CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of and priority to U.S. Provisional Application No. 63/222,728, titled “TWO-CHAMBER COMBUSTION SYSTEM,” filed on July 16, 2021, the entire contents of which are hereby incorporated herein by reference.

BACKGROUND

[0002] An estimated 4.5 billion people worldwide do not have access to safe, affordable sanitation systems. High levels of child death and disease have been linked to oral fecal contamination where pathogen laden fecal matter enters the food or water supply. Non-sewered sanitation systems are needed where traditional sanitary sewer systems are unavailable or impractical.

SUMMARY

[0003] Disclosed herein is a combustor comprising a combustion section, an exhaust duct, a reducer configured to connect the combustion section to the exhaust duct, and an exhaust vent. The combustion section comprises a containment wall, a first combustion chamber, and a second combustion chamber, the first combustion chamber positioned beneath the second combustion chamber and configured to receive a first fuel, the second combustion chamber configured to receive a second fuel, the second fuel comprising feces. The exhaust vent is connected to the exhaust duct at an end opposite the combustion section and at the top of the combustor. Also disclosed herein are methods of reducing mostly dried feces to inert ash using the combustor.

[0004] Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. In addition, all optional and preferred features and modifications of the described embodiments are usable in all aspects of the disclosure taught herein. Furthermore, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with one another. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, with emphasis instead being placed upon clearly illustrating the principles of the disclosure. In the drawings, like reference numerals designate corresponding parts throughout the several views.

[0006] FIG. 1 illustrates an example of a two-chamber combustion system according to various embodiments described herein.

[0007] FIG. 2 illustrates an example the combustion section of the two-chamber combustion system of FIG. 1 according to various embodiments described herein.

[0008] FIGS. 3A-3C illustrates an example of the combustion section, disassembled, the two-chamber combustion system of FIG. 1 according to various embodiments described herein.

[0009] FIGS. 4A and 4B illustrate example views of the heat retention insert for the two- chamber combustion system of FIG. 1 according to various embodiments described herein.

[0010] FIG. 5A and 5B illustrates an example of the chamber grate, tapered flow collar, and the interior collar positioned within the heat retention insert of the two-chamber combustion system of FIG. 1 according to various embodiments described herein.

[0011] FIG. 6 illustrates an example schematic a non-sewer ed single unit toilet system having a feces treatment system configured to produce feces cakes for combustion in the two- chamber combustion system according to various embodiments described herein.

DETAILED DESCRIPTION

[0012] Sanitation systems are needed for regions of the world where open defecation or lack of improved sanitation is common, which can lead to illness. Traditional sewage and wastewater treatment plants which receive waste from sewers can be expensive to implement and operate. Technologies for multi-unit toilets are being developed to process waste on a large scale. However, there is a need for technology to provide access to safe, affordable sanitation systems that can be deployed in a family home without sewer connections. Holistically, as water scarcity rises across the globe, sanitation systems that reduce reliance on large volumes of water for transport of waste over long distances will become increasingly important, not just in developing countries, but globally. [0013] To address these deficiencies, systems for use in a stand-alone non-sewer ed toilet system are discussed herein. The systems can be configured to inactivate pathogens from human waste and prepare the waste for safe disposal. The systems can also recover valuable resources such as clean water. The systems can be configured to operate without connection to input water or output sewers. Some example systems can be battery based or powered by off-grid renewables. The systems can be optimized for low cost fabrication and low operation costs. The systems can promote sustainable sanitation services that operate in poor, urban settings, as well as in developed and developing nations.

[0014] The ISO 30500 standard provides a technical standard for non-sewered sanitation systems designed to address basic sanitation needs and promote economic, social, and environmental sustainability through strategies that include minimizing water and energy consumption, and converting human excreta to safe output. These sanitation systems are intended to operate without connection to any sewer or drainage network and meet health and environmental safety and regulatory parameters. In some examples, systems described herein can be configured to provide treated output that meets or exceeds the ISO 30500 standard.

