Template:425inprogress W are becoming ubiquitous in the developed world, commonly found in public places such as shopping malls and waiting rooms. These hand cleaners contain a mixture of alcohol, water and a thickening agent to help the solution spread completely over the hands. Some solutions may contain moisturizers, perfumes or other non-medical additives. Alcohol-based solutions are known to eliminate a significant portion of germs carried on the hands, and are also used in medical facilities to sterilize equipment and surgeons' hands [1], [2], [3] .

This work will investigate the ability to produce hand sanitizers containing alcohol from local, natural resources by fermenting available sugars and starches from corn or potatoes and combining it with a thickening agent to increase spreading of the solution over the area to be cleaned. A comprehensive review of hand washing techniques and best practices can be found here, as provided by the Ontario Ministry for Health and Long-Term Care.

The target audience for this product is people in developing-world areas that would benefit from cleaner medical facilities and reduce illness and disease spread by unclean tools. The method of production outlined below has not yet been tested, however as been verified theoretically to effectively produce ethanol from the glucose contained in the original feed. The scale of production may be such that one person or party can satisfy the needs of their village, or perhaps would be able to sell the product at a market to people from neighbouring villages.

Production from food stuffs will be controversial in regions where food sources are limited to start, however reducing the spread of infection may improve overall health in the village to the point that the benefits outweigh the costs. This is a very difficult question to answer globally, and should be addressed on a regional basis. As mentioned previously, the best practice may be for a single producer to sell the product at market, although this sort of a monopoly may lead to charging exorbitant rates.

A mind map has been developed to indicate the projected flow for this investigation and will be updated as progress is made. (Mind maps created using MindMeister's free service.)

  • Version 1 - Download here
  • Version 2 - Download here
  • Version 3 - Download here

Introduction

A natural hand sanitizer should be composed of materials for production and use in the developing world, with its primary function being to reduce risk of infection during medical procedures such as surgery. In its simplest form, ethanol-based hand sanitizers have two components, each with a specific task and each with a natural occurring source or from naturally occurring compounds:

  • Alcohol: Typically either W or {{WP|isopropanol} is used in the solution to kill bacteria known to be the primary transmitter of illness and cause of infection. The quality and effectiveness of the hand sanitizer is dependent on the volume-fraction of alcohol contained in the solution, with a study by the Center for Disease Control (CDC) reporting 60% alcohol content to be more effective at eliminating bacteria and fungii from the skin than a 40% solution [4]. A study by Ontario's Provincial Infectious Disease Advisory Council (PIDAC) found that ethanol content in the range of 70-90% to be most effective at removing bacteria provided the hands are not visibly soiled (download the report here) [5]. This method is deigned to produce ethanol to by distilled in multiple steps to produce sufficiently high concentrations to be effective.
  • Thickening Agent: A thickening agent is included to slow the rate of evaporation of the alcohol and increase the 'wetting time' on the surface of the skin. The exact thickening agent used depends on the type of alcohol which governs solubility of all other components. Examples include W (derived from colagen in the bones and skin of animals, and presenting cultural limitations) and W. The rate of ethanol evaporation is slowed by the addition of the thickening agent [6], although the exact ratio is dependent on the sources of both ethanol and the compounds used to produce the thickening agent as this 'homemade' recipe may see significant differences in composition from one mixture to the next.

Both of the above components will be developed through appropriate processes, and alternative sources or methods of production will be provided where possible. Also, if the materials required to produce the thickening agent are not available the ethanol can be used independently, distribution by spray bottle may aid in increasing coverage before evaporation.

It is the responsibility of the user of the sanitizer to ensure adequate coverage during application, despite its inherent effectiveness. There are several spots on the hand that are frequently missed, so particular care should be taken during application.

Technical Specifications

The procedure required for producing ethanol from potatoes is relatively straight forward and most of the time commitment required is in allowing the fermentation process to occur. That is, there is very little time required by a skilled labourer meaning that little time is taken from other essential activities within the community. Furthermore, the process of W is well understood and by adding W to a mixture high in glucose maintained at modest temperatures (approximately 30 degrees C), fermentation is inevitable and follows a standard biochemical pathway from glucose ("reactant") to ethanol and carbon dioxide ("product").

Note: The following procedure has not yet been carried out by the original writer, but has been carefully considered for technical accuracy.

A detailed description of the procedure is provided here, complete with schematics and estimates of time requirements.

