Alternatives to Medical Waste Incineration by Dr. Jorge Emmanuel

Many hospitals are under the impression that incineration is the only way to deal with the problem of infectious wastes. More dangerously, hospitals are made to believe that incinerators are actually a sound technology to dispose medical wastes.
This article aims to inform hospital managers about the various non-incineration technologies available to deal with infectious waste (the most problematic component of discards from a medical establishment).

Of the total discards originating from health care facilities -- including hospitals, clinics, and biomedical laboratories -- less than 15 percent is infectious or hazardous. The remainder is not unlike municipal solid waste and includes paper, food waste, and other recyclable or compostable material.

Infectious wastes, if improperly handled and disposed, could lead to the spread of diseases especially among health workers, waste haulers and landfill workers, and communities living near waste dumps. Improper disposal could also result in the contamination of soil, groundwater, and surface waters.

Non-incineration alternatives are specifically designed to treat infectious waste. This includes sharps (needles, syringes, glassware), cultures and stocks of infectious agents, blood and body fluids, and pathological waste (tissues, organs).

Incineration, until recently a popular treatment for medical waste, creates a host of problems. Medical waste incinerators are a major source of dioxins and furans in the environment due to the large quantities of chlorinated plastics (primarily PVC) found in the medical waste stream. Incinerators also emit particulate matter, heavy metals (mercury, lead, cadmium), acid gases (hydrogen chloride, sulfur dioxide, nitrogen oxides), and other combustion byproducts such as carbon monoxide. Moreover, medical waste incinerators generate toxic ash. The practice of burning all waste from a hospital has impeded the implementation of waste segregation and minimization programs.

Many non-incineration alternatives exist for the treatment of medical waste. However, in order to maximize the benefits of non-incineration technologies, a strategic framework of waste segregation and minimization is needed. The strategic framework entails

a. an analysis of the waste stream;

b. implementation of an effective waste
collection, transport, and storage system;

c. development of waste management and
contingency plans;

d. occupational safety and health
considerations;

e. worker training; and

f. proper siting of the technology.

Four major processes are used to disinfect infectious waste: thermal, chemical, irradiative, or biological.

Thermal processes rely on heat to destroy pathogens. The low-heat thermal processes (operating below 180°C) utilize moist or dry heat and do not involve combustion. They are the most widely used alternatives and include autoclaves or retorts, advanced autoclaves, and microwave units.

Autoclaves have been around for many years and can be found in a wide range of capacities, from small units in clinics to large systems in centralized facilities capable of handling thousands of kilograms per hour.

An autoclave is simply a metal chamber designed to withstand elevated pressures and fitted with a door through which the waste is introduced. Steam is injected into an outer jacket and into the treatment chamber either by gravity displacement of air or after a pre-vacuum cycle. The levels of disinfection achieved are dependent on temperature and the length of time of exposure to steam.

Advanced autoclaves are autoclaves with added features such as automatic or continuous waste feeding; internal shredding and mixing to improve the penetration of heat; drying; and post-treatment grinding or compaction.

Other low-heat processes include microwave technologies that use microwave energy to provide moist heat and to generate steam from water in the waste. These units range from small batch processes to continuous systems that treat up to 400 kg per hour. Dry heat systems circulate heated air in the treatment chamber to disinfect the waste.

Medium-heat technologies (180 to 370°C) are under development. High-heat thermal processes (over 500°C) are mostly in the development or demonstration phase and may be targeted more towards health care waste that are difficult to treat such as bulk chemotherapy agents, used disinfectants or solvents, and expired pharmaceuticals. Some poorly designed high-heat systems have failed performance and emission criteria. These technologies are generally expensive and only a few are fully commercialized.

Chemical processes employ disinfectants to destroy pathogens, or chemicals to decompose the waste, or agents to encapsulate the waste. The use of chlorine disinfectants (in the form of bleach or chlorine dioxide) has raised concerns about the possible formation of chlorinated byproducts in the wastewater. Non-chlorine chemical systems include those that use lime powder, lime slurries, or peracetic acid (which eventually breaks down into vinegar).

Systems that use heated alkali to digest tissues, pathological waste, and animal carcasses have been found to be effective in also destroying chemotherapy agents as well as prion diseases such as mad cow disease.

Irradiation involves the use of ionizing radiation to destroy microorganisms. In the past, this technology has been used for sterilizing food and medical products. Biological processes use enzymes or microorganisms to decompose organic matter. Both irradiative and biological systems are in the development or demonstration stage. Small treatment technologies are available to treat only sharps by destroying needle portions or by melting and encapsulating syringes.

Although many alternatives exist, no one technology offers a panacea to the problem of medical waste disposal. Each technology has its advantages and disadvantages. Facilities have to determine which non-incineration technology best meets their particular needs while protecting health and the environment.

When selecting an alternative technology, the following factors should be considered:

the nature and quantum of wastes generated;

the technology's ease-of-use, throughput capacity and microbial inactivation efficacy;

the types of wastes treated by the technology;

the environmental emissions, noise, odour and waste residues;

regulatory acceptance;

space, utility (water/electricity etc) and other installation requirements;

waste reduction potential;

the technology's reliability, level of commercialization, track record and cost;

community and staff acceptance.

NOTE: This article is based on a new publication "Non-Incineration Medical Waste Treatment Technologies" by the Health Care Without Harm (HCWH). Inclusion of medium and high-heat thermal processes does not suggest approval of pyrolysis, gasification and plasma arc systems as substitutes to incineration. The HCWH will soon release an update that will show pyrolysis and gasification systems, while being promoted as clean non-burn alternatives, are still capable of generating dioxins, furans and other pollutants of concern, despite marketing and promotional claims to the contrary.

Read: "Non-Incineration Medical Waste Treatment Technologies"

For inquiries, e-mail Bryony Schwan, GAIA-HCWH Liaison Officcer at: swan@wildrockies.org.

Dr. Jorge Emmanuel is consultant to Health Care Without Harm on alternative medical waste treatment technologies.
e-mail: jemmanuel@mindspring.com