WO2002016287A2

WO2002016287A2 - Composting apparatus for organic waste

Info

Publication number: WO2002016287A2
Application number: PCT/CA2001/001181
Authority: WO
Inventors: Paul Sicotte
Original assignee: Unotec Services International Inc.
Priority date: 2000-08-22
Filing date: 2001-08-21
Publication date: 2002-02-28
Also published as: WO2002016287A3; AU2001283747A1

Abstract

A composting apparatus for organic waste material comprises a generally box shaped structure having side walls, end walls and a plurality of conduits extending between the side walls. The conduits are arranged in a plurality of layers and extend throughout the volume of the apparatus. The conduits have open ends and a plurality of perforations along their lengths to promote aeration of the waste material. The apparatus also includes air permeable walls to assist in aerating the waste material. The walls optionally are insulated to prevent heat loss from the compost heap.

Description

Apparatus And Method For Composting Organic Waste

BACKGROUND OF THE INVENTION The present invention relates to composting apparatus or systems for organic waste. In view of recent environmental and ecological concerns, the development of effective waste treatment systems has become increasingly important. Such systems, while serving to dispose of such waste, must not themselves cause pollution. Therefore, processes such as incineration etc. are not desirable or, in some cases, not acceptable. Composting processes offer several advantages over other waste treatment methods. With composting, organic waste is allowed to be biodegraded by microorganisms into base components such as O₂, CO₂₎ humic matter and water. Such processes do not require the addition of energy from an outside source nor do they emit hazardous pollutants. In general, the organic waste is provided in a pile or heap and allowed to ferment with the aid of indigenous microorganisms. In certain large-scale cases, a solution containing the desired microorganisms may be applied to the waste heap. Although the use of composting for treating waste has been known for many years, the effective "scale-up" of such methods has been hindered by various problems. For example, one of the problems associated with aerobic composting processes relates to the lack of oxygen to the composting microorganisms deep within the waste heap. Since oxygen in the atmosphere cannot penetrate the waste heap, the microorganisms not able to access oxygen revert to anaerobic composting of the waste material or no composting at all. Further, under anaerobic or septic conditions, undesirable noxious gases and odors are generated. This presents a large problem especially in the case of large scale composting processes. Thus, it is important in large scale composting systems, in particular, to ensure that adequate oxygen is supplied to the- entire content of the waste heap. Another problem with composting systems relates to temperature control of the heap. In some cases, in order to increase aeration of the waste heap, the surface area of the heap is increased so as to allow oxygen to be available for all portions. However, in doing so, the heap also undergoes large heat losses thereby lowering its surface and internal temperature. This temperature drop creates a non-optimal environment for microbial activity thereby lowering the efficiency of the composting process. Yet another problem with known composting methods relates to moisture control. Specifically, the desired moisture is normally lost from compost piles or windrows when they are "turned" or when air flow is increased. The loss of moisture is also related to the temperature of the compost material. In other words, moisture loss is increased if the temperature of the compost material is high. Various attempts have been made to improve the methods and apparatus known in the art in order to use composting methods for large-scale, commercial applications. For example, in some systems, air is applied under pressure in order to force oxygen into the interior regions of the waste heap. However, such system requires the use of an external energy source in order to power the required aeration equipment. Other examples of modifications to composting processes are provided in the following patents: US 4,521,517, US 5,023,178 and US 5,129,935. In all these cases, aeration is achieved by means of a pump or blower whereby air is injected into the waste heap, thereby increasing process costs and resulting in a pollution source. In US patent 6,056,800, a composting method is disclosed wherein waste material is periodically added to the waste heap and allowed to decompose either aerobically or anaerobically. This patent does not teach a one-step batch process, which would reduce processing costs and time. Thus, a need exists for a composting system that provides an efficient and cost effective composting process.

SUMMARY OF THE INVENTION Therefore, in one embodiment, the present invention provides an apparatus for composting waste organic material comprising a box having opposed side walls and opposed end walls, the box further including a plurality of air passages extending between the side walls for aerating the waste material.

