COMPOST INDUSTRY

Direct Measurement of Air Emissions from A Variety of Composting Technologies Using the USEA Flux Chamber

The compost industry is great!  The industry takes solid waste refuse of all sorts (greenwaste, biosolids waste from wastewater treatment, food waste, agriculture/animal waste) and makes a marketable product that is very useful.  The industry, for the most part, consists of area sources that lend themselves well to direct assessment using the USEPA flux chamber technology and the SCAQMD modified USEPA flux chamber technology (aerated sources).

The compost site characterization typically involves determining the air emissions from the site in order to meet the site permit requirements, and often includes destruction efficiency testing of air pollution control equipment (scrubbers and biofilters).  The site emissions are estimated from the life-cycle of the compost.  This is accomplished by measuring the flux from each unit process and these data are summed and expressed on a per ton of stock material received for composting.  The compost process includes material receipt, preparation of material for composting, blending of waste with a bulking agent such as wood chips, composting the mix in windrows, windrow maintenance including watering and turning, curing in windrows, screening, and product stockpiling.  By measuring emissions from each unit process, representative flux data are collected and used in the emissions estimate.  The different approaches to composting include static windrow pile (photo 1, below) and negative aeration static pile.  Negative aeration static pile composting often includes air pollution control.  The emissions are scrubbed typically by a biofilter (photo 2).  A cover system (photo 3) is employed with positive aeration - the cover serves as the air pollution control device.

The species included in a typical compost site assessment are total non-methane non-ethane organic carbon (TNMNEOC) by SCAQMD Method 25.3 (photo 4), ammonia by SCAQMD Method 207.1, sometimes olfactory odor (photo 5) and hydrocarbon speciation, and more recently the non-photoreactive family of siloxane compounds.  Greenhouse gas species emissions have also been studied, along with ozone reactivity (teaming with UC Davis research scientists).  The technical approach developed for a compost site assessment is usually fairly intense as related to the number of source-types (unit processes) on site and the type of sample collection required.  In addition, since these sources are porous and emitting gas at a fairly high flow rate, the modified USEPA flux chamber technology is employed for high advective flow sources.  Here, the advective flow into the flux chamber is determined by the recovery of a trace gas added to the flux chamber sweep air.  Assessment included at compost sites have been performed for a variety of project purposes and study compounds serving the needs of our clients.

Photo 1: Flux Chamber Testing on Compost Windrow

Photo 2: Modified SCAQMD USEPA Flux Chamber Measuring Emissions from A Compost Site Biofilter

Photo 3: Direct Measurement of Fugitive Air Emissions from Micropore Cover on Windrow

Photo 4: Flux Testing for Total Hydrocarbon Emissions from Compost Using SCAQMD Method 25.3

Photo 5: Flux Measurement of TO-15 Speciated Hydrocarbons and Odor Flux from Compost