LA IMPORTANCIA DE LA SANA DOCTRINA 1 Willie Alvarenga

Clive A. Edwards

I INtrODUCtION

The principles behind vermicomposting are relatively simple and related to those involved in traditional thermophilic composting. Certain species of earthworms, termed epigeic species, can consume organic residuals and wastes very rapidly and fragment them into much finer particles by passing them through a grinding gizzard in their mouths, an organ that all earthworms possess (Darwin 1881). The earth- worms derive their nourishment from the microorganisms that grow on the organic materials they consume. At the same time, they promote further microbial activ- ity in the residual wastes so that the fecal material, or “casts,” that they produce is much more fragmented and microbially active than the materials the earthworms consume. During this process, the important plant nutrients in the organic materi- als, particularly N, P, K, and Ca, are released from the organic matter and converted through microbial action into forms that are much more soluble and available to plants than those in the parent compounds.

CONtENtS

I Introduction ... 91 II Manually Operated Systems: Raised Continuous-Flow

Vermicomposting Beds ...93 III Fully Automated Continuous-Flow Vermicomposting Reactor Systems ...94 IV Indian Design of Top-Loading Vermicomposting System ...98 V Complete Urban Waste-Recycling Vermicomposting Systems ...99 VI Earthworm Toilet Systems ...99 VII Economics of Alternative Vermicomposting Systems ... 100 References ... 100

The retention time of the waste in the gut of the earthworm is short. Earthworms can digest several times their own weight each day, and large quantities of organic matter are passed through an average population of earthworms in a vermicompost- ing system so that in a finished vermicompost all of the organic matter has passed through the earthworms (see Chapter 2). In the traditional thermophilic aerobic com- posting process, the organic materials in windrows have to be turned regularly or aerated in some way, usually in containers, to maintain aerobic conditions. This often may involve extensive engineering to process the residual wastes as rapidly as possible on a large scale. In vermicomposting, the earthworms, which can survive only under aerobic conditions, take over the roles of both turning and maintaining the organics in aerobic conditions, thereby lessening much of the need for expen- sive engineering; they have been called “ecological engineers” (Edwards and Bohlen 1996).

The major constraint is that, in contrast to traditional composting (a thermophilic process that can raise temperatures in the waste to more than 70°C (158°F)), vermi- composting is a mesophilic process; vermicomposting systems must be maintained at temperatures below 35°C (95°F). Exposure of the earthworms to temperatures above this, even for relatively short periods, will kill them. Avoiding such overheating requires careful management and addition of wastes in thin, carefully managed layers. Earthworms are active and consume organic materials in a relatively narrow layer of 15–20 cm (6–9 in) below the surface of a compost heap or bed. The key to success- ful vermicomposting lies in adding materials to the surface of piles or beds in thin, successive layers so that any thermophilic-composting heating that occurs does not become excessive. The heating, however, should be managed to maintain the activity of the earthworms at high levels of efficiency. Generally speaking, adding 2.5 cm (1 in) of material to a system every day or two is usually enough, depending on the types of feedstock used in vermicomposting systems.

The processing of organic materials by most epigeic species of earthworms occurs most rapidly at temperatures between 15°C and 25°C (60°F to 79°F) and at moisture contents of 70%–90%. Outside these limits, earthworm activity and productivity, and thus the rate of waste processing, fall off dramatically. For maxi- mum efficiency, the feedstock should be maintained as close to these environ- mental limits as possible, hence should be under cover in a building or insulated plastic tunnel.

Almost any agricultural, urban, or industrial organic waste can be used for vermicomposting, but many may need some form of preprocessing to make them acceptable to earthworms. Such preliminary treatments can involve wash- ing, precomposting, macerating, or mixing. Often, mixtures of several different materials can be processed more readily than individual wastes, and mixtures are usually easier to maintain aerobically and can result in a better, if less standard- ized, product. This is primarily due to the wet and sloppy characteristics of some waste materials, which require the addition of a bulking agent for better handling. Organic cattle, pig, and horse wastes, residuals from the paper industry, food wastes, sewage biosolids, and urban organic wastes are particularly suitable for vermicomposting.

medium- and HigH-teCHnology vermiComPosting systems 93 The traditional smaller-scale methods of vermiculture described and reviewed in Chapters 7 and 24 are mainly based on beds or windrows on the ground containing materials to a depth of about 50 cm (18 in), but such methods have numerous draw- backs. They require large areas of land for large-scale production and are relatively labor-intensive, even when appropriate machinery is used for adding materials to the beds. More important, such systems process organics relatively slowly, taking any- where from 6 to 18 months to completely break them down (see Chapter 7). There is good evidence that a large proportion of the essential plant nutrients, which are in a relatively soluble form, are washed out during such a period. Moreover, a significant proportion of nutrients can volatilize during such a long processing period. Such nutrient losses are undesirable, particularly in relation to groundwater pollution, and result in a poor-quality product.