[0015] For example, human waste streams can include urine, feces, diarrhea, and the like. For example, sanitation incidentals can include toilet paper, feminine hygiene waste, diapers, other paper products, and the like. In some toilet systems, a portion of sanitation incidentals, including non-organic products such as diapers, can be received and processed separately from the human waste streams. In some examples, the wastes streams comprise human feces and urine, menstrual blood, bile, flushing water, anal cleansing water, toilet paper, other bodily fluids and/or solids. Additionally, the waste streams can comprise water, including flush water, rinse water, wash water, fresh water, consumable water, potable water, useable water, and the like.

[0016] For example, a stand-alone non-sewered toilet system can comprise a liquid treatment system and a solids treatment system, each of which can operate as a separate system or be interconnected for treatment of human waste. The stand-alone non-sewered toilet system can also comprise at least one separation system. In some examples, the content of human waste streams can be separated or processed separately. Separation of streams can provide more efficient processing than mixed-content human waste streams by dividing the source material into primarily feces, urine, and wastewater streams. Since 100% separation is not practical, a degree of cross contamination between the streams is acceptable for the subsequent downstream treatment approaches. As described herein, the feces stream, containing primarily feces, is also referred to as the “brown stream.” The brown stream is mostly feces, but can also be mixed with other liquid and solid waste. For example, the brown stream can include feces, toilet paper, some urine, and some water. As described herein, the “green stream” can include mostly water, some urine, and some toilet paper, and usually does not include feces. The green stream is mostly liquid with some solids. As described herein, the urine stream, containing primarily urine, is also referred to as the “yellow stream.” For example, a yellow stream can include urine and some water. As described herein, the wastewater stream is also referred to as the “blue stream.” For example, the blue stream can contain primarily wastewater in the form of flush water, anal rinse water, or excess water that is poured into the toilet. In some examples, the blue stream can also include some urine. Stream separation can enable lower cost and more robust treatment processes given the high degree of variability in low volume fecal deposits (recognized as primarily diarrhea), high volume urine deposits, and excessive amounts of flush and anal rinse water, given future water scarcity constraints.

[0017] In the context described above, various examples of a two-chamber combustion system are described herein. The two-chamber combustion system can be an external combustor that operates separately or can be configured for use as part of a solids treatment system in a conjunction with stand-alone non-sewered toilet system. In some examples, the stand-alone non- sewered toilet system can be configured to provide treated output that meets or exceeds the ISO 30500 standard that is received for combustion in the two-chamber combustion system. In some examples, the treated solids output or solid waste to be combusted can be reduced to ash within the two-chamber combustion system. The ash produced by the two-chamber combustion system can meet or exceed the ISO 30500 standard.

[0018] For example, the fecal waste streams can comprise feces, as well as urine, water, and other sanitation incidentals contained in a waste stream collected in a toilet system. A feces or solids treatment system can be integrated as a module for solids treatment in a stand-alone non- sewered sanitation system. In some examples, the feces or solids treatment system can be configured to operate as part of a single unit toilet system. For example, the feces or solids can be integrated for use in a single unit toilet system configured to render the bodily wastes of an adult human into water, CO2, and mineral ash. For example, the fecal waste streams can be processed by a feces treatment system to produce feces cakes that can be reduced to inert ash. In some examples, the process to produce the feces cakes includes inactivating most or all pathogens from the solid waste that includes feces. In some examples, the feces cakes can the meet or exceed the ISO 30500 standard.

[0019] The two-chamber combustion system can be configured for the combustion of solid waste containing feces. For example, the solid waste can be in the form of feces cakes formed by a solids treatment system of a toilet system. The feces cakes can be formed from fecal waste streams comprising feces, as well as urine, water, and other sanitation incidentals contained in a waste stream collected in a toilet system. For example, the two-chamber combustion system can receive cakes containing feces from a stand-alone non-sewered toilet system.

[0020] Various examples of the two-chamber combustion system are described herein. The two-chamber combustion system can comprise first and second chambers with an effective air flow for the evaporative drying and combustion of dried, volume reduced feces cakes, and reduction to ash using biofuel sources to initiate combustion. For example, the biofuel sources can be placed in a first chamber and the dried or partially dried feces cakes can be placed in a second chamber. The biofuel sources can include paper, twigs, wood, and the like. The two- chamber combustion system can be configured work in conjunction with a single-unit toilet system that forms feces cakes as treated solids output. For example, dried or partially dried feces cakes can be produced by a separate feces treatment system, then be transported, by the user, to the two-chamber combustion system to reduce a feces output to inert ash. In some examples, the feces cakes can be transported using a defined disposal bin to the two-chamber combustion system. The two-chamber combustion system is configured to be located on in an exterior location, outside of a house, ideally attached to an external wall for stability. The disposal bin can be designed to selectively interface with the two-chamber combustion system, both to enable clean transport of the cakes to the combustor and to prevent the introduction of other foreign material for burning. In some examples, feces cakes can be transported by other means to the two-chamber combustion system and the disposal bin is not necessary.