BRIEF DESCRIPTION OF THE DRAWINGS These and other features of the preferred embodiments of the invention will become more apparent in the following detailed description in which reference is made to the appended drawings wherein: Figure 1 is perspective view of a composting apparatus according to one embodiment of the invention. Figure 2 is a side elevation of the apparatus of Figure 1. Figure 3 is a plan view of the apparatus of Figure 2 through lines A- A. Figure 4 is a partial cross sectional view of a wall of the apparatus shown in Figure 1. Figure 5 is a graph illustrating the results from the example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Figures 1 - 3 illustrates one embodiment of a composting apparatus according to the invention. As shown, the apparatus 10 comprises, essentially, a box 12 having end walls 13 and 14 and side walls 15 and 16. In a preferred embodiment, the box 12 of the apparatus also includes a roof 18. As will be described below, the material to be composted, i.e. organic waste is placed within the box 10. In the preferred embodiment, the end and side walls 13 to 16 are designed to enable air to permeate there-through. For example, the walls are preferably made from a mesh material such as a metal screen. The roof 18 is preferably removable and is made of a material that is impervious to water. Known roofing materials such as sheet metal etc. may be used. As shown in Figures 1 - 3, a plurality of pipes 20 are provided inside box 12. The pipes 20 preferably extend between side walls 15 and 16. In a preferred embodiment, the pipes 20 are supported by the side walls 15 and 16. Further, for larger sizes of the apparatus, the pipes 20 can be supported internally with hangers or cradles (not shown). As shown in Figures 1 and 2, the pipes 20 are preferably arranged in rows and columns, when viewed on end. Further the rows of the pipes 20 are staggered, when viewed in elevation, so that pipes of adjacent rows are not in line. As shown in Figure 2, the pipes 20 have open ends. Figure 2 also illustrates the box 12 containing organic material 24 to be composted. Figure 3 illustrates a partial plan view of the box 12 of the apparatus 10 wherein only one row of the pipes 20 is shown. As can be seen, the pipes 20 are preferably supported in the desired position by the side walls 15 and 16. In the preferred embodiment, the pipes 20 extend through the side walls 15 and 16 as shown. Although the pipes 20 are shown generally parallel to the end walls 13 and 14, this is only a preferred embodiment for design considerations. Other orientations or dimensions of the pipes will be apparent to persons skilled in the art to achieve the function described below. As also illustrated in Figure 3, the pipes 20 are each provided with a plurality of apertures or perforations 22 along the lengths thereof. The purpose of perforations 22 will be discussed below in more detail. According to a preferred embodiment of the invention, the following method is used to compost organic waste material. Firstly, the material to be composted, 24, is placed within the box 12 of the apparatus 10. The material fills the box 12 and surrounds the pipes 20 already in place within the box 12. Following this, the roof 18 is placed over the box 12. In operation, the organic material 24 is allowed to decompose by action of indigenous microorganisms; however, if needed, desired microbial cultures may also be applied to the organic material 24. In order to promote aerobic decomposition, the pipes 20 through their openings and perforations 22 allow air to enter and permeate through the organic material 24. Further, the air permeable side and end walls 13-16 also allow air to permeate through the material 24. With the arrangement of the apparatus 10 of the invention, a large quantity of waste material 24 may be composted in an efficient manner. Further, due to the use of passive air flow, no external energy source is required to achieve desired aerobic decomposition of the waste material. However, as indicated below, in some cases, air flow may be enhanced by the use of a mechanical forced air system. As mentioned above, the side and end walls 13- 16 are air permeable and preferably consist of a mesh or screen material. In Figure 4, an optional partial section of the end wall 13 is illustrated wherein the wall 13 comprises two layers 26 and 28 of the screen material mentioned above sandwiching insulation 30. Insulation 30 provides thermal insulation to prevent heat loss from the waste material during the composting phase but does not prevent air from passing through the wall 13. An example of the insulation material that can be used with the present invention are foam "peanuts" or other similar material that will be apparent to those skilled in the art. Although Figure 4 depicts one wall 13, it will be understood that this is used merely as an example and a similar structure applies for all walls of the box 12. Further, it will be understood by persons skilled in the art that the need for insulation material 30 will depend on various factors such as the type of material being composted and the environmental conditions in the area where the apparatus is being used. For example, in warm climates, such insulation may not be necessary. Similarly, in cold conditions, insulation may be necessary in order to maintain the waste pile or compost heap being composted at an optimal temperature to promote decomposition. As is known in the art, microbial decomposition leads to the release of heat; therefore, the provision of an insulative layer in cold conditions prevents the heat generated in this process from escaping thereby leading to warming of the waste material heap. As mentioned above, the roof 18 is preferably made of a water impervious material. Such roof is optionally used with the apparatus of the invention in situations where rain is to be prevented from entering the waste material 24 thereby leading to leachate penetrating the soil. It will be understood, that such roof is an option for use with the box 12 of the invention. In cold conditions the roof will also serve to prevent heat loss from the top of the waste material heap. The box 12 of the invention may have any length of side walls 15 and 16, and would generally be limited by the amount of space available on site. The width of the box 12, that is the length of the end walls 13 and 14, and the height of the box will depend upon the amount of aeration required. Further, the height of the box 12 will also depend upon the material being composted. For example, very dense material should not be piled too high so as to avoid compaction of the material and, therefore, restriction of air flow there-through. Persons skilled in the art will be easily able to determine the needed height of the box 12 or, in the alternative, the height of the waste material placed within the box. In one embodiment, the box of the invention has the following dimensions: length (side walls) and width (end walls) of 8 ft.; height of 6 ft. Further, the pipes 20 are positioned in a box 12 of these dimensions such that three rows or layers are provided at 18", 28", and 48" from the bottom of the box. The pipes of each layer are spaced apart by 2ft. The pipes may be of any diameter and the perforations 22 of the pipes may be of any size. However, the diameter or size of the perforations must be small enough to prevent clogging by the waste material but large enough to allow air to pass through. The size of the perforations will be apparent to persons skilled in the art. It will be understood by persons skilled in the art that the air flow through the waste material and the moisture content thereof can be controlled by configuring the pipes of the apparatus. For example, in certain cases, the pipes can be damped by plugging them. In other cases, a forced air system can be used to increase air flow through the pipes or a moisture induction system can be used to introduce moisture into the waste material. Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the spirit and scope of the invention as outlined in the claims appended hereto.

