Design Review Package for Vermicomposting Machine

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Juliana Daniels
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1 Design Review Package for Vermicomposting Machine Dalhousie University Mechanical Engineering Department Final Year Design Project By: Joanna Check, Willow Sereda-Meichel, Lai-Shun Man, and Evan Macadam

2 Contents 1. Scope and Requirements Vermicomposting Research Summary Existing Vermicomposting systems High Risk Elements Preliminary Sketches... 11

3 1. Scope and Requirements Scope: The scope of this project entails designing a vermicomposting machine to be used by the Municipality of the District Chester for the purpose of composting their approximate 4.5 tonne/day of organic waste. The vermicomposting machine to be designed shall have a single point input and single point output and be a continuous process. It shall be designed to be used in a fixed location. The pre-processing of the organic waste entering the vermicomposting machine will be outside of the scope of this project. As such, for the design of this vermicomposting machine it will be assumed that the organic waste entering the machine has been ground to approximately but not less than 5 mm pieces and pre-composted for approximately 9 days. Requirement Procedure for Verification Date 1. The vermicomposting machine shall use a specified organic input to output vermicompost. - A known mass of the specified input will be added to a simple vermicomposting container with a known mass of worms. The container will be observed and the amount of time taken to fully compost the waste will be determined. This time will be proven to be less than or equal to the time that a given mass will be in the designed vermicomposting machine before it is outputted. -In addition, a known mass of the specified input will be added to a simple vermicomposting container with a known mass of worms. A known mass will be added to the prototype vermicomposting machine with a known mass of worms. After a given number of days the contents of the container and the contents of the vermicomposting machine will be analyzed and compared to prove they contain an equal ratio of vermicompost to un-composted materials. 10/23/2013

4 2. The full scale system shall be capable of processing 4.5 tonnes/day of organic waste. -The prototype will be scaled using consumption rates determined through stationary/control bin testing. When prototype build complete, the same population of worms and feedstock will be added to the prototype and the control bin. The prototype and control will be allowed to process for a given number of days. After the test period, the contents of each bin will be removed and examined to determine ratio of un-composted material to castings. If the ratio is the same for the prototype and control, the test will be considered 'successful'. This will be considered suitable proof of concept for the processing capacity of the full system. 10/23/ The environment inside the vermicomposting machine should optimize the vermicomposting process. -The temperature, ph level, and moisture content inside the built prototype will be measured and shown to be within the known range of these optimal values for the species of worms used. 10/23/2013

5 2. Vermicomposting Research Summary Benefits of Vermicomposting: Vermicomposting dramatically increases time between treatment and end use compared to composting (Recycled Organics Unit Inc., 2007, p. 9) Vermicompost is a better fertilizer than standard composting due to the worms adding microflora, enzymes, and hormones that are beneficial to plants (Tanseem, Gajalakshmi, & Abbasi, 2008, p. 180) How Vermicomposting Works: Worms cannot bite or chew, rely on the decomposition of organic matter by microorganisms before they can ingest the softened material along with the micro-organisms (Recycled Organics Unit Inc., 2007) Worms add beneficial micro-organisms and fine organic residuals to the soil which increase the decomposition rate and allows further ingestion of micro-organisms by worms (Recycled Organics Unit Inc., 2007, p. 15) Worms usually deposit their castings at top of the vermireactor contents (Tanseem, Gajalakshmi, & Abbasi, 2008, p. 180) Longest period that worms usually need to generate vermicompost from any substrate is 24 hours, harvesting vermicomposting could be done more frequently than existing continuous processes which take at least one month (Tanseem, Gajalakshmi, & Abbasi, 2008, p. 180) Output of vermicomposting is generally 10% to 50% of the weight of the input (Munroe, p. 15) Optimal Worm Conditions: Temperature of vermicomposting system should be between 15 C and 25 C with the general optimum condition generally considered to be 20 C. Constant temperatures above 30 C are deadly for all earthworm species (Recycled Organics Unit Inc., 2007, p. 26) 80% moisture level is recommended when using a mixture of worm species (Recycled Organics Unit Inc., 2007, p. 26) Vermicomposting is an aerobic process, studies recommend tossing to loosen and aerate the bedding substrate without inverting materials so that fresh waste materials are not buried (Recycled Organics Unit Inc., 2007, p. 28) If organic waste ground too finely (less than 5mm) it is difficult to maintain aerobic conditions (Recycled Organics Unit Inc., 2007, p. 30) Rapidly self-degrading waste such as food should be composted before vermicomposting as it requires a large intake of oxygen which could create anaerobic conditions in substrate (Tanseem, Gajalakshmi, & Abbasi, 2008, p. 181) Pre-processing food wastes for size reduction and blending with carbonaceous bulking agents will increase the performance of vermicomposting systems (Recycled Organics Unit Inc., 2007, p. 45) Ideally optimize worm density and surface to volume ratio of vermireactor (Tanseem, Gajalakshmi, & Abbasi, 2008, p. 181) One study showed a feeding rate of 0.75 kg of feed per kg of worm per day resulted in the most completely digested vermicompost (Ndegwa, Thompson, & Das, 2000, p. 11)