[0021] In an example, the two-chamber combustion system can be used for evaporative drying of feces cakes that contain some moisture. The two-chamber combustion system can contain or store the feces cakes without igniting the combustor. In some examples, the feces treatment system can form and partially dry the feces cakes but may require additional drying before combustion. In some examples, the two-chamber combustion system can include a turbine fan on the top of the combustor outlet. The turbine fan can be configured to promote air flow to continue the evaporative drying process of the feces cakes and to prevent potential pathogen regrowth. The two-chamber combustion system can be configured with a height such that the emission of the exhaust is above the heads of most users. For example, the two-chamber combustion system can be at least 8 ft in height. In an example, a non-sewered single unit toilet system can be configured to produce feces cakes, that can be transferred as needed. In some examples, the feces cakes can contain moisture and need to be dried in order to combust. The feces cakes can be temporarily stored in the combustor before the two-chamber combustion system is ignited. For example, the combustor can be lit once a week using biofuel to ignite and bring the feces cake chamber up to temperature for combustion.

[0022] In the following discussion, a general description of examples of the two-chamber combustion system and their components is provided, including a discussion of the operation of the same. Non-limiting examples of a two-chamber combustion system are discussed. The two- chamber combustion system can be configured to support both biofuel combustion and feces combustion on separate fuel beds.

[0023] As shown in FIG. 1, the two-chamber combustion system 100 can comprise a combustion section 102, a reduction section 104, an exhaust duct 106, and an exhaust vent 108. The combustion section 102 can include a first chamber 110 and a second chamber 112, which will be described in greater detail herein. The two-chamber combustion system 100 can also include a lower heat shield 138 configured to surround at least a portion of the combustion section 102, and an upper heat shield 140 configured to surround the reducer 118 and at least part of the exhaust duct 106. In some examples, there can be a ventilation gap 142 between the exhaust duct 106 and the top of the upper heat shield 140.

[0024] The two-chamber combustion system 100 can comprise a heat retention insert 150 configured to be positioned within a containment wall 122 of the combustion section 102 and rest on the first plate 130 of the two-chamber combustion system 100 to partially define a first chamber 110 and a second chamber 112. The first chamber 110 can be positioned below the second chamber 112. The first chamber 110 can be configured to burn biofuel at a higher temperature to ignite the feces cakes in the second chamber 112. For example, for example biofuel sources can include paper, twigs, wood, and the like. The first chamber 110, also called a lower chamber herein, can be configured to support a temperature of about 900°C or more for wood combustion. An elevated fuel grate 128 can be positioned on the first plate 130 within the first chamber 110 to elevate the biofuel sources and facilitate burning of the biofuel sources and allow inert ash to collect on the first plate 130. The second chamber 112, also called an upper chamber herein, can be configured to support a temperature of about 375°C for feces combustion. In some examples, the second chamber 112 can be accessed via a door 114 to place feces cakes inside the second chamber 112.

[0025] In an example, the exhaust duct 106 can be a stove pipe or conduit formed in one piece. In another example, the exhaust duct 106 can be provided as one or more sections of stove pipe to vary the length of the exhaust duct 106, thus the height of the two-chamber combustion system 100. For example, the total height of the two-chamber combustion system 100 can be configured based on guidance from local regulations regarding the exhaust or emissions. In an example, the total height of the two-chamber combustion system 100 can be over 8 feet tall. In an example, the exhaust vent 108 can be a turbine ventilator 120 secured to the exhaust duct 106 at an end opposite the combustion section 102 and at a top of the two- chamber combustion system 100. In some examples, the turbine ventilator 120 can be configured to passively dry the feces cakes containing moisture continually, without igniting fuel in either the first or second chamber 110, 112. Further, in some examples, the two-chamber combustion system 100 can have a plurality of adjustable feet 132 configured to level the two- chamber combustion system 100.