Step
Description
Schematic
Step 1
Cut whole, washed potatoes (dirt removed) into small cubes and bring to a steady boil in a pot over a fire or heating element. The smaller the cubes, the more quickly they will cook through. Since the potatoes are not going to be eaten, the goal of the first step is to reduce the mixture to a mush which increases the availability of starches for the yeast in the steps that follow. As the potatoes boil, they should be mashed with some flat instrument to reduce their size further. Once the potatoes have been reduced to a consistent mushy paste, the bulk of the remaining water should be removed to produce a thick slurry. (Note that a particular temperature is not crucial at this stage, and time will vary based on the quantity of potatoes and water used.)
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Step 2
Remove the potato mixture from heat, and let it cool to around 30-35 degrees C. Remove a small portion of the slurry to be used to feed the seed stock in the next step. Add yeast to the mixture and let stand for approximately one week in a closed container, occasionally opening the container slightly to vent the CO2 and prevent a build-up of pressure.
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Step 3
Remove a portion of the fermented slurry (potatoes and yeast) from the container to seed the next batch for fermentation. This 'seed' batch will contain some of the potato mixture and some of the yeast, which will allow the yeast to then be stored for several days. The semi-active yeast will consume the starchy mix, replicating and replenishing the yeast source in preparation for the next fermentation batch. Add the fresh (unfermented) potato slurry removed in the previous step to the seed stock so the yeast has some fresh glucose on which to feed and replenish itself.
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Step 4
Once fermentation is complete and a seed batch has been removed, it is time to extract the ethanol from the fermented mixture. Since ethanol evaporates at approximately 78 degrees C [7] and water boils at 100 degrees C, this can be accomplished by heating the mixture to some temperature in the range 78-100 degrees C (i.e. 80, or 82 degrees C) where the ethanol will evaporate and can be collected by a condenser but the water will not. The condensate can then be re-distiled as necessary to achieve sufficiently high alcohol concentration to produce an effective hand sanitizer.
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Production of the thickening agent (calcium acetate) is known to be possible by soaking egg shells in vinegar for extended periods of time (approximately two weeks), then evaporating the vinegar from the solution. One will then be left with a powdered form of calcium acetate which the ethanol can then be added to slowly to achieve the desired viscosity for rubbing on the hands. The exact ratio of thickening agent to ethanol (or solution, as 'ethanol' will actually be a solution of 70-90% ethanol and 10-30% water) has yet to be determined, but should be done so experimentally.

Engineering Aspects

As we see in the procedure, much of the production is carried out by biochemical processes of fermentation that cannot be significantly altered, even in the developed world by trained Chemical Engineers. However, there are a few techniques or tricks that can be employed to minimize losses from system hardware and to maximize product yield.

  • Ensure that the size of feed stock is reduced (by cutting, cubing, shreading, etc.) to decrease rates of reduction of starches, and increase glucose availability for yeast during fermentation.
  • Ensuring container is adequately sealed during fermentation to prevent oxygen from entering system and introducing secondary, competing chemical processes that consume fuel (glucose) and do not produce useful product (ethanol).
  • Properly collecting ethanol condensate to ensure none/little is lost during distillation.
  • Controlling temperature by control of heat source, such as the air/fuel ratio of an open flame.
  • Proper storage of flammable components during pre-production, production and storage of the sanitizer and its components.
  • Reducing contaminants to prevent the formation of toxic components or competing side-reactions reduce yield.

Medical Aspects

In the developed world where hand washing is essentially taken for granted, it is important to note the strong evidence linking hand washing to reductions in transmitted bacteria and viruses. The following reviews by reputable institutions discuss the benefits of hand washing in general, as well as the specific benefits of an alcohol-based hand disinfectant over traditional soap-and-water techniques. By demonstrating the effectiveness and considering limitations that must be met or exceeded to produce effective solutions, rates of transmitted infection can be reduced in the developing world as they have been in the developed world.

  • Mayo Clinic: Hand Hygiene - A frequently missed lifesaving opportunity during patient care (Download 59 kb PDF here)
  • Infection Control and Hospital Epidemiology, Chicago Journals: No Time for Handwashing!? Handwashing versus Alcoholic Rub: Can We Afford 100% Compliance? (Download 791 kb PDF here)
  • Division of Hospital Epidemiology, University Hospitals, Basel, Switzerland: Replace Hand Washing with Use of a Waterless Alcohol Hand Rub? (Download 85 kb PDF here)
  • The origins of hand washing in medical facilities (Download the 343 kb PDF here)

Regional Considerations

The process has been developed to consider locally available materials and resources, but does assume access to some more 'advanced' components that may need to be purchased from regional markets. Alternatives to these are being explored, but all efforts have been made to develop a simple, sustainable process.