II MANUALLY OPErAtED SYStEMS: rAISED CONtINUOUS-FLOW VErMICOMPOStING BEDS

It is essential for successful vermicomposting that organic wastes are added to beds or other systems in thin layers 2–3 cm (0.8–1.2 in) frequently to prevent thermo- philic composting from developing (Edwards and Neuhauser 1988; Edwards 2004; Edwards and Arancon 2004). This can be done in beds about 1 m (3 ft) deep and 4–5 m (12–15 ft) wide with floor drainage. However, such systems have to be har- vested when vermicomposting is complete using front-loading or other appropriate mechanical equipment. They will still require a stage of separation of earthworms from the processed organic waste using trommels or comb systems as described in Chapter 7.

The key principle of all efficient earthworm-based, organic-waste-processing systems, whatever their design configuration, is to add small, 1–3 cm (1–1.5 in) lay- ers of semisolid waste (75%–90% moisture content) to the surface of a system daily. This gradual addition of organic matter avoids any overheating developing from a thermophilic phase of composting, although with good management sufficient heat from thermophilic composting can be generated to keep the system operating through colder spells in the winter in colder regions. The system can be managed to keep temperatures in the building or tunnel lower in summer using fans and higher in winter within a range of 18°C–22°C (64–72°F). The earthworms remain active in the aerobic upper 10–15 cm (4–6 in) of waste, taking it through their guts, breaking it down into fine fragments and particles by a grinding gizzard, mixing it, and keep- ing it aerobic. As additional layers of waste are added at daily intervals, earthworms gradually move up vertically through the reactor so that they always remain in the top aerobic 10–15 cm (4–6 in) of the organic waste.

All of the most efficient vermicomposting techniques have used containers raised on legs above the ground. These allow waste feedstock to be added at the top from mobile gantries and be collected mechanically at the bottom through mesh floors using breaker bars to drop it to the floor. Such methods were developed and tested extensively by engineers at the National Institute for Agricultural Engineering,

Silsoe, in collaboration with soil ecologists from Rothamsted Experimental Station in England. The methods they designed ranged from relatively low-technology systems using manual loading and collection to completely automated systems. The fully pro- cessed vermicompost can be collected from the bottom of a system by mechanically releasing the lower levels of vermicompost through a mesh grid, by use of a breaker bar that travels along the length of the reactor, so that it can be collected with no loss of earthworms, which remain in the upper layers of the chamber.

III FULLY AUtOMAtED CONtINUOUS-FLOW VErMICOMPOStING rEACtOr SYStEMS

The full-scale continuous-flow reactor systems designed by Edwards at Rothamsted and colleagues from the National Institute of Agricultural Engineering (Edwards 2004) are 40 m (128 ft) long by 2.4 m (8 ft) wide, built in 2.4 m (8 ft) by 2.4 m (8 ft) modules (Figure 8.1), on a metal frame, with plywood or plastic sides sealed against moisture. The body of the reactor is 1 m (3.2 ft) deep, standing on legs 1 m (3.1 ft) high (Figure 8.2; Edwards 1998), and it must be maintained in a building under cover to control environmental processing conditions. It has a hydraulically winch-driven, gear-operated feed hopper (Figure 8.3) that runs on the rails at the top of the sides of the reactor and can automatically add a thin layer 1–3 cm (1–1.2 in) of waste to the surface of the reactor every 1–2 days in one or more horizontal tran- sit passes. The base of the upper part of the reactor has a metal mesh floor with a 5 cm × 10 cm (2–4 in) mesh aperture. Situated immediately above the perforated floor is an electrically winched breaker bar (Figures 8.4 through 8.6), which can be pulled along the full length of the reactor in either direction. As this bar moves along the length of the reactor, it disturbs the lowest 2.5–5.0 cm (1–2 in) of processed waste to release this layer through the perforated base to the ground. This processed

medium- and HigH-teCHnology vermiComPosting systems 95

waste can then be brought to one end of the reactor daily by a hydraulically driven, reversible scraper dairy-barn-cattle-waste flap-bar system (Figure 8.5) or moving belt. The reactor functions best with an equilibrium loading of about 9 kg.m–2 ₍₂ lb.ft–2_{)of earthworms (Eisenia fetida). A single full-scale reactor of this size, which} has a 30–60-day retention time for the waste to pass from the top to bottom, can pro- cess more than 1000 tons (984 t) of animal, plant, human, or food waste or sewage biosolids per annum or up to 3 tons (3 t) per day depending on the type of waste. If multiple reactors are used, there are considerable economic savings in construction and operation.