[0026] FIG. 2 illustrates a cross-section view of the two-chamber combustion system 100 of FIG. 1. The combustion section 102 can be substantially cylindrical and comprise a containment wall 122 and a heat retention insert 150 configured to fit within the containment wall 122. In some examples, the combustion section 102 also includes a lower heat shield 138 which at least partially surrounds the containment wall 122. The reduction section 104 can comprise the reducer 118 and the exhaust duct 106. In some examples, the combustion section 102 also includes an upper heat shield 140 which at least partially surrounds the reducer 118 and a portion of the exhaust duct 106.

[0027] As shown in FIG. 2, the main combustor body 116 comprises a containment wall 122, reducer 118, and exhaust duct 106. The containment wall 122 can be substantially cylindrical having a first diameter (di) or first cross-section. The exhaust duct 106 can be an elongated cylindrical pipe having a second diameter (d2) or second cross-section, where the first diameter is greater than the second diameter. The reducer 118 can connect the containment wall 122 to the exhaust duct 106. The reducer 118 can be configured to direct the exhaust from the first and second combustion chambers 110, 112 through the exhaust duct 106 for release via the exhaust vent 108. In some examples, the reducer 118 can be at least one reducer or comprise a plurality of reducers.

[0028] The first chamber 110 can be positioned below the second chamber 112. The first and second chambers 110, 112 can be at least partially defined by the heat retention insert 150 configured to fit within the containment wall 122. The heat retention insert 150 can comprise a tubular body 152, a chamber grate 156, tapered flow collar 154, the interior collar 158, first insert collar 160, and second insert collar 162. The first chamber 110 can comprise a volume defined by the first plate 130 and the portion of the heat retention insert 150 within tubular body 152, tapered flow collar 154, and chamber grate 156. The first chamber 110 can also include the volume for air intake between the tubular body 152 and the containment wall 122 and the first insert collar 160. The second chamber 112 can include the volume above chamber grate 156 and within the containment wall 122 including the portion of the heat retention insert 150 within tubular body 152, chamber grate 156, and interior collar 158.

[0029] The first chamber 110 can be configured to burn biofuel at a higher temperature to ignite the feces cakes in the second chamber 112. The second chamber 112 can be accessed via a door 114 in the combustion section 102. In some examples, the two-chamber combustion system 100 can include a rail system 148 configured to receive a solids disposal bin (not shown) containing feces cakes. The solids disposal bin and rail system are configured to reduce direct user contact with the feces cakes. For example, the feces cakes can be deposited directly into the solids disposal bin as they are formed by a feces treatment system. Then, a user can manually move the solids disposal bin containing the feces cakes to the two-chamber combustion system 100 and deposit the feces cakes into the second chamber 112 without the user handling the feces cakes directly. The bin can be removed after the feces cakes have been deposited.

[0030] The heat shields 138, 140 partially surround the main combustor body 116 and act as a thermal barrier to protect external objects from high heat. The upper heat shield 140 can be positioned with a ventilation gap 142 at one end of the reduction section 104 at the exhaust duct 106. As shown in FIG. 2, the heat shields 138, 140 can be positioned with a gap between the main combustor body 116 and the heat shields 138, 140. [0031] FIGS. 3A-3C show disassembled portion of the combustion section 102 of FIG. 1 in greater detail. The combustion section 102 can comprise a heat retention insert 150 configured to rest on the first plate 130 which defines the floor of a first chamber 110. The heat retention insert 150 also configured to fit within the containment wall 122. The first plate 130 can be a solid plate to eliminate air flow through the first plate 130 and provide a base for the heat retention insert 150. A first plate 130 configured with adjustable feet 132 can be the base for the combustion section 102 and the two-chamber combustion system 100. An elevated fuel grate 128 can be used to lift the wood or biofuel off the solid first plate 130 to increase the surface area of wood exposed to flame. In some examples, the combustion section 102 also includes a lower heat shield 138 which at least partially surrounds the containment wall 122.

