New technology from North Carolina State University and West Virginia University can reduce air pollutant emissions from some chicken and swine barns while also reducing their energy use by recovering and possibly generating heat. A proof-of-concept unit incorporates a biofilter and a heat exchanger to reduce ammonia emissions.
The pollution removal component utilizes a biofiltration mechanism, in which polluted air is passed through an organic medium, such as compost or wood chips, that contains bacteria. Those bacteria interact with the pollutants and break them down into harmless or less harmful constituents. Biofiltration also allows recycling of nitrogen because when the spent medium is applied on cropland, the nitrogen becomes available to the crops. Because biofiltration also introduces additional costs for animal agriculture operations, the researchers hope to defray such costs by reducing an operation’s energy consumption.
Heat is generated within the biofilter when heat-producing biochemical reactions occur – for example, when the ammonia is converted into nitrate by bacteria. The heat from the biofilter is also routed to the heat exchanger. Maintaining the appropriately high temperature is important for chicken and swine operations, because it is essential for rearing chicks and piglets to maturity.
Dr. Sanjay Shah, an associate professor of biological and agricultural engineering at NC State, says the researchers focused on ammonia removal because: it is released from chicken and swine houses in large quantities; it contributes to nutrient loading problems such as hypoxia; it is an indirect contributor to greenhouse gases (GHGs) because it can break down in to the potent GHG nitrous oxide in the ground; and because it is a precursor to very fine particulate matter, which contributes to haze and public health problems, such as asthma.