Such reactors have operated successfully in the United Kingdom, United States, Hong Kong, and Australia for periods of up to 12 years (Edwards 1998). The eco- nomics of reactor systems is discussed in Chapter 19. The earthworm populations in such reactors tend to reach an equilibrium biomass of about 9 kg.m–2 _{(2 lb. ft}2_),

Earthworms in top 10–15 cm (4–6 in) (a)

Organic waste

Mobile loading gantry Gantry rail track

Gantry winch

Breaker bar winch Hydraulic forward and reverse

Concrete floor Flap collection scraper

Winched breaker bar Raised mesh floor

Vermicompost

Vermicompost

32 m (128 ft) 2 m (6 ft)

Mobile loading gantry (b)

Flanged wheel Track for gantry

Earthworm inoculum Scraper bar

Reactor leg Mesh floor

Flap scraper bar Concrete floor

Direction of vermicompost movement Upright support

which may be attained as a mixed-age population of earthworms. These reactors can process fully the whole 1 m (3 ft) depth of suitable organic wastes that they contain in about 30 to 60 days, depending on the kind of waste being processed (Edwards 1995, 1998). Economic studies have shown that such reactors have a much greater economic potential to produce high-grade plant growth media, with little loss of material through leaching or volatilization, very quickly and much more efficiently than either windrows, wedge systems, or ground beds.

1 m3 _{(1.3 yd}3₎ hopper Trace-type floor High-speed side mounted rotor Travel direction Figure 8.3 gantry feed hopper with full-width rotor.

Side view _{Scraper runs in “U” channel} tracks supported by reactor structure

Reciprocating movement produced by double-acting hydraulic ram and auto shuttle valve

Waste delivered in direction shown on every forward stroke

Folding scraper blades hinged below frame. Hinges unaffected by falling waste Folding scraper blades lift on rearward

movement of scraper frame End view

medium- and HigH-teCHnology vermiComPosting systems 97

Suspended steel mesh floor eg: 6g 75mm mesh on supporting grid 0.6m × 0.8m Idler Cruciform breaker bar

Return chain runs beneath floor Drive sprocket Motor unit Figure 8.5 layout of breaker-bar discharge floor with one possible drive system. Figure 8.6 breaker-bar discharger and winch unit.

IV INDIAN DESIGN OF tOP-LOADING VErMICOMPOStING SYStEM

An interesting system of vermicomposting has been designed by the Rallis Fertilizer Company in India. The system is designed to process urban wastes, includ- ing food wastes, into vermicomposts in a continuous-flow pattern using an innova- tive concept (see Chapters 8 and 28). The processing units consist of two concrete walls 1 m (3 ft) deep on a concrete base, and the units are 3 m (9.2 ft) wide. Down the center of each unit, there is a line of upright pipes about 1 m (3.1 ft) high with multiple perforations, which are linked to an air-compression system running the length of each bed (Figure 8.7).

The systems use the tropical earthworm Eudrilus eugeniae to process food and urban organic wastes. The waste is added daily in 2.5–5.0 cm (1–2 in) layers, and the upper surface is kept moist by regular sprays. Each system is under cover so that moisture and temperature in the beds can be controlled. Organic wastes continue to be added above the heights of the bed walls until the waste is about 60 cm (2 ft) higher than the walls. At this point no more waste is added, watering of the bed stops, and compressed air is pumped into the bed, which makes it aerobic again. Within a few days, all of the earthworms retreat into the lower part of the bed. Then the surface layer of vermicompost, flush with the walls, can be removed with front- loading equipment. It is then screened through a very large rotating trommel and marketed in 50 kg (110 lb) plastic bags.

Five groups of vermicomposting systems of this kind are being operated in India. Each site has about 40 ha (100 acres) of land. Two sites are near Bangalore, two in Chennai, and one in Hyderabad. All sites process about 6000 (6096 tons) metric tons of urban wastes per day. Total vermicompost production is 20,000 metric tons (20,320 t) per annum, and total thermophilic compost production is 250,000 metric tons (254,000 tons) per annum. The vermicompost is sold under the trade name of Ralligold and the compost as Black Gold. These are marketed by a company called Caramandal Fertilizer Co.