[0032] As shown in FIG. 3 A, the two-chamber combustion system 100 can comprise a heat retention insert 150 configured to be positioned within a containment wall 122 of the combustion section 102 and rest on the first plate 130 of the two-chamber combustion system 100 to partially define a first chamber 110 and a second chamber 112. Shown also in FIGS. 3A-4B, the heat retention insert 150 comprises a tubular body 152, a chamber grate 156, tapered flow collar 154, the interior collar 158, first insert collar 160, and second insert collar 162. The tapered flow collar 154 and the interior collar 158 can be positioned below and above the chamber grate 156, to further define the first and second chambers 110, 112, respectively. The heat retention insert 150 can be configured with an opening 168 to allow access the first chamber 110. The heat retention insert 150 can have a plurality of air intake openings 164 at a level configured to allow air into the first chamber 110. Similarly, the heat retention insert 150 can have a plurality of air intake openings 165 at one or more levels configured to allow air into the second chamber 112. The first insert collar 160 and the second insert collar 162 can be positioned on an external surface of the tubular body 152 to further control the air intake. The heat retention insert 150 can be configured to fit within the containment wall 122. The first and second insert collars 160, 162 configured to direct airflow and to position the heat retention insert 150 within the containment wall 122 of the combustion section 102. The first and second insert collars 160, 162 can be configured to provide a snug fit against the interior surface of containment wall 122 and to direct airflow through a plurality of slots in the containment wall 122 to the second chamber 112 of the combustion section 102. An elevated fuel grate 128 can be inserted within the first chamber 110 to support the biofuel. [0033] FIG. 3B illustrates an example containment wall 122 of the combustion section 102. The containment wall 122 can be substantially cylindrical and extend to contain both first and second chambers 110, 112. The containment wall 122 can have a plurality of slots 136 can be arranged at an intake height (hi) corresponding to the second chamber 112. The plurality of slots 136 that can be configured with slots of uniform size or alternate with larger and smaller slots to regulate the air intake to the second chamber 112. When positioned to surround the heat retention insert 150, the containment wall 122 rests on the first plate 130 and/or the adjustable feet 132. The containment wall can be secured to the adjustable feet 132 to maintain the position of the containment wall 122. The opening 168 of the heat retention insert 150 and the first access opening 124 of the containment wall 122 are configured to align so that the biofuel can be added and positioned in the first chamber 110. The first insert collar 160 is configured to have a snug fit within the containment wall 122 such that the plurality of slots 136 are positioned above the perimeter where the first collar 160 meets the interior of the containment wall 122, directing air intake to the second chamber 112 and not the first chamber 110.

[0034] The containment wall 122 can be a combustion drum or a tubular section having an exterior surface, an interior surface, and a first diameter dl. For example, the containment wall 122 can be made of a high temperature material configured to contain a combustion temperature of about 900°C. For example, the containment wall 122 can comprise carbon steel, iron- chromium-aluminum, or other high-temperature material, high-temperature metal, high- temperature alloy, and the like. In some examples, carbon steel having a melting temperature of 1426°C, can be used for the containment wall with safe operation. In an example, the containment wall 122 of the combustion drum be made of 18-gauge steel and can have a thickness of about 0.046 inches thick. The combustion section 102 comprises a first access opening 124 in the containment wall 122 configured for access to the first chamber 110 and a second access opening 126 in the containment wall 122 configured for access to the second chamber 112.

[0035] In an example, the combustion drum can have a containment wall 122 about 32 inches high and about 12 inches in diameter. When the heat retention insert 150 is positioned within the containment wall 122, the first chamber 110 can be defined within the containment wall 122 between the first plate 130 and the chamber grate 128. The biofuel can be loaded in the first chamber 110 via the first access opening 124. In an example, the second chamber 112 can be defined as the volume above the chamber grate 128 defined within the containment wall 122. The feces cake can be deposited in the second chamber 112 via the second access opening 126. The second access opening 126 can be closed by a door (FIG. 1). In some examples, the door 114 can be configured to receive a transfer bin containing feces cakes from a single-unit non- sewered toilet system. In an example, the door 114 can be a hinged door. The second chamber 112 is configured to receive the feces cakes in a portion below the second access opening 126 and into the upper portion of the heat retention insert 150. In an example, the second access opening 126 can be positioned about 12 inches from the chamber grate 156. The second chamber 112 can be configured to hold at least 9250 cc of feces.

