Air Curtain Incinerator Trial

May 2005
Biosecurity New Zealand, a division of the Ministry of Agriculture and Forestry, is currently undertaking work on contingency planning for emergency disposal of animal carcasses in the event of an exotic animal disease outbreak.

Part of this work involved conducting a field trial on an air curtain incineration system (ACI) in order to assess its effectiveness for the disposal of carcasses. At the same time, the study gathered data to assess the potential environmental effects of discharges to air during a carcass disposal operation.

An ACI works by forcefully projecting a curtain of air across an open chamber in which combustion occurs. The products of combustion are mixed with air from above the air curtain to give a smokeless exit gas discharge into the air above the unit. The powerful curtain of air traps unburned particles under the curtain in the high temperature zone where temperatures can reach 1000C.

The trial was held in the Waikato region and involved the disposal of sheep and cattle carcasses. The ACI trial occupied the site for up to two weeks.

Engineering consultants were retained by MAF to find a suitable site, obtain any necessary resource consents, design and manage the ACI trial and rehabilitate the site.

At present there is only one ACI unit in New Zealand. This unit, which will be used for the trial, is a small pit burning model (3.4 m wide manifold).

The CP2000T manufactured by Concept Products Corporation, Paoli, US which will be used in the field trial.

Trial Requirements

The site needed to have the following requirements:

- Good weather access to allow equipment, fuel, carcasses, Port-a-Coms etc to be brought onto the site for the duration of the trial.

- Connections to water and electricity (preferred)

- Space to house equipment, Port-a-Com, fuel stockpile and carcasses.

- Good separation distances from trial site to neighbours.

- Resource consents can be obtained for the site.

- Groundwater is below 10m and there are no abstraction points nearby.

- Suitable soil for a vertically walled pit with the dimensions 5.8 m long by 2.3 m wide by 5 m deep

- The pit was excavated using a 12 tonne digger.

Once the trial was completed, the site was rehabilitated to a condition similar to that prior to the trial commencing.

Advantages of Air Curtain incineration

The very high temperature attained ensures complete destruction of all organisms, pathogenic and otherwise, yielding a sterile ash. ACI systems can also be used to help combat the spread of devastating beetles and other pests at the locations of infestation. The system is mobile and can be transported from place to place. ACIs were used in the 2001 UK Foot & Mouth Disease outbreak. They were trialled in the USA for pigs and extensively used in the 2004 Avian Influenza outbreak in Canada.

Environmental Risks

ACI's are considered pollution control devices that have the potential to play a major role in disaster recovery operations, such as the clean-up after a hurricane or tsunami or to deal with catastrophic animal disease outbreaks. Air quality testing has been conducted in the USA and the UK.

A literature review of air quality considerations has concluded that carbon monoxide, oxides of nitrogen, sulphur dioxide and dioxins are unlikely to be of environmental concern. However, BNZs trial will measure these gases as well as particulates, furans, polycyclic aromatic hydrocarbons (PAHs) and odour.