V csn

The detection of H₂, CO₂, CH₄ was carried out with gas-chromatographic analysis of the headspace of the following: the H cells; the serum bottles; and the gaseous phase of the reactor using a Dani Master GC equipped with a packed column and TCD detector set with the following conditions: injection volume 50 µL, carrier gas nitrogen, flow 12 mL/min, inlet temperature 120 °C, column temperature 70 °C and TCD detector at 150 °C. To sample the gaseous phase, a Gas tight syringe (Hamilton Company, Reno, Nevada, USA) was used. The analysis of volatile fatty acids (VFA) was performed by injecting 1 µL of liquid sample into a Dani Master gas chromatograph equipped with an FID detector with the following configuration: helium as carrier gas, flow 25 mL/min, temperature injector 200 °C, column temperature 175 °C and FID detector at 200 °C. The liquid samples were filtered (cellulose acetate filters, diameter 25 mm, pore diameter 0.2 µm) and prepared by adding to 1.0 mL of liquid sample (diluted or undiluted as needed) 100 µL of 0.33 M oxalic acid. Inorganic carbon was measured by TOC (total carbon analyzer)-V CSN (Shimadzu) on filtered samples.

A calibrated pH meter was used to measure pH (Hanna Hl-10530 pH meter). Moisture was analyzed according to the protocol described by the French Association for Standardization—AFNOR³² . The C/N ratio for the initial mix and the end products was calculated by analyzing the total C and N percentages using a TOC analyzer (Shimadzu-V CSN)^{33 (link)}. The total ammonium and nitrate ion (NH₄⁺/NO₃⁻) ratios for the pre-composted mix and the final products were calculated from the percentage of NH₄⁺ and NO₃⁻. This was performed using the method based on alkaline distillation for ammonium ions (NH₄⁺), and using reduction by Dewarda alloying for nitrate ions (NO₃⁻)⁹ .