[0036] The containment wall 122 can also comprise a plurality of slots. For example, as shown in FIG. 3B, a plurality of slots 136 can be arranged at a first intake height positioned above the first height hi of the first plate 130 to provide air intake to the second chamber 112. In some examples, additional slots can be configured to provide air intake to the first chamber. The plurality of slots 136 can be sized, shaped, and distributed as needed for the predetermined air intake for the respective chamber. For example, the plurality of slots can be elongated and evenly distributed about the circumference of the containment wall 122. In some examples, as shown in FIG. 3B, the distribution could vary or have a pattern with larger and smaller slots. In some examples, there could be a second layer of a plurality of slots for the first and/or second chamber. In some examples, the plurality of slots could be closed off or the containment wall formed without slots. In an example, the exhaust vent 108 can comprise a turbine ventilator 120 that can draw air upward through the plurality of slots 136 to promote air flow to continue the evaporative drying process of the feces cakes and to prevent potential pathogen regrowth. Eliminating the air flow through the first plate 130 and portion of the containment wall 122 of the first chamber 110 can increase draft velocity through the first chamber 110 causing an increase in thermal energy delivery to the specimen being dried in the second chamber 112. The plurality of slots 136 can also help provide enough air intake to support full combustion. For example, an air intake greater than 75 g/s can be needed.

[0037] Shown in FIG. 3C, the combustion section 102 can also comprise a lower heat shield 138 to impede direct contact with the exterior surface of the containment wall 122. The lower heat shield 138 can be configured to surround the containment wall 122 and rest positioned within slots of the adjustable feet 132. The lower heat shield 138 can be substantially cylindrical with first and second access portions 144, 146. The first access portion 144 configured to allow access to the first chamber 110 and the second access portion 146 configured to allow assess to second chamber 112 via the door 114 of the containment wall 122.

[0038] FIGS. 4 A and 4B illustrate a front view and cross-sectional view of the heat retention insert 150. The heat retention insert 150 can comprise a tubular body 152, a plurality of air intake openings 164, 165, and a chamber grate 156. The heat retention insert 150 can also comprise tapered flow collar 154 and the interior collar 158, positioned below and above the chamber grate 156, to further define the first and second chambers 110, 112, respectively. The heat retention insert 150 can also comprise first and second insert collars 160, 162 configured to direct airflow and to position the heat retention insert 150 within the containment wall 122 of the combustion section 102.

[0039] In this example, the heat retention insert 150 can include a chamber grate 156 to partially define the floor of the second chamber 112. The geometry of the heat retention insert 150 can add control of the air flow through the two-chamber combustion system 100 without modifying the containment wall 122. The heat retention insert 150 can focus thermal energy from the first chamber 110, such that more heat is retained in the second chamber 112. The heat retention insert 150 can be configured to more precisely control air flow. The heat retention insert 150 can provide increase thermal efficiency such that less wood, or other biomass, is needed to keep the system at operating temperature and burning.

[0040] In an example, the heat retention insert 150 can comprise a tubular body 152 having a diameter d3 smaller than the first diameter dl of the containment wall 122 and greater than the diameter d2 of the exhaust duct 106. The tubular body 152 can be made of steel or other high temperature metal or material. The heat retention insert 150 can be inserted within the containment wall 122 of the combustion section 102. The heat retention insert 150 can have a height that extends from the first plate 130 of the first chamber 110 to a height just below or about the bottom of the second access opening 126.

[0041] A tapered flow collar 154 can be provided at a first insert height xl of the tubular body 152, extending a reduced cross-section at the bottom of the chamber grate 156. The tapered flow collar 154 and the chamber grate 156 defining the top of the first chamber 110. The tapered flow collar 154 can be configured to direct the air flow to the reduced the cross-sectional area of the perforated floor of the second chamber 112. [0042] In this embodiment, the heat retention insert 150 can comprise a chamber grate 156 of the second chamber 112 provided within the tubular body 152. For example, the chamber grate 156 can be provided at a first insert height x2 and can have perforations. An interior collar 158 can further define the floor of the second chamber 112. The interior collar 158 tapering from the inside of the tubular body 152 at a third insert height x3 to the chamber grate 156 at the second insert height x2. The slope of the interior collar 158 can help prevent flat feces cakes from fully covering the chamber grate 156. The inner diameter of the interior collar 158 is the same as the reduced diameter of the tapered flow collar 154.