Processed vermicompost Layered waste Aeration pipes Concrete wall Concrete base 3 m (9.2 ft) 1 m (3.1 ft) Figure 8.7 indian top-harvesting vermicomposting system.

medium- and HigH-teCHnology vermiComPosting systems 99 V COMPLEtE UrBAN WAStE-rECYCLING

VErMICOMPOStING SYStEMS

A vermiculture-based urban waste-recycling system that can handle all the waste from a community was developed in Montelimar in southern France, under a system termed NATURBA with the commercial name of SOVADEC. This involves processing all the total urban waste stream from a community of 40,000 people by first passing it through a rotating selector that breaks up plastic materials and removes them by heating cables, followed by manual sorting, separation of rolling objects such as bottles, and separation of ferrous metal objects with magnets. The waste is then transported to a thermophilic composting system and kept there for 30 days, followed by vermicomposting in a very deep continuous-flow vermicom- post system for about 60 days (Figure 8.8); the earthworms are then removed and the vermicompost is packaged. This system was able to turn as much as 27% of a total urban waste stream into vermicompost. This vermicompost can be marketed profitably and adds to the commercial potential of complete waste recycling very considerably.

VI EArthWOrM tOILEt SYStEMS

Various systems of self-maintaining human toilets based on earthworms, as an alternative to septic systems, have been developed in various parts of the world. The most successful is the Dowmus Composting Toilet. This system is well engineered, completely odor free, and built in Australia. It needs little maintenance over several years and has been adopted for general use in some Australian state parks (Windust 1994) (Figure 8.9).

VII ECONOMICS OF ALtErNAtIVE VErMICOMPOStING SYStEMS The use of organic wastes to grow earthworms and produce vermicomposts is an extensive farm and garden cottage industry in the United States and other parts of the world. Many of these small-scale producers market the earthworm castings they produce locally for growing plants. Most such operations in the United States are based primarily on outdoor windrow systems, which have many economic and environmental drawbacks as discussed in Chapter 7. They are ground-based and

Wind vone vent hood

Vent stock

Fan power pack Fan assembly (see coupling detail at left) Exhaust vent Compost extraction chute Compost auger Evaporation and ventilation coils

Excess liquid drain Roof 350 to 450 Glazed ceramic pedestal Plastic drop chute

(400 dia) Max. compost level Composting zone Compost level at installation Breather tube 1900 Filter membrane 1770 Figure 8.9 australian dowmus vermicomposting toilet (all units cms (2.5 in)).

medium- and HigH-teCHnology vermiComPosting systems 101 require large areas of land, and they have potential for groundwater pollution with nutrients and other contaminants, because they are watered regularly and usually have no protection against leaching from the beds. The process is slow, often taking 6–12 months to complete. The harvesting of the vermicompost is laborious and time- consuming because the earthworms in the waste have to be separated, usually by a screening or trommel process, before the vermicompost is marketed. Although the initial capital outlay, other than land, is low, its labor costs are high at all stages of operation. As a good economic alternative, the wedge system designed by Edwards and colleagues, described in Chapter 7, has been used by a number of organizations. Although it uses an innovative but relatively inexpensive technology and requires less equipment, it overcomes many of the labor, economic, and environmental draw- backs associated with windrows. In particular, it uses less land, there is no leaching into groundwater, and there is no need to separate earthworms from the vermicom- post. The processing time is also shorter (3–4 months).

The automated continuous-flow reactor system designed by Edwards and his col- leagues (Edwards 1995, 1998) has totally different environmental, operating, and economic characteristics. The equipment has to be maintained under cover to ensure controlled environmental conditions, and the organic-waste compartment is raised above the floor and is maintained at 70%–80% moisture content and 20°–35°C; it is important that there is no leaching of nutrients. The retention or processing time of most organic wastes in the reactor is 30–60 days. The economics of such automated reactors (discussed in Chapter 19) are totally different from those of other systems because they involve a need for high initial capital inputs for reactors ($35,000– $50,000) each which can process up to 3 tons of waste per day, as well as ancillary loading and transport equipment, including: moving belts, macerators, and loaders for operation. However, their labor and running costs are extremely low, and the earthworm populations in reactors reach equilibrium and can usually be run trouble- free without adding or removing earthworms for a number of years. The capital expenditure can usually be recovered in 1–2 years. A number of relatively expensive smaller systems based on the principles of this system have been marketed in the United States but are much less attractive economically.

rEFErENCES

Darwin, C. 1881. The Formation of Vegetable Mould through the Action of Worms, with

Observation of Their Habits. Murray, London.

Edwards, C. A. (Ed.). 2004. Earthworm Ecology. 2nd ed. CRC Press, Boca Raton, FL. Edwards, C. A., and Arancon, N. Q. 2004. The use of earthworms in the breakdown of organic