Incineration (Small-Scale)

For many countries, modern large-scale incineration plants are not available because of a lack of know-how and financial resources. Also, properly managed landfills are not always available to dispose solid waste. Open dumps and poorly designed and managed landfills lead to (ground-)water pollution (landfill leachate) and contamination of surface water sources.

Small-scale incinerators can reduce the volume of non-recyclable wastes (e.g. household waste, medical waste, slaughter waste). Moreover, heat and energy may be recovered and it helps to avoid open burning of municipal waste, which creates much more harmful emissions and endangers human health and environment.

Open waste burning

Urban air pollution due to open incineration of municipal waste or incineration in systems without or with only poorly designed flue gas cleaning systems results in a serious health risk. Another big problem is uncontrolled landfill fires and open burning on the streets. Uncontrolled burning of waste is largely obsolete in developed countries, but continues to be practised in developing regions, causing the release of CO₂ and other greenhouse gases. Some landfills in developing countries, such as the Smokey Mountain site in Manila, smoulder continuously (UNEP 2010). Another big problem is the “recycling” of e-waste in developing countries. This waste contains toxic chemicals such as lead or mercury. It is often burned to remove plastic and reclaim the valuable metals (GREENPEACE 2008).

Open waste dumping

Open waste dumps are often located close to residential areas and cities. Igniting them or burning waste piles accounts for a higher share in the dioxin inventory than all industrial sources together. It also results in substantial contamination of the environment and in high exposures of people to dangerous toxins, as people in such areas are directly exposed to the plumes from fires and children often play around the burning sites (UNEP 2009).

Modular incinerator

Modular incinerators are normally prefabricated units with relatively small capacities of between 5 and 120 tons of solid waste per day. Read more about them in large scale incineration systems.

Pre-fabricated products

There are several pre-fabricated small-scale incinerators (12–100 kg/hour) for all kinds of waste (medical waste, waste oil, animal by-products, etc.) and locations (farms, mines, truck stops, construction sites, etc.). A collection of the products that are currently commercial available can be found in PATH (2010).

Medical waset incinerator

(Adapted from PRACTICAL ACTION 2000)

The medical waste incinerator, which could be built in almost every developing country, is a simple two-chamber natural-draught incinerator designed to be operated at temperatures of 800°C and higher. The performance of the incinerator varies depending on the moisture content of the medical waste but a throughput of up to 15 kg/hour can be achieved. The incinerator has been designed so that it can be built on site, using standard building bricks or blocks and lined with refractory bricks. All the steel components, such as the loading door, the ash removal door and air inlet apertures can be made using basic workshop equipment. The two-chamber design helps to ensure that the combustion time is sufficient to destroy the products of combustion and minimise any harmful emissions.

The costs for small incinerators depend on the technology of the incinerator. If the incinerator is constructed locally (e.g. the medical incinerator which is described above), costs are much lower than for a fancy pre-fabricated product. Beside capital costs, costs for operation and maintenance as well as fuel (dry wood, charcoal, fuel oil, waste vegetable oil, etc.) must be budgeted (PATH 2010).

It is important to choose the appropriate incinerator to guarantee a long lifetime and minimise costs. The following are key steps to follow when selecting the appropriate incinerator for HCW Management to meet country and programmatic needs (PATH 2010):

• Determine your health system needs for HCWM treatment and disposal solutions.

• Assess the infrastructure of the area.

• Identify locally available incinerator designs and exchange with other people from the region who have experience with small-scale incinerators.

• Determine the availability of local resources to support construction and operation.

• Assess the policy environment.

• Develop cost estimates.

• Choose designs and determine which units to procure.

As described above, open burning or dumping of waste creates many health hazards due to toxic smoke, poor hygienic conditions, and leaching of toxic substances into the groundwater and soil. The residents who live very close to open burning sites are directly exposed to the plumes of the fires. Poorly designed incinerators (e.g. if the temperature is too low or there is a malfunction of the flue gas cleaning system) often result in the release of high levels of particulates, acid gases, heavy metal vapours, carbon monoxide, dioxins, and other toxins, some of which are carcinogenic. These pollutants can cause very serious human health problems. One of the most harmful pollutants released during backyard burning of trash is dioxin. Dioxin is a known carcinogen and is associated with birth defects. Dioxin can be inhaled directly or deposited on soil, water and crops where it becomes part of the food chain (DES 2011).

Regardless of the type of incinerator that is in use, the operator must be trained to avoid accidents, damages, injuries, and to minimise health risks. Furthermore, the operator must wear heat-resistant gloves and boots, a respirator mask, safety goggles, clothes that cover the body, and a helmet. Proper operation of an incinerator ensures safe and optimal performance (e.g. temperature, loading rate, etc.) (PATH 2010). Regular inspection is necessary to prolong the lifetime and avoid damages.

Safety notes for the operator of small-scale incinerators (PRACTICAL ACTION 2000):

• Opening the loading door may cause blowback to occur and the flame to flare up out of the loading door.

• Particular care should be taken when using kerosene, as atomised vaporised fuel may be present at the top of the combustion chamber, which could ignite vigorously.

• If the loading door is designed so that it hinges from the front of the incinerator and opens towards the operator, the operator should open the door while standing at the front of the incinerator. This provides the operator with some protection from any blowback and keeps him/her away from the opening to the combustion chamber.

• The operator should wait a few moments to allow any blow back to die down before loading waste materials into the incinerator.