[0043] A first insert collar 160 can be positioned between the tubular body 152 and the containment wall 122 and extend in a tapered manner from third insert height x3 to the second insert height x2. The second insert collar 162 can extend outward from the tubular body 152 a tapered manner from a third insert height x4 to inside of the containment wall 122 at a fifth insert height x5, which is the top of the heat retention insert 150. For example, the height of the heat retention insert 150 can be about 17 inches from the bottom to the top.

[0044] The tubular body 152 can have a plurality of holes, slots, or other openings within the wall of the tubular body 152 to allow air flow. For example, as shown in FIG. 4A, a plurality of air intake openings 164 can be distributed at a predetermined level of the first chamber 110, where the openings are sized for a predetermined air intake to the first chamber 110. Similarly, a plurality of openings 165a, 165b can be distributed at a first and second level of the second chamber 112, where the openings are sized for a selected air intake to the second chamber 112. For example, each level containing the plurality of openings can be sized, shaped, and distributed as needed for the predetermined air intake for the respective chamber.

[0045] Shown in FIGS. 5A and 5B, the chamber grate 156, tapered flow collar 154, and the interior collar 158 of the heat retention insert 150 are shown in greater detail. The chamber grate 156 can define in part the division between the first chamber 110 and the second chamber 112. The tapered flow collar 154 can be shaped to direct the heat from the first chamber 110 to the bottom of the chamber grate 156 to combust the feces cakes collected in the second chamber 112. The heat retention insert 150 can include radial ribs 170 extending from the interior collar 158 to the chamber grate 156 within the second chamber 112 portion of the heat retention insert 150. The radial ribs 170 in combination with the interior collar 158 help guide the deposited feces cakes toward the chamber grate 156 of the second chamber 112 for better combustion. [0046] In some examples, the two-chamber combustion system can be configured work in conjunction with a stand-alone non-sewer sanitation system that forms feces cakes as treated solids output. The two-chamber combustion system can be configured to receive a transport bin that interfaces with a stand-alone non-sewer sanitation system that produces feces. The transport bin can be configured to allow transport of the feces cakes without the user being in direct contact with the feces cakes.

[0047] As discussed above, the two-chamber combustion system can be configured work in conjunction with a single-unit toilet system that forms feces cakes as treated solids output. FIG. 8 illustrates an example schematic of a non-sewered single unit toilet system that includes a frontend system 1, a buffer tank system 2, a urine and wastewater system 3, a volume reduction solids treatment system 5, and external combustor 6. For example, an external combustor 6 can also be part of the non-sewered single unit toilet system can be configured to receive the treated solids output from the volume reduction solids treatment system 5.

[0048] In this example, the external combustor 6 can comprise the two-chamber combustion system 100 described herein. In this example, the frontend system 1 is configured to capture the human waste and to separate the mixed waste stream into at least one of a green stream and a brown stream. In some examples, a yellow stream can also be separated. The separated green, brown, and/or yellow streams can be further processed by a buffer tank system 2. The buffer tank system 2 can be configured to output a clarified green stream to a urine and wastewater treatment system 3 and a brown stream slurry to the volume reduction solids treatment system 5, which can produce cakes of solid waste comprising feces. The single unit toilet system can further comprise a control unit comprising at least one controller for the operation of the system and/or one or more modules of the system, including valves, pumps, motors, sensors, and other devices. The single unit toilet system can be configured to deliver a treated liquid output and treated solids output. For example, clean water and/or treated water can be further used in the system for flush water in the frontend system 1 or used for processing in one or more of the systems or modules. The treated solid waste can be dried or partially dried feces cakes deposited in a disposal bin for a user to access. The user can transport the dried or partially dried cakes to the external combustor 6 to be burned.

[0049] ASPECTS [0050] The following list of exemplary aspects supports and is supported by the disclosure provided herein.

[0051] Aspect 1. A combustor, comprising: a combustion section comprising a containment wall, a first combustion chamber, and a second combustion chamber, the first combustion chamber positioned beneath the second combustion chamber and configured to receive a first fuel, the second combustion chamber configured to receive a second fuel, the second fuel comprising feces; an exhaust duct; a reducer configured to connect the combustion section to the exhaust duct; and an exhaust vent connected to the exhaust duct at an end opposite the combustion section and at a top of the combustor.

