What is an Air Curtain Incinerator?
Air curtain incinerators are devices that burn wood waste like trees and brush. ACIs have an insulated box to burn the wood waste and a fan powered by a diesel engine that blows a curtain of air over the box. Oregon uses ACIs for both wildfire cleanup and fire prevention efforts. ACIs are an alternative to traditional open burning and produce less harmful smoke and particulate matter.
There are two types of air curtain incinerators: one produces biochar
and the other produces ash. Both types are powered by a diesel engine that must
meet the cleanest Tier 4 engine standards available on the market. For more
information, please contact cleanerair@deq.oregon.gov.
What is emitted from an ACI?
Compared to traditional outdoor burning of wood waste, air curtain incinerators emit lower levels of air pollutants including PM2.5 and NOx. They burn more efficiently and produce significantly less smoke than traditional outdoor burning. Only authorized materials can be burned in an ACI and DEQ has created a list of authorized and prohibited materials.
Toxic air pollutants from ACIs come from the wood itself. The most concerning pollutants are metals, including manganese. Manganese is naturally occurring in soil and is taken into the tree through the roots. The metal can be released into the air when the wood is burned. Emissions from the diesel engine that powers the fan are also assessed as part of a DEQ air permit.
Although some ACI emissions tests have been performed in the past, insufficient data is available on toxic air emissions. For permitting, Cleaner Air Oregon is using conservative emission factors from a combination of open pile burning and woodfire boilers. To make more accurate decisions on these units DEQ is working to establish a complete set of emissions factors for ACIs. Learn more about the ACI emission testing happening spring of 2023.
How does the Cleaner Air Oregon program estimate health risk?
Oregon facilities are required to evaluate the health risk from toxic air pollutants. To do this, facilities first estimate the types and amounts of toxic air pollutants emitted. Next, they determine the risk from those toxic air pollutants to adults and children living, working, or going to school nearby. This is done through dispersion modeling that estimates how much of a given pollutant a person nearby may breathe in based on distance, time and amount.
DEQ compares the dispersion modeling estimates of risk with Oregon's established health standards. If the facility's risk is higher, DEQ requires it to reduce emissions.
An ACI is operating near me. What can I expect?
You may see brief periods of smoke when the ACI first turns on and when the operators load new material. You may briefly smell burning wood. Noise from the device is limited to the diesel engine and blower fan. Vehicles that load the ACI may also create noise.
The ACI should not be a constant source of heavy smoke. This may indicate that it's not being operated properly.
ACIs in Oregon
The following companies are currently permitted or are applying to operate in Oregon. If a company is listed as 'portable', they must notify DEQ anytime they move to a new location.
What other rules apply?
There are many safety protocols the operator must follow to protect those nearby. The ACI can't operate if the local fire department or U.S. Forest Service has banned burning, an air stagnation advisory is in place or the Air Quality Index is 100 or greater. Operators must be trained by a certified operator and they must follow all safety actions recommended by the manufacturer.
If you have concerns about the operation of an ACI near you, please contact DEQ.
Contact
For more information, please contact cleanerair@deq.oregon.gov.