Laboratory, Long Term, Automated GHG Monitoring System for Soil and Biochar Mix Core Samples.

Measuring soil respiration and understanding the potential of carbon sequestration with biochar amendments, is indeed a major challenge. Firstly, in situ small scale chemical and physical variability hinders the understanding of greenhouse gas emissions (GHG). Secondly, biochar type, feedstock origin, processing conditions and pre/post treatments have a different response over different soils and managements. And thirdly, other environmental and external parameters play also an important role interfering with soil and biochar GHG evolution, such as; soil temperature, rain events, crop type, tilling, liming, fertilizations, compaction, moisture content, etc. Thus, every variable that affects the soil physically and chemically will affect microbial development, oxidation of soil organic carbon, and ultimately biochar and soil organic and inorganic carbon content. In addition, to truly understand greenhouse gas emissions, other gasses apart from carbon dioxide (most importantly nitrous oxides and methane) have to be concurrently evaluated for a more comprehensive assessment of the overall emissions. Conventional laboratory closed vial analysis won’t be either a good representation of soil emissions, differing from in situ measurements due to several reasons. For example, the accumulation of co-products over time that would result in self inhibition or change in metabolic pathways, the alteration of soil structure for sample preparation will result in artificial respiration values, etc. Developing a continuous automatic system that could measure carbon dioxide, assisted with a GC to measure other gasses, with large undisturbed soil core samples could result in a truthful inexpensive alternative for in-field measurements of GHGs to soil and biochar treatments. When soil is brought to the lab and fixed those environmental conditions that make in situ measures so variable, respiration and metabolism of soil could be further understood. Real time measurements of carbon dioxide of different core soil and biochar samples are being evaluated with an automated IRGA. Gas chromatography it is being used for analysis of N₂O and CH₄ (with electron capture detector and flame ionization detector, respectively). Preliminary results show interesting dynamics of gasses over time. Different types of biochar tested in a Mollisoil type soils have different responses on the three gasses being measured. Preliminary results show that the integrated way of measuring GHG gasses such as carbon dioxide, methane and nitrous oxide could truly account for emissions, hence could be used for validating carbon sequestration managements.