The following example is used to illustrate the present invention and not to limit same in any way.

EXAMPLE

25 m of dewatered sewage sludge from the Red Deer water treatment plant was blended with hog fuel (wood waste) and placed into the composting apparatus, or conal, of the present invention. The conal consisted of a series of double screened metal panels filled with Styrofoam™ packing to form a permeable yet insulating matrix. All sidewall panels were equipped with a series of matching portals. Prior to filling the conal with compost material, 4" perforated pipes were placed between portals to span the width of the conal and allow passive airflow into the piping and compost material. Also, a 15cm mat of hog fuel was placed on the floor to provide insulation and encourage passive air induction. Compost material was then carefully loaded into the cell (conal). A 15cm layer of hog fuel was placed on top of the material prior the installation of the impermeable tarped roof.

Baseline samples were collected and analyzed for confirmatory moisture and carbon to nitrogen ratio analyses. Internal temperature and oxygen levels, along with ambient air temperature, weather and direction of prevailing winds, were collected and recorded by an Olds College composting student contracted for the project. Field recording was carried out on a daily basis for approximately one month and then continued on a weekly basis until the project was terminated.

Table 1 lists the results from the measurements of the conal during the process. The samples were taken in chronological order.

Table 1: Results

The temperature values of the above data are illustrated graphically in Figure 5.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An apparatus for composting waste organic material comprising a box having opposed side walls and opposed end walls, said box further including a plurality of air passages extending between said side walls for aerating said waste material.

2. The apparatus of claim 1 wherein said air passages comprise a series of hollow, perforated tubes having open ends, whereby air passes between said open ends and said perforations.

3. The apparatus of claim 1 wherein said side and end walls are formed of an air permeable material.

4. The apparatus of claim 1 further including a water impermeable roof.