[0052] Aspect 2. The combustor of aspect 1, further comprising a first plurality of slots in the containment wall at a first intake height.

[0053] Aspect 3. The combustor of aspect 1 or 2, wherein the first plurality of slots is configured to provide airflow to the second chamber.

[0054] Aspect 4. The combustor of any one of aspects 1-3, further comprising a first access opening in the containment wall to the first chamber and a second access opening in the containment wall to the second chamber.

[0055] Aspect 5. The combustor of aspect 4, further comprising a door to close the second access opening.

[0056] Aspect 6. The combustor of any one of aspects 1-5, wherein the exhaust vent comprises a turbine ventilator.

[0057] Aspect 7. The combustor of aspect 6, wherein the second fuel containing feces is one or more feces cakes and the turbine ventilator is configured rotate to draw air from the combustion section to continually passively dry the feces cakes.

[0058] Aspect 8. The combustor of any one of aspects 1-7, further comprising a first plate defining a floor of a first chamber and secured to the containment wall; and a heat retention insert configured to fit within the containment wall, the heat retention insert comprising: a tubular body comprising a plurality of air intake openings; and a chamber grate positioned at a second height within the tubular body to at least partially define a floor of the second chamber.

[0059] Aspect 9. The combustor of aspect 8, further comprising a tapered flow collar and an interior collar, the tapered flow collar positioned at a height within the tubular body below the chamber grate and extending to a reduced cross-section of the chamber grate, the interior collar positioned at a height within the tubular body above the chamber grate and extending to the reduced cross-section of the chamber grate.

[0060] Aspect 10. The combustor of aspect 8 or 9, further comprising first and second insert collars positioned on an external surface of the tubular body, the first and second insert collars configured to provide a snug fit against the containment wall.

[0061] Aspect 11. The combustor of aspect 10, wherein the first insert collar is positioned at the height of the interior collar and extends outward to contact the containment wall.

[0062] Aspect 12. The combustor of aspect 10, wherein the second insert collar is positioned at the top of the tubular body and extends outward to contact the containment wall at a height at or below an access opening to the second chamber.

[0063] Aspect 13. The combustor of aspect 10, wherein a first set of openings of the plurality of openings are distributed at a height to provide airflow to the first chamber and a second set of openings of the plurality of openings are distributed at a height to provide airflow to the second chamber.

[0064] Aspect 14. The combustor of any one of aspects 1-13, wherein the first chamber further comprises an elevated fuel grate configured to lift the first fuel.

[0065] Aspect 15. The combustor of any one of aspects 1-14, wherein the combustion section is configured to support a temperature of at least 900°C in the first chamber.

[0066] Aspect 16. The combustor of any one of aspects 1-15, wherein the second chamber is configured to support a temperature of at least 375°C.

[0067] Aspect 17. The combustor of any one of aspects 1-16, wherein the second chamber is configured to hold at least 9250cc of volume of feces cakes.

[0068] Aspect 18. A method of reducing mostly dried feces to inert ash, the method comprising: depositing a batch of feces cakes in an upper chamber of a two-chamber combustion system; when the batch of feces cakes contains some moisture, passively and continually drying the batch of feces cakes; igniting biofuel in a lower chamber of the combustion section of a combustor, and burning the batch of feces cakes.

[0069] Aspect 19. The method of aspect 18, wherein depositing a batch of feces cakes further comprises inserting a disposal bin from a volume reduction solids treatment system into a receiving interface, the disposal bin containing the batch of feces cakes.

[0070] Aspect 20. The method of aspect 18, wherein the combustion temperature for the biofuel in the lower chamber exceeds 900°C.

[0071] Aspect 21. The method of aspect 18, wherein the combustion temperature for the feces cakes in the upper chamber exceeds 375°C.

[0072] The features of the embodiments described herein are representative and, in alternative embodiments, certain features and elements can be added or omitted. It is to be understood that, unless otherwise indicated, the present disclosure is not limited to particular materials, manufacturing processes, or the like, as such can vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only and is not intended to be limiting. It is also possible in the present disclosure that steps can be executed in different sequence where this is logically possible.