Following the Carbon: Using Micrometeorology to Evaluate the Impact of Land Application of Industrial Co-Products.

Industrial fermentation uses microbial processes to manufacture food, pharmaceutical, fiber and chemical products, while the waste or by-products of the fermentation process contain valuable components that can be used as inputs into other industrial or agricultural processes. These microbial by-products may reduce fertilizer use and cost for the farmer, while reducing landfill disposal and cost for the manufacturer. By comparing maize yield and CO₂ emissions of industrial by-products applied on row crops with typical farmer practices, economic value and environmental impact of the agricultural use of industrial fermentation by-products can be evaluated. Industrial spent microbial biomass (SMB) consisting of an engineered microbial catalyst for use in 1,3-propanediol production was compared to fertilizer in maize (Zea mays L.) production to determine the potential impact of SMB on both maize yield and net CO₂ emissions in July 2016 on 21 ha of farmland in east Tennessee. Net ecosystem CO₂ exchange as represented by the net annual sum of CO₂ flux was measured using two micrometeorological methods including eddy covariance and Bowen ratio energy balance (BREB) systems. This effort explored some of the issues in estimating night-time respiration due to thermal stratification and reduced turbulence and wind speed at night. An aerodynamic method was applied when BREB measurements were not suitable for calculating turbulent diffusivity, which occurred mostly at night and a friction velocity (u_∗) correction was used to gap fill night-time eddy covariance CO₂ fluxes. Maize yield was significantly less on the SMB treatment than the farmer practice treatment at 7.73 and 8.64 t/ha respectively. Some of this difference may have been the result of application rate, uniformity, and timing given that the application occurred just before planting. Exploring optimal application rates and timing for waste by-products can quantify the waste product value as an agricultural resource. This research provides support for using micrometeorology to detect CO₂ emissions of white industrial biotechnological use in agriculture as well as detect greater biomass production where SMB was applied to quantify the potential of white biotechnology to reduce net CO₂ emissions.