6 Works Cited Munroe, G. (n.d.). Manual of on-farm vermicomposting and vermiculture. Organic Agriculture Centre of Canada. Ndegwa, P., Thompson, S., & Das, K. (2000). Effects of stocking density and feeding rate on vermicomposting of biosolids. Bioresource Technology. Recycled Organics Unit Inc. (2007). Literature review of worm in waste management. Sydney Australia. Tanseem, A., Gajalakshmi, S., & Abbasi, S. (2008). Towards modeling and design of vermicomposting systems: Mechanisms of composting/vermicomposting and their implications. Indian Journal of Biotechnology.

3. Existing Vermicomposting systems Batching: -common household design -feedstock is added to batches on rotating basis -worm castings manually sorted Windrow: -long piles of feedstock with worms

7 3. Existing Vermicomposting systems Batching: -common household design -feedstock is added to batches on rotating basis -worm castings manually sorted Windrow: -long piles of feedstock with worms added -modified wedge system adds feedstock to one end while collecting castings from the other -multiple location for input -manually intensive collecting Stacking: -stacked trays with feed added to top most tray -worms naturally move up to feedstock and bottom tray consisting of casting removed -currently tray rotation is done manually Figure 1 Continuous flow: -long raised containers with mesh floor -feedstock evenly distributed across top of containers -castings harvest from below mesh containers -distribution and collection -Existing facility at Vermigrand:

Figure 2 http://www.naturimgarten.at/sites/default/files/styles/einspaltig/public/spalte1/regenwurmfarm_vermigrand.

8 Figure 2 -Existing patent (WO ) APPARATUS AND METHOD FOR ON-SITE VERMICOMPOSTING ORGANIC WASTE: Figure 3 A4A1A098949E0EF8829.wapp1

9 4. High Risk Elements Risk Element Possible Risk Mitigation Methods Worm Sensitivity: Response of worms to auger Low rotation rate rotation Sensitivity to temperature Pre-composting ensures thermophilic bacterial action occurs outside worm chamber Layer ground material incrementally in worm chamber to ensure composting due to worm action rather than thermophile action Measure and control temperature Sensitivity to ph Pre-grinding to ensure homogenization of feedstock Pre-composting to homogenize Add castings to feedstock Sensitivity to content of feedstock Pre-sorting to remove contaminants (i.e. noncompostable materials, heavy metals, glass) Pre-grinding to ensure undesirable feed (ex. Onion) is distributed in small amounts throughout feedstock so as not to shock or kill worms Sensitive to moisture content Pre-composting and pre-grinding to homogenize mixture Pre-compost in open aired area so evaporation possible Measure moisture content Mix contents to ensure moisture distributed throughout worm chamber (from top-tobottom) Include drain to remove excess water built up at bottom of chamber Angle chamber slightly to allow drainage Worm movement: Possibility of worms in output Design chamber long enough to ensure worms move out of castings into feeding area Alternately reintroduce worms either after harvesting or with castings Mechanical Challenges: Mechanical Challenge of slow rotation Rather than continuous rotation of auger at 1-2 rev/day, operate for 1 hour at 1 rev/hour every 12 hours.

10 Measurements in container with auger Take incremental measurements during times when auger stopped, i.e. automated insertion of probe

11 5. Preliminary Sketches

Compost Quality Best Management Practices. Athena Lee Bradley Northeast Recycling Council, Inc.

Compost Quality Best Management Practices Athena Lee Bradley What is Compost? Value-added product: converts waste material to easy-to-handle, useful product. Soil-like material, rich in organic matter