Since food sources are to be used as feed for the process, regions that already suffer from low availability of such resources may choose not to produce such compounds, by may be able to purchase them from a market on an as-needed basis. It is interesting to note that in recent years, global potato production has shifted from the majority being produced in the developed world to the developing world [8].

The proposed thickening agent (calcium acetate) was selected for two reasons: (1) it can be produced from local materials at low cost, with little skill and equipment; (2) it does not carry the same sort of cultural limitations that another common thickening agent (W) does. Gelatin is made from collagen derived from the skin and bones of animals so several cultures and religious groups avoid its use and/or consumption since the source is considered sacred. This is not the case with calcium acetate, allowing for relatively easy adoption.

Skills and Knowledge

Although the procedure seems to be complex, most of the work in producing the ethanol in particular is done by the yeast via biochemical pathways in a process known as W. This process is complex in which W is converted into W which is then anaerobically converted into ethanol and CO2 via W.

Care needs to be taken, and the public (potential consumers) of the finished product need to be educated on the dangers of consuming the solution. As methanol may also be produced during fermentation in a competing process (which consumes glucose which fuels the desired process of ethanol production) and methanol consumption has been known to cause blindness and/or death in humans, its production should be minimized or avoided. Exact methods to do this are still to be investigated. View the material safety data sheet for methanol here.

Estimated Costs

Raw Material Costs

  • Potatoes (or corn, wheat)
  • Yeast ($5.19/lb or $11.50/kg here)
  • Metal containers (scrap?)
  • Metal sheet - to be bent for condensate collection
  • Heat source - fire
  • Shovel to dig hole for temperature 'controlled' storage
  • Thermometer for temperature monitoring - during distillation and fermentation

Other Resources

  • Time - up to two weeks to produce (start to finish)
  • Reallocation of food source - may not be an option in some regions

Mistakes and Precautionary Measures

Due to the relatively high alcohol content in some commercially available hand sanitizers, several reports of young children becoming intoxicated and at risk of alcohol poisoning after ingesting the sanitizing liquid have surfaced.

Ethanol-based materials are flammable. Semi-solidification, as in trapping ethanol in a gel, can slow the burning rate but the solid solution is still dangerous. See this videofor an example of the burning of a ethanol gel.

W are relatively resistant living organisms with many operating most efficiently at approximate temperature ranges from 20 degrees C to 40 degrees C. Heating them above this temperature may kill the organisms, while storage below this temperature will essentially render them inactive as they 'hibernate'. During hibernation, yeast still requires a food source (glucose), but will consume it much more slowly, and with their effectiveness decreasing over time. This process would use common W to produce ethanol (and CO2).

Methanol may also be produced by side reactions and must be extracted. Testing and trial attempts should be made to determine the relative quantities of ethanol and methanol produced by the reaction, and methods of extracting the methanol from solution should be explored. When consumed, methanol can lead to blindness or death, but can also be absorbed through the skin in low concentrations and may have negative effects on human health.

Fermentation is the biochemical process by which glucose (sugar) is converted into ethanol with a known biproduct being carbon dioxide (CO2). As such, care must be taken to adequately vent the space where fermentation will take place despite the process being carried out in sealed containers. Even small CO2 leaks can have negative effects on human health and well being including drowsiness and death.

Due to high ethanol content of the product and some of the intermediate steps of the process, care must be taken to not expose any ethanol-containing product to a direct flame as it is extremely flammable, especially in its pure state. Properly leak-proof and spill-proof containers should be used to reduce this risk.

Since the ethanol extraction process (distillation) is carried out over a heat source such as a fire, care must be taken around the hot elements of such a system. Containers will also heat up to 70-80 degrees C during the process, introducing the requirement for some sort of glove, sling or rack to remove the hot containers from the heat source. Since the shape of such containers will vary as a function of local resources and availability, a unique solution cannot be proposed, however the implemented solution should be reusable, strong (capable of holding container full of hot, fermented potato mash) and be used by one or two operators depending on the size, shape and weight of the container.

In order to continue the process, as the fermentation step is completed some of the potato and yeast slurry should be removed from the fermentation container and stored at a cool temperature (such as a safe, covered hold in the ground) for safe keeping. The yeast will remain in a less active state for a period of time but will still require a food source to life, grow and replenish. Fresh potato slurry should be added to this 'seed stock' for safe storage.

More Information

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