition of organic matter (biodegradation) in controlled aerobic conditions caused by rapidly multiplying organisms (microbes and also soil invertebrates, and protozoa), which generates heat and to form water, carbon dioxide and mineral nitrogen compounds - organic matter is stabilized (mineralized and partly humificated) - produced humus enriched with organic compost product. The process of MINERALIZATION (ammonification and nitrification) - organic nitrogen compounds transformation in mineral under the influence of micro-organisms it is very important. MATURITY is the main condition for describing the usability of compost - compost is mature when it becomes non-toxic for plants, i.e. when it never (no longer) contain toxic compounds for plants and / or microbes or these are negligibly small, as phytotoxic compounds and microbes inhibits plant growth. And I'm not sure what to have add something more...
  6. 6. 5  Autothermal Thermophilic Aerobic Digestion (ATAD) process it is well known technology, which is widely used for sewage sludges (biosolids) treatment. Autothermal means Self-heating or Exothermic process (but all Composting processes there are Exothermic (i.e. Self-heating)). Now it is used so named 2nd generation ATAD technologies - usually using 2 stages ATAD process: 1st sage from 40 °C up to 60 °C temperatures, and 2nd stage up to 75+ °C temperatures (so named hyper - thermophilic process, when act hyper – thermophilic microbes). Normally process takes from a few days up to 2 weeks. It is well known Fuchs ATAD process, and VERTAD™ (Noram Engineering and Constructors Ltd) process, and exist also a few other companies supplying this technology. ThermAer ™ 2 stages process state that 24 hours there are enough (?). The same ATAD process principles there are used for food/kitchen waste treatment. The key element - very intensive mixing inside reactors. There exist a number of so-called „high-speed composting machines“ (which never use heaters / boilers for biomass heating) most probaly using some version of ATAD process : EcoHERO digester (ASM Organic Recyclates), EnviroPure (EPD), ECO-Wiz® Dry System, Biotel ATAD unit and other. Many (but not all) of these „high- speed composting machines“ require enzymes to speed up the rate of the fermentation process. The cost of these enzymes is normally high. EcoHERO digester (ASM Organic Recyclates and Greentail Environmental Inc. - ecoOrganic™) never use expensive enzymes or chemical additives to accelerate the process, and converts food waste into organic fertiliser in 3 days. EnviroPure (EPD) systems use EP BioMix™, a proprietary blend of all natural organic nutrients. These nutrients are utilized by the naturally occurring bacteria present in the food waste to increase the metabolic efficiency and accelerate the biochemical reactions involved in the de- composition process. EnviroPure (EPD) systems general turnaround time for producing ferlilizers from food waste is between 24-48 hours.
  7. 7. 6 ECO-Wiz® Dry System work with a microbial additive that is specially designed and produced. This additive contains a powdered blend of organisms blended with crude enzymes and emulsifiers specifically designed to digest and deodorise organic wastes. Eco-Wiz® Dry System uses a natural process to decompose food waste at the highest speed (most probably per 24 hour). Biotel ATAD (Autogenous Thermophilic Aerobic Digestion) technology unit (PMA Biotel Ltd.) state that 24 hours it is enough to digest food/kitchen waste never using enzymes and to produce high quality organic fertilizers. But I always there are asking „high-speed composting machines“ suppliers - what it is a bio-stability of "product" made? Is it really bio-stable and mature product - compost - or not? Short remarks concerning BIO-DRYING process It seems that Bio-drying pricess presence in these ATAD machine, and also in DEHYDRATORS/dryers. Biodrying (autothermal drying process) is the process by which biodegradable waste is rapidly heated through initial stages of composting to remove moisture from a bio- waste stream and hence reduce its overall weight. In biodrying processes, the drying rates are augmented by biological heat in addition to forced aeration. This heat generation assists in reducing the moisture content of the biomass without the need for supplementary fossil fuels, and with minimal electricity consumption. But biodrying does not however greatly affect the biodegradability of the bio-waste and hence is not bio-stabilised. Biodried bio-waste will still continue to be (stay) non bio-stable, i.e. potentially biodegradable… Prepared by Alfonsas Brazas -------------------------- Managing Director Atlieku tvarkymo konsultantai, UAB P. Luksio str. 7, LT-08221, Vilnius, LITHUANIA E-mail: a.brazas@zebra.lt, atk@zebra.lt Skype a.brazas Mobile: +370 687 76633 ___________________

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